gsk: Make glyphy optional for now

Enable glyphy by default, but make it possible
to get the previous cairo rendering by setting
GSK_DEBUG=no-glyphy in the environment.

Keeping this optional will make it easier to
debug issues and compare output.

gsk/gl/gskgldriver.c

@@ -32,6 +32,7 @@
 #include "gskglcommandqueueprivate.h"
 #include "gskglcompilerprivate.h"
 #include "gskglglyphlibraryprivate.h"
+#include "gskglglyphylibraryprivate.h"
 #include "gskgliconlibraryprivate.h"
 #include "gskglprogramprivate.h"
 #include "gskglshadowlibraryprivate.h"
@@ -273,6 +274,7 @@ gsk_gl_driver_dispose (GObject *object)
     }
 
   g_clear_object (&self->glyphs_library);
+  g_clear_object (&self->glyphy_library);
   g_clear_object (&self->icons_library);
   g_clear_object (&self->shadows_library);
 
@@ -463,6 +465,7 @@ gsk_gl_driver_new (GskGLCommandQueue  *command_queue,
     }
 
   self->glyphs_library = gsk_gl_glyph_library_new (self);
+  self->glyphy_library = gsk_gl_glyphy_library_new (self);
   self->icons_library = gsk_gl_icon_library_new (self);
   self->shadows_library = gsk_gl_shadow_library_new (self);
 
@@ -573,6 +576,8 @@ gsk_gl_driver_begin_frame (GskGLDriver       *self,
                                       self->current_frame_id);
   gsk_gl_texture_library_begin_frame (GSK_GL_TEXTURE_LIBRARY (self->glyphs_library),
                                       self->current_frame_id);
+  gsk_gl_texture_library_begin_frame (GSK_GL_TEXTURE_LIBRARY (self->glyphy_library),
+                                      self->current_frame_id);
 
   /* Cleanup old shadows */
   gsk_gl_shadow_library_begin_frame (self->shadows_library);

gsk/gl/gskgldriverprivate.h

@@ -97,6 +97,7 @@ struct _GskGLDriver
   GskGLCommandQueue *command_queue;
 
   GskGLGlyphLibrary *glyphs_library;
+  GskGLGlyphyLibrary *glyphy_library;
   GskGLIconLibrary *icons_library;
   GskGLShadowLibrary *shadows_library;
 

gsk/gl/gskglglyphylibrary.c

@@ -0,0 +1,544 @@
+/* gskglglyphylibrary.c
+ *
+ * Copyright 2020 Christian Hergert <chergert@redhat.com>
+ *
+ * This library is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU Lesser General Public
+ * License as published by the Free Software Foundation; either
+ * version 2.1 of the License, or (at your option) any later version.
+ *
+ * This library is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+ * Lesser General Public License for more details.
+ *
+ * You should have received a copy of the GNU Lesser General Public
+ * License along with this program.  If not, see <http://www.gnu.org/licenses/>.
+ *
+ * SPDX-License-Identifier: LGPL-2.1-or-later
+ */
+
+/* Some of the glyphy cache is based upon the original glyphy code.
+ * It's license is provided below.
+ */
+/*
+ * Copyright 2012 Google, Inc. All Rights Reserved.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ *
+ * Google Author(s): Behdad Esfahbod
+ */
+
+#include "config.h"
+
+#include <gdk/gdkglcontextprivate.h>
+#include <gdk/gdkmemoryformatprivate.h>
+#include <gdk/gdkprofilerprivate.h>
+
+#include "gskglcommandqueueprivate.h"
+#include "gskgldriverprivate.h"
+#include "gskglglyphylibraryprivate.h"
+#include "gskdebugprivate.h"
+
+#include "gskpathprivate.h"
+
+#include <glyphy.h>
+
+#define TOLERANCE (1/2048.)
+#define MIN_FONT_SIZE 14
+#define GRID_SIZE 20 /* Per EM */
+#define ENLIGHTEN_MAX .01 /* Per EM */
+#define EMBOLDEN_MAX .024 /* Per EM */
+
+/* We split the atlas into cells of size 64x8, so the minimum number of
+ * bytes we store per glyph is 2048, and an atlas of size 2048x1024 can
+ * hold at most 4096 glyphs. We need 5 and 7 bits to store the position
+ * of a glyph in the atlas.
+ *
+ * We allocate each glyph a column of as many vertically adjacent cells
+ * as it needs.
+ */
+#define ITEM_W 64
+#define ITEM_H_QUANTUM 8
+
+G_DEFINE_TYPE (GskGLGlyphyLibrary, gsk_gl_glyphy_library, GSK_TYPE_GL_TEXTURE_LIBRARY)
+
+GskGLGlyphyLibrary *
+gsk_gl_glyphy_library_new (GskGLDriver *driver)
+{
+  g_return_val_if_fail (GSK_IS_GL_DRIVER (driver), NULL);
+
+  return g_object_new (GSK_TYPE_GL_GLYPHY_LIBRARY,
+                       "driver", driver,
+                       NULL);
+}
+
+static guint
+gsk_gl_glyphy_key_hash (gconstpointer data)
+{
+  const GskGLGlyphyKey *key = data;
+
+  /* malloc()'d pointers already guarantee 3 bits from the LSB on 64-bit and
+   * 2 bits from the LSB on 32-bit. Shift by enough to give us 256 entries
+   * in our front cache for the glyph since languages will naturally cluster
+   * for us.
+   */
+
+  return (key->font << 8) ^ key->glyph;
+}
+
+static gboolean
+gsk_gl_glyphy_key_equal (gconstpointer v1,
+                         gconstpointer v2)
+{
+  return memcmp (v1, v2, sizeof (GskGLGlyphyKey)) == 0;
+}
+
+static void
+gsk_gl_glyphy_key_free (gpointer data)
+{
+  GskGLGlyphyKey *key = data;
+
+  g_slice_free (GskGLGlyphyKey, key);
+}
+
+static void
+gsk_gl_glyphy_value_free (gpointer data)
+{
+  g_slice_free (GskGLGlyphyValue, data);
+}
+
+static void
+gsk_gl_glyphy_library_clear_cache (GskGLTextureLibrary *library)
+{
+  GskGLGlyphyLibrary *self = (GskGLGlyphyLibrary *)library;
+
+  g_assert (GSK_IS_GL_GLYPHY_LIBRARY (self));
+
+  memset (self->front, 0, sizeof self->front);
+}
+
+static void
+gsk_gl_glyphy_library_init_atlas (GskGLTextureLibrary *library,
+                                  GskGLTextureAtlas   *atlas)
+{
+  g_assert (GSK_IS_GL_GLYPHY_LIBRARY (library));
+  g_assert (atlas != NULL);
+
+  atlas->cursor_x = 0;
+  atlas->cursor_y = 0;
+}
+
+static gboolean
+gsk_gl_glyphy_library_allocate (GskGLTextureLibrary *library,
+                                GskGLTextureAtlas   *atlas,
+                                int                  width,
+                                int                  height,
+                                int                 *out_x,
+                                int                 *out_y)
+{
+  GskGLGlyphyLibrary *self = (GskGLGlyphyLibrary *)library;
+  int cursor_save_x;
+  int cursor_save_y;
+
+  g_assert (GSK_IS_GL_GLYPHY_LIBRARY (self));
+  g_assert (atlas != NULL);
+
+  cursor_save_x = atlas->cursor_x;
+  cursor_save_y = atlas->cursor_y;
+
+  if ((height & (self->item_h_q-1)) != 0)
+    height = (height + self->item_h_q - 1) & ~(self->item_h_q - 1);
+
+  /* Require allocations in columns of 64 and rows of 8 */
+  g_assert (width == self->item_w);
+  g_assert ((height % self->item_h_q) == 0);
+
+  if (atlas->cursor_y + height > atlas->height)
+    {
+      /* Go to next column */
+      atlas->cursor_x += self->item_w;
+      atlas->cursor_y = 0;
+    }
+
+  if (atlas->cursor_x + width <= atlas->width &&
+      atlas->cursor_y + height <= atlas->height)
+    {
+      *out_x = atlas->cursor_x;
+      *out_y = atlas->cursor_y;
+      atlas->cursor_y += height;
+      return TRUE;
+    }
+
+  atlas->cursor_x = cursor_save_x;
+  atlas->cursor_y = cursor_save_y;
+
+  return FALSE;
+}
+
+static void
+gsk_gl_glyphy_library_finalize (GObject *object)
+{
+  GskGLGlyphyLibrary *self = (GskGLGlyphyLibrary *)object;
+
+  g_clear_pointer (&self->acc, glyphy_arc_accumulator_destroy);
+  g_clear_pointer (&self->acc_endpoints, g_array_unref);
+
+  G_OBJECT_CLASS (gsk_gl_glyphy_library_parent_class)->finalize (object);
+}
+
+GQuark quark_glyphy_font_key;
+
+static void
+gsk_gl_glyphy_library_class_init (GskGLGlyphyLibraryClass *klass)
+{
+  GObjectClass *object_class = G_OBJECT_CLASS (klass);
+  GskGLTextureLibraryClass *library_class = GSK_GL_TEXTURE_LIBRARY_CLASS (klass);
+
+  quark_glyphy_font_key = g_quark_from_static_string ("glyphy-font-key");
+
+  object_class->finalize = gsk_gl_glyphy_library_finalize;
+
+  library_class->allocate = gsk_gl_glyphy_library_allocate;
+  library_class->clear_cache = gsk_gl_glyphy_library_clear_cache;
+  library_class->init_atlas = gsk_gl_glyphy_library_init_atlas;
+}
+
+static void
+gsk_gl_glyphy_library_init (GskGLGlyphyLibrary *self)
+{
+  GskGLTextureLibrary *tl = (GskGLTextureLibrary *)self;
+
+  tl->max_entry_size = 0;
+  tl->max_frame_age = 512;
+  tl->atlas_width = 2048;
+  tl->atlas_height = 1024;
+  gsk_gl_texture_library_set_funcs (tl,
+                                    gsk_gl_glyphy_key_hash,
+                                    gsk_gl_glyphy_key_equal,
+                                    gsk_gl_glyphy_key_free,
+                                    gsk_gl_glyphy_value_free);
+
+  self->acc = glyphy_arc_accumulator_create ();
+  self->acc_endpoints = g_array_new (FALSE, FALSE, sizeof (glyphy_arc_endpoint_t));
+  self->item_w = ITEM_W;
+  self->item_h_q = ITEM_H_QUANTUM;
+}
+
+static glyphy_bool_t
+accumulate_endpoint (glyphy_arc_endpoint_t *endpoint,
+                     GArray                *endpoints)
+{
+  g_array_append_vals (endpoints, endpoint, 1);
+  return TRUE;
+}
+
+static void
+move_to (hb_draw_funcs_t *dfuncs,
+         GskPathBuilder  *builder,
+         hb_draw_state_t *st,
+         float            x,
+         float            y,
+         void            *data)
+{
+  gsk_path_builder_move_to (builder, x, y);
+}
+
+static void
+line_to (hb_draw_funcs_t *dfuncs,
+         GskPathBuilder  *builder,
+         hb_draw_state_t *st,
+         float            x,
+         float            y,
+         void            *data)
+{
+  gsk_path_builder_line_to (builder, x, y);
+}
+
+static void
+cubic_to (hb_draw_funcs_t *dfuncs,
+          GskPathBuilder  *builder,
+          hb_draw_state_t *st,
+          float            x1,
+          float            y1,
+          float            x2,
+          float            y2,
+          float            x3,
+          float            y3,
+          void            *data)
+{
+  gsk_path_builder_cubic_to (builder, x1, y1, x2, y2, x3, y3);
+}
+
+static void
+close_path (hb_draw_funcs_t *dfuncs,
+            GskPathBuilder  *builder,
+            hb_draw_state_t *st,
+            void            *data)
+{
+  gsk_path_builder_close (builder);
+}
+
+static hb_draw_funcs_t *
+gsk_path_get_draw_funcs (void)
+{
+  static hb_draw_funcs_t *funcs = NULL;
+
+  if (!funcs)
+    {
+      funcs = hb_draw_funcs_create ();
+
+      hb_draw_funcs_set_move_to_func (funcs, (hb_draw_move_to_func_t) move_to, NULL, NULL);
+      hb_draw_funcs_set_line_to_func (funcs, (hb_draw_line_to_func_t) line_to, NULL, NULL);
+      hb_draw_funcs_set_cubic_to_func (funcs, (hb_draw_cubic_to_func_t) cubic_to, NULL, NULL);
+      hb_draw_funcs_set_close_path_func (funcs, (hb_draw_close_path_func_t) close_path, NULL, NULL);
+
+      hb_draw_funcs_make_immutable (funcs);
+    }
+
+  return funcs;
+}
+
+static gboolean
+acc_callback (GskPathOperation        op,
+              const graphene_point_t *pts,
+              gsize                   n_pts,
+              float                   weight,
+              gpointer                user_data)
+{
+  glyphy_arc_accumulator_t *acc = user_data;
+  glyphy_point_t p0, p1, p2, p3;
+
+  switch (op)
+    {
+    case GSK_PATH_MOVE:
+      p0.x = pts[0].x; p0.y = pts[0].y;
+      glyphy_arc_accumulator_move_to (acc, &p0);
+      break;
+    case GSK_PATH_CLOSE:
+      glyphy_arc_accumulator_close_path (acc);
+      break;
+    case GSK_PATH_LINE:
+      p1.x = pts[1].x; p1.y = pts[1].y;
+      glyphy_arc_accumulator_line_to (acc, &p1);
+      break;
+    case GSK_PATH_QUAD:
+      p1.x = pts[1].x; p1.y = pts[1].y;
+      p2.x = pts[2].x; p2.y = pts[2].y;
+      /* This glyphy api is mis-named */
+      glyphy_arc_accumulator_conic_to (acc, &p1, &p2);
+      break;
+    case GSK_PATH_CUBIC:
+      p1.x = pts[1].x; p1.y = pts[1].y;
+      p2.x = pts[2].x; p2.y = pts[2].y;
+      p3.x = pts[3].x; p3.y = pts[3].y;
+      glyphy_arc_accumulator_cubic_to (acc, &p1, &p2, &p3);
+      break;
+    case GSK_PATH_CONIC:
+    default:
+      g_assert_not_reached ();
+    }
+
+  return TRUE;
+}
+
+static inline gboolean
+encode_glyph (GskGLGlyphyLibrary *self,
+              hb_font_t          *font,
+              unsigned int        glyph_index,
+              double              tolerance_per_em,
+              glyphy_rgba_t      *buffer,
+              guint               buffer_len,
+              guint              *output_len,
+              guint              *nominal_width,
+              guint              *nominal_height,
+              glyphy_extents_t   *extents)
+{
+  hb_face_t *face = hb_font_get_face (font);
+  guint upem = hb_face_get_upem (face);
+  double tolerance = upem * tolerance_per_em;
+  double faraway = (double)upem / (MIN_FONT_SIZE * M_SQRT2);
+  double unit_size = (double) upem / GRID_SIZE;
+  double enlighten_max = (double) upem * ENLIGHTEN_MAX;
+  double embolden_max = (double) upem * EMBOLDEN_MAX;
+  double avg_fetch_achieved;
+  GskPathBuilder *builder;
+  GskPath *path, *simplified;
+
+  self->acc_endpoints->len = 0;
+
+  glyphy_arc_accumulator_reset (self->acc);
+  glyphy_arc_accumulator_set_tolerance (self->acc, tolerance);
+  glyphy_arc_accumulator_set_callback (self->acc,
+                                       (glyphy_arc_endpoint_accumulator_callback_t)accumulate_endpoint,
+                                       self->acc_endpoints);
+
+  builder = gsk_path_builder_new ();
+#if HB_VERSION_ATLEAST (7, 0, 0)
+  hb_font_draw_glyph (font, glyph_index, gsk_path_get_draw_funcs (), builder);
+#else
+  hb_font_get_glyph_shape (font, glyph_index, gsk_path_get_draw_funcs (), builder);
+#endif
+  path = gsk_path_builder_free_to_path (builder);
+  simplified = gsk_path_op (GSK_PATH_OP_SIMPLIFY, GSK_FILL_RULE_WINDING, path, NULL);
+  gsk_path_foreach (simplified, -1, acc_callback, self->acc);
+  gsk_path_unref (simplified);
+  gsk_path_unref (path);
+
+  if (!glyphy_arc_accumulator_successful (self->acc))
+    return FALSE;
+
+  g_assert (glyphy_arc_accumulator_get_error (self->acc) <= tolerance);
+
+  if (self->acc_endpoints->len > 0)
+    glyphy_outline_winding_from_even_odd ((gpointer)self->acc_endpoints->data,
+                                          self->acc_endpoints->len,
+                                          FALSE);
+
+  if (!glyphy_arc_list_encode_blob2 ((gpointer)self->acc_endpoints->data,
+                                     self->acc_endpoints->len,
+                                     buffer,
+                                     buffer_len,
+                                     faraway,
+                                     unit_size,
+                                     enlighten_max,
+                                     embolden_max,
+                                     &avg_fetch_achieved,
+                                     output_len,
+                                     nominal_width,
+                                     nominal_height,
+                                     extents))
+    return FALSE;
+
+  glyphy_extents_scale (extents, 1./upem, 1./upem);
+
+  return TRUE;
+}
+
+static inline hb_font_t *
+get_nominal_size_hb_font (PangoFont *font)
+{
+  hb_font_t *hbfont;
+  const float *coords;
+  unsigned int length;
+
+  hbfont = (hb_font_t *) g_object_get_data ((GObject *)font, "glyph-nominal-size-font");
+  if (hbfont == NULL)
+    {
+      hbfont = hb_font_create (hb_font_get_face (pango_font_get_hb_font (font)));
+      coords = hb_font_get_var_coords_design (pango_font_get_hb_font (font), &length);
+      if (length > 0)
+        hb_font_set_var_coords_design (hbfont, coords, length);
+
+      g_object_set_data_full ((GObject *)font, "glyphy-nominal-size-font",
+                              hbfont, (GDestroyNotify)hb_font_destroy);
+    }
+
+  return hbfont;
+}
+
+gboolean
+gsk_gl_glyphy_library_add (GskGLGlyphyLibrary      *self,
+                           GskGLGlyphyKey          *key,
+                           PangoFont               *font,
+                           const GskGLGlyphyValue **out_value)
+{
+  static glyphy_rgba_t buffer[4096 * 16];
+  GskGLTextureLibrary *tl = (GskGLTextureLibrary *)self;
+  GskGLGlyphyValue *value;
+  glyphy_extents_t extents;
+  hb_font_t *hbfont;
+  guint packed_x;
+  guint packed_y;
+  guint nominal_w, nominal_h;
+  guint output_len = 0;
+  guint texture_id;
+  guint width, height;
+
+  g_assert (GSK_IS_GL_GLYPHY_LIBRARY (self));
+  g_assert (key != NULL);
+  g_assert (font != NULL);
+  g_assert (out_value != NULL);
+
+  hbfont = get_nominal_size_hb_font (font);
+
+  /* Convert the glyph to a list of arcs */
+  if (!encode_glyph (self, hbfont, key->glyph, TOLERANCE,
+                     buffer, sizeof buffer, &output_len,
+                     &nominal_w, &nominal_h, &extents))
+    return FALSE;
+
+  /* Allocate space for list within atlas */
+  width = self->item_w;
+  height = (output_len + width - 1) / width;
+  GSK_DEBUG (GLYPH_CACHE, "font %u glyph %u: %u bytes (%u x %u)", key->font, key->glyph, output_len * 4, width, height);
+
+  value = gsk_gl_texture_library_pack (tl, key, sizeof *value,
+                                       width, height, 0,
+                                       &packed_x, &packed_y);
+
+  g_assert (packed_x % ITEM_W == 0);
+  g_assert (packed_y % ITEM_H_QUANTUM == 0);
+
+  /* Make sure we found space to pack */
+  texture_id = GSK_GL_TEXTURE_ATLAS_ENTRY_TEXTURE (value);
+  if (texture_id == 0)
+    return FALSE;
+
+  if (!glyphy_extents_is_empty (&extents))
+    {
+      /* Connect the texture for data upload */
+      glActiveTexture (GL_TEXTURE0);
+      glBindTexture (GL_TEXTURE_2D, texture_id);
+
+      g_assert (width > 0);
+      g_assert (height > 0);
+
+      /* Upload the arc list */
+      if (width * height == output_len)
+        {
+          glTexSubImage2D (GL_TEXTURE_2D, 0,
+                           packed_x, packed_y,
+                           width, height,
+                           GL_RGBA, GL_UNSIGNED_BYTE,
+                           buffer);
+        }
+      else
+        {
+          glTexSubImage2D (GL_TEXTURE_2D, 0,
+                           packed_x, packed_y,
+                           width, height - 1,
+                           GL_RGBA, GL_UNSIGNED_BYTE,
+                           buffer);
+          /* Upload the last row separately */
+          glTexSubImage2D (GL_TEXTURE_2D, 0,
+                           packed_x, packed_y + height - 1,
+                           output_len - (width * (height - 1)), 1,
+                           GL_RGBA, GL_UNSIGNED_BYTE,
+                           buffer + (width * (height - 1)));
+        }
+    }
+
+  value->extents.min_x = extents.min_x;
+  value->extents.min_y = extents.min_y;
+  value->extents.max_x = extents.max_x;
+  value->extents.max_y = extents.max_y;
+  value->nominal_w = nominal_w;
+  value->nominal_h = nominal_h;
+  value->atlas_x = packed_x / self->item_w;
+  value->atlas_y = packed_y / self->item_h_q;
+
+  *out_value = value;
+
+  return TRUE;
+}

gsk/gl/gskglglyphylibraryprivate.h

@@ -0,0 +1,142 @@
+/* gskglglyphylibraryprivate.h
+ *
+ * Copyright 2020-2022 Christian Hergert <chergert@redhat.com>
+ *
+ * This library is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU Lesser General Public
+ * License as published by the Free Software Foundation; either
+ * version 2.1 of the License, or (at your option) any later version.
+ *
+ * This library is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+ * Lesser General Public License for more details.
+ *
+ * You should have received a copy of the GNU Lesser General Public
+ * License along with this program.  If not, see <http://www.gnu.org/licenses/>.
+ *
+ * SPDX-License-Identifier: LGPL-2.1-or-later
+ */
+
+#ifndef __GSK_GL_GLYPHY_LIBRARY_PRIVATE_H__
+#define __GSK_GL_GLYPHY_LIBRARY_PRIVATE_H__
+
+#include <glyphy.h>
+#include <pango/pango.h>
+
+#include "gskgltexturelibraryprivate.h"
+
+G_BEGIN_DECLS
+
+#define GSK_TYPE_GL_GLYPHY_LIBRARY (gsk_gl_glyphy_library_get_type())
+
+typedef guint FontKey;
+
+extern GQuark quark_glyphy_font_key;
+
+static inline FontKey
+gsk_gl_glyphy_library_get_font_key (PangoFont *font)
+{
+  FontKey key;
+
+  key = (FontKey) GPOINTER_TO_UINT (g_object_get_qdata ((GObject *)font, quark_glyphy_font_key));
+  if (key == 0)
+    {
+      PangoFontDescription *desc = pango_font_describe (font);
+      pango_font_description_set_size (desc, 10 * PANGO_SCALE);
+      key = (FontKey) pango_font_description_hash (desc);
+      pango_font_description_free (desc);
+      g_object_set_qdata ((GObject *)font, quark_glyphy_font_key, GUINT_TO_POINTER (key));
+    }
+
+  return key;
+}
+
+static inline float
+gsk_gl_glyphy_library_get_font_scale (PangoFont *font)
+{
+  hb_font_t *hbfont;
+  int x_scale, y_scale;
+
+  hbfont = pango_font_get_hb_font (font);
+  hb_font_get_scale (hbfont, &x_scale, &y_scale);
+
+  return MAX (x_scale, y_scale) / 1000.0;
+}
+
+
+typedef struct _GskGLGlyphyKey
+{
+  FontKey font;
+  PangoGlyph glyph;
+} GskGLGlyphyKey;
+
+typedef struct _GskGLGlyphyValue
+{
+  GskGLTextureAtlasEntry entry;
+  struct {
+    float min_x;
+    float min_y;
+    float max_x;
+    float max_y;
+  } extents;
+  guint nominal_w;
+  guint nominal_h;
+  guint atlas_x;
+  guint atlas_y;
+} GskGLGlyphyValue;
+
+G_DECLARE_FINAL_TYPE (GskGLGlyphyLibrary, gsk_gl_glyphy_library, GSK, GL_GLYPHY_LIBRARY, GskGLTextureLibrary)
+
+struct _GskGLGlyphyLibrary
+{
+  GskGLTextureLibrary parent_instance;
+  glyphy_arc_accumulator_t *acc;
+  GArray *acc_endpoints;
+  guint item_w;
+  guint item_h_q;
+  struct {
+    GskGLGlyphyKey key;
+    const GskGLGlyphyValue *value;
+  } front[256];
+};
+
+GskGLGlyphyLibrary *gsk_gl_glyphy_library_new (GskGLDriver             *driver);
+gboolean            gsk_gl_glyphy_library_add (GskGLGlyphyLibrary      *self,
+                                               GskGLGlyphyKey          *key,
+                                               PangoFont               *font,
+                                               const GskGLGlyphyValue **out_value);
+
+static inline guint
+gsk_gl_glyphy_library_lookup_or_add (GskGLGlyphyLibrary      *self,
+                                     const GskGLGlyphyKey    *key,
+                                     PangoFont               *font,
+                                     const GskGLGlyphyValue **out_value)
+{
+  GskGLTextureAtlasEntry *entry;
+  guint front_index = key->glyph & 0xFF;
+
+  if (memcmp (key, &self->front[front_index], sizeof *key) == 0)
+    {
+      *out_value = self->front[front_index].value;
+    }
+  else if (gsk_gl_texture_library_lookup ((GskGLTextureLibrary *)self, key, &entry))
+    {
+      *out_value = (GskGLGlyphyValue *)entry;
+      self->front[front_index].key = *key;
+      self->front[front_index].value = *out_value;
+    }
+  else
+    {
+      GskGLGlyphyKey *k = g_slice_copy (sizeof *key, key);
+      gsk_gl_glyphy_library_add (self, k, font, out_value);
+      self->front[front_index].key = *key;
+      self->front[front_index].value = *out_value;
+    }
+
+  return GSK_GL_TEXTURE_ATLAS_ENTRY_TEXTURE (*out_value);
+}
+
+G_END_DECLS
+
+#endif /* __GSK_GL_GLYPHY_LIBRARY_PRIVATE_H__ */

gsk/gl/gskglprograms.defs

@@ -87,3 +87,21 @@ GSK_GL_DEFINE_PROGRAM (unblurred_outset_shadow,
                        GSK_GL_ADD_UNIFORM (1, UNBLURRED_OUTSET_SHADOW_SPREAD, u_spread)
                        GSK_GL_ADD_UNIFORM (2, UNBLURRED_OUTSET_SHADOW_OFFSET, u_offset)
                        GSK_GL_ADD_UNIFORM (3, UNBLURRED_OUTSET_SHADOW_OUTLINE_RECT, u_outline_rect))
+
+GSK_GL_DEFINE_PROGRAM (glyphy,
+                       GSK_GL_SHADER_JOINED (VERTEX,
+                                             GSK_GL_SHADER_RESOURCE ("glyphy.vs.glsl"),
+                                             NULL)
+                       GSK_GL_SHADER_JOINED (FRAGMENT,
+                                             GSK_GL_SHADER_RESOURCE ("glyphy.atlas.glsl"),
+                                             GSK_GL_SHADER_STRING (glyphy_common_shader_source ()),
+                                             GSK_GL_SHADER_STRING ("#define GLYPHY_SDF_PSEUDO_DISTANCE 1\n"),
+                                             GSK_GL_SHADER_STRING (glyphy_sdf_shader_source ()),
+                                             GSK_GL_SHADER_RESOURCE ("glyphy.fs.glsl"),
+                                             NULL),
+                       GSK_GL_ADD_UNIFORM (0, GLYPHY_CONTRAST, u_contrast)
+                       GSK_GL_ADD_UNIFORM (1, GLYPHY_GAMMA_ADJUST, u_gamma_adjust)
+                       GSK_GL_ADD_UNIFORM (2, GLYPHY_OUTLINE_THICKNESS, u_outline_thickness)
+                       GSK_GL_ADD_UNIFORM (3, GLYPHY_OUTLINE, u_outline)
+                       GSK_GL_ADD_UNIFORM (4, GLYPHY_BOLDNESS, u_boldness)
+                       GSK_GL_ADD_UNIFORM (6, GLYPHY_ATLAS_INFO, u_atlas_info))

gsk/gl/gskglrenderer.c

@@ -150,6 +150,13 @@ gsk_gl_renderer_realize (GskRenderer  *renderer,
   gsk_gl_command_queue_set_profiler (self->command_queue,
                                      gsk_renderer_get_profiler (renderer));
 
+#ifdef G_ENABLE_DEBUG
+  if (gsk_renderer_get_debug_flags (renderer) & GSK_DEBUG_NO_GLYPHY)
+    GSK_RENDERER_DEBUG (renderer, RENDERER, "GL Renderer will use cairo for glyph rendering");
+  else
+    GSK_RENDERER_DEBUG (renderer, RENDERER, "GL Renderer will use glyphy for glyph rendering");
+#endif
+
   ret = TRUE;
 
 failure:
@@ -307,10 +314,15 @@ gsk_gl_renderer_render (GskRenderer          *renderer,
 
   gsk_gl_driver_begin_frame (self->driver, self->command_queue);
   job = gsk_gl_render_job_new (self->driver, &viewport, scale, render_region, 0, clear_framebuffer);
+
+  if ((gsk_renderer_get_debug_flags (renderer) & GSK_DEBUG_NO_GLYPHY) == 0)
+    gsk_gl_render_job_set_use_glyphy (job, TRUE);
+
 #ifdef G_ENABLE_DEBUG
   if (GSK_RENDERER_DEBUG_CHECK (GSK_RENDERER (self), FALLBACK))
     gsk_gl_render_job_set_debug_fallback (job, TRUE);
 #endif
+
   gsk_gl_render_job_render (job, root);
   gsk_gl_driver_end_frame (self->driver);
   gsk_gl_render_job_free (job);

gsk/gl/gskglrenderjob.c

@@ -34,10 +34,14 @@
 #include <gsk/gskroundedrectprivate.h>
 #include <math.h>
 #include <string.h>
+#ifdef HAVE_PANGOFT
+#include <pango/pangofc-font.h>
+#endif
 
 #include "gskglcommandqueueprivate.h"
 #include "gskgldriverprivate.h"
 #include "gskglglyphlibraryprivate.h"
+#include "gskglglyphylibraryprivate.h"
 #include "gskgliconlibraryprivate.h"
 #include "gskglprogramprivate.h"
 #include "gskglrenderjobprivate.h"
@@ -149,6 +153,9 @@ struct _GskGLRenderJob
    */
   guint clear_framebuffer : 1;
 
+  /* Allow experimental glyph rendering with glyphy */
+  guint use_glyphy : 1;
+
   /* Format we want to use for intermediate textures, determined by
    * looking at the format of the framebuffer we are rendering on.
    */
@@ -2959,10 +2966,10 @@ compute_phase_and_pos (float value, float *pos)
 }
 
 static inline void
-gsk_gl_render_job_visit_text_node (GskGLRenderJob      *job,
-                                   const GskRenderNode *node,
-                                   const GdkRGBA       *color,
-                                   gboolean             force_color)
+gsk_gl_render_job_visit_text_node_legacy (GskGLRenderJob      *job,
+                                          const GskRenderNode *node,
+                                          const GdkRGBA       *color,
+                                          gboolean             force_color)
 {
   const PangoFont *font = gsk_text_node_get_font (node);
   const PangoGlyphInfo *glyphs = gsk_text_node_get_glyphs (node, NULL);
@@ -3098,6 +3105,263 @@ gsk_gl_render_job_visit_text_node (GskGLRenderJob      *job,
     }
 }
 
