gl: Use pad-extend for icon cache

Repeat the border pixels to avoid artifacts from
linear scaling.

gsk/gl/gskgldriver.c

@@ -669,7 +669,7 @@ gsk_gl_driver_create_render_target (GskGLDriver *self,
 
   texture_id = gsk_gl_driver_create_texture (self, width, height);
   gsk_gl_driver_bind_source_texture (self, texture_id);
-  gsk_gl_driver_init_texture_empty (self, texture_id);
+  gsk_gl_driver_init_texture_empty (self, texture_id, GL_NEAREST, GL_NEAREST);
 
   render_target = create_render_target (self, texture_id, FALSE, FALSE);
 
@@ -727,7 +727,9 @@ gsk_gl_driver_destroy_texture (GskGLDriver *self,
 
 void
 gsk_gl_driver_init_texture_empty (GskGLDriver *self,
-                                  int          texture_id)
+                                  int          texture_id,
+                                  int          min_filter,
+                                  int          mag_filter)
 {
   Texture *t;
 
@@ -746,6 +748,9 @@ gsk_gl_driver_init_texture_empty (GskGLDriver *self,
       return;
     }
 
+  t->min_filter = min_filter;
+  t->mag_filter = mag_filter;
+
   gsk_gl_driver_set_texture_parameters (self, t->min_filter, t->mag_filter);
 
   if (gdk_gl_context_get_use_es (self->gl_context))

gsk/gl/gskgldriverprivate.h

@@ -53,7 +53,9 @@ void            gsk_gl_driver_bind_source_texture       (GskGLDriver     *driver
                                                          int              texture_id);
 
 void            gsk_gl_driver_init_texture_empty        (GskGLDriver     *driver,
-                                                         int              texture_id);
+                                                         int              texture_id,
+                                                         int              min_filter,
+                                                         int              max_filter);
 void            gsk_gl_driver_init_texture_with_surface (GskGLDriver     *driver,
                                                          int              texture_id,
                                                          cairo_surface_t *surface,

gsk/gl/gskglglyphcache.c

@@ -4,6 +4,7 @@
 #include "gskgldriverprivate.h"
 #include "gskdebugprivate.h"
 #include "gskprivate.h"
+#include "gskgltextureatlasprivate.h"
 
 #include "gdk/gdkglcontextprivate.h"
 
@@ -16,13 +17,13 @@
  * Each cached glyph has an age that gets reset every time a cached glyph gets used.
  * Glyphs that have not been used for the MAX_AGE frames are considered old. We keep
  * count of the pixels of each atlas that are taken up by old glyphs. We check the
- * fraction of old pixels every CHECK_INTERVAL frames, and if it is above MAX_OLD, then
+ * fraction of old pixels every CHECK_INTERVAL frames, and if it is above MAX_OLD_RATIO, then
  * we drop the atlas an all the glyphs contained in it from the cache.
  */
 
 #define MAX_AGE 60
 #define CHECK_INTERVAL 10
-#define MAX_OLD 0.333
+#define MAX_OLD_RATIO 0.333
 
 #define ATLAS_SIZE 512
 
@@ -32,36 +33,28 @@ static gboolean glyph_cache_equal      (gconstpointer v1,
 static void     glyph_cache_key_free   (gpointer      v);
 static void     glyph_cache_value_free (gpointer      v);
 
-static GskGLGlyphAtlas *
+static GskGLTextureAtlas *
 create_atlas (GskGLGlyphCache *self,
               int              width,
               int              height)
 {
-  GskGLGlyphAtlas *atlas;
-
-  atlas = g_new0 (GskGLGlyphAtlas, 1);
-  atlas->width = MAX (width, ATLAS_SIZE);
-  atlas->height = MAX (height, ATLAS_SIZE);
-  atlas->y0 = 1;
-  atlas->y = 1;
-  atlas->x = 1;
-  atlas->image = NULL;
+  GskGLTextureAtlas *atlas;
 
   GSK_RENDERER_NOTE(self->renderer, GLYPH_CACHE, g_message ("Create atlas %d x %d", atlas->width, atlas->height));
 
+  atlas = g_new (GskGLTextureAtlas, 1);
+  gsk_gl_texture_atlas_init (atlas, MAX (width, ATLAS_SIZE), MAX (height, ATLAS_SIZE));
+
   return atlas;
 }
 
 static void
 free_atlas (gpointer v)
 {
-  GskGLGlyphAtlas *atlas = v;
+  GskGLTextureAtlas *atlas = v;
 
-  if (atlas->image)
-    {
-      g_assert (atlas->image->texture_id == 0);
-      g_free (atlas->image);
-    }
+  g_assert (atlas->image.texture_id == 0);
+  gsk_gl_texture_atlas_free (atlas);
 
   g_free (atlas);
 }
@@ -86,12 +79,12 @@ gsk_gl_glyph_cache_free (GskGLGlyphCache *self)
 
   for (i = 0; i < self->atlases->len; i ++)
     {
-      GskGLGlyphAtlas *atlas = g_ptr_array_index (self->atlases, i);
+      GskGLTextureAtlas *atlas = g_ptr_array_index (self->atlases, i);
 
-      if (atlas->image)
+      if (atlas->image.texture_id != 0)
         {
-          gsk_gl_image_destroy (atlas->image, self->gl_driver);
-          atlas->image->texture_id = 0;
+          gsk_gl_image_destroy (&atlas->image, self->gl_driver);
+          atlas->image.texture_id = 0;
         }
     }
 
@@ -138,54 +131,56 @@ add_to_cache (GskGLGlyphCache  *cache,
               GlyphCacheKey    *key,
               GskGLCachedGlyph *value)
 {
-  GskGLGlyphAtlas *atlas;
-  int i;
-  int width = value->draw_width * key->scale / 1024;
-  int height = value->draw_height * key->scale / 1024;
+  const int width = value->draw_width * key->scale / 1024;
+  const int height = value->draw_height * key->scale / 1024;
+  GskGLTextureAtlas *atlas = NULL;
+  guint i, p;
+  int packed_x, packed_y;
 
-  for (i = 0; i < cache->atlases->len; i++)
+  /* Try all the atlases and pick the first one that can hold
+   * our new glyph */
+  for (i = 0, p = cache->atlases->len; i < p; i ++)
     {
-      int x, y, y0;
+      GskGLTextureAtlas *test_atlas = g_ptr_array_index (cache->atlases, i);
+      gboolean was_packed;
 
-      atlas = g_ptr_array_index (cache->atlases, i);
-      x = atlas->x;
-      y = atlas->y;
-      y0 = atlas->y0;
+      was_packed = gsk_gl_texture_atlas_pack (test_atlas, width, height, &packed_x, &packed_y);
 
-      if (atlas->x + width + 1 >= atlas->width)
+      if (was_packed)
         {
-          /* start a new row */
-          y0 = y + 1;
-          x = 1;
-        }
-
-      if (y0 + height + 1 >= atlas->height)
-        continue;
-
-      atlas->y0 = y0;
-      atlas->x = x;
-      atlas->y = y;
+          atlas = test_atlas;
           break;
         }
-
-  if (i == cache->atlases->len)
-    {
-      atlas = create_atlas (cache, width + 2, height + 2);
-      g_ptr_array_add (cache->atlases, atlas);
     }
 
-  value->tx = (float)atlas->x / atlas->width;
-  value->ty = (float)atlas->y0 / atlas->height;
+  if (atlas == NULL)
+    {
+      gboolean was_packed;
+
+      atlas = create_atlas (cache, width + 2, height + 2);
+
+      g_ptr_array_add (cache->atlases, atlas);
+
+      was_packed = gsk_gl_texture_atlas_pack (atlas,
+                                              width + 2, height + 2,
+                                              &packed_x, &packed_y);
+
+      g_assert (was_packed);
+    }
+
+  value->tx = (float)(packed_x + 1) / atlas->width;
+  value->ty = (float)(packed_y + 1) / atlas->height;
   value->tw = (float)width    / atlas->width;
   value->th = (float)height   / atlas->height;
+  value->used = TRUE;
 
   value->atlas = atlas;
 