+/* Keep this in sync with glyph_vertex_transcode in glyphy.vs.glsl */
+typedef struct
+{
+  float x;
+  float y;
+  float g16hi;
+  float g16lo;
+} EncodedGlyph;
+
+static inline unsigned int
+glyph_encode (guint atlas_x ,  /* 7 bits */
+              guint atlas_y,   /* 7 bits */
+              guint corner_x,  /* 1 bit */
+              guint corner_y,  /* 1 bit */
+              guint nominal_w, /* 6 bits */
+              guint nominal_h) /* 6 bits */
+{
+  guint x, y;
+
+  g_assert (0 == (atlas_x & ~0x7F));
+  g_assert (0 == (atlas_y & ~0x7F));
+  g_assert (0 == (corner_x & ~1));
+  g_assert (0 == (corner_y & ~1));
+  g_assert (0 == (nominal_w & ~0x3F));
+  g_assert (0 == (nominal_h & ~0x3F));
+
+  x = (((atlas_x << 6) | nominal_w) << 1) | corner_x;
+  y = (((atlas_y << 6) | nominal_h) << 1) | corner_y;
+
+  return (x << 16) | y;
+}
+
+static inline void
+encoded_glyph_init (EncodedGlyph           *eg,
+                    float                   x,
+                    float                   y,
+                    guint                   corner_x,
+                    guint                   corner_y,
+                    const GskGLGlyphyValue *gi)
+{
+  guint encoded = glyph_encode (gi->atlas_x, gi->atlas_y, corner_x, corner_y, gi->nominal_w, gi->nominal_h);
+
+  eg->x = x;
+  eg->y = y;
+  eg->g16hi = encoded >> 16;
+  eg->g16lo = encoded & 0xFFFF;
+}
+
+static inline void
+add_encoded_glyph (GskGLDrawVertex    *vertices,
+                   const EncodedGlyph *eg,
+                   const guint16       c[4])
+{
+  *vertices = (GskGLDrawVertex) { .position = { eg->x, eg->y}, .uv = { eg->g16hi, eg->g16lo}, .color = { c[0], c[1], c[2], c[3] } };
+}
+
+static void
+get_synthetic_font_params (PangoFont   *font,
+                           gboolean    *embolden,
+                           PangoMatrix *matrix)
+{
+  *embolden = FALSE;
+  *matrix = (PangoMatrix) PANGO_MATRIX_INIT;
+
+#ifdef HAVE_PANGOFT
+  if (PANGO_IS_FC_FONT (font))
+    {
+      FcPattern *pattern = pango_fc_font_get_pattern (PANGO_FC_FONT (font));
+      FcBool b;
+      FcMatrix mat;
+      FcMatrix *m;
+
+      if (FcPatternGetBool (pattern, FC_EMBOLDEN, 0, &b) == FcResultMatch)
+        *embolden = b;
+
+      FcMatrixInit (&mat);
+      for (int i = 0; FcPatternGetMatrix (pattern, FC_MATRIX, i, &m) == FcResultMatch; i++)
+        FcMatrixMultiply (&mat, &mat, m);
+
+      matrix->xx = mat.xx;
+      matrix->xy = mat.xy;
+      matrix->yx = mat.yx;
+      matrix->yy = mat.yy;
+    }
+#endif
+}
+
+static inline void
+gsk_gl_render_job_visit_text_node_glyphy (GskGLRenderJob      *job,
+                                          const GskRenderNode *node,
+                                          const GdkRGBA       *color)
+{
+  const graphene_point_t *offset;
+  const PangoGlyphInfo *glyphs;
+  const PangoGlyphInfo *gi;
+  GskGLGlyphyLibrary *library;
+  GskGLCommandBatch *batch;
+  PangoFont *font;
+  GskGLDrawVertex *vertices;
+  const guint16 *c;
+  GskGLGlyphyKey lookup;
+  guint16 cc[4];
+  float x;
+  float y;
+  guint last_texture = 0;
+  guint num_glyphs;
+  guint used = 0;
+  guint i;
+  int x_position = 0;
+  float font_scale;
+  gboolean embolden;
+  PangoMatrix matrix = PANGO_MATRIX_INIT;
+
+#define GRID_SIZE 20
+
+  g_assert (!gsk_text_node_has_color_glyphs (node));
+
+  if (!(num_glyphs = gsk_text_node_get_num_glyphs (node)))
+    return;
+
+  if (RGBA_IS_CLEAR (color))
+    return;
+
+  font = (PangoFont *)gsk_text_node_get_font (node);
+  get_synthetic_font_params (font, &embolden, &matrix);
+
+  glyphs = gsk_text_node_get_glyphs (node, NULL);
+  library = job->driver->glyphy_library;
+  offset = gsk_text_node_get_offset (node);
+  x = offset->x + job->offset_x;
+  y = offset->y + job->offset_y;
+
+  rgba_to_half (color, cc);
+  c = cc;
+
+  gsk_gl_render_job_begin_draw (job, CHOOSE_PROGRAM (job, glyphy));
+
+  batch = gsk_gl_command_queue_get_batch (job->command_queue);
+  vertices = gsk_gl_command_queue_add_n_vertices (job->command_queue, num_glyphs);
+
+  lookup.font = gsk_gl_glyphy_library_get_font_key (font);
+  font_scale = gsk_gl_glyphy_library_get_font_scale (font);
+
+  for (i = 0, gi = glyphs; i < num_glyphs; i++, gi++)
+    {
+      const GskGLGlyphyValue *glyph;
+      float cx = 0, cy = 0;
+      guint texture_id;
+
+      lookup.glyph = gi->glyph;
+      texture_id = gsk_gl_glyphy_library_lookup_or_add (library, &lookup, font, &glyph);
+
+      if G_UNLIKELY (texture_id == 0)
+        continue;
+
+      if G_UNLIKELY (last_texture != texture_id || batch->draw.vbo_count + GSK_GL_N_VERTICES > 0xffff)
+        {
+          if G_LIKELY (last_texture != 0)
+            {
+              guint vbo_offset = batch->draw.vbo_offset + batch->draw.vbo_count;
+
+              /* Since we have batched added our VBO vertices to avoid repeated
+               * calls to the buffer, we need to manually tweak the vbo offset
+               * of the new batch as otherwise it will point at the end of our
+               * vbo array.
+               */
+              gsk_gl_render_job_split_draw (job);
+              batch = gsk_gl_command_queue_get_batch (job->command_queue);
+              batch->draw.vbo_offset = vbo_offset;
+            }
+
+          gsk_gl_program_set_uniform4i (job->current_program,
+                                        UNIFORM_GLYPHY_ATLAS_INFO, 0,
+                                        GSK_GL_TEXTURE_LIBRARY (library)->atlas_width,
+                                        GSK_GL_TEXTURE_LIBRARY (library)->atlas_height,
+                                        library->item_w,
+                                        library->item_h_q);
+          gsk_gl_program_set_uniform_texture (job->current_program,
+                                              UNIFORM_SHARED_SOURCE, 0,
+                                              GL_TEXTURE_2D,
+                                              GL_TEXTURE0,
+                                              texture_id);
+          gsk_gl_program_set_uniform1f (job->current_program,
+                                        UNIFORM_GLYPHY_GAMMA_ADJUST, 0,
+                                        1.0);
+          gsk_gl_program_set_uniform1f (job->current_program,
+                                        UNIFORM_GLYPHY_CONTRAST, 0,
+                                        1.0);
+
+          /* 0.0208 is the value used by freetype for synthetic emboldening */
+          gsk_gl_program_set_uniform1f (job->current_program,
+                                        UNIFORM_GLYPHY_BOLDNESS, 0,
+                                        embolden ? 0.0208 * GRID_SIZE : 0.0);
+
+#if 0
+          gsk_gl_program_set_uniform1f (job->current_program,
+                                        UNIFORM_GLYPHY_OUTLINE_THICKNESS, 0,
+                                        1.0);
+          gsk_gl_program_set_uniform1f (job->current_program,
+                                        UNIFORM_GLYPHY_OUTLINE, 0,
+                                        1.0);
+#endif
+
+          last_texture = texture_id;
+        }
+
+      cx = (float)(x_position + gi->geometry.x_offset) / PANGO_SCALE;
+      if G_UNLIKELY (gi->geometry.y_offset != 0)
+        cy = (float)(gi->geometry.y_offset) / PANGO_SCALE;
+
+      x_position += gi->geometry.width;
+
+      EncodedGlyph encoded[4];
+#define ENCODE_CORNER(_cx, _cy) \
+  G_STMT_START { \
+    float _dx = _cx * (glyph->extents.max_x - glyph->extents.min_x); \
+    float _dy = _cy * (glyph->extents.max_y - glyph->extents.min_y); \
+    float _vx = x + cx + font_scale * (glyph->extents.min_x + matrix.xx * _dx + matrix.xy * _dy); \
+    float _vy = y + cy - font_scale * (glyph->extents.min_y + matrix.yx * _dx + matrix.yy * _dy); \
+    encoded_glyph_init (&encoded[_cx * 2 + _cy], _vx, _vy, _cx, _cy, glyph); \
+  } G_STMT_END
+      ENCODE_CORNER (0, 0);
+      ENCODE_CORNER (0, 1);
+      ENCODE_CORNER (1, 0);
+      ENCODE_CORNER (1, 1);
+#undef ENCODE_CORNER
+
+      add_encoded_glyph (vertices++, &encoded[0], c);
+      add_encoded_glyph (vertices++, &encoded[1], c);
+      add_encoded_glyph (vertices++, &encoded[2], c);
+
+      add_encoded_glyph (vertices++, &encoded[1], c);
+      add_encoded_glyph (vertices++, &encoded[2], c);
+      add_encoded_glyph (vertices++, &encoded[3], c);
+
+      batch->draw.vbo_count += GSK_GL_N_VERTICES;
+      used++;
+    }
+
+  if (used != num_glyphs)
+    gsk_gl_command_queue_retract_n_vertices (job->command_queue, num_glyphs - used);
+
+  gsk_gl_render_job_end_draw (job);
+}
+
+static inline void
+gsk_gl_render_job_visit_text_node (GskGLRenderJob      *job,
+                                   const GskRenderNode *node,
+                                   const GdkRGBA       *color,
+                                   gboolean             force_color)
+{
+  if (job->use_glyphy && !gsk_text_node_has_color_glyphs (node))
+    gsk_gl_render_job_visit_text_node_glyphy (job, node, color);
+  else
+    gsk_gl_render_job_visit_text_node_legacy (job, node, color, force_color);
+}
+
 static inline void
 gsk_gl_render_job_visit_shadow_node (GskGLRenderJob      *job,
                                      const GskRenderNode *node)
@@ -4463,6 +4727,15 @@ gsk_gl_render_job_set_debug_fallback (GskGLRenderJob *job,
   job->debug_fallback = !!debug_fallback;
 }
 
+void
+gsk_gl_render_job_set_use_glyphy (GskGLRenderJob *job,
+                                  gboolean        use_glyphy)
+{
+  g_return_if_fail (job != NULL);
+
+  job->use_glyphy = !!use_glyphy;
+}
+
 static int
 get_framebuffer_format (GdkGLContext *context,
                         guint         framebuffer)

gsk/gl/gskglrenderjobprivate.h

@@ -35,4 +35,5 @@ void            gsk_gl_render_job_render_flipped     (GskGLRenderJob        *job
                                                       GskRenderNode         *root);
 void            gsk_gl_render_job_set_debug_fallback (GskGLRenderJob        *job,
                                                       gboolean               debug_fallback);
-
+void            gsk_gl_render_job_set_use_glyphy     (GskGLRenderJob        *job,
+                                                      gboolean               use_glyphy);

gsk/gl/gskgltexturelibraryprivate.h

@@ -36,9 +36,14 @@ G_BEGIN_DECLS
 
 typedef struct _GskGLTextureAtlas
 {
+  /* Used by Glyph/Icons */
   struct stbrp_context context;
   struct stbrp_node *nodes;
 
+  /* Used by Glyphy */
+  int cursor_x;
+  int cursor_y;
+
   int width;
   int height;
 
@@ -48,7 +53,6 @@ typedef struct _GskGLTextureAtlas
    * But are now unused.
    */
   int unused_pixels;
-
 } GskGLTextureAtlas;
 
 typedef struct _GskGLTextureAtlasEntry

gsk/gl/gskgltypesprivate.h

@@ -36,6 +36,7 @@ typedef struct _GskGLCompiler GskGLCompiler;
 typedef struct _GskGLDrawVertex GskGLDrawVertex;
 typedef struct _GskGLRenderTarget GskGLRenderTarget;
 typedef struct _GskGLGlyphLibrary GskGLGlyphLibrary;
+typedef struct _GskGLGlyphyLibrary GskGLGlyphyLibrary;
 typedef struct _GskGLIconLibrary GskGLIconLibrary;
 typedef struct _GskGLProgram GskGLProgram;
 typedef struct _GskGLRenderJob GskGLRenderJob;

gsk/gl/resources/glyphy.atlas.glsl

@@ -0,0 +1,15 @@
+uniform ivec4 u_atlas_info;
+
+#define GLYPHY_TEXTURE1D_EXTRA_DECLS , sampler2D _tex, ivec4 _atlas_info, ivec2 _atlas_pos
+#define GLYPHY_TEXTURE1D_EXTRA_ARGS , _tex, _atlas_info, _atlas_pos
+#define GLYPHY_DEMO_EXTRA_ARGS , u_source, u_atlas_info, gi.atlas_pos
+
+vec4
+glyphy_texture1D_func (int offset GLYPHY_TEXTURE1D_EXTRA_DECLS)
+{
+  ivec2 item_geom = _atlas_info.zw;
+  vec2 pos = (vec2 (_atlas_pos.xy * item_geom +
+		   ivec2 (mod (float (offset), float (item_geom.x)), offset / item_geom.x)) +
+	      + vec2 (.5, .5)) / vec2(_atlas_info.xy);
+  return GskTexture (_tex, pos);
+}

gsk/gl/resources/glyphy.fs.glsl

@@ -0,0 +1,62 @@
+// FRAGMENT_SHADER:
+// glyphy.fs.glsl
+
+uniform float u_contrast;
+uniform float u_gamma_adjust;
+uniform float u_outline_thickness;
+uniform bool  u_outline;
+uniform float u_boldness;
+
+_IN_ vec4 v_glyph;
+_IN_ vec4 final_color;
+
+#define SQRT2     1.4142135623730951
+#define SQRT2_INV 0.70710678118654757 /* 1 / sqrt(2.) */
+
+struct glyph_info_t {
+  ivec2 nominal_size;
+  ivec2 atlas_pos;
+};
+
+glyph_info_t
+glyph_info_decode (vec4 v)
+{
+  glyph_info_t gi;
+  gi.nominal_size = (ivec2 (mod (v.zw, 256.)) + 2) / 4;
+  gi.atlas_pos = ivec2 (v_glyph.zw) / 256;
+  return gi;
+}
+
+float
+antialias (float d)
+{
+  return smoothstep (-.75, +.75, d);
+}
+
+void
+main()
+{
+  vec2 p = v_glyph.xy;
+  glyph_info_t gi = glyph_info_decode (v_glyph);
+
+  /* isotropic antialiasing */
+  vec2 dpdx = dFdx (p);
+  vec2 dpdy = dFdy (p);
+  float m = length (vec2 (length (dpdx), length (dpdy))) * SQRT2_INV;
+
+  float gsdist = glyphy_sdf (p, gi.nominal_size GLYPHY_DEMO_EXTRA_ARGS);
+  gsdist -= u_boldness;
+  float sdist = gsdist / m * u_contrast;
+
+  if (u_outline)
+    sdist = abs (sdist) - u_outline_thickness * .5;
+
+  if (sdist > 1.)
+    discard;
+
+  float alpha = antialias (-sdist);
+  if (u_gamma_adjust != 1.)
+    alpha = pow (alpha, 1./u_gamma_adjust);
+
+  gskSetOutputColor(final_color * alpha);
+}

gsk/gl/resources/glyphy.vs.glsl

@@ -0,0 +1,25 @@
+// VERTEX_SHADER:
+// glyphy.vs.glsl
+
+_OUT_ vec4 v_glyph;
+_OUT_ vec4 final_color;
+
+// Keep this in sync with glyph_encode in gskglrenderjob.c
+vec4
+glyph_vertex_transcode (vec2 v)
+{
+  ivec2 g = ivec2 (v);
+  ivec2 corner = ivec2 (mod (v, 2.));
+  g /= 2;
+  ivec2 nominal_size = ivec2 (mod (vec2(g), 64.));
+  return vec4 (corner * nominal_size, g * 4);
+}
+
+void
+main()
+{
+  v_glyph = glyph_vertex_transcode(aUv);
+  vUv = v_glyph.zw;
+  gl_Position = u_projection * u_modelview * vec4(aPosition, 0.0, 1.0);
+  final_color = gsk_scaled_premultiply(aColor, u_alpha);
+}

gsk/gl/resources/preamble.glsl

@@ -1,3 +1,5 @@
+#extension GL_OES_standard_derivatives : enable
+
 #ifndef GSK_LEGACY
 precision highp float;
 #endif

gsk/gskboundingboxprivate.h

@@ -0,0 +1,100 @@
+#pragma once
+
+#include <gsk/gsktypes.h>
+
+G_BEGIN_DECLS
+
+typedef struct _GskBoundingBox GskBoundingBox;
+
+struct _GskBoundingBox {
+  graphene_point_t min;
+  graphene_point_t max;
+};
+
+static inline GskBoundingBox *
+gsk_bounding_box_init (GskBoundingBox         *self,
+                       const graphene_point_t *a,
+                       const graphene_point_t *b)
+{
+  self->min.x = MIN (a->x, b->x);
+  self->min.y = MIN (a->y, b->y);
+  self->max.x = MAX (a->x, b->x);
+  self->max.y = MAX (a->y, b->y);
+  return self;
+}
+
+static inline GskBoundingBox *
+gsk_bounding_box_init_copy (GskBoundingBox       *self,
+                            const GskBoundingBox *src)
+{
+  self->min = src->min;
+  self->max = src->max;
+  return self;
+}
+
+static inline GskBoundingBox *
+gsk_bounding_box_init_from_rect (GskBoundingBox        *self,
+                                 const graphene_rect_t *bounds)
+{
+  self->min = bounds->origin;
+  self->max.x = bounds->origin.x + bounds->size.width;
+  self->max.y = bounds->origin.y + bounds->size.height;
+  return self;
+}
+
+static inline void
+gsk_bounding_box_expand (GskBoundingBox         *self,
+                         const graphene_point_t *p)
+{
+  self->min.x = MIN (self->min.x, p->x);
+  self->min.y = MIN (self->min.y, p->y);
+  self->max.x = MAX (self->max.x, p->x);
+  self->max.y = MAX (self->max.y, p->y);
+}
+
+static inline graphene_rect_t *
+gsk_bounding_box_to_rect (const GskBoundingBox  *self,
+                          graphene_rect_t       *rect)
+{
+  rect->origin = self->min;
+  rect->size.width = self->max.x - self->min.x;
+  rect->size.height = self->max.y - self->min.y;
+  return rect;
+}
+
+static inline gboolean
+gsk_bounding_box_contains_point (const GskBoundingBox   *self,
+                                 const graphene_point_t *p)
+{
+  return self->min.x <= p->x && p->x <= self->max.x &&
+         self->min.y <= p->y && p->y <= self->max.y;
+}
+
+static inline gboolean
+gsk_bounding_box_contains_point_with_epsilon (const GskBoundingBox   *self,
+                                              const graphene_point_t *p,
+                                              float                   epsilon)
+{
+  return self->min.x - epsilon <= p->x && p->x <= self->max.x + epsilon &&
+         self->min.y - epsilon <= p->y && p->y <= self->max.y + epsilon;
+}
+
+static inline gboolean
+gsk_bounding_box_intersection (const GskBoundingBox *a,
+                               const GskBoundingBox *b,
+                               GskBoundingBox       *res)
+{
+  graphene_point_t min, max;
+
+  min.x = MAX (a->min.x, b->min.x);
+  min.y = MAX (a->min.y, b->min.y);
+  max.x = MIN (a->max.x, b->max.x);
+  max.y = MIN (a->max.y, b->max.y);
+
+  if (res)
+    gsk_bounding_box_init (res, &min, &max);
+
+  return min.x <= max.x && min.y <= max.y;
+}
+
+G_END_DECLS

gsk/gskcontourprivate.h

@@ -0,0 +1,103 @@
+/*
+ * Copyright © 2020 Benjamin Otte
+ *
+ * This library is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU Lesser General Public
+ * License as published by the Free Software Foundation; either
+ * version 2.1 of the License, or (at your option) any later version.
+ *
+ * This library is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+ * Lesser General Public License for more details.
+ *
+ * You should have received a copy of the GNU Lesser General Public
+ * License along with this library. If not, see <http://www.gnu.org/licenses/>.
+ *
+ * Authors: Benjamin Otte <otte@gnome.org>
+ */
+
+
+#pragma once
+
+#include "gskpath.h"
+
+#include "gskpathopprivate.h"
+
+G_BEGIN_DECLS
+
+typedef enum
+{
+  GSK_PATH_FLAT,
+  GSK_PATH_CLOSED
+} GskPathFlags;
+
+typedef struct _GskContour GskContour;
+
+GskContour *            gsk_rect_contour_new                    (const graphene_rect_t  *rect);
+GskContour *            gsk_rounded_rect_contour_new            (const GskRoundedRect   *rounded_rect);
+GskContour *            gsk_circle_contour_new                  (const graphene_point_t *center,
+                                                                 float                   radius,
+                                                                 float                   start_angle,
+                                                                 float                   end_angle);
+GskContour *            gsk_standard_contour_new                (GskPathFlags            flags,
+                                                                 const graphene_point_t *points,
+                                                                 gsize                   n_points,
+                                                                 const gskpathop        *ops,
+                                                                 gsize                   n_ops,
+                                                                 gssize                  offset);
+
+void                    gsk_contour_copy                        (GskContour *            dest,
+                                                                 const GskContour       *src);
+GskContour *            gsk_contour_dup                         (const GskContour       *src);
+GskContour *            gsk_contour_reverse                     (const GskContour       *src);
+
+gsize                   gsk_contour_get_size                    (const GskContour       *self);
+GskPathFlags            gsk_contour_get_flags                   (const GskContour       *self);
+void                    gsk_contour_print                       (const GskContour       *self,
+                                                                 GString                *string);
+gboolean                gsk_contour_get_bounds                  (const GskContour       *self,
+                                                                 graphene_rect_t        *bounds);
+gpointer                gsk_contour_init_measure                (const GskContour       *self,
+                                                                 float                   tolerance,
+                                                                 float                  *out_length);
+void                    gsk_contour_free_measure                (const GskContour       *self,
+                                                                 gpointer                data);
+gboolean                gsk_contour_foreach                     (const GskContour       *self,
+                                                                 float                   tolerance,
+                                                                 GskPathForeachFunc      func,
+                                                                 gpointer                user_data);
+void                    gsk_contour_get_start_end               (const GskContour       *self,
+                                                                 graphene_point_t       *start,
+                                                                 graphene_point_t       *end);
+void                    gsk_contour_get_point                   (const GskContour       *self,
+                                                                 gpointer                measure_data,
+                                                                 float                   distance,
+                                                                 GskPathDirection        direction,
+                                                                 graphene_point_t       *pos,
+                                                                 graphene_vec2_t        *tangent);
+gboolean                gsk_contour_get_closest_point           (const GskContour       *self,
+                                                                 gpointer                measure_data,
+                                                                 float                   tolerance,
+                                                                 const graphene_point_t *point,
+                                                                 float                   threshold,
+                                                                 float                  *out_distance,
+                                                                 graphene_point_t       *out_pos,
+                                                                 float                  *out_offset,
+                                                                 graphene_vec2_t        *out_tangent);
+int                     gsk_contour_get_winding                 (const GskContour       *self,
+                                                                 gpointer                measure_data,
+                                                                 const graphene_point_t *point);
+void                    gsk_contour_add_segment                 (const GskContour       *self,
+                                                                 GskPathBuilder         *builder,
+                                                                 gpointer                measure_data,
+                                                                 gboolean                emit_move_to,
+                                                                 float                   start,
+                                                                 float                   end);
+float                   gsk_contour_get_curvature               (const GskContour       *self,
+                                                                 gpointer                measure_data,
+                                                                 float                   distance,
+                                                                 graphene_point_t       *center);
+
+
+G_END_DECLS

gsk/gskcurveintersect.c

@@ -0,0 +1,879 @@
+/*
+ * Copyright © 2020 Red Hat, Inc
+ *
+ * This library is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU Lesser General Public
+ * License as published by the Free Software Foundation; either
+ * version 2.1 of the License, or (at your option) any later version.
+ *
+ * This library is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+ * Lesser General Public License for more details.
+ *
+ * You should have received a copy of the GNU Lesser General Public
+ * License along with this library. If not, see <http://www.gnu.org/licenses/>.
+ *
+ * Authors: Matthias Clasen <mclasen@redhat.com>
+ */
+
+#include "config.h"
+
+#include <math.h>
+
+#include "gskcurveprivate.h"
+
+/* {{{ Utilities */
+
+static void
+get_tangent (const graphene_point_t *p0,
+             const graphene_point_t *p1,
+             graphene_vec2_t        *t)
+{
+  graphene_vec2_init (t, p1->x - p0->x, p1->y - p0->y);
+  graphene_vec2_normalize (t, t);
+}
+
+static inline gboolean
+acceptable (float t)
+{
+  return 0 - FLT_EPSILON <= t && t <= 1 + FLT_EPSILON;
+}
+
+static inline void
+_sincosf (float  angle,
+          float *out_s,
+          float *out_c)
+{
+#ifdef HAVE_SINCOSF
+      sincosf (angle, out_s, out_c);
+#else
+      *out_s = sinf (angle);
+      *out_c = cosf (angle);
+#endif
+}
+
+static void
+align_points (const graphene_point_t *p,
+              const graphene_point_t *a,
+              const graphene_point_t *b,
+              graphene_point_t       *q,
+              int                     n)
+{
+  graphene_vec2_t n1;
+  float angle;
+  float s, c;
+
+  get_tangent (a, b, &n1);
+  angle = - atan2 (graphene_vec2_get_y (&n1), graphene_vec2_get_x (&n1));
+  _sincosf (angle, &s, &c);
+
+  for (int i = 0; i < n; i++)
+    {
+      q[i].x = (p[i].x - a->x) * c - (p[i].y - a->y) * s;
+      q[i].y = (p[i].x - a->x) * s + (p[i].y - a->y) * c;
+    }
+}
+
+static void
+find_point_on_line (const graphene_point_t *p1,
+                    const graphene_point_t *p2,
+                    const graphene_point_t *q,
+                    float                  *t)
+{
+  if (p2->x != p1->x)
+    *t = (q->x - p1->x) / (p2->x - p1->x);
+  else
+    *t = (q->y - p1->y) / (p2->y - p1->y);
+}
+
+/* find solutions for at^2 + bt + c = 0 */
+static int
+solve_quadratic (float a, float b, float c, float t[2])
+{
+  float d;
+  int n = 0;
+
+  if (fabs (a) > 0.0001)
+    {
+      if (b*b > 4*a*c)
+        {
+          d = sqrt (b*b - 4*a*c);
+          t[n++] = (-b + d)/(2*a);
+          t[n++] = (-b - d)/(2*a);
+        }
+      else
+        {
+          t[n++] = -b / (2*a);
+        }
+    }
+  else if (fabs (b) > 0.0001)
+    {
+      t[n++] = -c / b;
+    }
+
+  return n;
+}
+
+static int
+filter_allowable (float t[3],
+                  int   n)
+{
+  float g[3];
+  int j = 0;
+
+  for (int i = 0; i < n; i++)
+    if (0 < t[i] && t[i] < 1)
+      g[j++] = t[i];
+  for (int i = 0; i < j; i++)
+    t[i] = g[i];
+  return j;
+}
+
+/* Solve P = 0 where P is
+ * P = (1-t)^2*pa + 2*t*(1-t)*pb + t^2*pc
+ */
+static int
+get_quadratic_roots (float pa, float pb, float pc, float roots[2])
+{
+  float a, b, c, d;
+  int n_roots = 0;
+
+  a = pa - 2 * pb + pc;
+  b = 2 * (pb - pa);
+  c = pa;
+
+  d = b*b - 4*a*c;
+
+  if (d > 0.0001)
+    {
+      float q = sqrt (d);
+      roots[n_roots] = (-b + q) / (2 * a);
+      if (acceptable (roots[n_roots]))
+        n_roots++;
+      roots[n_roots] = (-b - q) / (2 * a);
+      if (acceptable (roots[n_roots]))
+        n_roots++;
+    }
+  else if (fabs (d) < 0.0001)
+    {
+      roots[n_roots] = -b / (2 * a);
+      if (acceptable (roots[n_roots]))
+        n_roots++;
+    }
+
+  return n_roots;
+}
+
+static float
+cuberoot (float v)
+{
+  if (v < 0)
+    return -pow (-v, 1.f / 3);
+  return pow (v, 1.f / 3);
+}
+
+/* Solve P = 0 where P is
+ * P = (1-t)^3*pa + 3*t*(1-t)^2*pb + 3*t^2*(1-t)*pc + t^3*pd
+ */
+static int
+get_cubic_roots (float pa, float pb, float pc, float pd, float roots[3])
+{
+  float a, b, c, d;
+  float q, q2;
+  float p, p3;
+  float discriminant;
+  float u1, v1, sd;
+  int n_roots = 0;
+
+  d = -pa + 3*pb - 3*pc + pd;
+  a = 3*pa - 6*pb + 3*pc;
+  b = -3*pa + 3*pb;
+  c = pa;
+
+  if (fabs (d) < 0.0001)
+    {
+      if (fabs (a) < 0.0001)
+        {
+          if (fabs (b) < 0.0001)
+            return 0;
+
+          if (acceptable (-c / b))
+            {
+              roots[0] = -c / b;
+
+              return 1;
+            }
+
+          return 0;
+        }
+      q = sqrt (b*b - 4*a*c);
+      roots[n_roots] = (-b + q) / (2 * a);
+      if (acceptable (roots[n_roots]))
+        n_roots++;
+
+      roots[n_roots] = (-b - q) / (2 * a);
+      if (acceptable (roots[n_roots]))
+        n_roots++;
+
+      return n_roots;
+    }
+
+  a /= d;
+  b /= d;
+  c /= d;
+
+  p = (3*b - a*a)/3;
+  p3 = p/3;
+  q = (2*a*a*a - 9*a*b + 27*c)/27;
+  q2 = q/2;
+  discriminant = q2*q2 + p3*p3*p3;
+
+  if (discriminant < 0)
+    {
+      float mp3 = -p/3;
+      float mp33 = mp3*mp3*mp3;
+      float r = sqrt (mp33);
+      float t = -q / (2*r);
+      float cosphi = t < -1 ? -1 : (t > 1 ? 1 : t);
+      float phi = acos (cosphi);
+      float crtr = cuberoot (r);
+      float t1 = 2*crtr;
+
+      roots[n_roots] = t1 * cos (phi/3) - a/3;
+      if (acceptable (roots[n_roots]))
+        n_roots++;
+      roots[n_roots] = t1 * cos ((phi + 2*M_PI) / 3) - a/3;
+      if (acceptable (roots[n_roots]))
+        n_roots++;
+      roots[n_roots] = t1 * cos ((phi + 4*M_PI) / 3) - a/3;
+      if (acceptable (roots[n_roots]))
+        n_roots++;
+
+    return n_roots;
+  }
+
+  if (discriminant == 0)
+    {
+      u1 = q2 < 0 ? cuberoot (-q2) : -cuberoot (q2);
+      roots[n_roots] = 2*u1 - a/3;
+      if (acceptable (roots[n_roots]))
+        n_roots++;
+      roots[n_roots] = -u1 - a/3;
+      if (acceptable (roots[n_roots]))
+        n_roots++;
+
+      return n_roots;
+    }
+
+  sd = sqrt (discriminant);
+  u1 = cuberoot (sd - q2);
+  v1 = cuberoot (sd + q2);
+  roots[n_roots] = u1 - v1 - a/3;
+  if (acceptable (roots[n_roots]))
+    n_roots++;
+
+  return n_roots;
+}
+
+/* }}} */
+/* {{{ Cusps and inflections */
+
+/* Get the points where the curvature of curve is
+ * zero, or a maximum or minimum, inside the open
+ * interval from 0 to 1.
+ */
+int
+gsk_curve_get_curvature_points (const GskCurve *curve,
+                                float           t[3])
+{
+  const graphene_point_t *pts = curve->cubic.points;
+  graphene_point_t p[4];
+  float a, b, c, d;
+  float x, y, z;
+  int n;
+
+  if (curve->op != GSK_PATH_CUBIC)
+    return 0;
+
+  align_points (pts, &pts[0], &pts[3], p, 4);
+
+  a = p[2].x * p[1].y;
+  b = p[3].x * p[1].y;
+  c = p[1].x * p[2].y;
+  d = p[3].x * p[2].y;
+
+  x = - 3*a + 2*b + 3*c - d;
+  y = 3*a - b - 3*c;
+  z = c - a;
+
+  n = solve_quadratic (x, y, z, t);
+  return filter_allowable (t, n);
+}
+
+/* Find cusps inside the open interval from 0 to 1.
+ *
+ * According to Stone & deRose, A Geometric Characterization
+ * of Parametric Cubic curves, a necessary and sufficient
+ * condition is that the first derivative vanishes.
+ */
+int
+gsk_curve_get_cusps (const GskCurve *curve,
+                     float           t[2])
+{
+  const graphene_point_t *pts = curve->cubic.points;
+  graphene_point_t p[3];
+  float ax, bx, cx;
+  float ay, by, cy;
+  float tx[3];
+  int nx;
+  int n = 0;
+
+  if (curve->op != GSK_PATH_CUBIC)
+    return 0;
+
+  p[0].x = 3 * (pts[1].x - pts[0].x);
+  p[0].y = 3 * (pts[1].y - pts[0].y);
+  p[1].x = 3 * (pts[2].x - pts[1].x);
+  p[1].y = 3 * (pts[2].y - pts[1].y);
+  p[2].x = 3 * (pts[3].x - pts[2].x);
+  p[2].y = 3 * (pts[3].y - pts[2].y);
+
+  ax = p[0].x - 2 * p[1].x + p[2].x;
+  bx = - 2 * p[0].x + 2 * p[1].x;
+  cx = p[0].x;
+
+  nx = solve_quadratic (ax, bx, cx, tx);
+  nx = filter_allowable (tx, nx);
+
+  ay = p[0].y - 2 * p[1].y + p[2].y;
+  by = - 2 * p[0].y + 2 * p[1].y;
+  cy = p[0].y;
+
+  for (int i = 0; i < nx; i++)
+    {
+      float ti = tx[i];
+
+      if (0 < ti && ti < 1 &&
+          fabs (ay * ti * ti + by * ti + cy) < 0.001)
+        t[n++] = ti;
+    }
+
+  return n;
+}
+
+/* }}} */
+/* {{{ Intersection */
+
+static int
+line_intersect (const GskCurve   *curve1,
+                const GskCurve   *curve2,
+                float            *t1,
+                float            *t2,
+                graphene_point_t *p,
+                int               n)
+{
+  const graphene_point_t *pts1 = curve1->line.points;
+  const graphene_point_t *pts2 = curve2->line.points;
+  float a1 = pts1[0].x - pts1[1].x;
+  float b1 = pts1[0].y - pts1[1].y;
+  float a2 = pts2[0].x - pts2[1].x;
+  float b2 = pts2[0].y - pts2[1].y;
+  float det = a1 * b2 - b1 * a2;
+
+  if (fabs(det) > 0.01)
+    {
+      float tt =   ((pts1[0].x - pts2[0].x) * b2 - (pts1[0].y - pts2[0].y) * a2) / det;
+      float ss = - ((pts1[0].y - pts2[0].y) * a1 - (pts1[0].x - pts2[0].x) * b1) / det;
+
+      if (acceptable (tt) && acceptable (ss))
+        {
+          p[0].x = pts1[0].x + tt * (pts1[1].x - pts1[0].x);
+          p[0].y = pts1[0].y + tt * (pts1[1].y - pts1[0].y);
+
+          t1[0] = tt;
+          t2[0] = ss;
+
+          return 1;
+        }
+    }
+  else /* parallel lines */
+    {
+      float r = a1 * (pts1[1].y - pts2[0].y) - (pts1[1].x - pts2[0].x) * b1;
+      float dist = (r * r) / (a1 * a1 + b1 * b1);
+      float t, s, tt, ss;
+
+      if (dist > 0.01)
+        return 0;
+
+      if (pts1[1].x != pts1[0].x)
+        {
+          t = (pts2[0].x - pts1[0].x) / (pts1[1].x - pts1[0].x);
+          s = (pts2[1].x - pts1[0].x) / (pts1[1].x - pts1[0].x);
+        }
+      else
+        {
+          t = (pts2[0].y - pts1[0].y) / (pts1[1].y - pts1[0].y);
+          s = (pts2[1].y - pts1[0].y) / (pts1[1].y - pts1[0].y);
+        }
+
+      if ((t < 0 && s < 0) || (t > 1 && s > 1))
+        return 0;
+
+      if (acceptable (t))
+        {
+          t1[0] = t;
+          t2[0] = 0;
+          p[0] = pts2[0];
+        }
+      else if (t < 0)
+        {
+          if (pts2[1].x != pts2[0].x)
+            tt = (pts1[0].x - pts2[0].x) / (pts2[1].x - pts2[0].x);
+          else
+            tt = (pts1[0].y - pts2[0].y) / (pts2[1].y - pts2[0].y);
+
+          t1[0] = 0;
+          t2[0] = tt;
+          p[0] = pts1[0];
+        }
+      else
+        {
+          if (pts2[1].x != pts2[0].x)
+            tt = (pts1[1].x - pts2[0].x) / (pts2[1].x - pts2[0].x);
+          else
+            tt = (pts1[1].y - pts2[0].y) / (pts2[1].y - pts2[0].y);
+
+          t1[0] = 1;
+          t2[0] = tt;
+          p[0] = pts1[1];
+        }
+
+      if (acceptable (s))
+        {
+          if (t2[0] == 1)
+            return 1;
+
+          t1[1] = s;
+          t2[1] = 1;
+          p[1] = pts2[1];
+        }
+      else if (s < 0)
+        {
+          if (t1[0] == 0)
+            return 1;
+
+          if (pts2[1].x != pts2[0].x)
+            ss = (pts1[0].x - pts2[0].x) / (pts2[1].x - pts2[0].x);
+          else
+            ss = (pts1[0].y - pts2[0].y) / (pts2[1].y - pts2[0].y);
+
+          t1[1] = 0;
+          t2[1] = ss;
+          p[1] = pts1[0];
+        }
+      else
+        {
+          if (t1[0] == 1)
+            return 1;
+
+          if (pts2[1].x != pts2[0].x)
+            ss = (pts1[1].x - pts2[0].x) / (pts2[1].x - pts2[0].x);
+          else
+            ss = (pts1[1].y - pts2[0].y) / (pts2[1].y - pts2[0].y);
+
+          t1[1] = 1;
+          t2[1] = ss;
+          p[1] = pts1[1];
+        }
+
+      return 2;
+    }
+
+  return 0;
+}
+
+static int
+line_quad_intersect (const GskCurve   *curve1,
+                     const GskCurve   *curve2,
+                     float            *t1,
+                     float            *t2,
+                     graphene_point_t *p,
+                     int               n)
+{
+  const graphene_point_t *a = &curve1->line.points[0];
+  const graphene_point_t *b = &curve1->line.points[1];
+  graphene_point_t pts[4];
+  float t[2];
+  int m, i, j;
+
+  /* Rotate things to place curve1 on the x axis,
+   * then solve curve2 for y == 0.
+   */
+  align_points (curve2->quad.points, a, b, pts, 3);
+
+  m = get_quadratic_roots (pts[0].y, pts[1].y, pts[2].y, t);
+
+  j = 0;
+  for (i = 0; i < m; i++)
+    {
+      t2[j] = t[i];
+      gsk_curve_get_point (curve2, t2[j], &p[j]);
+      find_point_on_line (a, b, &p[j], &t1[j]);
+      if (acceptable (t1[j]))
+        j++;
+      if (j == n)
+        break;
+    }
+
+  return j;
+}
+
+static int
+line_cubic_intersect (const GskCurve   *curve1,
+                      const GskCurve   *curve2,
+                      float            *t1,
+                      float            *t2,
+                      graphene_point_t *p,
+                      int               n)
+{
+  const graphene_point_t *a = &curve1->line.points[0];
+  const graphene_point_t *b = &curve1->line.points[1];
+  graphene_point_t pts[4];
+  float t[3];
+  int m, i, j;
+
+  /* Rotate things to place curve1 on the x axis,
+   * then solve curve2 for y == 0.
+   */
+  align_points (curve2->cubic.points, a, b, pts, 4);
+
+  m = get_cubic_roots (pts[0].y, pts[1].y, pts[2].y, pts[3].y, t);
+
+  j = 0;
+  for (i = 0; i < m; i++)
+    {
+      t2[j] = t[i];
+      gsk_curve_get_point (curve2, t2[j], &p[j]);
+      find_point_on_line (a, b, &p[j], &t1[j]);
+      if (acceptable (t1[j]))
+        j++;
+      if (j == n)
+        break;
+    }
+
+  return j;
+}
+
+#define MAX_LEVEL 25
+#define TOLERANCE 0.001
+
+static void
+cubic_intersect_recurse (const GskCurve   *curve1,
+                         const GskCurve   *curve2,
+                         float             t1l,
+                         float             t1r,
+                         float             t2l,
+                         float             t2r,
+                         float            *t1,
+                         float            *t2,
+                         graphene_point_t *p,
+                         int               n,
+                         int              *pos,
+                         int               level)
+{
+  GskCurve p11, p12, p21, p22;
+  GskBoundingBox b1, b2;
+  float d1, d2;
+
+  if (*pos == n)
+    return;
+
+  if (level == MAX_LEVEL)
+    return;
+
+  gsk_curve_get_bounds (curve1, &b1);
+  gsk_curve_get_bounds (curve2, &b2);
+  if (!gsk_bounding_box_intersection (&b1, &b2, NULL))
+    return;
+
+  gsk_curve_get_tight_bounds (curve1, &b1);
+  if (!gsk_bounding_box_intersection (&b1, &b2, NULL))
+    return;
+
+  gsk_curve_get_tight_bounds (curve2, &b2);
+  if (!gsk_bounding_box_intersection (&b1, &b2, NULL))
+    return;
+
+  d1 = (t1r - t1l) / 2;
+  d2 = (t2r - t2l) / 2;
+
+  if (b1.max.x - b1.min.x < TOLERANCE && b1.max.y - b1.min.y < TOLERANCE &&
+      b2.max.x - b2.min.x < TOLERANCE && b2.max.y - b2.min.y < TOLERANCE)
+    {
+      graphene_point_t c;
+      t1[*pos] = t1l + d1;
+      t2[*pos] = t2l + d2;
+      gsk_curve_get_point (curve1, 0.5, &c);
+
+      for (int i = 0; i < *pos; i++)
+        {
+          if (graphene_point_near (&c, &p[i], 0.1))
+            return;
+        }
+
+      p[*pos] = c;
+      (*pos)++;
+
+      return;
+    }
+
+  gsk_curve_split (curve1, 0.5, &p11, &p12);
+  gsk_curve_split (curve2, 0.5, &p21, &p22);
+
+  cubic_intersect_recurse (&p11, &p21, t1l,      t1l + d1, t2l,      t2l + d2, t1, t2, p, n, pos, level + 1);
+  cubic_intersect_recurse (&p11, &p22, t1l,      t1l + d1, t2l + d2, t2r,      t1, t2, p, n, pos, level + 1);
+  cubic_intersect_recurse (&p12, &p21, t1l + d1, t1r,      t2l,      t2l + d2, t1, t2, p, n, pos, level + 1);
+  cubic_intersect_recurse (&p12, &p22, t1l + d1, t1r,      t2l + d2, t2r,      t1, t2, p, n, pos, level + 1);
+}
+
+static int
+cubic_intersect (const GskCurve   *curve1,
+                 const GskCurve   *curve2,
+                 float            *t1,
+                 float            *t2,
+                 graphene_point_t *p,
+                 int               n)
+{
+  int pos = 0;
+
+  cubic_intersect_recurse (curve1, curve2, 0, 1, 0, 1, t1, t2, p, n, &pos, 0);
+
+  return pos;
+}
+
+static void
+get_bounds (const GskCurve  *curve,
+            float            tl,
+            float            tr,
+            GskBoundingBox  *bounds)
+{
+  GskCurve c;
+
+  gsk_curve_segment (curve, tl, tr, &c);
+  gsk_curve_get_tight_bounds (&c, bounds);
+}
+
+static void
+general_intersect_recurse (const GskCurve   *curve1,
+                           const GskCurve   *curve2,
+                           float             t1l,
+                           float             t1r,
+                           float             t2l,
+                           float             t2r,
+                           float            *t1,
+                           float            *t2,
+                           graphene_point_t *p,
+                           int               n,
+                           int              *pos,
+                           int               level)
+{
+  GskBoundingBox b1, b2;
+  float d1, d2;
+
+  if (*pos == n)
+    return;
+
+  if (level == MAX_LEVEL)
+    return;
+
+  get_bounds (curve1, t1l, t1r, &b1);
+  get_bounds (curve2, t2l, t2r, &b2);
+
+  if (!gsk_bounding_box_intersection (&b1, &b2, NULL))
+    return;
+
+  d1 = (t1r - t1l) / 2;
+  d2 = (t2r - t2l) / 2;
+
+  if (b1.max.x - b1.min.x < TOLERANCE && b1.max.y - b1.min.y < TOLERANCE &&
+      b2.max.x - b2.min.x < TOLERANCE && b2.max.y - b2.min.y < TOLERANCE)
+    {
+      graphene_point_t c;
+      t1[*pos] = t1l + d1;
+      t2[*pos] = t2l + d2;
+      gsk_curve_get_point (curve1, t1[*pos], &c);
+
+      for (int i = 0; i < *pos; i++)
+        {
+          if (graphene_point_near (&c, &p[i], 0.1))
+            return;
+        }
+
+      p[*pos] = c;
+      (*pos)++;
+
+      return;
+    }
+
+  /* Note that in the conic case, we cannot just split the curves and
+   * pass the two halves down, since splitting changes the parametrization,
+   * and we need the t's to be valid parameters wrt to the original curve.
+   *
+   * So, instead, we determine the bounding boxes above by always starting
+   * from the original curve. That is a bit less efficient, but also works
+   * for conics.
+   */
+  general_intersect_recurse (curve1, curve2, t1l,      t1l + d1, t2l,      t2l + d2, t1, t2, p, n, pos, level + 1);
+  general_intersect_recurse (curve1, curve2, t1l,      t1l + d1, t2l + d2, t2r,      t1, t2, p, n, pos, level + 1);
+  general_intersect_recurse (curve1, curve2, t1l + d1, t1r,      t2l,      t2l + d2, t1, t2, p, n, pos, level + 1);
+  general_intersect_recurse (curve1, curve2, t1l + d1, t1r,      t2l + d2, t2r,      t1, t2, p, n, pos, level + 1);
+}
+
+static int
+general_intersect (const GskCurve   *curve1,
+                   const GskCurve   *curve2,
+                   float            *t1,
+                   float            *t2,
+                   graphene_point_t *p,
+                   int               n)
+{
+  int pos = 0;
+
+  general_intersect_recurse (curve1, curve2, 0, 1, 0, 1, t1, t2, p, n, &pos, 0);
+
+  return pos;
+}
+
+static int
+curve_self_intersect (const GskCurve   *curve,
+                      float            *t1,
+                      float            *t2,
+                      graphene_point_t *p,
+                      int               n)
+{
+  float tt[3], ss[3], s;
+  graphene_point_t pp[3];
+  int m;
+  GskCurve cs, ce;
+
+  if (curve->op != GSK_PATH_CUBIC)
+    return 0;
+
+  s = 0.5;
+  m = gsk_curve_get_curvature_points (curve, tt);
+  for (int i = 0; i < m; i++)
+    {
+      if (gsk_curve_get_curvature (curve, tt[i], NULL) == 0)
+        {
+          s = tt[i];
+          break;
+        }
+    }
+
+  gsk_curve_split (curve, s, &cs, &ce);
+
+  m = cubic_intersect (&cs, &ce, tt, ss, pp, 3);
+
+  if (m > 1)
+    {
+      /* One of the (at most 2) intersections we found
+       * must be the common point where we split the curve.
+       * It will have a t value of 1 and an s value of 0.
+       */
+      if (fabs (tt[0] - 1) > 1e-3)
+        {
+          t1[0] = t2[0] = tt[0] * s;
+          p[0] = pp[0];
+        }
+      else if (fabs (tt[1] - 1) > 1e-3)
+        {
+          t1[0] = t2[0] = tt[1] * s;
+          p[0] = pp[1];
+        }
+
+      if (n == 1)
+        return 1;
+
+      if (fabs (ss[0]) > 1e-3)
+        {
+          t1[1] = t2[1] = s + ss[0] * (1 - s);
+          p[1] = pp[0];
+        }
+      else if (fabs (ss[1]) > 1e-3)
+        {
+          t1[1] = t2[1] = s + ss[1] * (1 - s);
+          p[1] = pp[1];
+        }
+
+      return 2;
+    }
+
+  return 0;
+}
+
+static inline gboolean
+curve_equal (const GskCurve *c1,
+             const GskCurve *c2)
+{
+  gsize curve_size[] = {
+    sizeof (GskLineCurve),
+    sizeof (GskLineCurve),
+    sizeof (GskLineCurve),
+    sizeof (GskQuadCurve),
+    sizeof (GskCubicCurve),
+    sizeof (GskConicCurve)
+  };
+
+  return c1->op == c2->op && memcmp (c1, c2, curve_size[c1->op]) == 0;
+}
+
+/* Place intersections between the curves in p, and their Bezier positions
+ * in t1 and t2, up to n. Return the number of intersections found.
+ *
+ * Note that two cubic Beziers can have up to 9 intersections.
+ */
+int
+gsk_curve_intersect (const GskCurve   *curve1,
+                     const GskCurve   *curve2,
+                     float            *t1,
+                     float            *t2,
+                     graphene_point_t *p,
+                     int               n)
+{
+  GskPathOperation op1 = curve1->op;
+  GskPathOperation op2 = curve2->op;
+
+  if (op1 == GSK_PATH_CLOSE)
+    op1 = GSK_PATH_LINE;
+
+  if (op2 == GSK_PATH_CLOSE)
+    op2 = GSK_PATH_LINE;
+
+  if (curve_equal (curve1, curve2))
+    return curve_self_intersect (curve1, t1, t2, p, n);
+
+  /* We special-case line-line and line-cubic intersections,
+   * since we can solve them directly.
+   * Everything else is done via bisection.
+   */
+  if (op1 == GSK_PATH_LINE && op2 == GSK_PATH_LINE)
+    return line_intersect (curve1, curve2, t1, t2, p, n);
+  else if (op1 == GSK_PATH_LINE && op2 == GSK_PATH_QUAD)
+    return line_quad_intersect (curve1, curve2, t1, t2, p, n);
+  else if (op1 == GSK_PATH_QUAD && op2 == GSK_PATH_LINE)
+    return line_quad_intersect (curve2, curve1, t2, t1, p, n);
+  else if (op1 == GSK_PATH_LINE && op2 == GSK_PATH_CUBIC)
+    return line_cubic_intersect (curve1, curve2, t1, t2, p, n);
+  else if (op1 == GSK_PATH_CUBIC && op2 == GSK_PATH_LINE)
+    return line_cubic_intersect (curve2, curve1, t2, t1, p, n);
+  else if ((op1 == GSK_PATH_QUAD || op1 == GSK_PATH_CUBIC) &&
+           (op2 == GSK_PATH_QUAD || op2 == GSK_PATH_CUBIC))
+    return cubic_intersect (curve1, curve2, t1, t2, p, n);
+  else
+    return general_intersect (curve1, curve2, t1, t2, p, n);
+}
+
+/* }}} */
+
+/* vim:set foldmethod=marker expandtab: */

gsk/gskcurveprivate.h

@@ -0,0 +1,181 @@
+/*
+ * Copyright © 2020 Benjamin Otte
+ *
+ * This library is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU Lesser General Public
+ * License as published by the Free Software Foundation; either
+ * version 2.1 of the License, or (at your option) any later version.
+ *
+ * This library is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+ * Lesser General Public License for more details.
+ *
+ * You should have received a copy of the GNU Lesser General Public
+ * License along with this library. If not, see <http://www.gnu.org/licenses/>.
+ *
+ * Authors: Benjamin Otte <otte@gnome.org>
+ */
+
+
+#pragma once
+
+#include "gskpathopprivate.h"
+#include "gskpath.h"
+#include "gskboundingboxprivate.h"
+
+G_BEGIN_DECLS
+
+typedef gpointer gskpathop;
+
+typedef union _GskCurve GskCurve;
+
+typedef struct _GskLineCurve GskLineCurve;
+typedef struct _GskQuadCurve GskQuadCurve;
+typedef struct _GskCubicCurve GskCubicCurve;
+typedef struct _GskConicCurve GskConicCurve;
+
+struct _GskLineCurve
+{
+  GskPathOperation op;
+
+  gboolean padding;
+
+  graphene_point_t points[2];
+};
+
+struct _GskQuadCurve
+{
+  GskPathOperation op;
+
+  gboolean has_coefficients;
+
+  graphene_point_t points[3];
+
+  graphene_point_t coeffs[3];
+};
+
+struct _GskCubicCurve
+{
+  GskPathOperation op;
+
+  gboolean has_coefficients;
+
+  graphene_point_t points[4];
+
+  graphene_point_t coeffs[4];
+};
+
+struct _GskConicCurve
+{
+  GskPathOperation op;
+
+  gboolean has_coefficients;
+
+  /* points[0], points[1], points[3] are the control points,
+   * points[2].x is the weight
+   */
+  graphene_point_t points[4];
+
+  graphene_point_t num[3];
+  graphene_point_t denom[3];
+};
+
+union _GskCurve
+{
+  GskPathOperation op;
+  GskLineCurve line;
+  GskQuadCurve quad;
+  GskCubicCurve cubic;
+  GskConicCurve conic;
+};
+
+typedef enum {
+  GSK_CURVE_LINE_REASON_STRAIGHT,
+  GSK_CURVE_LINE_REASON_SHORT
+} GskCurveLineReason;
+
+typedef gboolean (* GskCurveAddLineFunc) (const graphene_point_t *from,
+                                          const graphene_point_t *to,
+                                          float                   from_progress,
+                                          float                   to_progress,
+                                          GskCurveLineReason      reason,
+                                          gpointer                user_data);
+
+typedef gboolean (* GskCurveAddCurveFunc) (GskPathOperation        op,
+                                           const graphene_point_t *pts,
+                                           gsize                   n_pts,
+                                           float                   weight,
+                                           gpointer                user_data);
+
+void                    gsk_curve_init                          (GskCurve               *curve,
+                                                                 gskpathop               op);
+void                    gsk_curve_init_foreach                  (GskCurve               *curve,
+                                                                 GskPathOperation        op,
+                                                                 const graphene_point_t *pts,
+                                                                 gsize                   n_pts,
+                                                                 float                   weight);
+
+void                    gsk_curve_print                         (const GskCurve         *curve,
+                                                                 GString                *string);
+
+char *                  gsk_curve_to_string                     (const GskCurve         *curve);
+
+gskpathop               gsk_curve_pathop                        (const GskCurve         *curve);
+const graphene_point_t *gsk_curve_get_start_point               (const GskCurve         *curve);
+const graphene_point_t *gsk_curve_get_end_point                 (const GskCurve         *curve);
+void                    gsk_curve_get_start_tangent             (const GskCurve         *curve,
+                                                                 graphene_vec2_t        *tangent);
+void                    gsk_curve_get_end_tangent               (const GskCurve         *curve,
+                                                                 graphene_vec2_t        *tangent);
+void                    gsk_curve_get_point                     (const GskCurve         *curve,
+                                                                 float                   progress,
+                                                                 graphene_point_t       *pos);
+void                    gsk_curve_get_tangent                   (const GskCurve         *curve,
+                                                                 float                   progress,
+                                                                 graphene_vec2_t        *tangent);
+void                    gsk_curve_reverse                       (const GskCurve         *curve,
+                                                                 GskCurve               *reverse);
+void                    gsk_curve_split                         (const GskCurve         *curve,
+                                                                 float                   progress,
+                                                                 GskCurve               *start,
+                                                                 GskCurve               *end);
+void                    gsk_curve_segment                       (const GskCurve         *curve,
+                                                                 float                   start,
+                                                                 float                   end,
+                                                                 GskCurve               *segment);
+gboolean                gsk_curve_decompose                     (const GskCurve         *curve,
+                                                                 float                   tolerance,
+                                                                 GskCurveAddLineFunc     add_line_func,
+                                                                 gpointer                user_data);
+gboolean                gsk_curve_decompose_curve               (const GskCurve         *curve,
+                                                                 GskPathForeachFlags     flags,
+                                                                 float                   tolerance,
+                                                                 GskCurveAddCurveFunc    add_curve_func,
+                                                                 gpointer                user_data);
+
+#define gsk_curve_builder_to(curve, builder) gsk_path_builder_pathop_to ((builder), gsk_curve_pathop (curve))
+
+float                   gsk_curve_get_curvature                 (const GskCurve         *curve,
+                                                                 float                   t,
+                                                                 graphene_point_t       *center);
+void                    gsk_curve_get_bounds                    (const GskCurve         *curve,
+                                                                 GskBoundingBox         *bounds);
+void                    gsk_curve_get_tight_bounds              (const GskCurve         *curve,
+                                                                 GskBoundingBox         *bounds);
+
+int                     gsk_curve_get_curvature_points          (const GskCurve         *curve,
+                                                                 float                   t[3]);
+
+int                     gsk_curve_get_cusps                     (const GskCurve         *curve,
+                                                                 float                   t[2]);
+
+int                     gsk_curve_intersect                     (const GskCurve         *curve1,
+                                                                 const GskCurve         *curve2,
+                                                                 float                  *t1,
+                                                                 float                  *t2,
+                                                                 graphene_point_t       *p,
+                                                                 int                     n);
+
+G_END_DECLS
+

gsk/gskdebug.c

@@ -17,6 +17,7 @@ static const GdkDebugKey gsk_debug_keys[] = {
   { "full-redraw", GSK_DEBUG_FULL_REDRAW, "Force full redraws" },
   { "sync", GSK_DEBUG_SYNC, "Sync after each frame" },
   { "staging", GSK_DEBUG_STAGING, "Use a staging image for texture upload (Vulkan only)" },
+  { "no-glyphy", GSK_DEBUG_NO_GLYPHY, "Don't use GPU for glyph rendering (OpenGL only)", TRUE },
 };
 
 static guint gsk_debug_flags;

gsk/gskdebugprivate.h

@@ -19,7 +19,8 @@ typedef enum {
   GSK_DEBUG_GEOMETRY              = 1 <<  9,
   GSK_DEBUG_FULL_REDRAW           = 1 << 10,
   GSK_DEBUG_SYNC                  = 1 << 11,
-  GSK_DEBUG_STAGING               = 1 << 12
+  GSK_DEBUG_STAGING               = 1 << 12,
+  GSK_DEBUG_NO_GLYPHY             = 1 << 13
 } GskDebugFlags;
 
 #define GSK_DEBUG_ANY ((1 << 13) - 1)

gsk/gskenums.h

@@ -170,6 +170,49 @@ typedef enum {
   GSK_CORNER_BOTTOM_LEFT
 } GskCorner;
 
+/**
+ * GskPathOperation:
+ * @GSK_PATH_MOVE: A move-to operation, with 1 point describing the target point.
+ * @GSK_PATH_CLOSE: A close operation ending the current contour with a line back
+ *   to the starting point. Two points describe the start and end of the line.
+ * @GSK_PATH_LINE: A line-to operation, with 2 points describing the start and
+ *   end point of a straight line.
+ * @GSK_PATH_QUAD: A curve-to operation describing a quadratic Bézier curve
+ *   with 3 points describing the start point, the control point and the end
+ *   point of the curve.
+ * @GSK_PATH_CUBIC: A curve-to operation describing a cubic Bézier curve with 4
+ *   points describing the start point, the two control points and the end point
+ *   of the curve.
+ * @GSK_PATH_CONIC: A weighted quadratic Bézier curve with 3 points describing
+ *   the start point, control point and end point of the curve. A weight for the
+ *   curve will be passed, too.
+ *
+ * Path operations can be used to approximate a `GskPath`.
+ *
+ * More values may be added in the future.
+ **/
+typedef enum {
+  GSK_PATH_MOVE,
+  GSK_PATH_CLOSE,
+  GSK_PATH_LINE,
+  GSK_PATH_QUAD,
+  GSK_PATH_CUBIC,
+  GSK_PATH_CONIC,
+} GskPathOperation;
+
+/**
+ * GskPathDirection:
+ * @GSK_PATH_START: The side that leads to the start of the path
+ * @GSK_PATH_END: The side that leads to the end of the path
+ *
+ * The values of the `GskPathDirection` enum are used to pick one
+ * of the two sides of the path that at a given point on the path.
+ */
+typedef enum {
+  GSK_PATH_START,
+  GSK_PATH_END
+} GskPathDirection;
+
 /**
  * GskSerializationError:
  * @GSK_SERIALIZATION_UNSUPPORTED_FORMAT: The format can not be identified
@@ -274,4 +317,3 @@ typedef enum
   GSK_MASK_MODE_LUMINANCE,
   GSK_MASK_MODE_INVERTED_LUMINANCE
 } GskMaskMode;
-

gsk/gskpath.h

@@ -0,0 +1,98 @@
+/*
+ * Copyright © 2020 Benjamin Otte
+ *
+ * This library is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU Lesser General Public
+ * License as published by the Free Software Foundation; either
+ * version 2.1 of the License, or (at your option) any later version.
+ *
+ * This library is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+ * Lesser General Public License for more details.
+ *
+ * You should have received a copy of the GNU Lesser General Public
+ * License along with this library. If not, see <http://www.gnu.org/licenses/>.
+ *
+ * Authors: Benjamin Otte <otte@gnome.org>
+ */
+
+#pragma once
+
+#if !defined (__GSK_H_INSIDE__) && !defined (GTK_COMPILATION)
+#error "Only <gsk/gsk.h> can be included directly."
+#endif
+
+
+#include <gsk/gsktypes.h>
+
+G_BEGIN_DECLS
+
+typedef enum {
+  GSK_FILL_RULE_WINDING,
+  GSK_FILL_RULE_EVEN_ODD
+} GskFillRule;
+
+/**
+ * GskPathForeachFlags:
+ * @GSK_PATH_FOREACH_ALLOW_QUAD: Allow emission of `GSK_PATH_QUAD` operations
+ * @GSK_PATH_FOREACH_ALLOW_CUBIC: Allow emission of `GSK_PATH_CUBIC` operations.
+ * @GSK_PATH_FOREACH_ALLOW_CONIC: Allow emission of `GSK_PATH_CONIC` operations.
+ *
+ * Flags that can be passed to gsk_path_foreach() to enable additional
+ * features.
+ *
+ * By default, [method@Gsk.Path.foreach] will only emit a path with all operations
+ * flattened to straight lines to allow for maximum compatibility. The only
+ * operations emitted will be `GSK_PATH_MOVE`, `GSK_PATH_LINE` and `GSK_PATH_CLOSE`.
+ */
+typedef enum
+{
+  GSK_PATH_FOREACH_ALLOW_QUAD  = (1 << 0),
+  GSK_PATH_FOREACH_ALLOW_CUBIC = (1 << 1),
+  GSK_PATH_FOREACH_ALLOW_CONIC = (1 << 2),
+} GskPathForeachFlags;
+
+/**
+ * GskPathForeachFunc:
+ * @op: The operation to perform
+ * @pts: The points of the operation
+ * @n_pts: The number of points
+ * @weight: The weight for conic curves, or unused if not a conic curve.
+ * @user_data: The user data provided with the function
+ *
+ * Prototype of the callback to iterate throught the operations of
+ * a path.
+ *
+ * Returns: %TRUE to continue evaluating the path, %FALSE to
+ *     immediately abort and not call the function again.
+ */
+typedef gboolean (* GskPathForeachFunc) (GskPathOperation        op,
+                                         const graphene_point_t *pts,
+                                         gsize                   n_pts,
+                                         float                   weight,
+                                         gpointer                user_data);
+
+#define GSK_TYPE_PATH (gsk_path_get_type ())
+
+GType                   gsk_path_get_type                       (void) G_GNUC_CONST;
+
+GskPath *               gsk_path_ref                            (GskPath                *self);
+void                    gsk_path_unref                          (GskPath                *self);
+void                    gsk_path_print                          (GskPath                *self,
+                                                                 GString                *string);
+char *                  gsk_path_to_string                      (GskPath                *self);
+GskPath *               gsk_path_parse                          (const char             *string);
+void                    gsk_path_to_cairo                       (GskPath                *self,
+                                                                 cairo_t                *cr);
+gboolean                gsk_path_is_empty                       (GskPath                *self);
+gboolean                gsk_path_get_bounds                     (GskPath                *self,
+                                                                 graphene_rect_t        *bounds);
+gboolean                gsk_path_foreach                        (GskPath                *self,
+                                                                 GskPathForeachFlags     flags,
+                                                                 GskPathForeachFunc      func,
+                                                                 gpointer                user_data);
+
+G_DEFINE_AUTOPTR_CLEANUP_FUNC(GskPath, gsk_path_unref)
+
+G_END_DECLS