-  atlas->pending_glyph.key = key;
-  atlas->pending_glyph.value = value;
+  if (atlas->user_data == NULL)
+    atlas->user_data = g_new0 (DirtyGlyph, 1);
 
-  atlas->x = atlas->x + width + 1;
-  atlas->y = MAX (atlas->y, atlas->y0 + height + 1);
+  ((DirtyGlyph *)atlas->user_data)->key = key;
+  ((DirtyGlyph *)atlas->user_data)->value = value;
 
 #ifdef G_ENABLE_DEBUG
   if (GSK_RENDERER_DEBUG_CHECK (cache->renderer, GLYPH_CACHE))
@@ -193,18 +188,17 @@ add_to_cache (GskGLGlyphCache  *cache,
       for (i = 0; i < cache->atlases->len; i++)
         {
           atlas = g_ptr_array_index (cache->atlases, i);
-          g_message ("atlas %d (%dx%d): %.2g%% old pixels, filled to %d, %d / %d",
+          g_message ("atlas %d (%dx%d): %.2g%% old pixels",
                    i, atlas->width, atlas->height,
-                   100.0 * (double)atlas->old_pixels / (double)(atlas->width * atlas->height),
-                   atlas->x, atlas->y0, atlas->y);
+                   gsk_gl_texture_atlas_get_unused_ratio (atlas));
         }
     }
 #endif
 }
 
 static gboolean
-render_glyph (const GskGLGlyphAtlas *atlas,
-              DirtyGlyph            *glyph,
+render_glyph (const GskGLTextureAtlas *atlas,
+              const DirtyGlyph        *glyph,
               GskImageRegion          *region)
 {
   GlyphCacheKey *key = glyph->key;
@@ -271,26 +265,27 @@ render_glyph (const GskGLGlyphAtlas *atlas,
 
 static void
 upload_dirty_glyph (GskGLGlyphCache   *self,
-                    GskGLGlyphAtlas *atlas)
+                    GskGLTextureAtlas *atlas)
 {
   GskImageRegion region;
 
-  g_assert (atlas->pending_glyph.key != NULL);
+  g_assert (atlas->user_data != NULL);
 
   gdk_gl_context_push_debug_group_printf (gsk_gl_driver_get_gl_context (self->gl_driver),
-                                          "Uploading glyph %d", atlas->pending_glyph.key->glyph);
+                                          "Uploading glyph %d", ((DirtyGlyph *)atlas->user_data)->key->glyph);
 
-  if (render_glyph (atlas, &atlas->pending_glyph, &region))
+  if (render_glyph (atlas, (DirtyGlyph *)atlas->user_data, &region))
     {
 
-      gsk_gl_image_upload_regions (atlas->image, self->gl_driver, 1, &region);
+      gsk_gl_image_upload_region (&atlas->image, self->gl_driver, &region);
 
       g_free (region.data);
     }
 
   gdk_gl_context_pop_debug_group (gsk_gl_driver_get_gl_context (self->gl_driver));
-  atlas->pending_glyph.key = NULL;
-  atlas->pending_glyph.value = NULL;
+  /* TODO: This could be unnecessary. We can just reuse the allocated
+   *       DirtyGlyph next time. */
+  g_clear_pointer (&atlas->user_data, g_free);
 }
 
 const GskGLCachedGlyph *
@@ -315,10 +310,15 @@ gsk_gl_glyph_cache_lookup (GskGLGlyphCache *cache,
 
       if (MAX_AGE <= age)
         {
-          GskGLGlyphAtlas *atlas = value->atlas;
+          GskGLTextureAtlas *atlas = value->atlas;
 
-          if (atlas)
-            atlas->old_pixels -= value->draw_width * value->draw_height;
+          if (atlas && !value->used)
+            {
+              gsk_gl_texture_atlas_mark_used (atlas, value->draw_width, value->draw_height);
+              value->used = TRUE;
+            }
+
+          value->timestamp = cache->timestamp;
         }
 
       value->timestamp = cache->timestamp;
@@ -360,23 +360,22 @@ GskGLImage *
 gsk_gl_glyph_cache_get_glyph_image (GskGLGlyphCache        *self,
                                     const GskGLCachedGlyph *glyph)
 {
-  GskGLGlyphAtlas *atlas = glyph->atlas;
+  GskGLTextureAtlas *atlas = glyph->atlas;
 
   g_assert (atlas != NULL);
 
-  if (atlas->image == NULL)
+  if (atlas->image.texture_id == 0)
     {
-      atlas->image = g_new0 (GskGLImage, 1);
-      gsk_gl_image_create (atlas->image, self->gl_driver, atlas->width, atlas->height);
+      gsk_gl_image_create (&atlas->image, self->gl_driver, atlas->width, atlas->height, GL_LINEAR, GL_LINEAR);
       gdk_gl_context_label_object_printf (gsk_gl_driver_get_gl_context (self->gl_driver),
-                                          GL_TEXTURE, atlas->image->texture_id,
-                                          "Glyph atlas %d", atlas->image->texture_id);
+                                          GL_TEXTURE, atlas->image.texture_id,
+                                          "Glyph atlas %d", atlas->image.texture_id);
     }
 
-  if (atlas->pending_glyph.key != NULL)
+  if (atlas->user_data != NULL)
     upload_dirty_glyph (self, atlas);
 
-  return atlas->image;
+  return &atlas->image;
 }
 
 void
@@ -387,43 +386,37 @@ gsk_gl_glyph_cache_begin_frame (GskGLGlyphCache *self)
   GlyphCacheKey *key;
   GskGLCachedGlyph *value;
   GHashTable *removed = g_hash_table_new (g_direct_hash, g_direct_equal);
+  guint dropped = 0;
 
   self->timestamp++;
 
-
   if ((self->timestamp - 1) % CHECK_INTERVAL != 0)
     return;
 
-  /* look for glyphs that have grown old since last time */
-  g_hash_table_iter_init (&iter, self->hash_table);
-  while (g_hash_table_iter_next (&iter, (gpointer *)&key, (gpointer *)&value))
-    {
-      const guint age = self->timestamp - value->timestamp;
-
-      if (MAX_AGE <= age && age < MAX_AGE + CHECK_INTERVAL)
-        {
-          GskGLGlyphAtlas *atlas = value->atlas;
-
-          if (atlas)
-            atlas->old_pixels += value->draw_width * value->draw_height;
-        }
-    }
-
   /* look for atlases to drop, and create a mapping of updated texture indices */
   for (i = self->atlases->len - 1; i >= 0; i--)
     {
-      GskGLGlyphAtlas *atlas = g_ptr_array_index (self->atlases, i);
+      GskGLTextureAtlas *atlas = g_ptr_array_index (self->atlases, i);
 
-      if (atlas->old_pixels > MAX_OLD * atlas->width * atlas->height)
+      if (gsk_gl_texture_atlas_get_unused_ratio (atlas) > MAX_OLD_RATIO)
         {
           GSK_RENDERER_NOTE(self->renderer, GLYPH_CACHE,
-                   g_message ("Dropping atlas %d (%g.2%% old)",
-                            i, 100.0 * (double)atlas->old_pixels / (double)(atlas->width * atlas->height)));
+                   g_message ("Dropping atlas %d (%g.2%% old)", i,
+                              gsk_gl_texture_atlas_get_unused_ratio (atlas)));
 