gsk/gskpathbuilder.h

@@ -0,0 +1,118 @@
+/*
+ * Copyright © 2020 Benjamin Otte
+ *
+ * This library is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU Lesser General Public
+ * License as published by the Free Software Foundation; either
+ * version 2.1 of the License, or (at your option) any later version.
+ *
+ * This library is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+ * Lesser General Public License for more details.
+ *
+ * You should have received a copy of the GNU Lesser General Public
+ * License along with this library. If not, see <http://www.gnu.org/licenses/>.
+ *
+ * Authors: Benjamin Otte <otte@gnome.org>
+ */
+
+#pragma once
+
+#if !defined (__GSK_H_INSIDE__) && !defined (GTK_COMPILATION)
+#error "Only <gsk/gsk.h> can be included directly."
+#endif
+
+
+#include <gsk/gskroundedrect.h>
+#include <gsk/gsktypes.h>
+
+G_BEGIN_DECLS
+
+#define GSK_TYPE_PATH_BUILDER (gsk_path_builder_get_type ())
+
+GType                   gsk_path_builder_get_type               (void) G_GNUC_CONST;
+
+GskPathBuilder *        gsk_path_builder_new                    (void);
+GskPathBuilder *        gsk_path_builder_ref                    (GskPathBuilder         *self);
+void                    gsk_path_builder_unref                  (GskPathBuilder         *self);
+GskPath *               gsk_path_builder_free_to_path           (GskPathBuilder         *self) G_GNUC_WARN_UNUSED_RESULT;
+GskPath *               gsk_path_builder_to_path                (GskPathBuilder         *self) G_GNUC_WARN_UNUSED_RESULT;
+
+const graphene_point_t *gsk_path_builder_get_current_point      (GskPathBuilder         *self);
+
+void                    gsk_path_builder_add_path               (GskPathBuilder         *self,
+                                                                 GskPath                *path);
+void                    gsk_path_builder_add_reverse_path       (GskPathBuilder         *self,
+                                                                 GskPath                *path);
+void                    gsk_path_builder_add_cairo_path         (GskPathBuilder         *self,
+                                                                 const cairo_path_t     *path);
+void                    gsk_path_builder_add_layout             (GskPathBuilder         *self,
+                                                                 PangoLayout            *layout);
+void                    gsk_path_builder_add_rect               (GskPathBuilder         *self,
+                                                                 const graphene_rect_t  *rect);
+void                    gsk_path_builder_add_rounded_rect       (GskPathBuilder         *self,
+                                                                 const GskRoundedRect   *rect);
+void                    gsk_path_builder_add_circle             (GskPathBuilder         *self,
+                                                                 const graphene_point_t *center,
+                                                                 float                   radius);
+void                    gsk_path_builder_add_ellipse            (GskPathBuilder         *self,
+                                                                 const graphene_point_t *center,
+                                                                 const graphene_size_t  *radius);
+void                    gsk_path_builder_add_segment            (GskPathBuilder         *self,
+                                                                 GskPathMeasure         *measure,
+                                                                 float                   start,
+                                                                 float                   end);
+void                    gsk_path_builder_move_to                (GskPathBuilder         *self,
+                                                                 float                   x,
+                                                                 float                   y);
+void                    gsk_path_builder_rel_move_to            (GskPathBuilder         *self,
+                                                                 float                   x,
+                                                                 float                   y);
+void                    gsk_path_builder_line_to                (GskPathBuilder         *self,
+                                                                 float                   x,
+                                                                 float                   y);
+void                    gsk_path_builder_rel_line_to            (GskPathBuilder         *self,
+                                                                 float                   x,
+                                                                 float                   y);
+void                    gsk_path_builder_quad_to                (GskPathBuilder         *self,
+                                                                 float                   x1,
+                                                                 float                   y1,
+                                                                 float                   x2,
+                                                                 float                   y2);
+void                    gsk_path_builder_rel_quad_to            (GskPathBuilder         *self,
+                                                                 float                   x1,
+                                                                 float                   y1,
+                                                                 float                   x2,
+                                                                 float                   y2);
+void                    gsk_path_builder_cubic_to               (GskPathBuilder         *self,
+                                                                 float                   x1,
+                                                                 float                   y1,
+                                                                 float                   x2,
+                                                                 float                   y2,
+                                                                 float                   x3,
+                                                                 float                   y3);
+void                    gsk_path_builder_rel_cubic_to           (GskPathBuilder         *self,
+                                                                 float                   x1,
+                                                                 float                   y1,
+                                                                 float                   x2,
+                                                                 float                   y2,
+                                                                 float                   x3,
+                                                                 float                   y3);
+void                    gsk_path_builder_conic_to               (GskPathBuilder         *self,
+                                                                 float                   x1,
+                                                                 float                   y1,
+                                                                 float                   x2,
+                                                                 float                   y2,
+                                                                 float                   weight);
+void                    gsk_path_builder_rel_conic_to           (GskPathBuilder         *self,
+                                                                 float                   x1,
+                                                                 float                   y1,
+                                                                 float                   x2,
+                                                                 float                   y2,
+                                                                 float                   weight);
+void                    gsk_path_builder_close                  (GskPathBuilder         *self);
+
+G_DEFINE_AUTOPTR_CLEANUP_FUNC(GskPathBuilder, gsk_path_builder_unref)
+
+G_END_DECLS

gsk/gskpathmeasure.c

@@ -0,0 +1,489 @@
+/*
+ * Copyright © 2020 Benjamin Otte
+ *
+ * This library is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU Lesser General Public
+ * License as published by the Free Software Foundation; either
+ * version 2.1 of the License, or (at your option) any later version.
+ *
+ * This library is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+ * Lesser General Public License for more details.
+ *
+ * You should have received a copy of the GNU Lesser General Public
+ * License along with this library. If not, see <http://www.gnu.org/licenses/>.
+ *
+ * Authors: Benjamin Otte <otte@gnome.org>
+ */
+
+#include "config.h"
+
+#include "gskpathmeasure.h"
+
+#include "gskpathbuilder.h"
+#include "gskpathpointprivate.h"
+#include "gskpathprivate.h"
+
+/*< private >
+ * `GskPathMeasure` is an object that allows measurements
+ * on `GskPath`s such as determining the length of the path.
+ *
+ * Many measuring operations require approximating the path
+ * with simpler shapes. Therefore, a `GskPathMeasure` has
+ * a tolerance that determines what amount is required
+ * for such approximations.
+ *
+ * A `GskPathMeasure` struct is a reference counted struct
+ * and should be treated as opaque.
+ */
+
+typedef struct _GskContourMeasure GskContourMeasure;
+
+struct _GskContourMeasure
+{
+  float length;
+  gpointer contour_data;
+};
+
+struct _GskPathMeasure
+{
+  /*< private >*/
+  guint ref_count;
+
+  GskPath *path;
+  float tolerance;
+
+  float length;
+  gsize n_contours;
+  GskContourMeasure measures[];
+};
+
+G_DEFINE_BOXED_TYPE (GskPathMeasure, gsk_path_measure,
+                     gsk_path_measure_ref,
+                     gsk_path_measure_unref)
+
+/*< private >
+ * gsk_path_measure_new:
+ * @path: the path to measure
+ *
+ * Creates a measure object for the given @path.
+ *
+ * Returns: a new `GskPathMeasure` representing @path
+ */
+GskPathMeasure *
+gsk_path_measure_new (GskPath *path)
+{
+  return gsk_path_measure_new_with_tolerance (path, GSK_PATH_TOLERANCE_DEFAULT);
+}
+
+/*< private >
+ * gsk_path_measure_new_with_tolerance:
+ * @path: the path to measure
+ * @tolerance: the tolerance for measuring operations
+ *
+ * Creates a measure object for the given @path and @tolerance.
+ *
+ * Returns: a new `GskPathMeasure` representing @path
+ */
+GskPathMeasure *
+gsk_path_measure_new_with_tolerance (GskPath *path,
+                                     float    tolerance)
+{
+  GskPathMeasure *self;
+  gsize i, n_contours;
+
+  g_return_val_if_fail (path != NULL, NULL);
+  g_return_val_if_fail (tolerance > 0, NULL);
+
+  n_contours = gsk_path_get_n_contours (path);
+
+  self = g_malloc0 (sizeof (GskPathMeasure) + n_contours * sizeof (GskContourMeasure));
+
+  self->ref_count = 1;
+  self->path = gsk_path_ref (path);
+  self->tolerance = tolerance;
+  self->n_contours = n_contours;
+
+  for (i = 0; i < n_contours; i++)
+    {
+      self->measures[i].contour_data = gsk_contour_init_measure (gsk_path_get_contour (path, i),
+                                                                 self->tolerance,
+                                                                 &self->measures[i].length);
+      self->length += self->measures[i].length;
+    }
+
+  return self;
+}
+
+/*< private >
+ * gsk_path_measure_ref:
+ * @self: a `GskPathMeasure`
+ *
+ * Increases the reference count of a `GskPathMeasure` by one.
+ *
+ * Returns: the passed in `GskPathMeasure`.
+ */
+GskPathMeasure *
+gsk_path_measure_ref (GskPathMeasure *self)
+{
+  g_return_val_if_fail (self != NULL, NULL);
+
+  self->ref_count++;
+
+  return self;
+}
+
+/*< private >
+ * gsk_path_measure_unref:
+ * @self: a `GskPathMeasure`
+ *
+ * Decreases the reference count of a `GskPathMeasure` by one.
+ *
+ * If the resulting reference count is zero, frees the object.
+ */
+void
+gsk_path_measure_unref (GskPathMeasure *self)
+{
+  gsize i;
+
+  g_return_if_fail (self != NULL);
+  g_return_if_fail (self->ref_count > 0);
+
+  self->ref_count--;
+  if (self->ref_count > 0)
+    return;
+
+  for (i = 0; i < self->n_contours; i++)
+    {
+      gsk_contour_free_measure (gsk_path_get_contour (self->path, i),
+                                self->measures[i].contour_data);
+    }
+
+  gsk_path_unref (self->path);
+  g_free (self);
+}
+
+/*< private >
+ * gsk_path_measure_get_path:
+ * @self: a `GskPathMeasure`
+ *
+ * Returns the path that the measure was created for.
+ *
+ * Returns: (transfer none): the path of @self
+ */
+GskPath *
+gsk_path_measure_get_path (GskPathMeasure *self)
+{
+  return self->path;
+}
+
+/*< private >
+ * gsk_path_measure_get_tolerance:
+ * @self: a `GskPathMeasure`
+ *
+ * Returns the tolerance that the measure was created with.
+ *
+ * Returns: the tolerance of @self
+ */
+float
+gsk_path_measure_get_tolerance (GskPathMeasure *self)
+{
+  return self->tolerance;
+}
+
+/*< private >
+ * gsk_path_measure_get_length:
+ * @self: a `GskPathMeasure`
+ *
+ * Gets the length of the path being measured.
+ *
+ * The length is cached, so this function does not do any work.
+ *
+ * Returns: The length of the path measured by @self
+ */
+float
+gsk_path_measure_get_length (GskPathMeasure *self)
+{
+  g_return_val_if_fail (self != NULL, 0);
+
+  return self->length;
+}
+
+/*< private >
+ * gsk_path_measure_is_closed:
+ * @self: a `GskPathMeasure`
+ *
+ * Returns if the path being measured represents a single closed
+ * contour.
+ *
+ * Returns: `TRUE` if the current path is closed
+ */
+gboolean
+gsk_path_measure_is_closed (GskPathMeasure *self)
+{
+  const GskContour *contour;
+
+  g_return_val_if_fail (self != NULL, FALSE);
+
+  /* XXX: is the empty path closed? Currently it's not */
+  if (self->n_contours != 1)
+    return FALSE;
+
+  contour = gsk_path_get_contour (self->path, 0);
+  return gsk_contour_get_flags (contour) & GSK_PATH_CLOSED ? TRUE : FALSE;
+}
+
+static float
+gsk_path_measure_clamp_distance (GskPathMeasure *self,
+                                 float           distance)
+{
+  if (isnan (distance))
+    return 0;
+
+  return CLAMP (distance, 0, self->length);
+}
+
+/*< private >
+ * gsk_path_measure_in_fill:
+ * @self: a `GskPathMeasure`
+ * @point: the point to test
+ * @fill_rule: the fill rule to follow
+ *
+ * Returns whether the given point is inside the area
+ * that would be affected if the path was filled according
+ * to @fill_rule.
+ *
+ * Returns: `TRUE` if @point is inside
+ */
+gboolean
+gsk_path_measure_in_fill (GskPathMeasure         *self,
+                          const graphene_point_t *point,
+                          GskFillRule             fill_rule)
+{
+  int winding = 0;
+  int i;
+
+  for (i = 0; i < self->n_contours; i++)
+    winding += gsk_contour_get_winding (gsk_path_get_contour (self->path, i),
+                                        self->measures[i].contour_data,
+                                        point);
+
+  switch (fill_rule)
+    {
+    case GSK_FILL_RULE_EVEN_ODD:
+      return winding & 1;
+    case GSK_FILL_RULE_WINDING:
+      return winding != 0;
+    default:
+      g_assert_not_reached ();
+    }
+}
+
+static void
+gsk_path_builder_add_segment_chunk (GskPathBuilder *self,
+                                    GskPathMeasure *measure,
+                                    gboolean        emit_move_to,
+                                    float           start,
+                                    float           end)
+{
+  g_assert (start < end);
+
+  for (gsize i = 0; i < measure->n_contours; i++)
+    {
+      if (measure->measures[i].length < start)
+        {
+          start -= measure->measures[i].length;
+          end -= measure->measures[i].length;
+        }
+      else if (start > 0 || end < measure->measures[i].length)
+        {
+          float len = MIN (end, measure->measures[i].length);
+          gsk_contour_add_segment (gsk_path_get_contour (measure->path, i),
+                                   self,
+                                   measure->measures[i].contour_data,
+                                   emit_move_to,
+                                   start,
+                                   len);
+          end -= len;
+          start = 0;
+          if (end <= 0)
+            break;
+        }
+      else
+        {
+          end -= measure->measures[i].length;
+          gsk_path_builder_add_contour (self, gsk_contour_dup (gsk_path_get_contour (measure->path, i)));
+        }
+      emit_move_to = TRUE;
+    }
+}
+
+/*< private >
+ * gsk_path_builder_add_segment:
+ * @self: a `GskPathBuilder`
+ * @measure: the `GskPathMeasure` to take the segment to
+ * @start: start distance into the path
+ * @end: end distance into the path
+ *
+ * Adds to @self the segment of @measure from @start to @end.
+ *
+ * The distances are given relative to the length of @measure's path,
+ * from 0 for the beginning of the path to its length for the end
+ * of the path. The values will be clamped to that range. The length
+ * can be obtained with [method@Gsk.PathMeasure.get_length].
+ *
+ * If @start >= @end after clamping, the path will first add the segment
+ * from @start to the end of the path, and then add the segment from
+ * the beginning to @end. If the path is closed, these segments will
+ * be connected.
+ */
+void
+gsk_path_builder_add_segment (GskPathBuilder *self,
+                              GskPathMeasure *measure,
+                              float           start,
+                              float           end)
+{
+  g_return_if_fail (self != NULL);
+  g_return_if_fail (measure != NULL);
+
+  start = gsk_path_measure_clamp_distance (measure, start);
+  end = gsk_path_measure_clamp_distance (measure, end);
+
+  if (start < end)
+    {
+      gsk_path_builder_add_segment_chunk (self, measure, TRUE, start, end);
+    }
+  else
+    {
+      /* If the path is closed, we can connect the 2 subpaths. */
+      gboolean closed = gsk_path_measure_is_closed (measure);
+      gboolean need_move_to = !closed;
+
+      if (start < measure->length)
+        gsk_path_builder_add_segment_chunk (self, measure,
+                                            TRUE,
+                                            start, measure->length);
+      else
+        need_move_to = TRUE;
+
+      if (end > 0)
+        gsk_path_builder_add_segment_chunk (self, measure,
+                                            need_move_to,
+                                            0, end);
+      if (start == end && closed)
+        gsk_path_builder_close (self);
+    }
+}
+
+/*< private >
+ * gsk_path_measure_get_point:
+ * @self: a `GskPathMeasure`
+ * @distance: the distance
+ *
+ * Returns a `GskPathPoint` representing the point at the given
+ * distance into the path.
+ *
+ * An empty path has no points, so `NULL` is returned in that case.
+ *
+ * Returns: (transfer full) (nullable): a newly allocated `GskPathPoint`
+ */
+GskPathPoint *
+gsk_path_measure_get_point (GskPathMeasure *self,
+                            float           distance)
+{
+  gsize i;
+  float contour_offset;
+  float offset;
+  const GskContour *contour;
+
+  g_return_val_if_fail (self != NULL, NULL);
+
+  if (self->n_contours == 0)
+    return NULL;
+
+  contour_offset = 0;
+  offset = gsk_path_measure_clamp_distance (self, distance);
+
+  for (i = 0; i < self->n_contours - 1; i++)
+    {
+      if (offset < self->measures[i].length)
+        break;
+
+      contour_offset += self->measures[i].length;
+      offset -= self->measures[i].length;
+    }
+
+  g_assert (0 <= i && i < self->n_contours);
+
+  offset = CLAMP (offset, 0, self->measures[i].length);
+
+  contour = gsk_path_get_contour (self->path, i);
+
+  return gsk_path_point_new (self,
+                             contour, self->measures[i].contour_data,
+                             contour_offset, offset);
+}
+
+/*< private >
+ * gsk_path_measure_get_closest_point:
+ * @self: a `GskPathMeasure`
+ * @point: the point to fond the closest point to
+ * @threshold: The maximum allowed distance between the path and @point.
+ *   Use `INFINITY` to look for any point.
+ *
+ * Returns a `GskPathPoint` representing the point on the path
+ * that is closest to the given point.
+ *
+ * If no point on the path is closer than @threshold, `NULL` is returned.
+ *
+ * Returns: (transfer full) (nullable): a newly allocated `GskPathPoint`
+ */
+GskPathPoint *
+gsk_path_measure_get_closest_point (GskPathMeasure         *self,
+                                    const graphene_point_t *point,
+                                    float                   threshold)
+{
+  gssize best_idx;
+  float best_offset;
+  float best_contour_offset;
+  float contour_offset;
+
+  contour_offset = 0;
+  best_idx = -1;
+
+  for (gsize i = 0; i < self->n_contours; i++)
+    {
+      float distance, offset;
+
+      if (gsk_contour_get_closest_point (gsk_path_get_contour (self->path, i),
+                                         self->measures[i].contour_data,
+                                         self->tolerance,
+                                         point,
+                                         threshold,
+                                         &distance,
+                                         NULL,
+                                         &offset,
+                                         NULL))
+        {
+          best_idx = i;
+          best_offset = offset;
+          best_contour_offset = contour_offset;
+
+          if (distance < self->tolerance)
+            break;
+
+          threshold = distance - self->tolerance;
+        }
+
+      contour_offset += self->measures[i].length;
+    }
+
+  if (best_idx != -1)
+    return gsk_path_point_new (self,
+                               gsk_path_get_contour (self->path, best_idx),
+                               self->measures[best_idx].contour_data,
+                               best_contour_offset, best_offset);
+
+  return NULL;
+}

gsk/gskpathmeasure.h

@@ -0,0 +1,55 @@
+/*
+ * Copyright © 2020 Benjamin Otte
+ *
+ * This library is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU Lesser General Public
+ * License as published by the Free Software Foundation; either
+ * version 2.1 of the License, or (at your option) any later version.
+ *
+ * This library is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+ * Lesser General Public License for more details.
+ *
+ * You should have received a copy of the GNU Lesser General Public
+ * License along with this library. If not, see <http://www.gnu.org/licenses/>.
+ *
+ * Authors: Benjamin Otte <otte@gnome.org>
+ */
+
+#pragma once
+
+#if !defined (__GSK_H_INSIDE__) && !defined (GTK_COMPILATION)
+#error "Only <gsk/gsk.h> can be included directly."
+#endif
+
+
+#include <gsk/gskpath.h>
+#include <gsk/gskpathpoint.h>
+
+G_BEGIN_DECLS
+
+#define GSK_TYPE_PATH_MEASURE (gsk_path_measure_get_type ())
+
+GType                   gsk_path_measure_get_type               (void) G_GNUC_CONST;
+GskPathMeasure *        gsk_path_measure_new                    (GskPath                *path);
+GskPathMeasure *        gsk_path_measure_new_with_tolerance     (GskPath                *path,
+                                                                 float                   tolerance);
+GskPathMeasure *        gsk_path_measure_ref                    (GskPathMeasure         *self);
+void                    gsk_path_measure_unref                  (GskPathMeasure         *self);
+GskPath *               gsk_path_measure_get_path               (GskPathMeasure         *self) G_GNUC_PURE;
+float                   gsk_path_measure_get_tolerance          (GskPathMeasure         *self) G_GNUC_PURE;
+float                   gsk_path_measure_get_length             (GskPathMeasure         *self);
+gboolean                gsk_path_measure_is_closed              (GskPathMeasure         *self);
+gboolean                gsk_path_measure_in_fill                (GskPathMeasure         *self,
+                                                                 const graphene_point_t *point,
+                                                                 GskFillRule             fill_rule);
+GskPathPoint *          gsk_path_measure_get_point              (GskPathMeasure         *self,
+                                                                 float                   distance);
+GskPathPoint *          gsk_path_measure_get_closest_point      (GskPathMeasure         *self,
+                                                                 const graphene_point_t *point,
+                                                                 float                   threshold);
+
+G_DEFINE_AUTOPTR_CLEANUP_FUNC(GskPathMeasure, gsk_path_measure_unref)
+
+G_END_DECLS

gsk/gskpathopprivate.h

@@ -0,0 +1,186 @@
+/*
+ * Copyright © 2020 Benjamin Otte
+ *
+ * This library is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU Lesser General Public
+ * License as published by the Free Software Foundation; either
+ * version 2.1 of the License, or (at your option) any later version.
+ *
+ * This library is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+ * Lesser General Public License for more details.
+ *
+ * You should have received a copy of the GNU Lesser General Public
+ * License along with this library. If not, see <http://www.gnu.org/licenses/>.
+ *
+ * Authors: Benjamin Otte <otte@gnome.org>
+ */
+
+
+#pragma once
+
+#include "gskpath.h"
+#include "gskpathbuilder.h"
+
+G_BEGIN_DECLS
+
+typedef gpointer gskpathop;
+
+static inline
+gskpathop               gsk_pathop_encode                       (GskPathOperation        op,
+                                                                 const graphene_point_t *pts);
+static inline
+const graphene_point_t *gsk_pathop_points                       (gskpathop               pop);
+static inline
+GskPathOperation        gsk_pathop_op                           (gskpathop               pop);
+
+static inline
+gboolean                gsk_pathop_foreach                      (gskpathop               pop,
+                                                                 GskPathForeachFunc      func,
+                                                                 gpointer                user_data);
+
+/* included inline so tests can use them */
+static inline
+void                    gsk_path_builder_pathop_to              (GskPathBuilder         *builder,
+                                                                 gskpathop               op);
+static inline
+void                    gsk_path_builder_pathop_reverse_to      (GskPathBuilder         *builder,
+                                                                 gskpathop               op);
+
+/* IMPLEMENTATION */
+
+#define GSK_PATHOP_OPERATION_MASK (0x7)
+
+static inline gskpathop
+gsk_pathop_encode (GskPathOperation        op,
+                   const graphene_point_t *pts)
+{
+  /* g_assert (op & GSK_PATHOP_OPERATION_MASK == op); */
+  g_assert ((GPOINTER_TO_SIZE (pts) & GSK_PATHOP_OPERATION_MASK) == 0);
+
+  return GSIZE_TO_POINTER (GPOINTER_TO_SIZE (pts) | op);
+}
+
+static inline const graphene_point_t *
+gsk_pathop_points (gskpathop pop)
+{
+  return GSIZE_TO_POINTER (GPOINTER_TO_SIZE (pop) & ~GSK_PATHOP_OPERATION_MASK);
+}
+
+static inline
+GskPathOperation gsk_pathop_op (gskpathop pop)
+{
+  return GPOINTER_TO_SIZE (pop) & GSK_PATHOP_OPERATION_MASK;
+}
+
+static inline gboolean
+gsk_pathop_foreach (gskpathop          pop,
+                    GskPathForeachFunc func,
+                    gpointer           user_data)
+{
+  switch (gsk_pathop_op (pop))
+  {
+    case GSK_PATH_MOVE:
+      return func (gsk_pathop_op (pop), gsk_pathop_points (pop), 1, 0, user_data);
+
+    case GSK_PATH_CLOSE:
+    case GSK_PATH_LINE:
+      return func (gsk_pathop_op (pop), gsk_pathop_points (pop), 2, 0, user_data);
+
+    case GSK_PATH_QUAD:
+      return func (gsk_pathop_op (pop), gsk_pathop_points (pop), 3, 0, user_data);
+
+    case GSK_PATH_CUBIC:
+      return func (gsk_pathop_op (pop), gsk_pathop_points (pop), 4, 0, user_data);
+
+    case GSK_PATH_CONIC:
+      {
+        const graphene_point_t *pts = gsk_pathop_points (pop);
+        return func (gsk_pathop_op (pop), (graphene_point_t[3]) { pts[0], pts[1], pts[3] }, 3, pts[2].x, user_data);
+      }
+
+    default:
+      g_assert_not_reached ();
+      return TRUE;
+    }
+}
+
+static inline void
+gsk_path_builder_pathop_to (GskPathBuilder *builder,
+                            gskpathop       op)
+{
+  const graphene_point_t *pts = gsk_pathop_points (op);
+
+  switch (gsk_pathop_op (op))
+  {
+    case GSK_PATH_MOVE:
+      gsk_path_builder_move_to (builder, pts[0].x, pts[0].y);
+      break;
+
+    case GSK_PATH_CLOSE:
+      gsk_path_builder_close (builder);
+      break;
+
+    case GSK_PATH_LINE:
+      gsk_path_builder_line_to (builder, pts[1].x, pts[1].y);
+      break;
+
+    case GSK_PATH_QUAD:
+      gsk_path_builder_quad_to (builder, pts[1].x, pts[1].y, pts[2].x, pts[2].y);
+      break;
+
+    case GSK_PATH_CUBIC:
+      gsk_path_builder_cubic_to (builder, pts[1].x, pts[1].y, pts[2].x, pts[2].y, pts[3].x, pts[3].y);
+      break;
+
+    case GSK_PATH_CONIC:
+      gsk_path_builder_conic_to (builder, pts[1].x, pts[1].y, pts[3].x, pts[3].y, pts[2].x);
+      break;
+
+    default:
+      g_assert_not_reached ();
+      break;
+  }
+}
+
+static inline void
+gsk_path_builder_pathop_reverse_to (GskPathBuilder *builder,
+                                    gskpathop       op)
+{
+  const graphene_point_t *pts = gsk_pathop_points (op);
+
+  switch (gsk_pathop_op (op))
+  {
+    case GSK_PATH_MOVE:
+      gsk_path_builder_move_to (builder, pts[0].x, pts[0].y);
+      break;
+
+    case GSK_PATH_CLOSE:
+      gsk_path_builder_line_to (builder, pts[0].x, pts[0].y);
+      break;
+
+    case GSK_PATH_LINE:
+      gsk_path_builder_line_to (builder, pts[1].x, pts[1].y);
+      break;
+
+    case GSK_PATH_QUAD:
+      gsk_path_builder_quad_to (builder, pts[1].x, pts[1].y, pts[0].x, pts[0].y);
+      break;
+
+    case GSK_PATH_CUBIC:
+      gsk_path_builder_cubic_to (builder, pts[2].x, pts[2].y, pts[1].x, pts[1].y, pts[0].x, pts[0].y);
+      break;
+
+    case GSK_PATH_CONIC:
+      gsk_path_builder_conic_to (builder, pts[1].x, pts[1].y, pts[0].x, pts[0].y, pts[2].x);
+      break;
+
+    default:
+      g_assert_not_reached ();
+      break;
+  }
+}
+
+
+G_END_DECLS

gsk/gskpathpoint.c

@@ -0,0 +1,195 @@
+#include "config.h"
+
+#include "gskpathpointprivate.h"
+
+#include "gskcontourprivate.h"
+#include "gskpathmeasure.h"
+
+#include "gdk/gdkprivate.h"
+
+
+/**
+ * GskPathPoint:
+ *
+ * `GskPathPoint` is an opaque, immutable type representing a point on a path.
+ *
+ * It can be queried for properties of the path at that point, such as its
+ * tangent or its curvature.
+ *
+ * To obtain a `GskPathPoint`, use [method@Gsk.PathMeasure.get_path_point]
+ * or [method@Gsk.PathMeasure.get_closest_point].
+ */
+
+struct _GskPathPoint
+{
+  guint ref_count;
+
+  GskPathMeasure *measure;
+  const GskContour *contour;
+  gpointer measure_data;
+  float contour_offset;  /* distance from beginning of path to contour */
+  float offset;          /* offset of point inside contour */
+};
+
+G_DEFINE_BOXED_TYPE (GskPathPoint, gsk_path_point,
+                     gsk_path_point_ref,
+                     gsk_path_point_unref)
+
+GskPathPoint *
+gsk_path_point_new (GskPathMeasure   *measure,
+                    const GskContour *contour,
+                    gpointer          measure_data,
+                    float             contour_offset,
+                    float             offset)
+{
+  GskPathPoint *self;
+
+  self = g_new0 (GskPathPoint, 1);
+
+  self->ref_count = 1;
+
+  self->measure = gsk_path_measure_ref (measure);
+  self->contour = contour;
+  self->measure_data = measure_data;
+  self->contour_offset = contour_offset;
+  self->offset = offset;
+
+  return self;
+}
+
+/**
+ * gsk_path_point_ref:
+ * @self: a `GskPathPoint`
+ *
+ * Increases the reference count of a `GskPathPoint` by one.
+ *
+ * Returns: the passed in `GskPathPoint`
+ */
+GskPathPoint *
+gsk_path_point_ref (GskPathPoint *self)
+{
+  g_return_val_if_fail (self != NULL, NULL);
+
+  self->ref_count++;
+
+  return self;
+}
+
+/**
+ * gsk_path_point_unref:
+ * @self: a `GskPathPoint`
+ *
+ * Decreases the reference count of a `GskPathPoint` by one.
+ *
+ * If the resulting reference count is zero, frees the path_measure.
+ */
+void
+gsk_path_point_unref (GskPathPoint *self)
+{
+  g_return_if_fail (self != NULL);
+  g_return_if_fail (self->ref_count > 0);
+
+  self->ref_count--;
+  if (self->ref_count > 0)
+    return;
+
+  gsk_path_measure_unref (self->measure);
+
+  g_free (self);
+}
+
+GskPathMeasure *
+gsk_path_point_get_measure (GskPathPoint *self)
+{
+  return self->measure;
+}
+
+/**
+ * gsk_path_point_get_distance:
+ * @self: a `GskPathPoint`
+ *
+ * Returns the distance of the given point from the start of the path.
+ *
+ * This is the length of the contour from the beginning of the path
+ * to the point.
+ *
+ * Returns: The offset of point in path
+ */
+float
+gsk_path_point_get_distance (GskPathPoint *self)
+{
+  return self->contour_offset + self->offset;
+}
+
+/**
+ * gsk_path_point_get_position:
+ * @self: a `GskPathPoint`
+ * @position: (out caller-allocates): Return location for
+ *   the coordinates of the point
+ *
+ * Gets the position of the point.
+ */
+void
+gsk_path_point_get_position (GskPathPoint     *self,
+                             graphene_point_t *position)
+{
+  gsk_contour_get_point (self->contour,
+                         self->measure_data,
+                         self->offset,
+                         GSK_PATH_END,
+                         position, NULL);
+}
+
+/**
+ * gsk_path_point_get_tangent:
+ * @self: a `GskPathPoint`
+ * @direction: the direction for which to return the tangent
+ * @tangent: (out caller-allocates): Return location for
+ *   the tangent at the point
+ *
+ * Gets the tangent of the path at the point.
+ *
+ * Note that certain points on a path may not have a single
+ * tangent, such as sharp turns. At such points, there are
+ * two tangents -- the direction of the path going into the
+ * point, and the direction coming out of it.
+ *
+ * The @direction argument lets you choose which one to get.
+ */
+void
+gsk_path_point_get_tangent (GskPathPoint     *self,
+                            GskPathDirection  direction,
+                            graphene_vec2_t  *tangent)
+{
+  gsk_contour_get_point (self->contour,
+                         self->measure_data,
+                         self->offset,
+                         direction,
+                         NULL, tangent);
+}
+
+/**
+ * gsk_path_point_get_curvature:
+ * @self: a `GskPathPoint`
+ * @center: (out caller-allocates): Return location for
+ *   the center of the osculating circle
+ *
+ * Calculates the curvature at the point @distance units into
+ * the path.
+ *
+ * Optionally, returns the center of the osculating circle as well.
+ *
+ * If the curvature is infinite (at line segments), zero is returned,
+ * and @center is not modified.
+ *
+ * Returns: The curvature of the path at the given point
+ */
+float
+gsk_path_point_get_curvature (GskPathPoint     *self,
+                              graphene_point_t *center)
+{
+  return gsk_contour_get_curvature (self->contour,
+                                    self->measure_data,
+                                    self->offset,
+                                    center);
+}

gsk/gskpathpoint.h

@@ -0,0 +1,29 @@
+#pragma once
+
+#if !defined (__GSK_H_INSIDE__) && !defined (GTK_COMPILATION)
+#error "Only <gsk/gsk.h> can be included directly."
+#endif
+
+
+#include <gsk/gsktypes.h>
+
+G_BEGIN_DECLS
+
+#define GSK_TYPE_PATH_POINT (gsk_path_point_get_type ())
+
+GType                   gsk_path_point_get_type        (void) G_GNUC_CONST;
+GskPathPoint *          gsk_path_point_ref             (GskPathPoint *self);
+void                    gsk_path_point_unref           (GskPathPoint *self);
+GskPathMeasure *        gsk_path_point_get_measure     (GskPathPoint     *self);
+float                   gsk_path_point_get_distance    (GskPathPoint     *self);
+void                    gsk_path_point_get_position    (GskPathPoint     *self,
+                                                        graphene_point_t *position);
+void                    gsk_path_point_get_tangent     (GskPathPoint     *self,
+                                                        GskPathDirection  direction,
+                                                        graphene_vec2_t  *tangent);
+float                   gsk_path_point_get_curvature   (GskPathPoint     *self,
+                                                        graphene_point_t *center);
+
+G_DEFINE_AUTOPTR_CLEANUP_FUNC(GskPathPoint, gsk_path_point_unref)
+
+G_END_DECLS

gsk/gskpathpointprivate.h

@@ -0,0 +1,16 @@
+#pragma once
+
+#include "gskpathpoint.h"
+#include "gskcontourprivate.h"
+#include "gskpathmeasure.h"
+
+G_BEGIN_DECLS
+
+GskPathPoint * gsk_path_point_new (GskPathMeasure *measure,
+                                   const GskContour *contour,
+                                   gpointer          measure_data,
+                                   float             contour_offset,
+                                   float             offset);
+
+G_END_DECLS
+

gsk/gskpathprivate.h

@@ -0,0 +1,77 @@
+/*
+ * Copyright © 2020 Benjamin Otte
+ *
+ * This library is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU Lesser General Public
+ * License as published by the Free Software Foundation; either
+ * version 2.1 of the License, or (at your option) any later version.
+ *
+ * This library is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+ * Lesser General Public License for more details.
+ *
+ * You should have received a copy of the GNU Lesser General Public
+ * License along with this library. If not, see <http://www.gnu.org/licenses/>.
+ *
+ * Authors: Benjamin Otte <otte@gnome.org>
+ */
+
+
+#pragma once
+
+#include "gskpath.h"
+
+#include "gskcontourprivate.h"
+#include "gskpathopprivate.h"
+
+G_BEGIN_DECLS
+
+/* Same as Skia, so looks like a good value. ¯\_(ツ)_/¯ */
+#define GSK_PATH_TOLERANCE_DEFAULT (0.5)
+
+GskPath *               gsk_path_new_from_contours              (const GSList           *contours);
+
+gsize                   gsk_path_get_n_contours                 (GskPath                *path);
+const GskContour *      gsk_path_get_contour                    (GskPath                *path,
+                                                                 gsize                   i);
+
+GskPathFlags            gsk_path_get_flags                      (GskPath                *self);
+
+gboolean                gsk_path_foreach_with_tolerance         (GskPath                *self,
+                                                                 GskPathForeachFlags     flags,
+                                                                 double                  tolerance,
+                                                                 GskPathForeachFunc      func,
+                                                                 gpointer                user_data);
+
+
+void                    gsk_path_builder_add_contour            (GskPathBuilder         *builder,
+                                                                 GskContour             *contour);
+
+void                    gsk_path_builder_svg_arc_to             (GskPathBuilder         *builder,
+                                                                 float                   rx,
+                                                                 float                   ry,
+                                                                 float                   x_axis_rotation,
+                                                                 gboolean                large_arc,
+                                                                 gboolean                positive_sweep,
+                                                                 float                   x,
+                                                                 float                   y);
+
+
+typedef enum
+{
+  GSK_PATH_OP_SIMPLIFY,
+  GSK_PATH_OP_UNION,
+  GSK_PATH_OP_INTERSECTION,
+  GSK_PATH_OP_DIFFERENCE,
+  GSK_PATH_OP_XOR
+} GskPathOp;
+
+GskPath *               gsk_path_op                             (GskPathOp               operation,
+                                                                 GskFillRule             fill_rule,
+                                                                 GskPath                *first,
+                                                                 GskPath                *second);
+
+
+G_END_DECLS
+

gsk/gskspline.c

@@ -0,0 +1,208 @@
+/*
+ * Copyright © 2002 University of Southern California
+ *             2020 Benjamin Otte
+ *
+ * This library is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU Lesser General Public
+ * License as published by the Free Software Foundation; either
+ * version 2.1 of the License, or (at your option) any later version.
+ *
+ * This library is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+ * Lesser General Public License for more details.
+ *
+ * You should have received a copy of the GNU Lesser General Public
+ * License along with this library. If not, see <http://www.gnu.org/licenses/>.
+ *
+ * Authors: Benjamin Otte <otte@gnome.org>
+ *          Carl D. Worth <cworth@cworth.org>
+ */
+
+#include "config.h"
+
+#include "gsksplineprivate.h"
+
+#include <math.h>
+
+/* Spline deviation from the circle in radius would be given by:
+
+        error = sqrt (x**2 + y**2) - 1
+
+   A simpler error function to work with is:
+
+        e = x**2 + y**2 - 1
+
+   From "Good approximation of circles by curvature-continuous Bezier
+   curves", Tor Dokken and Morten Daehlen, Computer Aided Geometric
+   Design 8 (1990) 22-41, we learn:
+
+        abs (max(e)) = 4/27 * sin**6(angle/4) / cos**2(angle/4)
+
+   and
+        abs (error) =~ 1/2 * e
+
+   Of course, this error value applies only for the particular spline
+   approximation that is used in _cairo_gstate_arc_segment.
+*/
+static float
+arc_error_normalized (float angle)
+{
+  return 2.0/27.0 * pow (sin (angle / 4), 6) / pow (cos (angle / 4), 2);
+}
+
+static float
+arc_max_angle_for_tolerance_normalized (float tolerance)
+{
+  float angle, error;
+  guint i;
+
+  /* Use table lookup to reduce search time in most cases. */
+  struct {
+    float angle;
+    float error;
+  } table[] = {
+    { G_PI / 1.0,   0.0185185185185185036127 },
+    { G_PI / 2.0,   0.000272567143730179811158 },
+    { G_PI / 3.0,   2.38647043651461047433e-05 },
+    { G_PI / 4.0,   4.2455377443222443279e-06 },
+    { G_PI / 5.0,   1.11281001494389081528e-06 },
+    { G_PI / 6.0,   3.72662000942734705475e-07 },
+    { G_PI / 7.0,   1.47783685574284411325e-07 },
+    { G_PI / 8.0,   6.63240432022601149057e-08 },
+    { G_PI / 9.0,   3.2715520137536980553e-08 },
+    { G_PI / 10.0,  1.73863223499021216974e-08 },
+    { G_PI / 11.0,  9.81410988043554039085e-09 },
+  };
+
+  for (i = 0; i < G_N_ELEMENTS (table); i++)
+    {
+      if (table[i].error < tolerance)
+        return table[i].angle;
+    }
+
+  i++;
+  do {
+    angle = G_PI / i++;
+    error = arc_error_normalized (angle);
+  } while (error > tolerance);
+
+  return angle;
+}
+
+static guint
+arc_segments_needed (float angle,
+                     float radius,
+                     float tolerance)
+{
+  float max_angle;
+
+  /* the error is amplified by at most the length of the
+   * major axis of the circle; see cairo-pen.c for a more detailed analysis
+   * of this. */
+  max_angle = arc_max_angle_for_tolerance_normalized (tolerance / radius);
+
+  return ceil (fabs (angle) / max_angle);
+}
+
+/* We want to draw a single spline approximating a circular arc radius
+   R from angle A to angle B. Since we want a symmetric spline that
+   matches the endpoints of the arc in position and slope, we know
+   that the spline control points must be:
+
+        (R * cos(A), R * sin(A))
+        (R * cos(A) - h * sin(A), R * sin(A) + h * cos (A))
+        (R * cos(B) + h * sin(B), R * sin(B) - h * cos (B))
+        (R * cos(B), R * sin(B))
+
+   for some value of h.
+
+   "Approximation of circular arcs by cubic polynomials", Michael
+   Goldapp, Computer Aided Geometric Design 8 (1991) 227-238, provides
+   various values of h along with error analysis for each.
+
+   From that paper, a very practical value of h is:
+
+        h = 4/3 * R * tan(angle/4)
+
+   This value does not give the spline with minimal error, but it does
+   provide a very good approximation, (6th-order convergence), and the
+   error expression is quite simple, (see the comment for
+   _arc_error_normalized).
+*/
+static gboolean
+gsk_spline_decompose_arc_segment (const graphene_point_t *center,
+                                  float                   radius,
+                                  float                   angle_A,
+                                  float                   angle_B,
+                                  GskSplineAddCurveFunc   curve_func,
+                                  gpointer                user_data)
+{
+  float r_sin_A, r_cos_A;
+  float r_sin_B, r_cos_B;
+  float h;
+
+  r_sin_A = radius * sin (angle_A);
+  r_cos_A = radius * cos (angle_A);
+  r_sin_B = radius * sin (angle_B);
+  r_cos_B = radius * cos (angle_B);
+
+  h = 4.0/3.0 * tan ((angle_B - angle_A) / 4.0);
+
+  return curve_func ((graphene_point_t[4]) {
+                       GRAPHENE_POINT_INIT (
+                         center->x + r_cos_A,
+                         center->y + r_sin_A
+                       ),
+                       GRAPHENE_POINT_INIT (
+                         center->x + r_cos_A - h * r_sin_A,
+                         center->y + r_sin_A + h * r_cos_A
+                       ),
+                       GRAPHENE_POINT_INIT (
+                         center->x + r_cos_B + h * r_sin_B,
+                         center->y + r_sin_B - h * r_cos_B
+                       ),
+                       GRAPHENE_POINT_INIT (
+                         center->x + r_cos_B,
+                         center->y + r_sin_B
+                       )
+                     },
+                     user_data);
+}
+
+gboolean
+gsk_spline_decompose_arc (const graphene_point_t *center,
+                          float                   radius,
+                          float                   tolerance,
+                          float                   start_angle,
+                          float                   end_angle,
+                          GskSplineAddCurveFunc   curve_func,
+                          gpointer                user_data)
+{
+  float step = start_angle - end_angle;
+  guint i, n_segments;
+
+  /* Recurse if drawing arc larger than pi */
+  if (ABS (step) > G_PI)
+    {
+      float mid_angle = (start_angle + end_angle) / 2.0;
+
+      return gsk_spline_decompose_arc (center, radius, tolerance, start_angle, mid_angle, curve_func, user_data)
+          && gsk_spline_decompose_arc (center, radius, tolerance, mid_angle, end_angle, curve_func, user_data);
+    }
+  else if (ABS (step) < tolerance)
+    {
+      return gsk_spline_decompose_arc_segment (center, radius, start_angle, end_angle, curve_func, user_data);
+    }
+
+  n_segments = arc_segments_needed (ABS (step), radius, tolerance);
+  step = (end_angle - start_angle) / n_segments;
+
+  for (i = 0; i < n_segments - 1; i++, start_angle += step)
+    {
+      if (!gsk_spline_decompose_arc_segment (center, radius, start_angle, start_angle + step, curve_func, user_data))
+        return FALSE;
+    }
+  return gsk_spline_decompose_arc_segment (center, radius, start_angle, end_angle, curve_func, user_data);
+}
+

gsk/gsksplineprivate.h

@@ -0,0 +1,41 @@
+/*
+ * Copyright © 2020 Benjamin Otte
+ *
+ * This library is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU Lesser General Public
+ * License as published by the Free Software Foundation; either
+ * version 2.1 of the License, or (at your option) any later version.
+ *
+ * This library is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+ * Lesser General Public License for more details.
+ *
+ * You should have received a copy of the GNU Lesser General Public
+ * License along with this library. If not, see <http://www.gnu.org/licenses/>.
+ *
+ * Authors: Benjamin Otte <otte@gnome.org>
+ */
+
+
+#ifndef __GSK_SPLINE_PRIVATE_H__
+#define __GSK_SPLINE_PRIVATE_H__
+
+#include "gskpath.h"
+
+G_BEGIN_DECLS
+
+typedef gboolean (* GskSplineAddCurveFunc) (const graphene_point_t curve[4],
+                                            gpointer               user_data);
+gboolean                gsk_spline_decompose_arc                (const graphene_point_t *center,
+                                                                 float                   radius,
+                                                                 float                   tolerance,
+                                                                 float                   start_angle,
+                                                                 float                   end_angle,
+                                                                 GskSplineAddCurveFunc   curve_func,
+                                                                 gpointer                user_data);
+
+G_END_DECLS
+
+#endif /* __GSK_SPLINE_PRIVATE_H__ */
+

gsk/gsktypes.h

@@ -25,6 +25,10 @@
 #include <gdk/gdk.h>
 #include <gsk/gskenums.h>
 
+typedef struct _GskPath                 GskPath;
+typedef struct _GskPathBuilder          GskPathBuilder;
+typedef struct _GskPathMeasure          GskPathMeasure;
+typedef struct _GskPathPoint            GskPathPoint;
 typedef struct _GskRenderer             GskRenderer;
 typedef struct _GskTransform            GskTransform;
 

gsk/meson.build

@@ -20,11 +20,14 @@ gsk_private_gl_shaders = [
   'gl/resources/custom.glsl',
   'gl/resources/filled_border.glsl',
   'gl/resources/mask.glsl',
+  'gl/resources/glyphy.atlas.glsl',
+  'gl/resources/glyphy.fs.glsl',
+  'gl/resources/glyphy.vs.glsl',
 ]
 
 gsk_public_sources = files([
-  'gskdiff.c',
   'gskcairorenderer.c',
+  'gskdiff.c',
   'gskglshader.c',
   'gskrenderer.c',
   'gskrendernode.c',
@@ -37,15 +40,25 @@ gsk_public_sources = files([
 
 gsk_private_sources = files([
   'gskcairoblur.c',
+  'gskcontour.c',
+  'gskcurve.c',
+  'gskcurveintersect.c',
   'gskdebug.c',
+  'gskpath.c',
+  'gskpathbuilder.c',
+  'gskpathmeasure.c',
+  'gskpathops.c',
+  'gskpathpoint.c',
   'gskprivate.c',
   'gskprofiler.c',
+  'gskspline.c',
   'gl/gskglattachmentstate.c',
   'gl/gskglbuffer.c',
   'gl/gskglcommandqueue.c',
   'gl/gskglcompiler.c',
   'gl/gskgldriver.c',
   'gl/gskglglyphlibrary.c',
+  'gl/gskglglyphylibrary.c',
   'gl/gskgliconlibrary.c',
   'gl/gskglprogram.c',
   'gl/gskglrenderjob.c',
@@ -185,6 +198,7 @@ gsk_deps = [
   cairo_csi_dep,
   pixbuf_dep,
   libgdk_dep,
+  libglyphy_dep
 ]
 
 libgsk_f16c = static_library('gsk_f16c',

gtk/meson.build

@@ -1015,6 +1015,7 @@ gtk_deps = [
   epoxy_dep,
   libm,
   graphene_dep,
+  libglyphy_dep,
 ]
 
 if x11_enabled

meson.build

@@ -14,7 +14,7 @@ project('gtk', 'c',
 glib_req           = '>= 2.76.0'
 introspection_req  = '>= 1.76.0' # keep this in sync with glib
 pango_req          = '>= 1.50.0' # keep this in sync with .gitlab-ci/test-msys.sh
-harfbuzz_req       = '>= 2.6.0'
+harfbuzz_req       = '>= 4.0.0'
 fribidi_req        = '>= 1.0.6'
 cairo_req          = '>= 1.14.0'
 gdk_pixbuf_req     = '>= 2.30.0'
@@ -25,6 +25,7 @@ epoxy_req          = '>= 1.4'
 cloudproviders_req = '>= 0.3.1'
 xkbcommon_req      = '>= 0.2.0'
 sysprof_req        = '>= 3.38.0'
+libglyphy_req      = '>= 0.2.0'
 
 fs = import('fs')
 gnome = import('gnome')
@@ -378,6 +379,9 @@ fribidi_dep    = dependency('fribidi', version: fribidi_req,
                             default_options: ['docs=false'])
 harfbuzz_dep   = dependency('harfbuzz', version: harfbuzz_req,
                             default_options: ['coretext=enabled'])
+libglyphy_dep  = dependency('glyphy', version: libglyphy_req,
+                             default_options: ['default_library=static', 'demo=disabled'],
+                            fallback : ['glyphy', 'libglyphy_dep'])
 
 # Require PangoFT2 if on X11 or wayland
 pangoft_dep    = dependency('pangoft2', version: pango_req,

subprojects/glyphy.wrap

@@ -0,0 +1,6 @@
+[wrap-git]
+directory=glyphy
+url=https://github.com/behdad/glyphy.git
+revision=master
+depth=1
+

tests/bigfont.c

@@ -0,0 +1,123 @@
+#include <gtk/gtk.h>
+
+#define DEMO_TYPE_WIDGET (demo_widget_get_type ())
+G_DECLARE_FINAL_TYPE (DemoWidget, demo_widget, DEMO, WIDGET, GtkWidget)
+
+struct _DemoWidget
+{
+  GtkWidget parent_instance;
+};
+
+struct _DemoWidgetClass
+{
+  GtkWidgetClass parent_class;
+};
+
+G_DEFINE_TYPE (DemoWidget, demo_widget, GTK_TYPE_WIDGET)
+
+static void
+demo_widget_init (DemoWidget *self)
+{
+}
+
+static void
+demo_widget_snapshot (GtkWidget   *widget,
+                      GtkSnapshot *snapshot)
+{
+  DemoWidget *self = DEMO_WIDGET (widget);
+  PangoLayout *layout;
+  int width, height;
+  int pwidth, pheight;
+  PangoFontDescription *desc;
+  int size;
+  double scale;
+  int x, y;
+  GdkRGBA color;
+
+  width = gtk_widget_get_width (widget);
+  height = gtk_widget_get_height (widget);
+
+  gtk_widget_get_color (widget, &color);
+
+  layout = gtk_widget_create_pango_layout (GTK_WIDGET (self), "Best Aa");
+
+  pango_layout_get_pixel_size (layout, &pwidth, &pheight);
+  desc = pango_font_description_copy_static (pango_context_get_font_description (pango_layout_get_context (layout)));
+  size = pango_font_description_get_size (desc);
+
+  scale = MIN (width / (double)pwidth, height / (double)pheight);
+
+  pango_font_description_set_size (desc, size * scale * 0.5);
+  pango_layout_set_font_description (layout, desc);
+  pango_font_description_free (desc);
+
+  pango_layout_get_pixel_size (layout, &pwidth, &pheight);
+
+  x = floor ((width - pwidth) / 2);
+  y = floor ((height - pheight) / 2);
+
+  gtk_snapshot_save (snapshot);
+
+  gtk_snapshot_translate (snapshot, &GRAPHENE_POINT_INIT (x, y));
+
+  gtk_snapshot_append_layout (snapshot, layout, &color);
+
+  gtk_snapshot_restore (snapshot);
+
+  g_object_unref (layout);
+}
+
+static void
+demo_widget_dispose (GObject *object)
+{
+  G_OBJECT_CLASS (demo_widget_parent_class)->dispose (object);
+}
+
+static void
+demo_widget_class_init (DemoWidgetClass *class)
+{
+  GObjectClass *object_class = G_OBJECT_CLASS (class);
+  GtkWidgetClass *widget_class = GTK_WIDGET_CLASS (class);
+
+  object_class->dispose = demo_widget_dispose;
+
+  widget_class->snapshot = demo_widget_snapshot;
+}
+
+static GtkWidget *
+demo_widget_new (void)
+{
+  return g_object_new (DEMO_TYPE_WIDGET, NULL);
+}
+
+static const char css[] =
+  "* {\n"
+  "  font-family: Cantarell;\n"
+  "  font-weight: 520;\n"
+  "}";
+
+int
+main (int argc, char *argv[])
+{
+  GtkCssProvider *style;
+  GtkWidget *window;
+
+  gtk_init ();
+
+  style = gtk_css_provider_new ();
+  gtk_css_provider_load_from_string (style, css);
+  gtk_style_context_add_provider_for_display (gdk_display_get_default (),
+                                              GTK_STYLE_PROVIDER (style),
+                                              800);
+
+  window = gtk_window_new ();
+
+  gtk_window_set_child (GTK_WINDOW (window), demo_widget_new ());
+
+  gtk_window_present (GTK_WINDOW (window));
+
+  while (g_list_model_get_n_items (gtk_window_get_toplevels ()) > 0)
+    g_main_context_iteration (NULL, TRUE);
+
+  return 0;
+}

tests/meson.build

@@ -1,5 +1,7 @@
 gtk_tests = [
   # testname, optional extra sources
+  ['movingtext'],
+  ['bigfont'],
   ['testsections'],
   ['testfilelauncher'],
   ['input'],

tests/movingtext.c

@@ -0,0 +1,210 @@
+#include <gtk/gtk.h>
+
+#define DEMO_TYPE_WIDGET (demo_widget_get_type ())
+G_DECLARE_FINAL_TYPE (DemoWidget, demo_widget, DEMO, WIDGET, GtkWidget)
+
+struct _DemoWidget
+{
+  GtkWidget parent_instance;
+
+  guint tick_cb;
+  guint64 start_time;
+  guint64 stop_time;
+
+  char *text;
+
+  float angle;
+  float size;
+};
+
+struct _DemoWidgetClass
+{
+  GtkWidgetClass parent_class;
+};
+
+G_DEFINE_TYPE (DemoWidget, demo_widget, GTK_TYPE_WIDGET)
+
+static gboolean
+tick_cb (GtkWidget     *widget,
+         GdkFrameClock *frame_clock,
+         gpointer       user_data)
+{
+  DemoWidget *self = DEMO_WIDGET (widget);
+  guint64 now;
+
+  now = gdk_frame_clock_get_frame_time (frame_clock);
+
+  if (self->start_time == 0)
+    self->start_time = now;
+
+  self->angle = 360 * (now - self->start_time) / (double)(G_TIME_SPAN_SECOND * 10);
+  self->size = 150 + 130 * sin (2 * G_PI * (now - self->start_time) / (double)(G_TIME_SPAN_SECOND * 5));
+
+  gtk_widget_queue_draw (widget);
+
+  return G_SOURCE_CONTINUE;
+}
+
+static gboolean
+pressed_cb (GtkEventController *controller,
+            guint               keyval,
+            guint               keycode,
+            GdkModifierType     state,
+            gpointer            data)
+{
+  DemoWidget *self = (DemoWidget *)gtk_event_controller_get_widget (controller);
+
+  if (keyval == GDK_KEY_space)
+    {
+      GdkFrameClock *frame_clock;
+      guint64 now;
+
+      frame_clock = gtk_widget_get_frame_clock (GTK_WIDGET (self));
+      now = gdk_frame_clock_get_frame_time (frame_clock);
+
+      if (self->tick_cb)
+        {
+          gtk_widget_remove_tick_callback (GTK_WIDGET (self), self->tick_cb);
+          self->tick_cb = 0;
+          self->stop_time = now;
+        }
+      else
+        {
+          self->start_time += now - self->stop_time;
+          self->tick_cb = gtk_widget_add_tick_callback (GTK_WIDGET (self), tick_cb, NULL, NULL);
+        }
+    }
+
+  return TRUE;
+}
+
+static void
+demo_widget_init (DemoWidget *self)
+{
+  GtkEventController *controller;
+
+  self->start_time = 0;
+  self->tick_cb = gtk_widget_add_tick_callback (GTK_WIDGET (self), tick_cb, NULL, NULL);
+
+  controller = gtk_event_controller_key_new ();
+  g_signal_connect (controller, "key-pressed", G_CALLBACK (pressed_cb), NULL);
+  gtk_widget_add_controller (GTK_WIDGET (self), controller);
+  gtk_widget_set_focusable (GTK_WIDGET (self), TRUE);
+}
+
+static void
+demo_widget_snapshot (GtkWidget   *widget,
+                      GtkSnapshot *snapshot)
+{
+  DemoWidget *self = DEMO_WIDGET (widget);
+  PangoLayout *layout;
+  int width, height;
+  int pwidth, pheight;
+  PangoFontDescription *desc;
+  GdkRGBA color;
+
+  width = gtk_widget_get_width (widget);
+  height = gtk_widget_get_height (widget);
+
+  gtk_widget_get_color (widget, &color);
+
+  layout = gtk_widget_create_pango_layout (GTK_WIDGET (self), self->text);
+  desc = pango_font_description_new ();
+  pango_font_description_set_family (desc, "Cantarell");
+  pango_font_description_set_weight (desc, 520);
+  pango_font_description_set_size (desc, self->size * PANGO_SCALE);
+  pango_layout_set_font_description (layout, desc);
+  pango_font_description_free (desc);
+  pango_layout_get_pixel_size (layout, &pwidth, &pheight);
+
+  gtk_snapshot_save (snapshot);
+
+  gtk_snapshot_translate (snapshot, &GRAPHENE_POINT_INIT (0.5 * width, 0.5 * height));
+  gtk_snapshot_rotate (snapshot, self->angle);
+  gtk_snapshot_translate (snapshot, &GRAPHENE_POINT_INIT (- 0.5 * pwidth, - 0.5 * pheight));
+
+  gtk_snapshot_append_layout (snapshot, layout, &color);
+
+  gtk_snapshot_restore (snapshot);
+
+  g_object_unref (layout);
+}
+
+static void
+demo_widget_dispose (GObject *object)
+{
+  DemoWidget *self = DEMO_WIDGET (object);
+
+  g_free (self->text);
+
+  G_OBJECT_CLASS (demo_widget_parent_class)->dispose (object);
+}
+
+static void
+demo_widget_class_init (DemoWidgetClass *class)
+{
+  GObjectClass *object_class = G_OBJECT_CLASS (class);
+  GtkWidgetClass *widget_class = GTK_WIDGET_CLASS (class);
+
+  object_class->dispose = demo_widget_dispose;
+
+  widget_class->snapshot = demo_widget_snapshot;
+}
+
+static GtkWidget *
+demo_widget_new (const char *text,
+                 gsize       length)
+{
+  DemoWidget *demo;
+
+  demo = g_object_new (DEMO_TYPE_WIDGET, NULL);
+
+  demo->text = g_strndup (text, length);
+
+  return GTK_WIDGET (demo);
+}
+
+int
+main (int argc, char *argv[])
+{
+  GtkWidget *window;
+  GtkWidget *demo;
+  char *text = NULL;
+  gsize length;
+
+  gtk_init ();
+
+  window = gtk_window_new ();
+
+  if (argc > 1)
+    {
+      GError *error = NULL;
+
+      if (!g_file_get_contents (argv[1], &text, &length, &error))
+        {
+          g_warning ("%s", error->message);
+          g_error_free (error);
+          text = NULL;
+        }
+    }
+
+  if (!text)
+    {
+      text = g_strdup ("Best Aa");
+      length = strlen (text);
+    }
+
+  demo = demo_widget_new (text, length);
+  gtk_window_set_child (GTK_WINDOW (window), demo);
+
+  g_free (text);
+
+  gtk_window_present (GTK_WINDOW (window));
+
+  gtk_widget_grab_focus (demo);
+
+  while (g_list_model_get_n_items (gtk_window_get_toplevels ()) > 0)
+    g_main_context_iteration (NULL, TRUE);
+
+  return 0;
+}

testsuite/gsk/curve-special-cases.c

@@ -0,0 +1,164 @@
+/*
+ * Copyright © 2020 Benjamin Otte
+ *
+ * This library is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU Lesser General Public
+ * License as published by the Free Software Foundation; either
+ * version 2.1 of the License, or (at your option) any later version.
+ *
+ * This library is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+ * Lesser General Public License for more details.
+ *
+ * You should have received a copy of the GNU Lesser General Public
+ * License along with this library. If not, see <http://www.gnu.org/licenses/>.
+ *
+ * Authors: Benjamin Otte <otte@gnome.org>
+ */
+
+#include <gtk/gtk.h>
+
+#include "gsk/gskcurveprivate.h"
+
+static gboolean
+measure_segment (const graphene_point_t *from,
+                 const graphene_point_t *to,
+                 float                   from_t,
+                 float                   to_t,
+                 GskCurveLineReason      reason,
+                 gpointer                data)
+{
+  float *length = data;
+
+  *length += graphene_point_distance (from, to, NULL, NULL);
+
+  return TRUE;
+}
+
+static float
+measure_length (const GskCurve *curve)
+{
+  float result = 0;
+
+  gsk_curve_decompose (curve, 0.5, measure_segment, &result);
+
+  return result;
+}
+
+/* This is a pretty nasty conic that makes it obvious that split()
+ * does not respect the progress values, so split() twice  with
+ * scaled factor won't work.
+ */
+static void
+test_conic_segment (void)
+{
+  GskCurve c, s, e, m;
+  graphene_point_t pts[4] = {
+    GRAPHENE_POINT_INIT (-1856.131591796875, 46.217609405517578125),
+    GRAPHENE_POINT_INIT (-1555.9866943359375, 966.0810546875),
+    GRAPHENE_POINT_INIT (98.94945526123046875, 0),
+    GRAPHENE_POINT_INIT (-1471.33154296875, 526.701171875)
+  };
+  float start = 0.02222645096480846405029296875;
+  float end = 0.982032716274261474609375;
+
+  gsk_curve_init (&c, gsk_pathop_encode (GSK_PATH_CONIC, pts));
+
+  gsk_curve_split (&c, start, &s, NULL);
+  gsk_curve_segment (&c, start, end, &m);
+  gsk_curve_split (&c, end, NULL, &e);
+
+  g_assert_cmpfloat_with_epsilon (measure_length (&c), measure_length (&s) + measure_length (&m) + measure_length (&e), 0.03125);
+}
+
+static void
+test_curve_tangents (void)
+{
+  GskCurve c;
+  graphene_point_t p[4];
+  graphene_vec2_t t;
+
+  graphene_point_init (&p[0], 0, 0);
+  graphene_point_init (&p[1], 100, 0);
+  gsk_curve_init (&c, gsk_pathop_encode (GSK_PATH_LINE, p));
+
+  gsk_curve_get_start_tangent (&c, &t);
+  g_assert_true (graphene_vec2_near (&t, graphene_vec2_x_axis (), 0.0001));
+  gsk_curve_get_end_tangent (&c, &t);
+  g_assert_true (graphene_vec2_near (&t, graphene_vec2_x_axis (), 0.0001));
+
+  graphene_point_init (&p[0], 0, 0);
+  graphene_point_init (&p[1], 0, 100);
+  gsk_curve_init (&c, gsk_pathop_encode (GSK_PATH_LINE, p));
+
+  gsk_curve_get_start_tangent (&c, &t);
+  g_assert_true (graphene_vec2_near (&t, graphene_vec2_y_axis (), 0.0001));
+  gsk_curve_get_end_tangent (&c, &t);
+  g_assert_true (graphene_vec2_near (&t, graphene_vec2_y_axis (), 0.0001));
+
+  graphene_point_init (&p[0], 0, 0);
+  graphene_point_init (&p[1], 100, 0);
+  p[2] = GRAPHENE_POINT_INIT (g_test_rand_double_range (0, 20), 0);
+  graphene_point_init (&p[3], 100, 100);
+  gsk_curve_init (&c, gsk_pathop_encode (GSK_PATH_CONIC, p));
+
+  gsk_curve_get_start_tangent (&c, &t);
+  g_assert_true (graphene_vec2_near (&t, graphene_vec2_x_axis (), 0.0001));
+  gsk_curve_get_end_tangent (&c, &t);
+  g_assert_true (graphene_vec2_near (&t, graphene_vec2_y_axis (), 0.0001));
+
+  graphene_point_init (&p[0], 0, 0);
+  graphene_point_init (&p[1], 50, 0);
+  graphene_point_init (&p[2], 100, 50);
+  graphene_point_init (&p[3], 100, 100);
+  gsk_curve_init (&c, gsk_pathop_encode (GSK_PATH_CUBIC, p));
+
+  gsk_curve_get_start_tangent (&c, &t);
+  g_assert_true (graphene_vec2_near (&t, graphene_vec2_x_axis (), 0.0001));
+  gsk_curve_get_end_tangent (&c, &t);
+  g_assert_true (graphene_vec2_near (&t, graphene_vec2_y_axis (), 0.0001));
+}
+
+static void
+test_curve_degenerate_tangents (void)
+{
+  GskCurve c;
+  graphene_point_t p[4];
+  graphene_vec2_t t;
+
+  graphene_point_init (&p[0], 0, 0);
+  graphene_point_init (&p[1], 0, 0);
+  graphene_point_init (&p[2], 100, 0);
+  graphene_point_init (&p[3], 100, 0);
+  gsk_curve_init (&c, gsk_pathop_encode (GSK_PATH_CUBIC, p));
+
+  gsk_curve_get_start_tangent (&c, &t);
+  g_assert_true (graphene_vec2_near (&t, graphene_vec2_x_axis (), 0.0001));
+  gsk_curve_get_end_tangent (&c, &t);
+  g_assert_true (graphene_vec2_near (&t, graphene_vec2_x_axis (), 0.0001));
+
+  graphene_point_init (&p[0], 0, 0);
+  graphene_point_init (&p[1], 50, 0);
+  graphene_point_init (&p[2], 50, 0);
+  graphene_point_init (&p[3], 100, 0);
+  gsk_curve_init (&c, gsk_pathop_encode (GSK_PATH_CUBIC, p));
+
+  gsk_curve_get_start_tangent (&c, &t);
+  g_assert_true (graphene_vec2_near (&t, graphene_vec2_x_axis (), 0.0001));
+  gsk_curve_get_end_tangent (&c, &t);
+  g_assert_true (graphene_vec2_near (&t, graphene_vec2_x_axis (), 0.0001));
+}
+
+int
+main (int   argc,
+      char *argv[])
+{
+  gtk_test_init (&argc, &argv, NULL);
+
+  g_test_add_func ("/curve/special/conic-segment", test_conic_segment);
+  g_test_add_func ("/curve/special/tangents", test_curve_tangents);
+  g_test_add_func ("/curve/special/degenerate-tangents", test_curve_degenerate_tangents);
+
+  return g_test_run ();
+}