-          if (atlas->image)
+#if 0
+          static int kk;
+
+          g_message ("Dropping glyph cache... Ratio: %f",
+                     gsk_gl_texture_atlas_get_unused_ratio (atlas));
+          gsk_gl_image_write_to_png (&atlas->image, self->gl_driver,
+                                     g_strdup_printf ("dropped_%d.png", kk++));
+#endif
+
+          if (atlas->image.texture_id != 0)
             {
-              gsk_gl_image_destroy (atlas->image, self->gl_driver);
-              atlas->image->texture_id = 0;
+              gsk_gl_image_destroy (&atlas->image, self->gl_driver);
+              atlas->image.texture_id = 0;
             }
 
           g_hash_table_add (removed, atlas);
@@ -432,11 +425,9 @@ gsk_gl_glyph_cache_begin_frame (GskGLGlyphCache *self)
        }
     }
 
-  if (g_hash_table_size (removed) > 0)
-    {
-      guint dropped = 0;
-
-      /* Remove all glyphs whose atlas was removed */
+  /* Remove all glyphs whose atlas was removed, and
+   * mark old glyphs as unused
+   */
   g_hash_table_iter_init (&iter, self->hash_table);
   while (g_hash_table_iter_next (&iter, (gpointer *)&key, (gpointer *)&value))
     {
@@ -445,12 +436,25 @@ gsk_gl_glyph_cache_begin_frame (GskGLGlyphCache *self)
           g_hash_table_iter_remove (&iter);
           dropped++;
         }
+      else
+        {
+          const guint age = self->timestamp - value->timestamp;
+
+          if (MAX_AGE <= age && age < MAX_AGE + CHECK_INTERVAL)
+            {
+              GskGLTextureAtlas *atlas = value->atlas;
+
+              if (atlas && value->used)
+                {
+                  gsk_gl_texture_atlas_mark_unused (atlas, value->draw_width, value->draw_height);
+                  value->used = FALSE;
                 }
+            }
+        }
+    }
+  g_hash_table_unref (removed);
 
   GSK_RENDERER_NOTE(self->renderer, GLYPH_CACHE, if (dropped > 0) g_message ("Dropped %d glyphs", dropped));
-    }
-
-  g_hash_table_unref (removed);
 
 #if 0
   for (i = 0; i < self->atlases->len; i++)

gsk/gl/gskglglyphcacheprivate.h

@@ -4,6 +4,7 @@
 #include "gskgldriverprivate.h"
 #include "gskglimageprivate.h"
 #include "gskrendererprivate.h"
+#include "gskgltextureatlasprivate.h"
 #include <pango/pango.h>
 #include <gdk/gdk.h>
 
@@ -34,19 +35,9 @@ struct _DirtyGlyph
   GskGLCachedGlyph *value;
 };
 
-typedef struct
-{
-  GskGLImage *image;
-  int width, height;
-  int x, y, y0;
-  guint old_pixels;
-
-  DirtyGlyph pending_glyph;
-} GskGLGlyphAtlas;
-
 struct _GskGLCachedGlyph
 {
-  GskGLGlyphAtlas *atlas;
+  GskGLTextureAtlas *atlas;
 
   float tx;
   float ty;
@@ -61,6 +52,7 @@ struct _GskGLCachedGlyph
   float scale;
 
   guint64 timestamp;
+  guint used: 1;
 };
 
 

gsk/gl/gskgliconcache.c

@@ -0,0 +1,260 @@
+#include "gskgliconcacheprivate.h"
+#include "gskgltextureatlasprivate.h"
+#include "gdk/gdktextureprivate.h"
+
+#include <epoxy/gl.h>
+
+#define ATLAS_SIZE    (1024)
+#define MAX_FRAME_AGE (5 * 60)
+#define MAX_UNUSED_RATIO 0.8
+
+typedef struct
+{
+  graphene_rect_t texture_rect;
+  GskGLTextureAtlas *atlas;
+  int frame_age; /* Number of frames this icon is unused */
+  guint used: 1;
+} IconData;
+
+static void
+icon_data_free (gpointer p)
+{
+  g_free (p);
+}
+
+static void
+free_atlas (gpointer v)
+{
+  GskGLTextureAtlas *atlas = v;
+
+  g_assert (atlas->image.texture_id == 0);
+  gsk_gl_texture_atlas_free (atlas);
+
+  g_free (atlas);
+}
+
+void
+gsk_gl_icon_cache_init (GskGLIconCache *self,
+                        GskRenderer    *renderer,
+                        GskGLDriver    *gl_driver)
+{
+  self->renderer = renderer;
+  self->gl_driver = gl_driver;
+
+  self->atlases = g_ptr_array_new_with_free_func ((GDestroyNotify)free_atlas);
+  self->icons = g_hash_table_new_full (NULL, NULL, NULL, icon_data_free);
+}
+
+void
+gsk_gl_icon_cache_free (GskGLIconCache *self)
+{
+  guint i, p;
+
+  for (i = 0, p = self->atlases->len; i < p; i ++)
+    {
+      GskGLTextureAtlas *atlas = g_ptr_array_index (self->atlases, i);
+
+      if (atlas->image.texture_id != 0)
+        {
+          gsk_gl_image_destroy (&atlas->image, self->gl_driver);
+          atlas->image.texture_id = 0;
+        }
+
+      gsk_gl_texture_atlas_free (atlas);
+
+      g_free (atlas);
+    }
+  g_ptr_array_free (self->atlases, TRUE);
+
+  g_hash_table_unref (self->icons);
+}
+
+void
+gsk_gl_icon_cache_begin_frame (GskGLIconCache *self)
+{
+  gint i, p;
+  GHashTableIter iter;
+  GdkTexture *texture;
+  IconData *icon_data;
+
+  /* Increase frame age of all icons */
+  g_hash_table_iter_init (&iter, self->icons);
+  while (g_hash_table_iter_next (&iter, (gpointer *)&texture, (gpointer *)&icon_data))
+    {
+      icon_data->frame_age ++;
+
+      if (icon_data->frame_age > MAX_FRAME_AGE)
+        {
+
+          if (icon_data->used)
+            {
+              const int w = icon_data->texture_rect.size.width  * ATLAS_SIZE;
+              const int h = icon_data->texture_rect.size.height * ATLAS_SIZE;
+
+              gsk_gl_texture_atlas_mark_unused (icon_data->atlas, w + 2, h + 2);
+              icon_data->used = FALSE;
+            }
+          /* We do NOT remove the icon here. Instead, We wait until we drop the entire atlas.
+           * This way we can revive it when we use it again. */
+        }
+    }
+
+  for (i = 0, p = self->atlases->len; i < p; i ++)
+    {
+      GskGLTextureAtlas *atlas = g_ptr_array_index (self->atlases, i);
+
+      if (gsk_gl_texture_atlas_get_unused_ratio (atlas) > MAX_UNUSED_RATIO)
+        {
+          g_hash_table_iter_init (&iter, self->icons);
+          while (g_hash_table_iter_next (&iter, (gpointer *)&texture, (gpointer *)&icon_data))
+            {
+              if (icon_data->atlas == atlas)
+                g_hash_table_iter_remove (&iter);
+            }
+
+          if (atlas->image.texture_id != 0)
+            {
+              gsk_gl_image_destroy (&atlas->image, self->gl_driver);
+              atlas->image.texture_id = 0;
+            }
+
+          g_ptr_array_remove_index_fast (self->atlases, i);
+          i --; /* Check the current index again */
+        }
+    }
+}
+
+/* FIXME: this could probably be done more efficiently */
+static cairo_surface_t *
+pad_surface (cairo_surface_t *surface)
+{
+  cairo_surface_t *padded;
+  cairo_t *cr;
+  cairo_pattern_t *pattern;
+  cairo_matrix_t matrix;
+
+  padded = cairo_image_surface_create (CAIRO_FORMAT_ARGB32,
+                                       cairo_image_surface_get_width (surface) + 2,
+                                       cairo_image_surface_get_height (surface) + 2);
+
+  cr = cairo_create (padded);
+
+  pattern = cairo_pattern_create_for_surface (surface);
+  cairo_pattern_set_extend (pattern, CAIRO_EXTEND_PAD);
+
+  cairo_matrix_init_translate (&matrix, -1, -1);
+  cairo_pattern_set_matrix (pattern, &matrix);
+
+  cairo_set_source (cr, pattern);
+  cairo_paint (cr);
+
+  cairo_destroy (cr);
+  cairo_pattern_destroy (pattern);
+
+  return padded;
+}
+
+void
+gsk_gl_icon_cache_lookup_or_add (GskGLIconCache  *self,
+                                 GdkTexture      *texture,
+                                 int             *out_texture_id,
+                                 graphene_rect_t *out_texture_rect)
+{
+  IconData *icon_data = g_hash_table_lookup (self->icons, texture);
+
+  if (icon_data)
+    {
+      icon_data->frame_age = 0;
+      if (!icon_data->used)
+        {
+          const int w = icon_data->texture_rect.size.width  * ATLAS_SIZE;
+          const int h = icon_data->texture_rect.size.height * ATLAS_SIZE;
+
+          gsk_gl_texture_atlas_mark_used (icon_data->atlas, w + 2, h + 2);
+          icon_data->used = TRUE;
+        }
+
+      *out_texture_id = icon_data->atlas->image.texture_id;
+      *out_texture_rect = icon_data->texture_rect;
+      return;
+    }
+
+  /* texture not on any atlas yet. Find a suitable one. */
+  {
+    const int twidth = gdk_texture_get_width (texture);
+    const int theight = gdk_texture_get_height (texture);
+    int packed_x, packed_y;
+    GskGLTextureAtlas *atlas = NULL;
+    guint i, p;
+    GskImageRegion region;
+    cairo_surface_t *surface;
+    cairo_surface_t *padded_surface;
+
+    g_assert (twidth  < ATLAS_SIZE);
+    g_assert (theight < ATLAS_SIZE);
+
+    for (i = 0, p = self->atlases->len; i < p; i ++)
+      {
+        atlas = g_ptr_array_index (self->atlases, i);
+
+        if (gsk_gl_texture_atlas_pack (atlas, twidth + 2, theight + 2, &packed_x, &packed_y))
+          {
+            packed_x += 1;
+            packed_y += 1;
+            break;
+          }
+
+        atlas = NULL;
+      }
+
+    if (!atlas)
+      {
+        /* No atlas has enough space, so create a new one... */
+        atlas = g_malloc (sizeof (GskGLTextureAtlas));
+        gsk_gl_texture_atlas_init (atlas, ATLAS_SIZE, ATLAS_SIZE);
+        gsk_gl_image_create (&atlas->image, self->gl_driver, atlas->width, atlas->height, GL_LINEAR, GL_LINEAR);
+        /* Pack it onto that one, which surely has enought space... */
+        gsk_gl_texture_atlas_pack (atlas, twidth + 2, theight + 2, &packed_x, &packed_y);
+        packed_x += 1;
+        packed_y += 1;
+
+        g_ptr_array_add (self->atlases, atlas);
+      }
+
+    icon_data = g_new0 (IconData, 1);
+    icon_data->atlas = atlas;
+    icon_data->frame_age = 0;
+    icon_data->used = TRUE;
+    graphene_rect_init (&icon_data->texture_rect,
+                        (float)packed_x / ATLAS_SIZE,
+                        (float)packed_y / ATLAS_SIZE,
+                        (float)twidth   / ATLAS_SIZE,
+                        (float)theight  / ATLAS_SIZE);
+
+    g_hash_table_insert (self->icons, texture, icon_data);
+
+    /* actually upload the texture */
+    surface = gdk_texture_download_surface (texture);
+    padded_surface = pad_surface (surface);
+    region.x = packed_x - 1;
+    region.y = packed_y - 1;
+    region.width = twidth + 2;
+    region.height = theight + 2;
+    region.data = cairo_image_surface_get_data (padded_surface);
+
+    gsk_gl_image_upload_region (&atlas->image, self->gl_driver, &region);
+
+    *out_texture_id = atlas->image.texture_id;
+    *out_texture_rect = icon_data->texture_rect;
+
+    cairo_surface_destroy (surface);
+    cairo_surface_destroy (padded_surface);
+
+#if 0
+    /* Some obvious debugging */
+    static int k;
+    gsk_gl_image_write_to_png (&atlas->image, self->gl_driver,
+                               g_strdup_printf ("icon%d.png", k ++));
+#endif
+  }
+}