testsuite/gsk/curve.c

@@ -0,0 +1,423 @@
+#include <gtk/gtk.h>
+#include "gsk/gskcurveprivate.h"
+#include "gsk/gskpath.h"
+#include "gsk/gskpathmeasure.h"
+
+static void
+init_random_point (graphene_point_t *p)
+{
+  p->x = g_test_rand_double_range (0, 1000);
+  p->y = g_test_rand_double_range (0, 1000);
+}
+
+static float
+random_weight (void)
+{
+  if (g_test_rand_bit ())
+    return g_test_rand_double_range (1, 20);
+  else
+    return 1.0 / g_test_rand_double_range (1, 20);
+}
+
+static void
+init_random_curve_with_op (GskCurve         *curve,
+                           GskPathOperation  min_op,
+                           GskPathOperation  max_op)
+{
+  switch (g_test_rand_int_range (min_op, max_op + 1))
+    {
+    case GSK_PATH_LINE:
+      {
+        graphene_point_t p[2];
+
+        init_random_point (&p[0]);
+        init_random_point (&p[1]);
+        gsk_curve_init (curve, gsk_pathop_encode (GSK_PATH_LINE, p));
+      }
+      break;
+
+    case GSK_PATH_QUAD:
+      {
+        graphene_point_t p[3];
+
+        init_random_point (&p[0]);
+        init_random_point (&p[1]);
+        init_random_point (&p[2]);
+        gsk_curve_init (curve, gsk_pathop_encode (GSK_PATH_QUAD, p));
+      }
+    break;
+
+    case GSK_PATH_CUBIC:
+      {
+        graphene_point_t p[4];
+
+        init_random_point (&p[0]);
+        init_random_point (&p[1]);
+        init_random_point (&p[2]);
+        init_random_point (&p[3]);
+        gsk_curve_init (curve, gsk_pathop_encode (GSK_PATH_CUBIC, p));
+      }
+    break;
+
+    case GSK_PATH_CONIC:
+      {
+        graphene_point_t p[4];
+
+        init_random_point (&p[0]);
+        init_random_point (&p[1]);
+        p[2] = GRAPHENE_POINT_INIT (random_weight(), 0);
+        init_random_point (&p[3]);
+        gsk_curve_init (curve, gsk_pathop_encode (GSK_PATH_CONIC, p));
+      }
+      break;
+
+    default:
+      g_assert_not_reached ();
+    }
+}
+
+static void
+init_random_curve (GskCurve *curve)
+{
+  init_random_curve_with_op (curve, GSK_PATH_LINE, GSK_PATH_CONIC);
+}
+
+static void
+test_curve_tangents (void)
+{
+  for (int i = 0; i < 100; i++)
+    {
+      GskCurve c;
+      graphene_vec2_t vec, exact;
+
+      init_random_curve (&c);
+
+      gsk_curve_get_tangent (&c, 0, &vec);
+      g_assert_cmpfloat_with_epsilon (graphene_vec2_length (&vec), 1.0f, 0.00001);
+      gsk_curve_get_start_tangent (&c, &exact);
+      g_assert_cmpfloat_with_epsilon (graphene_vec2_length (&exact), 1.0f, 0.00001);
+      g_assert_true (graphene_vec2_near (&vec, &exact, 0.05));
+
+      gsk_curve_get_tangent (&c, 1, &vec);
+      g_assert_cmpfloat_with_epsilon (graphene_vec2_length (&vec), 1.0f, 0.00001);
+      gsk_curve_get_end_tangent (&c, &exact);
+      g_assert_cmpfloat_with_epsilon (graphene_vec2_length (&exact), 1.0f, 0.00001);
+      g_assert_true (graphene_vec2_near (&vec, &exact, 0.05));
+    }
+}
+
+static void
+test_curve_points (void)
+{
+  for (int i = 0; i < 100; i++)
+    {
+      GskCurve c;
+      graphene_point_t p;
+
+      init_random_curve (&c);
+
+      /* We can assert equality here because evaluating the polynomials with 0
+       * has no effect on accuracy.
+       */
+      gsk_curve_get_point (&c, 0, &p);
+      g_assert_true (graphene_point_equal (gsk_curve_get_start_point (&c), &p));
+      /* But here we evaluate the polynomials with 1 which gives the highest possible
+       * accuracy error. So we'll just be generous here.
+       */
+      gsk_curve_get_point (&c, 1, &p);
+      g_assert_true (graphene_point_near (gsk_curve_get_end_point (&c), &p, 0.05));
+    }
+}
+
+/* at this point the subdivision stops and the decomposer
+ * violates tolerance rules
+ */
+#define MIN_PROGRESS (1/1024.f)
+
+typedef struct
+{
+  graphene_point_t p;
+  float t;
+} PointOnLine;
+
+static gboolean
+add_line_to_array (const graphene_point_t *from,
+                   const graphene_point_t *to,
+                   float                   from_progress,
+                   float                   to_progress,
+                   GskCurveLineReason      reason,
+                   gpointer                user_data)
+{
+  GArray *array = user_data;
+  PointOnLine *last = &g_array_index (array, PointOnLine, array->len - 1);
+
+  g_assert_true (array->len > 0);
+  g_assert_cmpfloat (from_progress, >=, 0.0f);
+  g_assert_cmpfloat (from_progress, <, to_progress);
+  g_assert_cmpfloat (to_progress, <=, 1.0f);
+
+  g_assert_true (graphene_point_equal (&last->p, from));
+  g_assert_cmpfloat (last->t, ==, from_progress);
+
+  g_array_append_vals (array, (PointOnLine[1]) { { *to, to_progress } }, 1);
+
+  return TRUE;
+}
+
+static void
+test_curve_decompose (void)
+{
+  static const float tolerance = 0.5;
+
+  for (int i = 0; i < 100; i++)
+    {
+      GArray *array;
+      GskCurve c;
+
+      init_random_curve (&c);
+
+      array = g_array_new (FALSE, FALSE, sizeof (PointOnLine));
+      g_array_append_vals (array, (PointOnLine[1]) { { *gsk_curve_get_start_point (&c), 0.f } }, 1);
+
+      g_assert_true (gsk_curve_decompose (&c, tolerance, add_line_to_array, array));
+
+      g_assert_cmpint (array->len, >=, 2); /* We at least got a line to the end */
+      g_assert_cmpfloat (g_array_index (array, PointOnLine, array->len - 1).t, ==, 1.0);
+
+      for (int j = 0; j < array->len; j++)
+        {
+          PointOnLine *pol = &g_array_index (array, PointOnLine, j);
+          graphene_point_t p;
+
+          /* Check that the points we got are actually on the line */
+          gsk_curve_get_point (&c, pol->t, &p);
+          g_assert_true (graphene_point_near (&pol->p, &p, 0.05));
+
+          /* Check that the mid point is not further than the tolerance */
+          if (j > 0)
+            {
+              PointOnLine *last = &g_array_index (array, PointOnLine, j - 1);
+              graphene_point_t mid;
+
+              if (pol->t - last->t > MIN_PROGRESS)
+                {
+                  graphene_point_interpolate (&last->p, &pol->p, 0.5, &mid);
+                  gsk_curve_get_point (&c, (pol->t + last->t) / 2, &p);
+                  /* The decomposer does this cheaper Manhattan distance test,
+                   * so graphene_point_near() does not work */
+                  g_assert_cmpfloat (fabs (mid.x - p.x), <=, tolerance);
+                  g_assert_cmpfloat (fabs (mid.y - p.y), <=, tolerance);
+                }
+            }
+        }
+
+      g_array_unref (array);
+    }
+}
+
+static gboolean
+add_curve_to_array (GskPathOperation        op,
+                    const graphene_point_t *pts,
+                    gsize                   n_pts,
+                    float                   weight,
+                    gpointer                user_data)
+{
+  GArray *array = user_data;
+  GskCurve c;
+
+  gsk_curve_init_foreach (&c, op, pts, n_pts, weight);
+  g_array_append_val (array, c);
+
+  return TRUE;
+}
+
+static void
+test_curve_decompose_conic (void)
+{
+  g_test_skip ("No good error bounds for decomposing conics");
+  return;
+
+  for (int i = 0; i < 100; i++)
+    {
+      GArray *array;
+      GskCurve c;
+      GskPathBuilder *builder;
+      GskPath *path;
+      GskPathMeasure *measure;
+      const graphene_point_t *s;
+
+      init_random_curve_with_op (&c, GSK_PATH_CONIC, GSK_PATH_CONIC);
+
+      builder = gsk_path_builder_new ();
+
+      s = gsk_curve_get_start_point (&c);
+      gsk_path_builder_move_to (builder, s->x, s->y);
+      gsk_curve_builder_to (&c, builder);
+      path = gsk_path_builder_free_to_path (builder);
+      measure = gsk_path_measure_new_with_tolerance (path, 0.1);
+
+      array = g_array_new (FALSE, FALSE, sizeof (GskCurve));
+
+      g_assert_true (gsk_curve_decompose_curve (&c, GSK_PATH_FOREACH_ALLOW_CUBIC, 0.1, add_curve_to_array, array));
+
+      g_assert_cmpint (array->len, >=, 1);
+
+      for (int j = 0; j < array->len; j++)
+        {
+          GskCurve *c2 = &g_array_index (array, GskCurve, j);
+
+          g_assert_true (c2->op == GSK_PATH_CUBIC);
+
+          /* Check that the curves we got are approximating the conic */
+          for (int k = 0; k < 11; k++)
+            {
+              GskPathPoint *point;
+              graphene_point_t p, q;
+
+              gsk_curve_get_point (c2, k/10.0, &p);
+              point = gsk_path_measure_get_closest_point (measure, &p, INFINITY);
+              gsk_path_point_get_position (point, &q);
+              g_assert_true (graphene_point_near (&p, &q, 0.5));
+              gsk_path_point_unref (point);
+            }
+        }
+
+      g_array_unref (array);
+
+      gsk_path_measure_unref (measure);
+      gsk_path_unref (path);
+    }
+}
+
+static void
+test_curve_decompose_into (GskPathForeachFlags flags)
+{
+  for (int i = 0; i < 100; i++)
+    {
+      GskCurve c;
+      GskPathBuilder *builder;
+      const graphene_point_t *s;
+      GskPath *path;
+      GArray *array;
+
+      init_random_curve (&c);
+
+      builder = gsk_path_builder_new ();
+
+      s = gsk_curve_get_start_point (&c);
+      gsk_path_builder_move_to (builder, s->x, s->y);
+      gsk_curve_builder_to (&c, builder);
+      path = gsk_path_builder_free_to_path (builder);
+
+      array = g_array_new (FALSE, FALSE, sizeof (GskCurve));
+
+      g_assert_true (gsk_curve_decompose_curve (&c, flags, 0.1, add_curve_to_array, array));
+
+      g_assert_cmpint (array->len, >=, 1);
+
+      for (int j = 0; j < array->len; j++)
+        {
+          GskCurve *c2 = &g_array_index (array, GskCurve, j);
+
+          switch (c2->op)
+            {
+            case GSK_PATH_MOVE:
+            case GSK_PATH_CLOSE:
+            case GSK_PATH_LINE:
+              break;
+            case GSK_PATH_QUAD:
+              g_assert_true (flags & GSK_PATH_FOREACH_ALLOW_QUAD);
+              break;
+            case GSK_PATH_CUBIC:
+              g_assert_true (flags & GSK_PATH_FOREACH_ALLOW_CUBIC);
+              break;
+            case GSK_PATH_CONIC:
+              g_assert_true (flags & GSK_PATH_FOREACH_ALLOW_CONIC);
+              break;
+            default:
+              g_assert_not_reached ();
+            }
+        }
+
+      g_array_unref (array);
+      gsk_path_unref (path);
+    }
+}
+
+static void
+test_curve_decompose_into_line (void)
+{
+  test_curve_decompose_into (0);
+}
+
+static void
+test_curve_decompose_into_quad (void)
+{
+  test_curve_decompose_into (GSK_PATH_FOREACH_ALLOW_QUAD);
+}
+
+static void
+test_curve_decompose_into_cubic (void)
+{
+  test_curve_decompose_into (GSK_PATH_FOREACH_ALLOW_CUBIC);
+}
+
+/* Some sanity checks for splitting curves. */
+static void
+test_curve_split (void)
+{
+  for (int i = 0; i < 100; i++)
+    {
+      GskCurve c;
+      GskCurve c1, c2;
+      graphene_point_t p;
+      graphene_vec2_t t, t1, t2;
+
+      init_random_curve (&c);
+
+      gsk_curve_split (&c, 0.5, &c1, &c2);
+
+      g_assert_true (c1.op == c.op);
+      g_assert_true (c2.op == c.op);
+
+      g_assert_true (graphene_point_near (gsk_curve_get_start_point (&c),
+                                          gsk_curve_get_start_point (&c1), 0.005));
+      g_assert_true (graphene_point_near (gsk_curve_get_end_point (&c1),
+                                          gsk_curve_get_start_point (&c2), 0.005));
+      g_assert_true (graphene_point_near (gsk_curve_get_end_point (&c),
+                                          gsk_curve_get_end_point (&c2), 0.005));
+      gsk_curve_get_point (&c, 0.5, &p);
+      gsk_curve_get_tangent (&c, 0.5, &t);
+      g_assert_true (graphene_point_near (gsk_curve_get_end_point (&c1), &p, 0.005));
+      g_assert_true (graphene_point_near (gsk_curve_get_start_point (&c2), &p, 0.005));
+
+      gsk_curve_get_start_tangent (&c, &t1);
+      gsk_curve_get_start_tangent (&c1, &t2);
+      g_assert_true (graphene_vec2_near (&t1, &t2, 0.005));
+      gsk_curve_get_end_tangent (&c1, &t1);
+      gsk_curve_get_start_tangent (&c2, &t2);
+      g_assert_true (graphene_vec2_near (&t1, &t2, 0.005));
+      g_assert_true (graphene_vec2_near (&t, &t1, 0.005));
+      g_assert_true (graphene_vec2_near (&t, &t2, 0.005));
+      gsk_curve_get_end_tangent (&c, &t1);
+      gsk_curve_get_end_tangent (&c2, &t2);
+      g_assert_true (graphene_vec2_near (&t1, &t2, 0.005));
+    }
+}
+
+int
+main (int argc, char *argv[])
+{
+  (g_test_init) (&argc, &argv, NULL);
+
+  g_test_add_func ("/curve/points", test_curve_points);
+  g_test_add_func ("/curve/tangents", test_curve_tangents);
+  g_test_add_func ("/curve/decompose", test_curve_decompose);
+  g_test_add_func ("/curve/decompose/conic", test_curve_decompose_conic);
+  g_test_add_func ("/curve/decompose/into/line", test_curve_decompose_into_line);
+  g_test_add_func ("/curve/decompose/into/quad", test_curve_decompose_into_quad);
+  g_test_add_func ("/curve/decompose/into/cubic", test_curve_decompose_into_cubic);
+  g_test_add_func ("/curve/split", test_curve_split);
+
+  return g_test_run ();
+}

testsuite/gsk/measure-special-cases.c

@@ -0,0 +1,252 @@
+/*
+ * Copyright © 2020 Benjamin Otte
+ *
+ * This library is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU Lesser General Public
+ * License as published by the Free Software Foundation; either
+ * version 2.1 of the License, or (at your option) any later version.
+ *
+ * This library is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+ * Lesser General Public License for more details.
+ *
+ * You should have received a copy of the GNU Lesser General Public
+ * License along with this library. If not, see <http://www.gnu.org/licenses/>.
+ *
+ * Authors: Benjamin Otte <otte@gnome.org>
+ */
+
+#include <gtk/gtk.h>
+#include <gtk/gtk.h>
+#include "gsk/gskpath.h"
+#include "gsk/gskpathbuilder.h"
+#include "gsk/gskpathmeasure.h"
+#include "gsk/gskpathpoint.h"
+
+static void
+test_bad_split (void)
+{
+  GskPath *path, *path1;
+  GskPathMeasure *measure, *measure1;
+  GskPathBuilder *builder;
+  float split, length, epsilon;
+
+  /* An example that was isolated from the /path/segment test path.c
+   * It shows how uneven parametrization of cubics can lead to bad
+   * lengths reported by the measure.
+   */
+
+  path = gsk_path_parse ("M 0 0 C 2 0 4 0 4 0");
+
+  measure = gsk_path_measure_new (path);
+  split = 2.962588;
+  length = gsk_path_measure_get_length (measure);
+  epsilon = MAX (length / 256, 1.f / 1024);
+
+  builder = gsk_path_builder_new ();
+  gsk_path_builder_add_segment (builder, measure, 0, split);
+  path1 = gsk_path_builder_free_to_path (builder);
+  measure1 = gsk_path_measure_new (path1);
+
+  g_assert_cmpfloat_with_epsilon (split, gsk_path_measure_get_length (measure1), epsilon);
+
+  gsk_path_measure_unref (measure1);
+  gsk_path_unref (path1);
+  gsk_path_measure_unref (measure);
+  gsk_path_unref (path);
+}
+
+static void
+test_bad_in_fill (void)
+{
+  GskPath *path;
+  GskPathMeasure *measure;
+  gboolean inside;
+
+  /* A fat Cantarell W */
+  path = gsk_path_parse ("M -2 694 M 206.1748046875 704 L 390.9371337890625 704 L 551.1888427734375 99.5035400390625 L 473.0489501953125 99.5035400390625 L 649.1048583984375 704 L 828.965087890625 704 L 1028.3077392578125 10 L 857.8111572265625 10 L 710.0489501953125 621.251708984375 L 775.9720458984375 598.426513671875 L 614.5245361328125 14.0489501953125 L 430.2237548828125 14.0489501953125 L 278.6783447265625 602.230712890625 L 330.0909423828125 602.230712890625 L 195.88818359375 10 L 5.7342529296875 10 L 206.1748046875 704 Z");
+
+  measure = gsk_path_measure_new (path);
+
+  /* The midpoint of the right foot of a fat Cantarell X */
+  inside = gsk_path_measure_in_fill (measure, &GRAPHENE_POINT_INIT (552.360107, 704.000000), GSK_FILL_RULE_WINDING);
+
+  g_assert_false (inside);
+
+  gsk_path_measure_unref (measure);
+  gsk_path_unref (path);
+}
+
+static void
+test_rect (void)
+{
+  GskPathBuilder *builder;
+  GskPath *path;
+  GskPathMeasure *measure;
+  GskPathPoint *point;
+  graphene_point_t p;
+  graphene_vec2_t tangent, expected_tangent;
+  float length;
+
+  builder = gsk_path_builder_new ();
+  gsk_path_builder_add_rect (builder, &GRAPHENE_RECT_INIT (0, 0, 100, 50));
+  path = gsk_path_builder_free_to_path (builder);
+  measure = gsk_path_measure_new (path);
+  length = gsk_path_measure_get_length (measure);
+
+  g_assert_true (length == 300);
+
+#define TEST_POS_AT(distance, X, Y) \
+  point = gsk_path_measure_get_point (measure, distance); \
+  gsk_path_point_get_position (point, &p); \
+  g_assert_true (graphene_point_near (&p, &GRAPHENE_POINT_INIT (X, Y), 0.01)); \
+  gsk_path_point_unref (point); \
+  point = gsk_path_measure_get_closest_point (measure, &GRAPHENE_POINT_INIT (X, Y), INFINITY); \
+  if (distance < length) \
+    g_assert_true (fabs (gsk_path_point_get_distance (point) - distance) < 0.01); \
+  else \
+    g_assert_true (fabs (gsk_path_point_get_distance (point)) < 0.01); \
+  gsk_path_point_get_position (point, &p); \
+  g_assert_true (graphene_point_near (&p, &GRAPHENE_POINT_INIT (X, Y), 0.01)); \
+  gsk_path_point_unref (point);
+
+#define TEST_TANGENT_AT(distance, x1, y1, x2, y2) \
+  point = gsk_path_measure_get_point (measure, distance); \
+  gsk_path_point_get_tangent (point, GSK_PATH_START, &tangent); \
+  g_assert_true (graphene_vec2_near (&tangent, graphene_vec2_init (&expected_tangent, x1, y1), 0.01)); \
+  gsk_path_point_get_tangent (point, GSK_PATH_END, &tangent); \
+  g_assert_true (graphene_vec2_near (&tangent, graphene_vec2_init (&expected_tangent, x2, y2), 0.01)); \
+  gsk_path_point_unref (point); \
+
+#define TEST_POS_AT2(distance, X, Y, expected_distance) \
+  point = gsk_path_measure_get_point (measure, distance); \
+  gsk_path_point_get_position (point, &p); \
+  g_assert_true (graphene_point_near (&p, &GRAPHENE_POINT_INIT (X, Y), 0.01)); \
+  gsk_path_point_unref (point); \
+  point = gsk_path_measure_get_closest_point (measure, &GRAPHENE_POINT_INIT (X, Y), INFINITY); \
+  g_assert_true (fabs (gsk_path_point_get_distance (point) - expected_distance) < 0.01); \
+  gsk_path_point_get_position (point, &p); \
+  g_assert_true (graphene_point_near (&p, &GRAPHENE_POINT_INIT (X, Y), 0.01)); \
+  gsk_path_point_unref (point);
+
+  TEST_POS_AT (0, 0, 0)
+  TEST_POS_AT (25, 25, 0)
+  TEST_POS_AT (100, 100, 0)
+  TEST_POS_AT (110, 100, 10)
+  TEST_POS_AT (150, 100, 50)
+  TEST_POS_AT (175, 75, 50)
+  TEST_POS_AT (250, 0, 50)
+  TEST_POS_AT (260, 0, 40)
+  TEST_POS_AT (300, 0, 0)
+
+  TEST_TANGENT_AT (0, 0, -1, 1, 0)
+  TEST_TANGENT_AT (50, 1, 0, 1, 0)
+  TEST_TANGENT_AT (100, 1, 0, 0, 1)
+  TEST_TANGENT_AT (125, 0, 1, 0, 1)
+  TEST_TANGENT_AT (150, 0, 1, -1, 0)
+  TEST_TANGENT_AT (200, -1, 0, -1, 0)
+  TEST_TANGENT_AT (250, -1, 0, 0, -1)
+  TEST_TANGENT_AT (275, 0, -1, 0, -1)
+
+  gsk_path_measure_unref (measure);
+  gsk_path_unref (path);
+
+  builder = gsk_path_builder_new ();
+  gsk_path_builder_add_rect (builder, &GRAPHENE_RECT_INIT (100, 50, -100, -50));
+  path = gsk_path_builder_free_to_path (builder);
+  measure = gsk_path_measure_new (path);
+  length = gsk_path_measure_get_length (measure);
+
+  g_assert_true (length == 300);
+
+  TEST_POS_AT (0, 100, 50)
+  TEST_POS_AT (25, 75, 50)
+  TEST_POS_AT (100, 0, 50)
+  TEST_POS_AT (110, 0, 40)
+  TEST_POS_AT (150, 0, 0)
+  TEST_POS_AT (175, 25, 0)
+  TEST_POS_AT (250, 100, 0)
+  TEST_POS_AT (260, 100, 10)
+  TEST_POS_AT (300, 100, 50)
+
+  builder = gsk_path_builder_new ();
+  gsk_path_builder_add_rect (builder, &GRAPHENE_RECT_INIT (100, 0, -100, 50));
+  path = gsk_path_builder_free_to_path (builder);
+  measure = gsk_path_measure_new (path);
+  length = gsk_path_measure_get_length (measure);
+
+  g_assert_true (length == 300);
+
+  TEST_POS_AT (0, 100, 0)
+  TEST_POS_AT (25, 75, 0)
+  TEST_POS_AT (100, 0, 0)
+  TEST_POS_AT (110, 0, 10)
+  TEST_POS_AT (150, 0, 50)
+  TEST_POS_AT (175, 25, 50)
+  TEST_POS_AT (250, 100, 50)
+  TEST_POS_AT (260, 100, 40)
+  TEST_POS_AT (300, 100, 0)
+
+  builder = gsk_path_builder_new ();
+  gsk_path_builder_add_rect (builder, &GRAPHENE_RECT_INIT (0, 0, 100, 0));
+  path = gsk_path_builder_free_to_path (builder);
+  measure = gsk_path_measure_new (path);
+  length = gsk_path_measure_get_length (measure);
+
+  g_assert_true (length == 200);
+
+  TEST_POS_AT2 (0, 0, 0, 0)
+  TEST_POS_AT2 (25, 25, 0, 25)
+  TEST_POS_AT2 (100, 100, 0, 100)
+  TEST_POS_AT2 (110, 90, 0, 90)
+  TEST_POS_AT2 (200, 0, 0, 0)
+
+  builder = gsk_path_builder_new ();
+  gsk_path_builder_add_rect (builder, &GRAPHENE_RECT_INIT (100, 0, -100, 0));
+  path = gsk_path_builder_free_to_path (builder);
+  measure = gsk_path_measure_new (path);
+  length = gsk_path_measure_get_length (measure);
+
+  g_assert_true (length == 200);
+
+  TEST_POS_AT2 (0, 100, 0, 0)
+  TEST_POS_AT2 (25, 75, 0, 25)
+  TEST_POS_AT2 (100, 0, 0, 100)
+  TEST_POS_AT2 (110, 10, 0, 90)
+  TEST_POS_AT2 (200, 100, 0, 0)
+
+  builder = gsk_path_builder_new ();
+  gsk_path_builder_add_rect (builder, &GRAPHENE_RECT_INIT (0, 100, 0, -100));
+  path = gsk_path_builder_free_to_path (builder);
+  measure = gsk_path_measure_new (path);
+  length = gsk_path_measure_get_length (measure);
+
+  g_assert_true (length == 200);
+
+  TEST_POS_AT2 (0, 0, 100, 0)
+  TEST_POS_AT2 (25, 0, 75, 25)
+  TEST_POS_AT2 (100, 0, 0, 100)
+  TEST_POS_AT2 (110, 0, 10, 90)
+  TEST_POS_AT2 (200, 0, 100, 0)
+
+#undef TEST_POS_AT
+#undef TEST_POS_AT2
+#undef TEST_TANGENT_AT
+
+  gsk_path_measure_unref (measure);
+  gsk_path_unref (path);
+}
+
+int
+main (int   argc,
+      char *argv[])
+{
+  gtk_test_init (&argc, &argv, NULL);
+
+  g_test_add_func ("/measure/bad-split", test_bad_split);
+  g_test_add_func ("/measure/bad-in-fill", test_bad_in_fill);
+  g_test_add_func ("/measure/rect", test_rect);
+
+  return g_test_run ();
+}