gsk/gl/gskgliconcacheprivate.h

@@ -0,0 +1,31 @@
+#ifndef __GSK_GL_ICON_CACHE_PRIVATE_H__
+#define __GSK_GL_ICON_CACHE_PRIVATE_H__
+
+#include "gskgldriverprivate.h"
+#include "gskglimageprivate.h"
+#include "gskrendererprivate.h"
+#include "gskgltextureatlasprivate.h"
+#include <pango/pango.h>
+#include <gdk/gdk.h>
+
+typedef struct
+{
+  GskGLDriver *gl_driver;
+  GskRenderer *renderer;
+
+  GPtrArray *atlases;
+  GHashTable *icons; /* GdkTexture -> IconData */
+
+} GskGLIconCache;
+
+void             gsk_gl_icon_cache_init           (GskGLIconCache        *self,
+                                                   GskRenderer            *renderer,
+                                                   GskGLDriver            *gl_driver);
+void             gsk_gl_icon_cache_free           (GskGLIconCache        *self);
+void             gsk_gl_icon_cache_begin_frame    (GskGLIconCache        *self);
+void             gsk_gl_icon_cache_lookup_or_add  (GskGLIconCache        *self,
+                                                   GdkTexture            *texture,
+                                                   int                   *out_texture_id,
+                                                   graphene_rect_t       *out_texture_rect);
+
+#endif

gsk/gl/gskglimage.c

@@ -6,14 +6,16 @@ void
 gsk_gl_image_create (GskGLImage  *self,
                      GskGLDriver *gl_driver,
                      int          width,
-                     int          height)
+                     int          height,
+                     int          min_filter,
+                     int          mag_filter)
 {
   self->texture_id = gsk_gl_driver_create_texture (gl_driver, width, height);
   self->width = width;
   self->height = height;
 
   gsk_gl_driver_bind_source_texture (gl_driver, self->texture_id);
-  gsk_gl_driver_init_texture_empty (gl_driver, self->texture_id);
+  gsk_gl_driver_init_texture_empty (gl_driver, self->texture_id, min_filter, mag_filter);
   gsk_gl_driver_mark_texture_permanent (gl_driver, self->texture_id);
 }
 
@@ -22,6 +24,7 @@ gsk_gl_image_destroy (GskGLImage  *self,
                       GskGLDriver *gl_driver)
 {
   gsk_gl_driver_destroy_texture (gl_driver, self->texture_id);
+  self->texture_id = 0;
 }
 
 void
@@ -43,23 +46,15 @@ gsk_gl_image_write_to_png (const GskGLImage *self,
 }
 
 void
-gsk_gl_image_upload_regions (GskGLImage           *self,
+gsk_gl_image_upload_region (GskGLImage           *self,
                             GskGLDriver          *gl_driver,
-                             guint                 n_regions,
-                             const GskImageRegion *regions)
+                            const GskImageRegion *region)
 {
-  guint i;
-
-  for (i = 0; i < n_regions; i ++)
-    {
-      const GskImageRegion *region = &regions[i];
-
   gsk_gl_driver_bind_source_texture (gl_driver, self->texture_id);
   glBindTexture (GL_TEXTURE_2D, self->texture_id);
 
   glTexSubImage2D (GL_TEXTURE_2D, 0, region->x, region->y, region->width, region->height,
                    GL_BGRA, GL_UNSIGNED_INT_8_8_8_8_REV, region->data);
-    }
 