testsuite/gsk/measure.c

@@ -0,0 +1,910 @@
+/*
+ * Copyright © 2020 Benjamin Otte
+ *
+ * This library is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU Lesser General Public
+ * License as published by the Free Software Foundation; either
+ * version 2.1 of the License, or (at your option) any later version.
+ *
+ * This library is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+ * Lesser General Public License for more details.
+ *
+ * You should have received a copy of the GNU Lesser General Public
+ * License along with this library. If not, see <http://www.gnu.org/licenses/>.
+ *
+ * Authors: Benjamin Otte <otte@gnome.org>
+ */
+
+#include <gtk/gtk.h>
+#include "gsk/gskpath.h"
+#include "gsk/gskpathbuilder.h"
+#include "gsk/gskpathmeasure.h"
+
+static float
+random_weight (void)
+{
+  if (g_test_rand_bit ())
+    return g_test_rand_double_range (1, 20);
+  else
+    return 1.0 / g_test_rand_double_range (1, 20);
+}
+
+static GskPath *
+create_random_degenerate_path (guint max_contours)
+{
+#define N_DEGENERATE_PATHS 15
+  GskPathBuilder *builder;
+  guint i;
+
+  builder = gsk_path_builder_new ();
+
+  switch (g_test_rand_int_range (0, N_DEGENERATE_PATHS))
+  {
+    case 0:
+      /* empty path */
+      break;
+
+    case 1:
+      /* a single point */
+      gsk_path_builder_move_to (builder, 
+                                g_test_rand_double_range (-1000, 1000),
+                                g_test_rand_double_range (-1000, 1000));
+      break;
+
+    case 2:
+      /* N points */
+      for (i = 0; i < MIN (10, max_contours); i++)
+        {
+          gsk_path_builder_move_to (builder, 
+                                    g_test_rand_double_range (-1000, 1000),
+                                    g_test_rand_double_range (-1000, 1000));
+        }
+      break;
+
+    case 3:
+      /* 1 closed point */
+      gsk_path_builder_move_to (builder, 
+                                g_test_rand_double_range (-1000, 1000),
+                                g_test_rand_double_range (-1000, 1000));
+      gsk_path_builder_close (builder);
+      break;
+
+    case 4:
+      /* the same point closed N times */
+      gsk_path_builder_move_to (builder, 
+                                g_test_rand_double_range (-1000, 1000),
+                                g_test_rand_double_range (-1000, 1000));
+      for (i = 0; i < MIN (10, max_contours); i++)
+        {
+          gsk_path_builder_close (builder);
+        }
+      break;
+
+    case 5:
+      /* a zero-width and zero-height rect */
+      gsk_path_builder_add_rect (builder,
+                                 &GRAPHENE_RECT_INIT (g_test_rand_double_range (-1000, 1000),
+                                                      g_test_rand_double_range (-1000, 1000),
+                                                      0, 0));
+      break;
+
+    case 6:
+      /* a zero-width rect */
+      gsk_path_builder_add_rect (builder,
+                                 &GRAPHENE_RECT_INIT (g_test_rand_double_range (-1000, 1000),
+                                                      g_test_rand_double_range (-1000, 1000),
+                                                      0,
+                                                      g_test_rand_double_range (-1000, 1000)));
+      break;
+
+    case 7:
+      /* a zero-height rect */
+      gsk_path_builder_add_rect (builder,
+                                 &GRAPHENE_RECT_INIT (g_test_rand_double_range (-1000, 1000),
+                                                      g_test_rand_double_range (-1000, 1000),
+                                                      g_test_rand_double_range (-1000, 1000),
+                                                      0));
+      break;
+
+    case 8:
+      /* a negative-size rect */
+      gsk_path_builder_add_rect (builder,
+                                 &GRAPHENE_RECT_INIT (g_test_rand_double_range (-1000, 1000),
+                                                      g_test_rand_double_range (-1000, 1000),
+                                                      g_test_rand_double_range (-1000, 0),
+                                                      g_test_rand_double_range (-1000, 0)));
+      break;
+
+    case 9:
+      /* an absolutely random rect */
+      gsk_path_builder_add_rect (builder,
+                                 &GRAPHENE_RECT_INIT (g_test_rand_double_range (-1000, 1000),
+                                                      g_test_rand_double_range (-1000, 1000),
+                                                      g_test_rand_double_range (-1000, 1000),
+                                                      g_test_rand_double_range (-1000, 1000)));
+      break;
+
+    case 10:
+      /* an absolutely random rect */
+      gsk_path_builder_add_rect (builder,
+                                 &GRAPHENE_RECT_INIT (g_test_rand_double_range (-1000, 1000),
+                                                      g_test_rand_double_range (-1000, 1000),
+                                                      g_test_rand_double_range (-1000, 1000),
+                                                      g_test_rand_double_range (-1000, 1000)));
+      break;
+
+    case 11:
+      /* an absolutely random circle */
+      gsk_path_builder_add_circle (builder,
+                                   &GRAPHENE_POINT_INIT (g_test_rand_double_range (-1000, 1000),
+                                                         g_test_rand_double_range (-1000, 1000)),
+                                   g_test_rand_double_range (1, 1000));
+      break;
+
+    case 12:
+      /* a zero-length line */
+      {
+        graphene_point_t point = GRAPHENE_POINT_INIT (g_test_rand_double_range (-1000, 1000),
+                                                      g_test_rand_double_range (-1000, 1000));
+        gsk_path_builder_move_to (builder, point.x, point.y);
+        gsk_path_builder_line_to (builder, point.x, point.y);
+      }
+      break;
+
+    case 13:
+      /* a curve with start == end */
+      {
+        graphene_point_t point = GRAPHENE_POINT_INIT (g_test_rand_double_range (-1000, 1000),
+                                                      g_test_rand_double_range (-1000, 1000));
+        gsk_path_builder_move_to (builder, point.x, point.y);
+        gsk_path_builder_cubic_to (builder,
+                                   g_test_rand_double_range (-1000, 1000),
+                                   g_test_rand_double_range (-1000, 1000),
+                                   g_test_rand_double_range (-1000, 1000),
+                                   g_test_rand_double_range (-1000, 1000),
+                                   point.x, point.y);
+      }
+      break;
+
+    case 14:
+      /* a conic with start == end */
+      {
+        graphene_point_t point = GRAPHENE_POINT_INIT (g_test_rand_double_range (-1000, 1000),
+                                                      g_test_rand_double_range (-1000, 1000));
+        gsk_path_builder_move_to (builder, point.x, point.y);
+        gsk_path_builder_conic_to (builder,
+                                   g_test_rand_double_range (-1000, 1000),
+                                   g_test_rand_double_range (-1000, 1000),
+                                   point.x, point.y,
+                                   random_weight ());
+      }
+      break;
+
+    case N_DEGENERATE_PATHS:
+    default:
+      g_assert_not_reached ();
+  }
+
+  return gsk_path_builder_free_to_path (builder);
+}
+
+static GskPath *
+create_random_path (guint max_contours);
+
+static void
+add_shape_contour (GskPathBuilder *builder)
+{
+#define N_SHAPE_CONTOURS 3
+  switch (g_test_rand_int_range (0, N_SHAPE_CONTOURS))
+  {
+    case 0:
+      gsk_path_builder_add_rect (builder,
+                                 &GRAPHENE_RECT_INIT (g_test_rand_double_range (-1000, 1000),
+                                                      g_test_rand_double_range (-1000, 1000),
+                                                      g_test_rand_double_range (1, 1000),
+                                                      g_test_rand_double_range (1, 1000)));
+      break;
+
+    case 1:
+      gsk_path_builder_add_circle (builder,
+                                   &GRAPHENE_POINT_INIT (g_test_rand_double_range (-1000, 1000),
+                                                         g_test_rand_double_range (-1000, 1000)),
+                                   g_test_rand_double_range (1, 1000));
+      break;
+
+    case 2:
+      {
+        GskPath *path = create_random_path (1);
+        gsk_path_builder_add_path (builder, path);
+        gsk_path_unref (path);
+      }
+      break;
+
+    case N_SHAPE_CONTOURS:
+    default:
+      g_assert_not_reached ();
+      break;
+  }
+}
+
+static void
+add_standard_contour (GskPathBuilder *builder)
+{
+  guint i, n;
+
+  if (g_test_rand_bit ())
+    {
+      if (g_test_rand_bit ())
+        gsk_path_builder_move_to (builder,
+                                  g_test_rand_double_range (-1000, 1000),
+                                  g_test_rand_double_range (-1000, 1000));
+      else
+        gsk_path_builder_rel_move_to (builder,
+                                      g_test_rand_double_range (-1000, 1000),
+                                      g_test_rand_double_range (-1000, 1000));
+    }
+
+  /* that 20 is random, but should be enough to get some
+   * crazy self-intersecting shapes */
+  n = g_test_rand_int_range (1, 20);
+  for (i = 0; i < n; i++)
+    {
+      switch (g_test_rand_int_range (0, 8))
+      {
+        case 0:
+          gsk_path_builder_line_to (builder,
+                                    g_test_rand_double_range (-1000, 1000),
+                                    g_test_rand_double_range (-1000, 1000));
+          break;
+
+        case 1:
+          gsk_path_builder_rel_line_to (builder,
+                                        g_test_rand_double_range (-1000, 1000),
+                                        g_test_rand_double_range (-1000, 1000));
+          break;
+
+        case 2:
+          gsk_path_builder_quad_to (builder,
+                                    g_test_rand_double_range (-1000, 1000),
+                                    g_test_rand_double_range (-1000, 1000),
+                                    g_test_rand_double_range (-1000, 1000),
+                                    g_test_rand_double_range (-1000, 1000));
+          break;
+
+        case 3:
+          gsk_path_builder_rel_quad_to (builder,
+                                        g_test_rand_double_range (-1000, 1000),
+                                        g_test_rand_double_range (-1000, 1000),
+                                        g_test_rand_double_range (-1000, 1000),
+                                        g_test_rand_double_range (-1000, 1000));
+          break;
+
+        case 4:
+          gsk_path_builder_cubic_to (builder,
+                                     g_test_rand_double_range (-1000, 1000),
+                                     g_test_rand_double_range (-1000, 1000),
+                                     g_test_rand_double_range (-1000, 1000),
+                                     g_test_rand_double_range (-1000, 1000),
+                                     g_test_rand_double_range (-1000, 1000),
+                                     g_test_rand_double_range (-1000, 1000));
+          break;
+
+        case 5:
+          gsk_path_builder_rel_cubic_to (builder,
+                                         g_test_rand_double_range (-1000, 1000),
+                                         g_test_rand_double_range (-1000, 1000),
+                                         g_test_rand_double_range (-1000, 1000),
+                                         g_test_rand_double_range (-1000, 1000),
+                                         g_test_rand_double_range (-1000, 1000),
+                                         g_test_rand_double_range (-1000, 1000));
+          break;
+
+        case 6:
+          gsk_path_builder_conic_to (builder,
+                                     g_test_rand_double_range (-1000, 1000),
+                                     g_test_rand_double_range (-1000, 1000),
+                                     g_test_rand_double_range (-1000, 1000),
+                                     g_test_rand_double_range (-1000, 1000),
+                                     random_weight ());
+          break;
+
+        case 7:
+          gsk_path_builder_rel_conic_to (builder,
+                                         g_test_rand_double_range (-1000, 1000),
+                                         g_test_rand_double_range (-1000, 1000),
+                                         g_test_rand_double_range (-1000, 1000),
+                                         g_test_rand_double_range (-1000, 1000),
+                                         random_weight ());
+          break;
+
+        default:
+          g_assert_not_reached();
+          break;
+      }
+    }
+
+  if (g_test_rand_bit ())
+    gsk_path_builder_close (builder);
+}
+
+static GskPath *
+create_random_path (guint max_contours)
+{
+  GskPathBuilder *builder;
+  guint i, n;
+
+  /* 5% chance for a weird shape */
+  if (!g_test_rand_int_range (0, 20))
+    return create_random_degenerate_path (max_contours);
+
+  builder = gsk_path_builder_new ();
+  n = g_test_rand_int_range (1, 10);
+  n = MIN (n, max_contours);
+
+  for (i = 0; i < n; i++)
+    {
+      /* 2/3 of shapes are standard contours */
+      if (g_test_rand_int_range (0, 3))
+        add_standard_contour (builder);
+      else
+        add_shape_contour (builder);
+    }
+
+  return gsk_path_builder_free_to_path (builder);
+}
+
+typedef struct {
+  GskPathOperation op;
+  graphene_point_t pts[4];
+  float weight;
+} PathOperation;
+
+static void
+test_segment_start (void)
+{
+  GskPath *path, *path1;
+  GskPathMeasure *measure, *measure1;
+  GskPathBuilder *builder;
+  float epsilon, length;
+  guint i;
+
+  path = create_random_path (G_MAXUINT);
+  measure = gsk_path_measure_new (path);
+  length = gsk_path_measure_get_length (measure);
+  epsilon = MAX (length / 1024, G_MINFLOAT);
+
+  for (i = 0; i < 100; i++)
+    {
+      float seg_length = length * i / 100.0f;
+
+      builder = gsk_path_builder_new ();
+      gsk_path_builder_add_segment (builder, measure, 0, seg_length);
+      path1 = gsk_path_builder_free_to_path (builder);
+      measure1 = gsk_path_measure_new (path1);
+
+      if (seg_length == 0)
+        g_assert_cmpfloat_with_epsilon (gsk_path_measure_get_length (measure), gsk_path_measure_get_length (measure1), epsilon);
+      else
+        g_assert_cmpfloat_with_epsilon (seg_length, gsk_path_measure_get_length (measure1), epsilon);
+
+      gsk_path_measure_unref (measure1);
+      gsk_path_unref (path1);
+    }
+
+  gsk_path_measure_unref (measure);
+  gsk_path_unref (path);
+}
+
+static void
+test_segment_end (void)
+{
+  GskPath *path, *path1;
+  GskPathMeasure *measure, *measure1;
+  GskPathBuilder *builder;
+  float epsilon, length;
+  guint i;
+
+  path = create_random_path (G_MAXUINT);
+  measure = gsk_path_measure_new (path);
+  length = gsk_path_measure_get_length (measure);
+  epsilon = MAX (length / 1024, G_MINFLOAT);
+
+  for (i = 0; i < 100; i++)
+    {
+      float seg_length = length * i / 100.0f;
+
+      builder = gsk_path_builder_new ();
+      gsk_path_builder_add_segment (builder, measure, length - seg_length, length);
+      path1 = gsk_path_builder_free_to_path (builder);
+      measure1 = gsk_path_measure_new (path1);
+
+      if (seg_length == 0)
+        g_assert_cmpfloat_with_epsilon (gsk_path_measure_get_length (measure), gsk_path_measure_get_length (measure1), epsilon);
+      else
+        g_assert_cmpfloat_with_epsilon (seg_length, gsk_path_measure_get_length (measure1), epsilon);
+
+      gsk_path_measure_unref (measure1);
+      gsk_path_unref (path1);
+    }
+
+  gsk_path_measure_unref (measure);
+  gsk_path_unref (path);
+}
+
+static void
+test_segment_chunk (void)
+{
+  GskPath *path, *path1, *path2;
+  GskPathMeasure *measure, *measure1, *measure2;
+  GskPathBuilder *builder;
+  float epsilon, length;
+  guint i;
+
+  path = create_random_path (G_MAXUINT);
+  measure = gsk_path_measure_new (path);
+  length = gsk_path_measure_get_length (measure);
+  epsilon = MAX (length / 1024, G_MINFLOAT);
+
+  for (i = 0; i <= 100; i++)
+    {
+      float seg_start = length * i / 200.0f;
+
+      builder = gsk_path_builder_new ();
+      gsk_path_builder_add_segment (builder, measure, seg_start, seg_start + length / 2);
+      path1 = gsk_path_builder_free_to_path (builder);
+      measure1 = gsk_path_measure_new (path1);
+
+      g_assert_cmpfloat_with_epsilon (length / 2, gsk_path_measure_get_length (measure1), epsilon);
+
+      builder = gsk_path_builder_new ();
+      gsk_path_builder_add_segment (builder, measure, seg_start + length / 2, seg_start);
+      path2 = gsk_path_builder_free_to_path (builder);
+      measure2 = gsk_path_measure_new (path2);
+
+      g_assert_cmpfloat_with_epsilon (length / 2, gsk_path_measure_get_length (measure2), epsilon);
+
+      gsk_path_measure_unref (measure2);
+      gsk_path_unref (path2);
+      gsk_path_measure_unref (measure1);
+      gsk_path_unref (path1);
+    }
+
+  gsk_path_measure_unref (measure);
+  gsk_path_unref (path);
+}
+
+static void
+test_segment (void)
+{
+  GskPath *path, *path1, *path2, *path3;
+  GskPathMeasure *measure, *measure1, *measure2, *measure3;
+  GskPathBuilder *builder;
+  guint i;
+  float split1, split2, epsilon, length;
+
+  for (i = 0; i < 1000; i++)
+    {
+      path = create_random_path (G_MAXUINT);
+      measure = gsk_path_measure_new (path);
+      length = gsk_path_measure_get_length (measure);
+      /* chosen high enough to stop the testsuite from failing */
+      epsilon = MAX (length / 64, 1.f / 1024);
+
+      split1 = g_test_rand_double_range (0, length);
+      split2 = g_test_rand_double_range (split1, length);
+
+      builder = gsk_path_builder_new ();
+      gsk_path_builder_add_segment (builder, measure, 0, split1);
+      path1 = gsk_path_builder_free_to_path (builder);
+      measure1 = gsk_path_measure_new (path1);
+
+      builder = gsk_path_builder_new ();
+      gsk_path_builder_add_segment (builder, measure, split1, split2);
+      path2 = gsk_path_builder_free_to_path (builder);
+      measure2 = gsk_path_measure_new (path2);
+
+      builder = gsk_path_builder_new ();
+      gsk_path_builder_add_segment (builder, measure, split2, length);
+      path3 = gsk_path_builder_free_to_path (builder);
+      measure3 = gsk_path_measure_new (path3);
+
+      g_assert_cmpfloat_with_epsilon (split1, gsk_path_measure_get_length (measure1), epsilon);
+      g_assert_cmpfloat_with_epsilon (split2 - split1, gsk_path_measure_get_length (measure2), epsilon);
+      g_assert_cmpfloat_with_epsilon (length - split2, gsk_path_measure_get_length (measure3), epsilon);
+
+      gsk_path_measure_unref (measure2);
+      gsk_path_measure_unref (measure1);
+      gsk_path_measure_unref (measure);
+      gsk_path_unref (path2);
+      gsk_path_unref (path1);
+      gsk_path_unref (path);
+    }
+}
+
+static void
+test_get_point (void)
+{
+  static const guint max_contours = 5;
+  static const float tolerance = 1.0;
+  GskPath *path;
+  GskPathMeasure *measure;
+  GskPathPoint *point;
+  guint n_discontinuities;
+  float length, offset, last_offset;
+  graphene_point_t p, last_point;
+  guint i, j;
+
+  for (i = 0; i < 10; i++)
+    {
+      path = create_random_path (max_contours);
+      measure = gsk_path_measure_new_with_tolerance (path, tolerance);
+      length = gsk_path_measure_get_length (measure);
+      n_discontinuities = 0;
+
+      point = gsk_path_measure_get_point (measure, 0);
+      if (point == NULL)
+        {
+          g_assert_true (gsk_path_is_empty (path));
+          continue;
+        }
+      gsk_path_point_get_position (point, &last_point);
+      gsk_path_point_unref (point);
+
+      /* FIXME: anything we can test with tangents here? */
+      last_offset = 0;
+
+      for (j = 1; j <= 1024; j++)
+        {
+          offset = length * j / 1024;
+          point = gsk_path_measure_get_point (measure, offset);
+          gsk_path_point_get_position (point, &p);
+          gsk_path_point_unref (point);
+
+          if (graphene_point_distance (&last_point, &p, NULL, NULL) > 2 * (offset - last_offset))
+            {
+              n_discontinuities++;
+              g_assert_cmpint (n_discontinuities, <, max_contours);
+            }
+
+          last_offset = offset;
+          last_point = p;
+        }
+
+      gsk_path_measure_unref (measure);
+      gsk_path_unref (path);
+    }
+}
+
+static void
+test_closest_point (void)
+{
+  static const float tolerance = 0.5;
+  GskPath *path, *path1, *path2;
+  GskPathMeasure *measure, *measure1, *measure2;
+  GskPathBuilder *builder;
+  GskPathPoint *point;
+  guint i, j;
+
+  for (i = 0; i < 10; i++)
+    {
+      path1 = create_random_path (G_MAXUINT);
+      measure1 = gsk_path_measure_new_with_tolerance (path1, tolerance);
+      path2 = create_random_path (G_MAXUINT);
+      measure2 = gsk_path_measure_new_with_tolerance (path2, tolerance);
+
+      builder = gsk_path_builder_new ();
+      gsk_path_builder_add_path (builder, path1);
+      gsk_path_builder_add_path (builder, path2);
+      path = gsk_path_builder_free_to_path (builder);
+      measure = gsk_path_measure_new_with_tolerance (path, tolerance);
+
+      for (j = 0; j < 100; j++)
+        {
+          graphene_point_t test = GRAPHENE_POINT_INIT (g_test_rand_double_range (-1000, 1000),
+                                                       g_test_rand_double_range (-1000, 1000));
+          graphene_point_t p1, p2, p;
+          graphene_vec2_t t1, t2, t;
+          float offset1, offset2, offset;
+          float distance1, distance2, distance;
+
+          offset1 = offset2 = offset = 0;
+          distance1 = distance2 = distance = 0;
+          point = gsk_path_measure_get_closest_point (measure1, &test, INFINITY);
+          g_assert_true (point != NULL);
+
+          gsk_path_point_get_position (point, &p1);
+          gsk_path_point_get_tangent (point, GSK_PATH_END, &t1);
+          offset1 = gsk_path_point_get_distance (point);
+          distance1 = graphene_point_distance (&p1, &test, NULL, NULL);
+          gsk_path_point_unref (point);
+
+          point = gsk_path_measure_get_closest_point (measure2, &test, INFINITY);
+          g_assert_true (point != NULL);
+
+          gsk_path_point_get_position (point, &p2);
+          gsk_path_point_get_tangent (point, GSK_PATH_END, &t2);
+          offset2 = gsk_path_point_get_distance (point);
+          distance2 = graphene_point_distance (&p2, &test, NULL, NULL);
+          gsk_path_point_unref (point);
+
+          point = gsk_path_measure_get_closest_point (measure, &test, INFINITY);
+          g_assert_true (point != NULL);
+
+          gsk_path_point_get_position (point, &p);
+          gsk_path_point_get_tangent (point, GSK_PATH_END, &t);
+          offset = gsk_path_point_get_distance (point);
+          distance = graphene_point_distance (&p, &test, NULL, NULL);
+          gsk_path_point_unref (point);
+
+          if (distance1 < distance2 + tolerance)
+            {
+              g_assert_cmpfloat (distance1, ==, distance);
+              g_assert_cmpfloat (p1.x, ==, p.x);
+              g_assert_cmpfloat (p1.y, ==, p.y);
+              g_assert_cmpfloat (offset1, ==, offset);
+              g_assert_true (graphene_vec2_equal (&t1, &t));
+            }
+          else
+            {
+              g_assert_cmpfloat (distance2, ==, distance);
+              g_assert_cmpfloat (p2.x, ==, p.x);
+              g_assert_cmpfloat (p2.y, ==, p.y);
+              g_assert_cmpfloat_with_epsilon (offset2 + gsk_path_measure_get_length (measure1), offset, MAX (G_MINFLOAT, offset / 1024));
+              g_assert_true (graphene_vec2_equal (&t2, &t));
+            }
+        }
+
+      gsk_path_measure_unref (measure2);
+      gsk_path_measure_unref (measure1);
+      gsk_path_measure_unref (measure);
+      gsk_path_unref (path2);
+      gsk_path_unref (path1);
+      gsk_path_unref (path);
+    }
+}
+
+static void
+test_closest_point_for_point (void)
+{
+  static const float tolerance = 0.5;
+  GskPath *path;
+  GskPathMeasure *measure;
+  GskPathPoint *point;
+  float length, offset, closest_offset, distance;
+  graphene_point_t p, closest_point;
+  guint i, j;
+
+  for (i = 0; i < 100; i++)
+    {
+      path = create_random_path (G_MAXUINT);
+      if (gsk_path_is_empty (path))
+        {
+          /* empty paths have no closest point to anything */
+          gsk_path_unref (path);
+          continue;
+        }
+
+      measure = gsk_path_measure_new_with_tolerance (path, tolerance);
+      length = gsk_path_measure_get_length (measure);
+
+      for (j = 0; j < 100; j++)
+        {
+          offset = g_test_rand_double_range (0, length);
+
+          point = gsk_path_measure_get_point (measure, offset);
+          gsk_path_point_get_position (point, &p);
+          gsk_path_point_unref (point);
+          point = gsk_path_measure_get_closest_point (measure, &p, tolerance);
+          g_assert_nonnull (point);
+          gsk_path_point_get_position (point, &closest_point);
+          closest_offset = gsk_path_point_get_distance (point);
+          distance = graphene_point_distance (&p, &closest_point, NULL, NULL);
+          gsk_path_point_unref (point);
+
+          /* should be given due to the TRUE return above, but who knows... */
+          g_assert_cmpfloat (distance, <=, tolerance);
+          g_assert_cmpfloat (graphene_point_distance (&p, &closest_point, NULL, NULL), <=, tolerance);
+          /* can't do == here because points may overlap if we're unlucky */
+          g_assert_cmpfloat (closest_offset, <, offset + tolerance);
+        }
+
+      gsk_path_measure_unref (measure);
+      gsk_path_unref (path);
+    }
+}
+
+#define N_PATHS 3
+static void
+test_in_fill_union (void)
+{
+  GskPath *path;
+  GskPathMeasure *measure, *measures[N_PATHS];
+  GskPathBuilder *builder;
+  guint i, j, k;
+
+  for (i = 0; i < 100; i++)
+    {
+      builder = gsk_path_builder_new ();
+      for (k = 0; k < N_PATHS; k++)
+        {
+          path = create_random_path (G_MAXUINT);
+          measures[k] = gsk_path_measure_new (path);
+          gsk_path_builder_add_path (builder, path);
+          gsk_path_unref (path);
+        }
+      path = gsk_path_builder_free_to_path (builder);
+      measure = gsk_path_measure_new (path);
+      gsk_path_unref (path);
+
+      for (j = 0; j < 100; j++)
+        {
+          graphene_point_t test = GRAPHENE_POINT_INIT (g_test_rand_double_range (-1000, 1000),
+                                                       g_test_rand_double_range (-1000, 1000));
+          GskFillRule fill_rule;
+
+          for (fill_rule = GSK_FILL_RULE_WINDING; fill_rule <= GSK_FILL_RULE_EVEN_ODD; fill_rule++)
+            {
+              guint n_in_fill = 0;
+              gboolean in_fill;
+
+              for (k = 0; k < N_PATHS; k++)
+                {
+                  if (gsk_path_measure_in_fill (measures[k], &test, GSK_FILL_RULE_EVEN_ODD))
+                    n_in_fill++;
+                }
+
+              in_fill = gsk_path_measure_in_fill (measure, &test, GSK_FILL_RULE_EVEN_ODD);
+
+              switch (fill_rule)
+              {
+                case GSK_FILL_RULE_WINDING:
+                  if (n_in_fill == 0)
+                    g_assert_false (in_fill);
+                  else if (n_in_fill == 1)
+                    g_assert_true (in_fill);
+                  /* else we can't say anything because the winding rule doesn't give enough info */
+                  break;
+
+                case GSK_FILL_RULE_EVEN_ODD:
+                  g_assert_cmpint (in_fill, ==, n_in_fill & 1);
+                  break;
+
+                default:
+                  g_assert_not_reached ();
+                  break;
+              }
+            }
+        }
+
+      gsk_path_measure_unref (measure);
+      for (k = 0; k < N_PATHS; k++)
+        {
+          gsk_path_measure_unref (measures[k]);
+        }
+    }
+}
+#undef N_PATHS
+
+/* This is somewhat sucky because using foreach breaks up the contours
+ * (like rects and circles) and replaces everything with the standard
+ * contour.
+ * But at least it extensively tests the standard contour.
+ */
+static gboolean
+rotate_path_cb (GskPathOperation        op,
+                const graphene_point_t *pts,
+                gsize                   n_pts,
+                float                   weight,
+                gpointer                user_data)
+{
+  GskPathBuilder **builders = user_data;
+
+  switch (op)
+  {
+    case GSK_PATH_MOVE:
+      gsk_path_builder_move_to (builders[0], pts[0].x, pts[0].y);
+      gsk_path_builder_move_to (builders[1], pts[0].y, -pts[0].x);
+      break;
+
+    case GSK_PATH_CLOSE:
+      gsk_path_builder_close (builders[0]);
+      gsk_path_builder_close (builders[1]);
+      break;
+
+    case GSK_PATH_LINE:
+      gsk_path_builder_line_to (builders[0], pts[1].x, pts[1].y);
+      gsk_path_builder_line_to (builders[1], pts[1].y, -pts[1].x);
+      break;
+
+    case GSK_PATH_QUAD:
+      gsk_path_builder_quad_to (builders[0], pts[1].x, pts[1].y, pts[2].x, pts[2].y);
+      gsk_path_builder_quad_to (builders[1], pts[1].y, -pts[1].x, pts[2].y, -pts[2].x);
+      break;
+
+    case GSK_PATH_CUBIC:
+      gsk_path_builder_cubic_to (builders[0], pts[1].x, pts[1].y, pts[2].x, pts[2].y, pts[3].x, pts[3].y);
+      gsk_path_builder_cubic_to (builders[1], pts[1].y, -pts[1].x, pts[2].y, -pts[2].x, pts[3].y, -pts[3].x);
+      break;
+
+    case GSK_PATH_CONIC:
+      gsk_path_builder_conic_to (builders[0], pts[1].x, pts[1].y, pts[2].x, pts[2].y, weight);
+      gsk_path_builder_conic_to (builders[1], pts[1].y, -pts[1].x, pts[2].y, -pts[2].x, weight);
+      break;
+
+    default:
+      g_assert_not_reached ();
+      return FALSE;
+  }
+
+  return TRUE;
+}
+
+static void
+test_in_fill_rotated (void)
+{
+  GskPath *path;
+  GskPathBuilder *builders[2];
+  GskPathMeasure *measures[2];
+  guint i, j;
+
+#define N_FILL_RULES 2
+  /* if this triggers, you added a new enum value to GskFillRule, so the define above needs
+   * an update */
+  //g_assert_null (g_enum_get_value (g_type_class_ref (GSK_TYPE_FILL_RULE), N_FILL_RULES));
+
+  for (i = 0; i < 100; i++)
+    {
+      path = create_random_path (G_MAXUINT);
+      builders[0] = gsk_path_builder_new ();
+      builders[1] = gsk_path_builder_new ();
+      /* Use -1 here because we want all the flags, even future additions */
+      gsk_path_foreach (path, -1, rotate_path_cb, builders);
+      gsk_path_unref (path);
+
+      path = gsk_path_builder_free_to_path (builders[0]);
+      measures[0] = gsk_path_measure_new (path);
+      gsk_path_unref (path);
+      path = gsk_path_builder_free_to_path (builders[1]);
+      measures[1] = gsk_path_measure_new (path);
+      gsk_path_unref (path);
+
+      for (j = 0; j < 100; j++)
+        {
+          GskFillRule fill_rule = g_random_int_range (0, N_FILL_RULES);
+          float x = g_test_rand_double_range (-1000, 1000);
+          float y = g_test_rand_double_range (-1000, 1000);
+  
+          g_assert_cmpint (gsk_path_measure_in_fill (measures[0], &GRAPHENE_POINT_INIT (x, y), fill_rule),
+                           ==,
+                           gsk_path_measure_in_fill (measures[1], &GRAPHENE_POINT_INIT (y, -x), fill_rule));
+          g_assert_cmpint (gsk_path_measure_in_fill (measures[0], &GRAPHENE_POINT_INIT (y, x), fill_rule),
+                           ==,
+                           gsk_path_measure_in_fill (measures[1], &GRAPHENE_POINT_INIT (x, -y), fill_rule));
+        }
+
+      gsk_path_measure_unref (measures[0]);
+      gsk_path_measure_unref (measures[1]);
+    }
+#undef N_FILL_RULES
+}
+
+int
+main (int   argc,
+      char *argv[])
+{
+  gtk_test_init (&argc, &argv, NULL);
+
+  g_test_add_func ("/measure/segment_start", test_segment_start);
+  g_test_add_func ("/measure/segment_end", test_segment_end);
+  g_test_add_func ("/measure/segment_chunk", test_segment_chunk);
+  g_test_add_func ("/measure/segment", test_segment);
+  g_test_add_func ("/measure/get_point", test_get_point);
+  g_test_add_func ("/measure/closest_point", test_closest_point);
+  g_test_add_func ("/measure/closest_point_for_point", test_closest_point_for_point);
+  g_test_add_func ("/measure/in-fill-union", test_in_fill_union);
+  g_test_add_func ("/measure/in-fill-rotated", test_in_fill_rotated);
+
+  return g_test_run ();
+}

testsuite/gsk/meson.build

@@ -389,6 +389,12 @@ foreach t : tests
 endforeach
 
 internal_tests = [
+  ['measure'],
+  ['measure-special-cases'],
+  ['path'],
+  ['path-special-cases'],
+  [ 'curve' ],
+  [ 'curve-special-cases' ],
   [ 'diff' ],
   [ 'half-float' ],
   ['rounded-rect'],