 #ifdef G_ENABLE_DEBUG
   /*gsk_gl_driver_bind_source_texture (gl_driver, self->texture_id);*/

gsk/gl/gskglimageprivate.h

@@ -24,16 +24,17 @@ typedef struct
 void gsk_gl_image_create         (GskGLImage           *self,
                                   GskGLDriver          *gl_driver,
                                   int                   width,
-                                  int                   height);
+                                  int                   height,
+                                  int                   min_filter,
+                                  int                   mag_filter);
 void gsk_gl_image_destroy        (GskGLImage           *self,
                                   GskGLDriver          *gl_driver);
 void gsk_gl_image_write_to_png   (const GskGLImage     *self,
                                   GskGLDriver          *gl_driver,
                                   const char           *filename);
-void gsk_gl_image_upload_regions (GskGLImage           *self,
+void gsk_gl_image_upload_region  (GskGLImage           *self,
                                   GskGLDriver          *gl_driver,
-                                  guint                 n_regions,
-                                  const GskImageRegion *regions);
+                                  const GskImageRegion *region);
 
 
 #endif

gsk/gl/gskglrenderer.c

@@ -11,6 +11,7 @@
 #include "gsktransformprivate.h"
 #include "gskshaderbuilderprivate.h"
 #include "gskglglyphcacheprivate.h"
+#include "gskgliconcacheprivate.h"
 #include "gskglrenderopsprivate.h"
 #include "gskcairoblurprivate.h"
 #include "gskglshadowcacheprivate.h"
@@ -335,6 +336,7 @@ struct _GskGLRenderer
   GArray *render_ops;
 
   GskGLGlyphCache glyph_cache;
+  GskGLIconCache icon_cache;
   GskGLShadowCache shadow_cache;
 
 #ifdef G_ENABLE_DEBUG
@@ -823,27 +825,45 @@ render_texture_node (GskGLRenderer       *self,
     }
   else
     {
-      int gl_min_filter = GL_NEAREST, gl_mag_filter = GL_NEAREST;
       int texture_id;
+      float tx = 0, ty = 0, tx2 = 1, ty2 = 1;
 
+      if (texture->width <= 64 &&
+          texture->height <= 64)
+        {
+          graphene_rect_t trect;
+
+          gsk_gl_icon_cache_lookup_or_add (&self->icon_cache,
+                                           texture,
+                                           &texture_id,
+                                           &trect);
+          tx = trect.origin.x;
+          ty = trect.origin.y;
+          tx2 = tx + trect.size.width;
+          ty2 = ty + trect.size.height;
+        }
+      else
+        {
+          int gl_min_filter = GL_NEAREST, gl_mag_filter = GL_NEAREST;
           get_gl_scaling_filters (node, &gl_min_filter, &gl_mag_filter);
 
           texture_id = gsk_gl_driver_get_texture_for_texture (self->gl_driver,
                                                               texture,
                                                               gl_min_filter,
                                                               gl_mag_filter);
+        }
+
       ops_set_program (builder, &self->blit_program);
       ops_set_texture (builder, texture_id);
 
-
       ops_draw (builder, (GskQuadVertex[GL_N_VERTICES]) {
-        { { min_x, min_y }, { 0, 0 }, },
-        { { min_x, max_y }, { 0, 1 }, },
-        { { max_x, min_y }, { 1, 0 }, },
+        { { min_x, min_y }, { tx,  ty  }, },
+        { { min_x, max_y }, { tx,  ty2 }, },
+        { { max_x, min_y }, { tx2, ty  }, },
 
-        { { max_x, max_y }, { 1, 1 }, },
-        { { min_x, max_y }, { 0, 1 }, },
-        { { max_x, min_y }, { 1, 0 }, },
+        { { max_x, max_y }, { tx2, ty2 }, },
+        { { min_x, max_y }, { tx,  ty2 }, },
+        { { max_x, min_y }, { tx2, ty  }, },
       });
     }
 }
@@ -2476,6 +2496,7 @@ gsk_gl_renderer_realize (GskRenderer  *renderer,
     return FALSE;
 
   gsk_gl_glyph_cache_init (&self->glyph_cache, renderer, self->gl_driver);
+  gsk_gl_icon_cache_init (&self->icon_cache, renderer, self->gl_driver);
   gsk_gl_shadow_cache_init (&self->shadow_cache);
 
   return TRUE;
@@ -2501,6 +2522,7 @@ gsk_gl_renderer_unrealize (GskRenderer *renderer)
     glDeleteProgram (self->programs[i].id);
 
   gsk_gl_glyph_cache_free (&self->glyph_cache);
+  gsk_gl_icon_cache_free (&self->icon_cache);
   gsk_gl_shadow_cache_free (&self->shadow_cache, self->gl_driver);
 
   g_clear_object (&self->gl_profiler);
@@ -3067,6 +3089,7 @@ gsk_gl_renderer_do_render (GskRenderer           *renderer,
   graphene_matrix_scale (&projection, 1, -1, 1);
 
   gsk_gl_glyph_cache_begin_frame (&self->glyph_cache);
+  gsk_gl_icon_cache_begin_frame (&self->icon_cache);
   gsk_gl_shadow_cache_begin_frame (&self->shadow_cache, self->gl_driver);
 
   ops_set_projection (&self->op_builder, &projection);

gsk/gl/gskgltextureatlas.c

@@ -0,0 +1,84 @@
+
+#include "gskgltextureatlasprivate.h"
+
+
+void
+gsk_gl_texture_atlas_init (GskGLTextureAtlas *self,
+                           int                width,
+                           int                height)
+{
+  memset (self, 0, sizeof (*self));
+
+  self->image.texture_id = 0;
+  self->width = width;
+  self->height = height;
+
+  /* TODO: We might want to change the strategy about the amount of
+   *       nodes here? stb_rect_pack.h says with is optimal. */
+  self->nodes = g_malloc0 (sizeof (struct stbrp_node) * width);
+  stbrp_init_target (&self->context,
+                     width, height,
+                     self->nodes,
+                     width);
+}
+
+void
+gsk_gl_texture_atlas_free (GskGLTextureAtlas *self)
+{
+  g_clear_pointer (&self->nodes, g_free);
+}
+
+void
+gsk_gl_texture_atlas_mark_unused (GskGLTextureAtlas *self,
+                                  int                width,
+                                  int                height)
+{
+  self->unused_pixels += (width * height);
+}
+
+
+void
+gsk_gl_texture_atlas_mark_used (GskGLTextureAtlas *self,
+                                int                width,
+                                int                height)
+{
+  self->unused_pixels -= (width * height);
+
+  g_assert (self->unused_pixels >= 0);
+}
+
+gboolean
+gsk_gl_texture_atlas_pack (GskGLTextureAtlas *self,
+                           int                width,
+                           int                height,
+                           int               *out_x,
+                           int               *out_y)
+{
+  stbrp_rect rect;
+
+  g_assert (out_x);
+  g_assert (out_y);
+
+  rect.w = width;
+  rect.h = height;
+
+  stbrp_pack_rects (&self->context, &rect, 1);
+
+  if (rect.was_packed)
+    {
+      *out_x = rect.x;
+      *out_y = rect.y;
+    }
+
+  return rect.was_packed;
+}
+
+double
+gsk_gl_texture_atlas_get_unused_ratio (const GskGLTextureAtlas *self)
+{
+  if (self->unused_pixels > 0)
+    return (double)(self->unused_pixels) / (double)(self->width * self->height);
+
+  return 0.0;
+}
+

gsk/gl/gskgltextureatlasprivate.h

@@ -0,0 +1,49 @@
+
+#ifndef __GSK_GL_TEXTURE_ATLAS_H__
+#define __GSK_GL_TEXTURE_ATLAS_H__
+
+#include "stb_rect_pack.h"
+#include "gskglimageprivate.h"
+#include "gskgldriverprivate.h"
+
+struct _GskGLTextureAtlas
+{
+  struct stbrp_context context;
+  struct stbrp_node *nodes;
+
+  int width;
+  int height;
+
+  GskGLImage image;
+
+  int unused_pixels; /* Pixels of rects that have been used at some point,
+                        But are now unused. */
+
+  void *user_data;
+};
+typedef struct _GskGLTextureAtlas GskGLTextureAtlas;
+
+void        gsk_gl_texture_atlas_init              (GskGLTextureAtlas       *self,
+                                                    int                      width,
+                                                    int                      height);
+
+void        gsk_gl_texture_atlas_free              (GskGLTextureAtlas       *self);
+
+void        gsk_gl_texture_atlas_mark_unused       (GskGLTextureAtlas       *self,
+                                                    int                      width,
+                                                    int                      height);
+
+void        gsk_gl_texture_atlas_mark_used         (GskGLTextureAtlas       *self,
+                                                    int                      width,
+                                                    int                      height);
+
+
+gboolean    gsk_gl_texture_atlas_pack              (GskGLTextureAtlas       *self,
+                                                    int                      width,
+                                                    int                      height,
+                                                    int                     *out_x,
+                                                    int                     *out_y);
+
+double      gsk_gl_texture_atlas_get_unused_ratio  (const GskGLTextureAtlas *self);
+
+#endif