testsuite/gsk/path-special-cases.c

@@ -0,0 +1,322 @@
+/*
+ * Copyright © 2020 Benjamin Otte
+ *
+ * This library is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU Lesser General Public
+ * License as published by the Free Software Foundation; either
+ * version 2.1 of the License, or (at your option) any later version.
+ *
+ * This library is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+ * Lesser General Public License for more details.
+ *
+ * You should have received a copy of the GNU Lesser General Public
+ * License along with this library. If not, see <http://www.gnu.org/licenses/>.
+ *
+ * Authors: Benjamin Otte <otte@gnome.org>
+ */
+
+#include <gtk/gtk.h>
+#include "gsk/gskpath.h"
+#include "gsk/gskpathbuilder.h"
+
+/* testcases from path_parser.rs in librsvg */
+static void
+test_rsvg_parse (void)
+{
+  struct {
+    const char *in;
+    const char *out;
+  } tests[] = {
+    { "", "" },
+    // numbers
+    { "M 10 20", "M 10 20" },
+    { "M -10 -20", "M -10 -20" },
+    { "M .10 0.20", "M 0.1 0.2" },
+    { "M -.10 -0.20", "M -0.1 -0.2" },
+    { "M-.10-0.20", "M -0.1 -0.2" },
+    { "M10.5.50", "M 10.5 0.5" },
+    { "M.10.20", "M 0.1 0.2" },
+    { "M .10E1 .20e-4", "M 1 2e-05" },
+    { "M-.10E1-.20", "M -1 -0.2" },
+    { "M10.10E2 -0.20e3", "M 1010 -200" },
+    { "M-10.10E2-0.20e-3", "M -1010 -0.0002" },
+    { "M1e2.5", "M 100 0.5" },
+    { "M1e-2.5", "M 0.01 0.5" },
+    { "M1e+2.5", "M 100 0.5" },
+    // bogus numbers
+    { "M+", NULL },
+    { "M-", NULL },
+    { "M+x", NULL },
+    { "M10e", NULL },
+    { "M10ex", NULL },
+    { "M10e-", NULL },
+    { "M10e+x", NULL },
+    // numbers with comma
+    { "M 10, 20", "M 10 20" },
+    { "M -10,-20", "M -10 -20" },
+    { "M.10    ,     0.20", "M 0.1 0.2" },
+    { "M -.10, -0.20   ", "M -0.1 -0.2" },
+    { "M-.10-0.20", "M -0.1 -0.2" },
+    { "M.10.20", "M 0.1 0.2" },
+    { "M .10E1,.20e-4", "M 1 2e-05" },
+    { "M-.10E-2,-.20", "M -0.001 -0.2" },
+    { "M10.10E2,-0.20e3", "M 1010 -200" },
+    { "M-10.10E2,-0.20e-3", "M -1010 -0.0002" },
+    // single moveto
+    { "M 10 20 ", "M 10 20" },
+    { "M10,20  ", "M 10 20" },
+    { "M10 20   ", "M 10 20" },
+    { "    M10,20     ", "M 10 20" },
+    // relative moveto
+    { "m10 20", "M 10 20" },
+    // absolute moveto with implicit lineto
+    { "M10 20 30 40", "M 10 20 L 30 40" },
+    { "M10,20,30,40", "M 10 20 L 30 40" },
+    { "M.1-2,3E2-4", "M 0.1 -2 L 300 -4" },
+    // relative moveto with implicit lineto
+    { "m10 20 30 40", "M 10 20 L 40 60" },
+    // relative moveto with relative lineto sequence
+    { "m 46,447 l 0,0.5 -1,0 -1,0 0,1 0,12",
+      "M 46 447 L 46 447.5 L 45 447.5 L 44 447.5 L 44 448.5 L 44 460.5" },
+    // absolute moveto with implicit linetos
+    { "M10,20 30,40,50 60", "M 10 20 L 30 40 L 50 60" },
+    // relative moveto with implicit linetos
+    { "m10 20 30 40 50 60", "M 10 20 L 40 60 L 90 120" },
+    // absolute moveto moveto
+    { "M10 20 M 30 40", "M 10 20 M 30 40" },
+    // relative moveto moveto
+    { "m10 20 m 30 40", "M 10 20 M 40 60" },
+    // relative moveto lineto moveto
+    { "m10 20 30 40 m 50 60", "M 10 20 L 40 60 M 90 120" },
+    // absolute moveto lineto
+    { "M10 20 L30,40", "M 10 20 L 30 40" },
+    // relative moveto lineto
+    { "m10 20 l30,40", "M 10 20 L 40 60" },
+    // relative moveto lineto lineto abs lineto
+    { "m10 20 30 40l30,40,50 60L200,300",
+      "M 10 20 L 40 60 L 70 100 L 120 160 L 200 300" },
+    // horizontal lineto
+    { "M10 20 H30", "M 10 20 L 30 20" },
+    { "M 10 20 H 30 40",  "M 10 20 L 30 20 L 40 20" },
+    { "M10 20 H30,40-50", "M 10 20 L 30 20 L 40 20 L -50 20" },
+    { "m10 20 h30,40-50", "M 10 20 L 40 20 L 80 20 L 30 20" },
+    // vertical lineto
+    { "M10 20 V30", "M 10 20 L 10 30" },
+    { "M10 20 V30 40", "M 10 20 L 10 30 L 10 40" },
+    { "M10 20 V30,40-50", "M 10 20 L 10 30 L 10 40 L 10 -50" },
+    { "m10 20 v30,40-50", "M 10 20 L 10 50 L 10 90 L 10 40" },
+    // curveto
+    { "M10 20 C 30,40 50 60-70,80", "M 10 20 C 30 40, 50 60, -70 80" },
+    { "M10 20 C 30,40 50 60-70,80,90 100,110 120,130,140",
+      "M 10 20 C 30 40, 50 60, -70 80 C 90 100, 110 120, 130 140" },
+    { "m10 20 c 30,40 50 60-70,80,90 100,110 120,130,140",
+      "M 10 20 C 40 60, 60 80, -60 100 C 30 200, 50 220, 70 240" },
+    { "m10 20 c 30,40 50 60-70,80 90 100,110 120,130,140",
+      "M 10 20 C 40 60, 60 80, -60 100 C 30 200, 50 220, 70 240" },
+    // smooth curveto
+    { "M10 20 S 30,40-50,60", "M 10 20 C 10 20, 30 40, -50 60" },
+    { "M10 20 S 30,40 50 60-70,80,90 100",
+      "M 10 20 C 10 20, 30 40, 50 60 C 70 80, -70 80, 90 100" },
+    // quadratic curveto
+    { "M10 20 Q30 40 50 60", "M 10 20 Q 30 40, 50 60" },
+    { "M10 20 Q30 40 50 60,70,80-90 100",
+      "M 10 20 Q 30 40, 50 60 Q 70 80, -90 100" },
+    { "m10 20 q 30,40 50 60-70,80 90 100",
+      "M 10 20 Q 40 60, 60 80 Q -10 160, 150 180" },
+    // smooth quadratic curveto
+    { "M10 20 T30 40", "M 10 20 Q 10 20, 30 40" },
+    { "M10 20 Q30 40 50 60 T70 80", "M 10 20 Q 30 40, 50 60 Q 70 80, 70 80" },
+    { "m10 20 q 30,40 50 60t-70,80",
+      "M 10 20 Q 40 60, 60 80 Q 80 100, -10 160" },
+    // elliptical arc. Exact numbers depend on too much math, so just verify
+    // that these parse successfully
+    { "M 1 3 A 1 2 3 00 6 7", "path" },
+    { "M 1 2 A 1 2 3 016 7", "path" },
+    { "M 1 2 A 1 2 3 10,6 7", "path" },
+    { "M 1 2 A 1 2 3 1,1 6 7", "path" },
+    { "M 1 2 A 1 2 3 1 1 6 7", "path" },
+    { "M 1 2 A 1 2 3 1 16 7", "path" },
+    // close path
+    { "M10 20 Z", "M 10 20 Z" },
+    { "m10 20 30 40 m 50 60 70 80 90 100z", "M 10 20 L 40 60 M 90 120 L 160 200 L 250 300 Z" },
+    // must start with moveto
+    { " L10 20", NULL },
+    // moveto args
+    { "M", NULL },
+    { "M,", NULL },
+    { "M10", NULL },
+    { "M10,", NULL },
+    { "M10x", NULL },
+    { "M10,x", NULL },
+    { "M10-20,", NULL },
+    { "M10-20-30", NULL },
+    { "M10-20-30 x", NULL },
+    // closepath args
+    { "M10-20z10", NULL },
+    { "M10-20z,", NULL },
+    // lineto args
+    { "M10-20L10", NULL },
+    { "M 10,10 L 20,20,30", NULL },
+    { "M 10,10 L 20,20,", NULL },
+    // horizontal lineto args
+    { "M10-20H", NULL },
+    { "M10-20H,", NULL },
+    { "M10-20H30,", NULL },
+    // vertical lineto args
+    { "M10-20v", NULL },
+    { "M10-20v,", NULL },
+    { "M10-20v30,", NULL },
+    // curveto args
+    { "M10-20C1", NULL },
+    { "M10-20C1,", NULL },
+    { "M10-20C1 2", NULL },
+    { "M10-20C1,2,", NULL },
+    { "M10-20C1 2 3", NULL },
+    { "M10-20C1,2,3", NULL },
+    { "M10-20C1,2,3,", NULL },
+    { "M10-20C1 2 3 4", NULL },
+    { "M10-20C1,2,3,4", NULL },
+    { "M10-20C1,2,3,4,", NULL },
+    { "M10-20C1 2 3 4 5", NULL },
+    { "M10-20C1,2,3,4,5", NULL },
+    { "M10-20C1,2,3,4,5,", NULL },
+    { "M10-20C1,2,3,4,5,6,", NULL },
+    // smooth curveto args
+    { "M10-20S1", NULL },
+    { "M10-20S1,", NULL },
+    { "M10-20S1 2", NULL },
+    { "M10-20S1,2,", NULL },
+    { "M10-20S1 2 3", NULL },
+    { "M10-20S1,2,3,", NULL },
+    { "M10-20S1,2,3,4,", NULL },
+    // quadratic curveto args
+    { "M10-20Q1", NULL },
+    { "M10-20Q1,", NULL },
+    { "M10-20Q1 2", NULL },
+    { "M10-20Q1,2,", NULL },
+    { "M10-20Q1 2 3", NULL },
+    { "M10-20Q1,2,3", NULL },
+    { "M10-20Q1,2,3,", NULL },
+    { "M10 20 Q30 40 50 60,", NULL },
+    // smooth quadratic curveto args
+    { "M10-20T1", NULL },
+    { "M10-20T1,", NULL },
+    { "M10 20 T 30 40,", NULL },
+    // elliptical arc args
+    { "M10-20A1", NULL },
+    { "M10-20A1,", NULL },
+    { "M10-20A1 2", NULL },
+    { "M10-20A1 2,", NULL },
+    { "M10-20A1 2 3", NULL },
+    { "M10-20A1 2 3,", NULL },
+    { "M10-20A1 2 3 4", NULL },
+    { "M10-20A1 2 3 1", NULL },
+    { "M10-20A1 2 3,1,", NULL },
+    { "M10-20A1 2 3 1 5", NULL },
+    { "M10-20A1 2 3 1 1", NULL },
+    { "M10-20A1 2 3,1,1,", NULL },
+    { "M10-20A1 2 3 1 1 6", NULL },
+    { "M10-20A1 2 3,1,1,6,", NULL },
+    { "M 1 2 A 1 2 3 1.0 0.0 6 7", NULL },
+    { "M10-20A1 2 3,1,1,6,7,", NULL },
+    // misc
+    { "M.. 1,0 0,100000", NULL },
+    { "M 10 20,M 10 20", NULL },
+    { "M 10 20, M 10 20", NULL },
+    { "M 10 20, M 10 20", NULL },
+    { "M 10 20, ", NULL },
+  };
+  int i;
+
+  for (i = 0; i < G_N_ELEMENTS (tests); i++)
+    {
+      GskPath *path;
+      char *string;
+      char *string2;
+
+      if (g_test_verbose ())
+        g_print ("%d: %s\n", i, tests[i].in);
+
+      path = gsk_path_parse (tests[i].in);
+      if (tests[i].out)
+        {
+          g_assert_nonnull (path);
+          string = gsk_path_to_string (path);
+          gsk_path_unref (path);
+
+          if (strcmp (tests[i].out, "path") != 0)
+            {
+              /* Preferred, but doesn't work, because gsk_path_print()
+               * prints numbers with insane accuracy
+               */
+              /* g_assert_cmpstr (tests[i].out, ==, string); */
+              path = gsk_path_parse (tests[i].out);
+              g_assert_nonnull (path);
+
+              string2 = gsk_path_to_string (path);
+              gsk_path_unref (path);
+
+              g_assert_cmpstr (string, ==, string2);
+
+              g_free (string2);
+            }
+
+          path = gsk_path_parse (string);
+          g_assert_nonnull (path);
+
+          string2 = gsk_path_to_string (path);
+          gsk_path_unref (path);
+
+          g_assert_cmpstr (string, ==, string2);
+
+          g_free (string);
+          g_free (string2);
+        }
+      else
+        g_assert_null (path);
+    }
+}
+
+/* Test that circles and rectangles serialize as expected and can be
+ * round-tripped through strings.
+ */
+static void
+test_serialize_custom_contours (void)
+{
+  GskPathBuilder *builder;
+  GskPath *path;
+  GskPath *path1;
+  char *string;
+  char *string1;
+
+  builder = gsk_path_builder_new ();
+  gsk_path_builder_add_circle (builder, &GRAPHENE_POINT_INIT (100, 100), 50);
+  gsk_path_builder_add_rect (builder, &GRAPHENE_RECT_INIT (111, 222, 333, 444));
+  path = gsk_path_builder_free_to_path (builder);
+
+  string = gsk_path_to_string (path);
+  g_assert_cmpstr ("M 150 100 A 50 50 0 0 0 50 100 A 50 50 0 0 0 150 100 z M 111 222 h 333 v 444 h -333 z", ==, string);
+
+  path1 = gsk_path_parse (string);
+  string1 = gsk_path_to_string (path1);
+  g_assert_cmpstr (string, ==, string1);
+
+  g_free (string);
+  g_free (string1);
+  gsk_path_unref (path);
+  gsk_path_unref (path1);
+}
+
+int
+main (int   argc,
+      char *argv[])
+{
+  gtk_test_init (&argc, &argv, NULL);
+
+  g_test_add_func ("/path/rsvg-parse", test_rsvg_parse);
+  g_test_add_func ("/path/serialize-custom-contours", test_serialize_custom_contours);
+
+  return g_test_run ();
+}

testsuite/gsk/path.c

@@ -0,0 +1,656 @@
+/*
+ * Copyright © 2020 Benjamin Otte
+ *
+ * This library is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU Lesser General Public
+ * License as published by the Free Software Foundation; either
+ * version 2.1 of the License, or (at your option) any later version.
+ *
+ * This library is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+ * Lesser General Public License for more details.
+ *
+ * You should have received a copy of the GNU Lesser General Public
+ * License along with this library. If not, see <http://www.gnu.org/licenses/>.
+ *
+ * Authors: Benjamin Otte <otte@gnome.org>
+ */
+
+#include <gtk/gtk.h>
+#include "gsk/gskpath.h"
+#include "gsk/gskpathbuilder.h"
+
+static float
+random_weight (void)
+{
+  if (g_test_rand_bit ())
+    return g_test_rand_double_range (1, 20);
+  else
+    return 1.0 / g_test_rand_double_range (1, 20);
+}
+
+static GskPath *
+create_random_degenerate_path (guint max_contours)
+{
+#define N_DEGENERATE_PATHS 15
+  GskPathBuilder *builder;
+  guint i;
+
+  builder = gsk_path_builder_new ();
+
+  switch (g_test_rand_int_range (0, N_DEGENERATE_PATHS))
+  {
+    case 0:
+      /* empty path */
+      break;
+
+    case 1:
+      /* a single point */
+      gsk_path_builder_move_to (builder, 
+                                g_test_rand_double_range (-1000, 1000),
+                                g_test_rand_double_range (-1000, 1000));
+      break;
+
+    case 2:
+      /* N points */
+      for (i = 0; i < MIN (10, max_contours); i++)
+        {
+          gsk_path_builder_move_to (builder, 
+                                    g_test_rand_double_range (-1000, 1000),
+                                    g_test_rand_double_range (-1000, 1000));
+        }
+      break;
+
+    case 3:
+      /* 1 closed point */
+      gsk_path_builder_move_to (builder, 
+                                g_test_rand_double_range (-1000, 1000),
+                                g_test_rand_double_range (-1000, 1000));
+      gsk_path_builder_close (builder);
+      break;
+
+    case 4:
+      /* the same point closed N times */
+      gsk_path_builder_move_to (builder, 
+                                g_test_rand_double_range (-1000, 1000),
+                                g_test_rand_double_range (-1000, 1000));
+      for (i = 0; i < MIN (10, max_contours); i++)
+        {
+          gsk_path_builder_close (builder);
+        }
+      break;
+
+    case 5:
+      /* a zero-width and zero-height rect */
+      gsk_path_builder_add_rect (builder,
+                                 &GRAPHENE_RECT_INIT (g_test_rand_double_range (-1000, 1000),
+                                                      g_test_rand_double_range (-1000, 1000),
+                                                      0, 0));
+      break;
+
+    case 6:
+      /* a zero-width rect */
+      gsk_path_builder_add_rect (builder,
+                                 &GRAPHENE_RECT_INIT (g_test_rand_double_range (-1000, 1000),
+                                                      g_test_rand_double_range (-1000, 1000),
+                                                      0,
+                                                      g_test_rand_double_range (-1000, 1000)));
+      break;
+
+    case 7:
+      /* a zero-height rect */
+      gsk_path_builder_add_rect (builder,
+                                 &GRAPHENE_RECT_INIT (g_test_rand_double_range (-1000, 1000),
+                                                      g_test_rand_double_range (-1000, 1000),
+                                                      g_test_rand_double_range (-1000, 1000),
+                                                      0));
+      break;
+
+    case 8:
+      /* a negative-size rect */
+      gsk_path_builder_add_rect (builder,
+                                 &GRAPHENE_RECT_INIT (g_test_rand_double_range (-1000, 1000),
+                                                      g_test_rand_double_range (-1000, 1000),
+                                                      g_test_rand_double_range (-1000, 0),
+                                                      g_test_rand_double_range (-1000, 0)));
+      break;
+
+    case 9:
+      /* an absolutely random rect */
+      gsk_path_builder_add_rect (builder,
+                                 &GRAPHENE_RECT_INIT (g_test_rand_double_range (-1000, 1000),
+                                                      g_test_rand_double_range (-1000, 1000),
+                                                      g_test_rand_double_range (-1000, 1000),
+                                                      g_test_rand_double_range (-1000, 1000)));
+      break;
+
+    case 10:
+      /* an absolutely random rect */
+      gsk_path_builder_add_rect (builder,
+                                 &GRAPHENE_RECT_INIT (g_test_rand_double_range (-1000, 1000),
+                                                      g_test_rand_double_range (-1000, 1000),
+                                                      g_test_rand_double_range (-1000, 1000),
+                                                      g_test_rand_double_range (-1000, 1000)));
+      break;
+
+    case 11:
+      /* an absolutely random circle */
+      gsk_path_builder_add_circle (builder,
+                                   &GRAPHENE_POINT_INIT (g_test_rand_double_range (-1000, 1000),
+                                                         g_test_rand_double_range (-1000, 1000)),
+                                   g_test_rand_double_range (1, 1000));
+      break;
+
+    case 12:
+      /* a zero-length line */
+      {
+        graphene_point_t point = GRAPHENE_POINT_INIT (g_test_rand_double_range (-1000, 1000),
+                                                      g_test_rand_double_range (-1000, 1000));
+        gsk_path_builder_move_to (builder, point.x, point.y);
+        gsk_path_builder_line_to (builder, point.x, point.y);
+      }
+      break;
+
+    case 13:
+      /* a curve with start == end */
+      {
+        graphene_point_t point = GRAPHENE_POINT_INIT (g_test_rand_double_range (-1000, 1000),
+                                                      g_test_rand_double_range (-1000, 1000));
+        gsk_path_builder_move_to (builder, point.x, point.y);
+        gsk_path_builder_cubic_to (builder,
+                                   g_test_rand_double_range (-1000, 1000),
+                                   g_test_rand_double_range (-1000, 1000),
+                                   g_test_rand_double_range (-1000, 1000),
+                                   g_test_rand_double_range (-1000, 1000),
+                                   point.x, point.y);
+      }
+      break;
+
+    case 14:
+      /* a conic with start == end */
+      {
+        graphene_point_t point = GRAPHENE_POINT_INIT (g_test_rand_double_range (-1000, 1000),
+                                                      g_test_rand_double_range (-1000, 1000));
+        gsk_path_builder_move_to (builder, point.x, point.y);
+        gsk_path_builder_conic_to (builder,
+                                   g_test_rand_double_range (-1000, 1000),
+                                   g_test_rand_double_range (-1000, 1000),
+                                   point.x, point.y,
+                                   random_weight ());
+      }
+      break;
+
+    case N_DEGENERATE_PATHS:
+    default:
+      g_assert_not_reached ();
+  }
+
+  return gsk_path_builder_free_to_path (builder);
+}
+
+static GskPath *
+create_random_path (guint max_contours);
+
+static void
+add_shape_contour (GskPathBuilder *builder)
+{
+#define N_SHAPE_CONTOURS 3
+  switch (g_test_rand_int_range (0, N_SHAPE_CONTOURS))
+  {
+    case 0:
+      gsk_path_builder_add_rect (builder,
+                                 &GRAPHENE_RECT_INIT (g_test_rand_double_range (-1000, 1000),
+                                                      g_test_rand_double_range (-1000, 1000),
+                                                      g_test_rand_double_range (1, 1000),
+                                                      g_test_rand_double_range (1, 1000)));
+      break;
+
+    case 1:
+      gsk_path_builder_add_circle (builder,
+                                   &GRAPHENE_POINT_INIT (g_test_rand_double_range (-1000, 1000),
+                                                         g_test_rand_double_range (-1000, 1000)),
+                                   g_test_rand_double_range (1, 1000));
+      break;
+
+    case 2:
+      {
+        GskPath *path = create_random_path (1);
+        gsk_path_builder_add_path (builder, path);
+        gsk_path_unref (path);
+      }
+      break;
+
+    case N_SHAPE_CONTOURS:
+    default:
+      g_assert_not_reached ();
+      break;
+  }
+}
+
+static void
+add_standard_contour (GskPathBuilder *builder)
+{
+  guint i, n;
+
+  if (g_test_rand_bit ())
+    {
+      if (g_test_rand_bit ())
+        gsk_path_builder_move_to (builder,
+                                  g_test_rand_double_range (-1000, 1000),
+                                  g_test_rand_double_range (-1000, 1000));
+      else
+        gsk_path_builder_rel_move_to (builder,
+                                      g_test_rand_double_range (-1000, 1000),
+                                      g_test_rand_double_range (-1000, 1000));
+    }
+
+  /* that 20 is random, but should be enough to get some
+   * crazy self-intersecting shapes */
+  n = g_test_rand_int_range (1, 20);
+  for (i = 0; i < n; i++)
+    {
+      switch (g_test_rand_int_range (0, 8))
+      {
+        case 0:
+          gsk_path_builder_line_to (builder,
+                                    g_test_rand_double_range (-1000, 1000),
+                                    g_test_rand_double_range (-1000, 1000));
+          break;
+
+        case 1:
+          gsk_path_builder_rel_line_to (builder,
+                                        g_test_rand_double_range (-1000, 1000),
+                                        g_test_rand_double_range (-1000, 1000));
+          break;
+
+        case 2:
+          gsk_path_builder_quad_to (builder,
+                                    g_test_rand_double_range (-1000, 1000),
+                                    g_test_rand_double_range (-1000, 1000),
+                                    g_test_rand_double_range (-1000, 1000),
+                                    g_test_rand_double_range (-1000, 1000));
+          break;
+
+        case 3:
+          gsk_path_builder_rel_quad_to (builder,
+                                        g_test_rand_double_range (-1000, 1000),
+                                        g_test_rand_double_range (-1000, 1000),
+                                        g_test_rand_double_range (-1000, 1000),
+                                        g_test_rand_double_range (-1000, 1000));
+          break;
+
+        case 4:
+          gsk_path_builder_cubic_to (builder,
+                                     g_test_rand_double_range (-1000, 1000),
+                                     g_test_rand_double_range (-1000, 1000),
+                                     g_test_rand_double_range (-1000, 1000),
+                                     g_test_rand_double_range (-1000, 1000),
+                                     g_test_rand_double_range (-1000, 1000),
+                                     g_test_rand_double_range (-1000, 1000));
+          break;
+
+        case 5:
+          gsk_path_builder_rel_cubic_to (builder,
+                                         g_test_rand_double_range (-1000, 1000),
+                                         g_test_rand_double_range (-1000, 1000),
+                                         g_test_rand_double_range (-1000, 1000),
+                                         g_test_rand_double_range (-1000, 1000),
+                                         g_test_rand_double_range (-1000, 1000),
+                                         g_test_rand_double_range (-1000, 1000));
+          break;
+
+        case 6:
+          gsk_path_builder_conic_to (builder,
+                                     g_test_rand_double_range (-1000, 1000),
+                                     g_test_rand_double_range (-1000, 1000),
+                                     g_test_rand_double_range (-1000, 1000),
+                                     g_test_rand_double_range (-1000, 1000),
+                                     random_weight ());
+          break;
+
+        case 7:
+          gsk_path_builder_rel_conic_to (builder,
+                                         g_test_rand_double_range (-1000, 1000),
+                                         g_test_rand_double_range (-1000, 1000),
+                                         g_test_rand_double_range (-1000, 1000),
+                                         g_test_rand_double_range (-1000, 1000),
+                                         random_weight ());
+          break;
+
+        default:
+          g_assert_not_reached();
+          break;
+      }
+    }
+
+  if (g_test_rand_bit ())
+    gsk_path_builder_close (builder);
+}
+
+static GskPath *
+create_random_path (guint max_contours)
+{
+  GskPathBuilder *builder;
+  guint i, n;
+
+  /* 5% chance for a weird shape */
+  if (!g_test_rand_int_range (0, 20))
+    return create_random_degenerate_path (max_contours);
+
+  builder = gsk_path_builder_new ();
+  n = g_test_rand_int_range (1, 10);
+  n = MIN (n, max_contours);
+
+  for (i = 0; i < n; i++)
+    {
+      /* 2/3 of shapes are standard contours */
+      if (g_test_rand_int_range (0, 3))
+        add_standard_contour (builder);
+      else
+        add_shape_contour (builder);
+    }
+
+  return gsk_path_builder_free_to_path (builder);
+}
+
+typedef struct {
+  GskPathOperation op;
+  graphene_point_t pts[4];
+  float weight;
+} PathOperation;
+
+static void
+_g_string_append_double (GString *string,
+                         double   d)
+{
+  char buf[G_ASCII_DTOSTR_BUF_SIZE];
+
+  g_ascii_dtostr (buf, G_ASCII_DTOSTR_BUF_SIZE, d);
+  g_string_append (string, buf);
+}
+
+static void
+_g_string_append_point (GString                *string,
+                        const graphene_point_t *pt)
+{
+  _g_string_append_double (string, pt->x);
+  g_string_append_c (string, ' ');
+  _g_string_append_double (string, pt->y);
+}
+
+static void
+path_operation_print (const PathOperation *p,
+                      GString             *string)
+{
+  switch (p->op)
+  {
+    case GSK_PATH_MOVE:
+      g_string_append (string, "M ");
+      _g_string_append_point (string, &p->pts[0]);
+      break;
+
+    case GSK_PATH_CLOSE:
+      g_string_append (string, " Z");
+      break;
+
+    case GSK_PATH_LINE:
+      g_string_append (string, " L ");
+      _g_string_append_point (string, &p->pts[1]);
+      break;
+
+    case GSK_PATH_QUAD:
+      g_string_append (string, " Q ");
+      _g_string_append_point (string, &p->pts[1]);
+      g_string_append (string, ", ");
+      _g_string_append_point (string, &p->pts[2]);
+      break;
+
+    case GSK_PATH_CUBIC:
+      g_string_append (string, " C ");
+      _g_string_append_point (string, &p->pts[1]);
+      g_string_append (string, ", ");
+      _g_string_append_point (string, &p->pts[2]);
+      g_string_append (string, ", ");
+      _g_string_append_point (string, &p->pts[3]);
+      break;
+
+    case GSK_PATH_CONIC:
+      /* This is not valid SVG */
+      g_string_append (string, " O ");
+      _g_string_append_point (string, &p->pts[1]);
+      g_string_append (string, ", ");
+      _g_string_append_point (string, &p->pts[2]);
+      g_string_append (string, ", ");
+      _g_string_append_double (string, p->weight);
+      break;
+
+    default:
+      g_assert_not_reached();
+      return;
+  }
+}
+
+static gboolean
+path_operation_equal (const PathOperation *p1,
+                      const PathOperation *p2,
+                      float                epsilon)
+{
+  if (p1->op != p2->op)
+    return FALSE;
+
+  /* No need to compare pts[0] for most ops, that's just
+   * duplicate work. */
+  switch (p1->op)
+    {
+      case GSK_PATH_MOVE:
+        return graphene_point_near (&p1->pts[0], &p2->pts[0], epsilon);
+
+      case GSK_PATH_LINE:
+      case GSK_PATH_CLOSE:
+        return graphene_point_near (&p1->pts[1], &p2->pts[1], epsilon);
+
+      case GSK_PATH_QUAD:
+        return graphene_point_near (&p1->pts[1], &p2->pts[1], epsilon)
+            && graphene_point_near (&p1->pts[2], &p2->pts[2], epsilon);
+
+      case GSK_PATH_CUBIC:
+        return graphene_point_near (&p1->pts[1], &p2->pts[1], epsilon)
+            && graphene_point_near (&p1->pts[2], &p2->pts[2], epsilon)
+            && graphene_point_near (&p1->pts[3], &p2->pts[3], epsilon);
+
+      case GSK_PATH_CONIC:
+        return graphene_point_near (&p1->pts[1], &p2->pts[1], epsilon)
+            && graphene_point_near (&p1->pts[2], &p2->pts[2], epsilon)
+            && G_APPROX_VALUE (p1->weight, p2->weight, epsilon);
+
+      default:
+        g_return_val_if_reached (FALSE);
+    }
+}
+
+static gboolean 
+collect_path_operation_cb (GskPathOperation        op,
+                           const graphene_point_t *pts,
+                           gsize                   n_pts,
+                           float                   weight,
+                           gpointer                user_data)
+{
+  g_array_append_vals (user_data,
+                       (PathOperation[1])  { {
+                         op,
+                         {
+                           GRAPHENE_POINT_INIT(pts[0].x, pts[0].y),
+                           GRAPHENE_POINT_INIT(n_pts > 1 ? pts[1].x : 0,
+                                               n_pts > 1 ? pts[1].y : 0),
+                           GRAPHENE_POINT_INIT(n_pts > 2 ? pts[2].x : 0,
+                                               n_pts > 2 ? pts[2].y : 0),
+                           GRAPHENE_POINT_INIT(n_pts > 3 ? pts[3].x : 0,
+                                               n_pts > 3 ? pts[3].y : 0)
+                         },
+                         weight
+                       } },
+                       1);
+  return TRUE;
+}
+
+static GArray *
+collect_path (GskPath *path)
+{
+  GArray *array = g_array_new (FALSE, FALSE, sizeof (PathOperation));
+
+  /* Use -1 here because we want all the flags, even future additions */
+  gsk_path_foreach (path, -1, collect_path_operation_cb, array);
+
+  return array;
+}
+
+static void
+assert_path_equal_func (const char *domain,
+                        const char *file,
+                        int         line,
+                        const char *func,
+                        GskPath    *path1,
+                        GskPath    *path2,
+                        float       epsilon)
+{
+  GArray *ops1, *ops2;
+  guint i;
+
+  ops1 = collect_path (path1);
+  ops2 = collect_path (path2);
+
+  for (i = 0; i < MAX (ops1->len, ops2->len); i++)
+    {
+      PathOperation *op1 = i < ops1->len ? &g_array_index (ops1, PathOperation, i) : NULL;
+      PathOperation *op2 = i < ops2->len ? &g_array_index (ops2, PathOperation, i) : NULL;
+
+      if (op1 == NULL || op2 == NULL || !path_operation_equal (op1, op2, epsilon))
+        {
+          GString *string;
+          guint j;
+
+          /* Find the operation we start to print */
+          for (j = i; j-- > 0; )
+            {
+              PathOperation *op = &g_array_index (ops1, PathOperation, j);
+              if (op->op == GSK_PATH_MOVE)
+                break;
+              if (j + 3 == i)
+                {
+                  j = i - 1;
+                  break;
+                }
+            }
+
+          string = g_string_new (j == 0 ? "" : "... ");
+          for (; j < i; j++)
+            {
+              PathOperation *op = &g_array_index (ops1, PathOperation, j);
+              path_operation_print (op, string);
+              g_string_append_c (string, ' ');
+            }
+
+          g_string_append (string, "\\\n    ");
+          if (op1)
+            {
+              path_operation_print (op1, string);
+              if (ops1->len > i + 1)
+                g_string_append (string, " ...");
+            }
+          g_string_append (string, "\n    ");
+          if (op1)
+            {
+              path_operation_print (op2, string);
+              if (ops2->len > i + 1)
+                g_string_append (string, " ...");
+            }
+
+          g_assertion_message (domain, file, line, func, string->str);
+
+          g_string_free (string, TRUE);
+        }
+    }
+
+  g_array_free (ops1, TRUE);
+  g_array_free (ops2, TRUE);
+}
+#define assert_path_equal(p1,p2) assert_path_equal_func(G_LOG_DOMAIN, __FILE__, __LINE__, G_STRFUNC, (p1),(p2), FLOAT_EPSILON)
+#define assert_path_equal_with_epsilon(p1,p2, epsilon) \
+    assert_path_equal_func(G_LOG_DOMAIN, __FILE__, __LINE__, G_STRFUNC, (p1),(p2), (epsilon))
+
+static void
+test_create (void)
+{
+  GskPath *path1, *path2, *built;
+  GskPathBuilder *builder;
+  guint i;
+  char *s;
+  GString *str;
+
+  for (i = 0; i < 1000; i++)
+    {
+      builder = gsk_path_builder_new ();
+      path1 = create_random_path (G_MAXUINT);
+      gsk_path_builder_add_path (builder, path1);
+      path2 = create_random_path (G_MAXUINT);
+      gsk_path_builder_add_path (builder, path2);
+      built = gsk_path_builder_free_to_path (builder);
+
+      str = g_string_new (NULL);
+      gsk_path_print (path1, str);
+      if (!gsk_path_is_empty (path1) && !gsk_path_is_empty (path2))
+        g_string_append_c (str, ' ');
+      gsk_path_print (path2, str);
+
+      s = gsk_path_to_string (built);
+
+      g_assert_cmpstr (s, ==, str->str);
+      g_string_free (str, TRUE);
+      g_free (s);
+
+      gsk_path_unref (built);
+      gsk_path_unref (path2);
+      gsk_path_unref (path1);
+    }
+}
+
+static void
+test_parse (void)
+{
+  int i;
+
+  for (i = 0; i < 1000; i++)
+    {
+      GskPath *path1, *path2;
+      char *string1, *string2;
+
+      path1 = create_random_path (G_MAXUINT);
+      string1 = gsk_path_to_string (path1);
+      g_assert_nonnull (string1);
+
+      path2 = gsk_path_parse (string1);
+      g_assert_nonnull (path2);
+      string2 = gsk_path_to_string (path2);
+      g_assert_nonnull (string2);
+
+      assert_path_equal_with_epsilon (path1, path2, 1.f / 1024);
+
+      gsk_path_unref (path2);
+      gsk_path_unref (path1);
+      g_free (string2);
+      g_free (string1);
+    }
+}
+
+int
+main (int   argc,
+      char *argv[])
+{
+  gtk_test_init (&argc, &argv, NULL);
+
+  g_test_add_func ("/path/create", test_create);
+  g_test_add_func ("/path/parse", test_parse);
+
+  return g_test_run ();
+}