gsk/gl/stb_rect_pack.c

@@ -0,0 +1,431 @@
+
+#include "stb_rect_pack.h"
+#define STB_RECT_PACK_IMPLEMENTATION
+//////////////////////////////////////////////////////////////////////////////
+//
+//     IMPLEMENTATION SECTION
+//
+
+#ifdef STB_RECT_PACK_IMPLEMENTATION
+#ifndef STBRP_SORT
+#include <stdlib.h>
+#define STBRP_SORT qsort
+#endif
+
+#ifndef STBRP_ASSERT
+#include <assert.h>
+#define STBRP_ASSERT assert
+#endif
+
+#ifdef _MSC_VER
+#define STBRP__NOTUSED(v)  (void)(v)
+#else
+#define STBRP__NOTUSED(v)  (void)sizeof(v)
+#endif
+
+enum
+{
+   STBRP__INIT_skyline = 1
+};
+
+STBRP_DEF void stbrp_setup_heuristic(stbrp_context *context, int heuristic)
+{
+   switch (context->init_mode) {
+      case STBRP__INIT_skyline:
+         STBRP_ASSERT(heuristic == STBRP_HEURISTIC_Skyline_BL_sortHeight || heuristic == STBRP_HEURISTIC_Skyline_BF_sortHeight);
+         context->heuristic = heuristic;
+         break;
+      default:
+         STBRP_ASSERT(0);
+   }
+}
+
+STBRP_DEF void stbrp_setup_allow_out_of_mem(stbrp_context *context, int allow_out_of_mem)
+{
+   if (allow_out_of_mem)
+      // if it's ok to run out of memory, then don't bother aligning them;
+      // this gives better packing, but may fail due to OOM (even though
+      // the rectangles easily fit). @TODO a smarter approach would be to only
+      // quantize once we've hit OOM, then we could get rid of this parameter.
+      context->align = 1;
+   else {
+      // if it's not ok to run out of memory, then quantize the widths
+      // so that num_nodes is always enough nodes.
+      //
+      // I.e. num_nodes * align >= width
+      //                  align >= width / num_nodes
+      //                  align = ceil(width/num_nodes)
+
+      context->align = (context->width + context->num_nodes-1) / context->num_nodes;
+   }
+}
+
+STBRP_DEF void stbrp_init_target(stbrp_context *context, int width, int height, stbrp_node *nodes, int num_nodes)
+{
+   int i;
+#ifndef STBRP_LARGE_RECTS
+   STBRP_ASSERT(width <= 0xffff && height <= 0xffff);
+#endif
+
+   for (i=0; i < num_nodes-1; ++i)
+      nodes[i].next = &nodes[i+1];
+   nodes[i].next = NULL;
+   context->init_mode = STBRP__INIT_skyline;
+   context->heuristic = STBRP_HEURISTIC_Skyline_default;
+   context->free_head = &nodes[0];
+   context->active_head = &context->extra[0];
+   context->width = width;
+   context->height = height;
+   context->num_nodes = num_nodes;
+   stbrp_setup_allow_out_of_mem(context, 0);
+
+   // node 0 is the full width, node 1 is the sentinel (lets us not store width explicitly)
+   context->extra[0].x = 0;
+   context->extra[0].y = 0;
+   context->extra[0].next = &context->extra[1];
+   context->extra[1].x = (stbrp_coord) width;
+#ifdef STBRP_LARGE_RECTS
+   context->extra[1].y = (1<<30);
+#else
+   context->extra[1].y = 65535;
+#endif
+   context->extra[1].next = NULL;
+}
+
+// find minimum y position if it starts at x1
+static int stbrp__skyline_find_min_y(stbrp_context *c, stbrp_node *first, int x0, int width, int *pwaste)
+{
+   stbrp_node *node = first;
+   int x1 = x0 + width;
+   int min_y, visited_width, waste_area;
+
+   STBRP__NOTUSED(c);
+
+   STBRP_ASSERT(first->x <= x0);
+
+   #if 0
+   // skip in case we're past the node
+   while (node->next->x <= x0)
+      ++node;
+   #else
+   STBRP_ASSERT(node->next->x > x0); // we ended up handling this in the caller for efficiency
+   #endif
+
+   STBRP_ASSERT(node->x <= x0);
+
+   min_y = 0;
+   waste_area = 0;
+   visited_width = 0;
+   while (node->x < x1) {
+      if (node->y > min_y) {
+         // raise min_y higher.
+         // we've accounted for all waste up to min_y,
+         // but we'll now add more waste for everything we've visted
+         waste_area += visited_width * (node->y - min_y);
+         min_y = node->y;
+         // the first time through, visited_width might be reduced
+         if (node->x < x0)
+            visited_width += node->next->x - x0;
+         else
+            visited_width += node->next->x - node->x;
+      } else {
+         // add waste area
+         int under_width = node->next->x - node->x;
+         if (under_width + visited_width > width)
+            under_width = width - visited_width;
+         waste_area += under_width * (min_y - node->y);
+         visited_width += under_width;
+      }
+      node = node->next;
+   }
+
+   *pwaste = waste_area;
+   return min_y;
+}
+
+typedef struct
+{
+   int x,y;
+   stbrp_node **prev_link;
+} stbrp__findresult;
+
+static stbrp__findresult stbrp__skyline_find_best_pos(stbrp_context *c, int width, int height)
+{
+   int best_waste = (1<<30), best_x, best_y = (1 << 30);
+   stbrp__findresult fr;
+   stbrp_node **prev, *node, *tail, **best = NULL;
+
+   // align to multiple of c->align
+   width = (width + c->align - 1);
+   width -= width % c->align;
+   STBRP_ASSERT(width % c->align == 0);
+
+   node = c->active_head;
+   prev = &c->active_head;
+   while (node->x + width <= c->width) {
+      int y,waste;
+      y = stbrp__skyline_find_min_y(c, node, node->x, width, &waste);
+      if (c->heuristic == STBRP_HEURISTIC_Skyline_BL_sortHeight) { // actually just want to test BL
+         // bottom left
+         if (y < best_y) {
+            best_y = y;
+            best = prev;
+         }
+      } else {
+         // best-fit
+         if (y + height <= c->height) {
+            // can only use it if it first vertically
+            if (y < best_y || (y == best_y && waste < best_waste)) {
+               best_y = y;
+               best_waste = waste;
+               best = prev;
+            }
+         }
+      }
+      prev = &node->next;
+      node = node->next;
+   }
+
+   best_x = (best == NULL) ? 0 : (*best)->x;
+
+   // if doing best-fit (BF), we also have to try aligning right edge to each node position
+   //
+   // e.g, if fitting
+   //
+   //     ____________________
+   //    |____________________|
+   //
+   //            into
+   //
+   //   |                         |
+   //   |             ____________|
+   //   |____________|
+   //
+   // then right-aligned reduces waste, but bottom-left BL is always chooses left-aligned
+   //
+   // This makes BF take about 2x the time
+
+   if (c->heuristic == STBRP_HEURISTIC_Skyline_BF_sortHeight) {
+      tail = c->active_head;
+      node = c->active_head;
+      prev = &c->active_head;
+      // find first node that's admissible
+      while (tail->x < width)
+         tail = tail->next;
+      while (tail) {
+         int xpos = tail->x - width;
+         int y,waste;
+         STBRP_ASSERT(xpos >= 0);
+         // find the left position that matches this
+         while (node->next->x <= xpos) {
+            prev = &node->next;
+            node = node->next;
+         }
+         STBRP_ASSERT(node->next->x > xpos && node->x <= xpos);
+         y = stbrp__skyline_find_min_y(c, node, xpos, width, &waste);
+         if (y + height < c->height) {
+            if (y <= best_y) {
+               if (y < best_y || waste < best_waste || (waste==best_waste && xpos < best_x)) {
+                  best_x = xpos;
+                  STBRP_ASSERT(y <= best_y);
+                  best_y = y;
+                  best_waste = waste;
+                  best = prev;
+               }
+            }
+         }
+         tail = tail->next;
+      }
+   }
+
+   fr.prev_link = best;
+   fr.x = best_x;
+   fr.y = best_y;
+   return fr;
+}
+
+static stbrp__findresult stbrp__skyline_pack_rectangle(stbrp_context *context, int width, int height)
+{
+   // find best position according to heuristic
+   stbrp__findresult res = stbrp__skyline_find_best_pos(context, width, height);
+   stbrp_node *node, *cur;
+
+   // bail if:
+   //    1. it failed
+   //    2. the best node doesn't fit (we don't always check this)
+   //    3. we're out of memory
+   if (res.prev_link == NULL || res.y + height > context->height || context->free_head == NULL) {
+      res.prev_link = NULL;
+      return res;
+   }
+
+   // on success, create new node
+   node = context->free_head;
+   node->x = (stbrp_coord) res.x;
+   node->y = (stbrp_coord) (res.y + height);
+
+   context->free_head = node->next;
+
+   // insert the new node into the right starting point, and
+   // let 'cur' point to the remaining nodes needing to be
+   // stiched back in
+
+   cur = *res.prev_link;
+   if (cur->x < res.x) {
+      // preserve the existing one, so start testing with the next one
+      stbrp_node *next = cur->next;
+      cur->next = node;
+      cur = next;
+   } else {
+      *res.prev_link = node;
+   }
+
+   // from here, traverse cur and free the nodes, until we get to one
+   // that shouldn't be freed
+   while (cur->next && cur->next->x <= res.x + width) {
+      stbrp_node *next = cur->next;
+      // move the current node to the free list
+      cur->next = context->free_head;
+      context->free_head = cur;
+      cur = next;
+   }
+
+   // stitch the list back in
+   node->next = cur;
+
+   if (cur->x < res.x + width)
+      cur->x = (stbrp_coord) (res.x + width);
+
+#ifdef _DEBUG
+   cur = context->active_head;
+   while (cur->x < context->width) {
+      STBRP_ASSERT(cur->x < cur->next->x);
+      cur = cur->next;
+   }
+   STBRP_ASSERT(cur->next == NULL);
+
+   {
+      int count=0;
+      cur = context->active_head;
+      while (cur) {
+         cur = cur->next;
+         ++count;
+      }
+      cur = context->free_head;
+      while (cur) {
+         cur = cur->next;
+         ++count;
+      }
+      STBRP_ASSERT(count == context->num_nodes+2);
+   }
+#endif
+
+   return res;
+}
+
+static int rect_height_compare(const void *a, const void *b)
+{
+   const stbrp_rect *p = (const stbrp_rect *) a;
+   const stbrp_rect *q = (const stbrp_rect *) b;
+   if (p->h > q->h)
+      return -1;
+   if (p->h < q->h)
+      return  1;
+   return (p->w > q->w) ? -1 : (p->w < q->w);
+}
+
+static int rect_original_order(const void *a, const void *b)
+{
+   const stbrp_rect *p = (const stbrp_rect *) a;
+   const stbrp_rect *q = (const stbrp_rect *) b;
+   return (p->was_packed < q->was_packed) ? -1 : (p->was_packed > q->was_packed);
+}
+
+#ifdef STBRP_LARGE_RECTS
+#define STBRP__MAXVAL  0xffffffff
+#else
+#define STBRP__MAXVAL  0xffff
+#endif
+
+STBRP_DEF int stbrp_pack_rects(stbrp_context *context, stbrp_rect *rects, int num_rects)
+{
+   int i, all_rects_packed = 1;
+
+   // we use the 'was_packed' field internally to allow sorting/unsorting
+   for (i=0; i < num_rects; ++i) {
+      rects[i].was_packed = i;
+   }
+
+   // sort according to heuristic
+   STBRP_SORT(rects, num_rects, sizeof(rects[0]), rect_height_compare);
+
+   for (i=0; i < num_rects; ++i) {
+      if (rects[i].w == 0 || rects[i].h == 0) {
+         rects[i].x = rects[i].y = 0;  // empty rect needs no space
+      } else {
+         stbrp__findresult fr = stbrp__skyline_pack_rectangle(context, rects[i].w, rects[i].h);
+         if (fr.prev_link) {
+            rects[i].x = (stbrp_coord) fr.x;
+            rects[i].y = (stbrp_coord) fr.y;
+         } else {
+            rects[i].x = rects[i].y = STBRP__MAXVAL;
+         }
+      }
+   }
+
+   // unsort
+   STBRP_SORT(rects, num_rects, sizeof(rects[0]), rect_original_order);
+
+   // set was_packed flags and all_rects_packed status
+   for (i=0; i < num_rects; ++i) {
+      rects[i].was_packed = !(rects[i].x == STBRP__MAXVAL && rects[i].y == STBRP__MAXVAL);
+      if (!rects[i].was_packed)
+         all_rects_packed = 0;
+   }
+
+   // return the all_rects_packed status
+   return all_rects_packed;
+}
+#endif
+
+/*
+------------------------------------------------------------------------------
+This software is available under 2 licenses -- choose whichever you prefer.
+------------------------------------------------------------------------------
+ALTERNATIVE A - MIT License
+Copyright (c) 2017 Sean Barrett
+Permission is hereby granted, free of charge, to any person obtaining a copy of
+this software and associated documentation files (the "Software"), to deal in
+the Software without restriction, including without limitation the rights to
+use, copy, modify, merge, publish, distribute, sublicense, and/or sell copies
+of the Software, and to permit persons to whom the Software is furnished to do
+so, subject to the following conditions:
+The above copyright notice and this permission notice shall be included in all
+copies or substantial portions of the Software.
+THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
+SOFTWARE.
+------------------------------------------------------------------------------
+ALTERNATIVE B - Public Domain (www.unlicense.org)
+This is free and unencumbered software released into the public domain.
+Anyone is free to copy, modify, publish, use, compile, sell, or distribute this
+software, either in source code form or as a compiled binary, for any purpose,
+commercial or non-commercial, and by any means.
+In jurisdictions that recognize copyright laws, the author or authors of this
+software dedicate any and all copyright interest in the software to the public
+domain. We make this dedication for the benefit of the public at large and to
+the detriment of our heirs and successors. We intend this dedication to be an
+overt act of relinquishment in perpetuity of all present and future rights to
+this software under copyright law.
+THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+AUTHORS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN
+ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION
+WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
+------------------------------------------------------------------------------
+*/

gsk/gl/stb_rect_pack.h

@@ -0,0 +1,191 @@
+// stb_rect_pack.h - v0.99 - public domain - rectangle packing
+// Sean Barrett 2014
+//
+// Useful for e.g. packing rectangular textures into an atlas.
+// Does not do rotation.
+//
+// Not necessarily the awesomest packing method, but better than
+// the totally naive one in stb_truetype (which is primarily what
+// this is meant to replace).
+//
+// Has only had a few tests run, may have issues.
+//
+// More docs to come.
+//
+// No memory allocations; uses qsort() and assert() from stdlib.
+// Can override those by defining STBRP_SORT and STBRP_ASSERT.
+//
+// This library currently uses the Skyline Bottom-Left algorithm.
+//
+// Please note: better rectangle packers are welcome! Please
+// implement them to the same API, but with a different init
+// function.
+//
+// Credits
+//
+//  Library
+//    Sean Barrett
+//  Minor features
+//    Martins Mozeiko
+//    github:IntellectualKitty
+//
+//  Bugfixes / warning fixes
+//    Jeremy Jaussaud
+//
+// Version history:
+//
+//     0.99  (2019-02-07)  warning fixes
+//     0.11  (2017-03-03)  return packing success/fail result
+//     0.10  (2016-10-25)  remove cast-away-const to avoid warnings
+//     0.09  (2016-08-27)  fix compiler warnings
+//     0.08  (2015-09-13)  really fix bug with empty rects (w=0 or h=0)
+//     0.07  (2015-09-13)  fix bug with empty rects (w=0 or h=0)
+//     0.06  (2015-04-15)  added STBRP_SORT to allow replacing qsort
+//     0.05:  added STBRP_ASSERT to allow replacing assert
+//     0.04:  fixed minor bug in STBRP_LARGE_RECTS support
+//     0.01:  initial release
+//
+// LICENSE
+//
+//   See end of file for license information.
+
+//////////////////////////////////////////////////////////////////////////////
+//
+//       INCLUDE SECTION
+//
+
+#ifndef STB_INCLUDE_STB_RECT_PACK_H
+#define STB_INCLUDE_STB_RECT_PACK_H
+
+#define STB_RECT_PACK_VERSION  1
+
+#ifdef STBRP_STATIC
+#define STBRP_DEF static
+#else
+#define STBRP_DEF extern
+#endif
+
+#ifdef __cplusplus
+extern "C" {
+#endif
+
+typedef struct stbrp_context stbrp_context;
+typedef struct stbrp_node    stbrp_node;
+typedef struct stbrp_rect    stbrp_rect;
+
+#ifdef STBRP_LARGE_RECTS
+typedef int            stbrp_coord;
+#else
+typedef unsigned short stbrp_coord;
+#endif
+
+STBRP_DEF int stbrp_pack_rects (stbrp_context *context, stbrp_rect *rects, int num_rects);
+// Assign packed locations to rectangles. The rectangles are of type
+// 'stbrp_rect' defined below, stored in the array 'rects', and there
+// are 'num_rects' many of them.
+//
+// Rectangles which are successfully packed have the 'was_packed' flag
+// set to a non-zero value and 'x' and 'y' store the minimum location
+// on each axis (i.e. bottom-left in cartesian coordinates, top-left
+// if you imagine y increasing downwards). Rectangles which do not fit
+// have the 'was_packed' flag set to 0.
+//
+// You should not try to access the 'rects' array from another thread
+// while this function is running, as the function temporarily reorders
+// the array while it executes.
+//
+// To pack into another rectangle, you need to call stbrp_init_target
+// again. To continue packing into the same rectangle, you can call
+// this function again. Calling this multiple times with multiple rect
+// arrays will probably produce worse packing results than calling it
+// a single time with the full rectangle array, but the option is
+// available.
+//
+// The function returns 1 if all of the rectangles were successfully
+// packed and 0 otherwise.
+
+struct stbrp_rect
+{
+   // reserved for your use:
+   int            id;
+
+   // input:
+   stbrp_coord    w, h;
+
+   // output:
+   stbrp_coord    x, y;
+   int            was_packed;  // non-zero if valid packing
+
+}; // 16 bytes, nominally
+
+
+STBRP_DEF void stbrp_init_target (stbrp_context *context, int width, int height, stbrp_node *nodes, int num_nodes);
+// Initialize a rectangle packer to:
+//    pack a rectangle that is 'width' by 'height' in dimensions
+//    using temporary storage provided by the array 'nodes', which is 'num_nodes' long
+//
+// You must call this function every time you start packing into a new target.
+//
+// There is no "shutdown" function. The 'nodes' memory must stay valid for
+// the following stbrp_pack_rects() call (or calls), but can be freed after
+// the call (or calls) finish.
+//
+// Note: to guarantee best results, either:
+//       1. make sure 'num_nodes' >= 'width'
+//   or  2. call stbrp_allow_out_of_mem() defined below with 'allow_out_of_mem = 1'
+//
+// If you don't do either of the above things, widths will be quantized to multiples
+// of small integers to guarantee the algorithm doesn't run out of temporary storage.
+//
+// If you do #2, then the non-quantized algorithm will be used, but the algorithm
+// may run out of temporary storage and be unable to pack some rectangles.
+
+STBRP_DEF void stbrp_setup_allow_out_of_mem (stbrp_context *context, int allow_out_of_mem);
+// Optionally call this function after init but before doing any packing to
+// change the handling of the out-of-temp-memory scenario, described above.
+// If you call init again, this will be reset to the default (false).
+
+
+STBRP_DEF void stbrp_setup_heuristic (stbrp_context *context, int heuristic);
+// Optionally select which packing heuristic the library should use. Different
+// heuristics will produce better/worse results for different data sets.
+// If you call init again, this will be reset to the default.
+
+enum
+{
+   STBRP_HEURISTIC_Skyline_default=0,
+   STBRP_HEURISTIC_Skyline_BL_sortHeight = STBRP_HEURISTIC_Skyline_default,
+   STBRP_HEURISTIC_Skyline_BF_sortHeight
+};
+
+
+//////////////////////////////////////////////////////////////////////////////
+//
+// the details of the following structures don't matter to you, but they must
+// be visible so you can handle the memory allocations for them
+
+struct stbrp_node
+{
+   stbrp_coord  x,y;
+   stbrp_node  *next;
+};
+
+struct stbrp_context
+{
+   int width;
+   int height;
+   int align;
+   int init_mode;
+   int heuristic;
+   int num_nodes;
+   stbrp_node *active_head;
+   stbrp_node *free_head;
+   stbrp_node extra[2]; // we allocate two extra nodes so optimal user-node-count is 'width' not 'width+2'
+};
+
+#ifdef __cplusplus
+}
+#endif
+
+#endif
+

gsk/meson.build

@@ -45,6 +45,9 @@ gsk_private_sources = files([
   'gl/gskglrenderops.c',
   'gl/gskglshadowcache.c',
   'gl/gskglnodesample.c',
+  'gl/gskgltextureatlas.c',
+  'gl/gskgliconcache.c',
+  'gl/stb_rect_pack.c',
 ])
 
 gsk_public_headers = files([

tests/testblur.c

@@ -36,7 +36,9 @@ snapshot_blur (GtkWidget   *widget,
 
 
 static void
-gtk_blur_box_init (GtkBlurBox *box) {}
+gtk_blur_box_init (GtkBlurBox *box) {
+  box->radius = 1;
+}
 
 static void
 gtk_blur_box_class_init (GtkBlurBoxClass *klass)
@@ -99,7 +101,7 @@ main (int argc, char **argv)
   gtk_container_add (GTK_CONTAINER (blur_box), value_label);
 
 
-  scale = gtk_scale_new_with_range (GTK_ORIENTATION_HORIZONTAL, 0, 10, 0.5);
+  scale = gtk_scale_new_with_range (GTK_ORIENTATION_HORIZONTAL, 0, 10, 0.05);
   gtk_widget_set_size_request (scale, 200, -1);
   gtk_widget_set_halign (scale, GTK_ALIGN_CENTER);
   gtk_widget_set_valign (scale, GTK_ALIGN_CENTER);