Add another shader node demo

This one does stack-like transitions, using
some examples from gl-transitions.com.

demos/gtk-demo/demo.gresource.xml

@@ -133,6 +133,17 @@
     <file>cogs.glsl</file>
     <file>glowingstars.glsl</file>
   </gresource>
+  <gresource prefix="/glshader">
+    <file>fire.glsl</file>
+  </gresource>
+  <gresource prefix="/gltransition">
+    <file>gtkshaderstack.c</file>
+    <file>gtkshaderstack.h</file>
+    <file>transition1.glsl</file>
+    <file>transition2.glsl</file>
+    <file>transition3.glsl</file>
+    <file>transition4.glsl</file>
+  </gresource>
   <gresource prefix="/iconscroll">
     <file>iconscroll.ui</file>
   </gresource>
@@ -247,6 +258,8 @@
     <file>gears.c</file>
     <file>gestures.c</file>
     <file>glarea.c</file>
+    <file>glshader.c</file>
+    <file>gltransition.c</file>
     <file>headerbar.c</file>
     <file>hypertext.c</file>
     <file>iconscroll.c</file>

demos/gtk-demo/fire.glsl

@@ -0,0 +1,72 @@
+/* 2D -> [0..1] random number generator */
+float random(vec2 st) {
+  return fract(sin(dot(st.xy,
+                       vec2(12.9898,78.233))) *
+               43758.5453123);
+}
+
+/* Generate a smoothed 2d noise based on random() */
+float noise(vec2 v) {
+  /* Round point v to integer grid grid */
+  vec2 grid_point = floor(v);
+  /* Randomize in grid corners */
+  float corner1 = random(grid_point);
+  float corner2 = random(grid_point + vec2(1, 0));
+  float corner3 = random(grid_point + vec2(0, 1));
+  float corner4 = random(grid_point + vec2(1, 1));
+  /* Interpolate smoothly between grid points */
+  vec2 fraction = smoothstep(vec2(0.0), vec2(1.0), fract(v));
+  return mix(mix(corner1, corner2, fraction.x),
+             mix(corner3, corner4, fraction.x),
+             fraction.y);
+}
+
+/* fractal brownian motion noice, see https://www.iquilezles.org/www/articles/fbm/fbm.htm */
+float fbm(in vec2 x)
+{
+  const float octaveScale = 1.9;
+  const float G = 0.5;
+  float f = 1.0;
+  float a = 1.0;
+  float t = 0.0;
+  int numOctaves = 5;
+  for (int i = 0; i < numOctaves; i++) {
+    t += a*noise(f*x);
+    f *= octaveScale;
+    a *= G;
+  }
+
+  return t;
+}
+
+
+void mainImage(out vec4 fragColor, in vec2 fragCoord, in vec2 resolution, in vec2 uv)
+{
+  float time = u_args.x;
+
+  vec2 xy = fragCoord / resolution;
+
+  float zoom = 3.0 - sin(time*0.5)*0.3;
+
+  // Normalize coord to height of widget
+  vec2 p = (vec2 (-resolution.x/2 + fragCoord.x, resolution.y - fragCoord.y) / resolution.yy)* zoom;
+
+    // Use recursive incantations of fbm
+  float q1 = fbm(p - vec2(0.8, 0.3) * time);
+  float q2 = fbm(p - vec2(0.5, 1.3) * time);
+  float r = fbm(2.0*p + vec2(q1,q2) - vec2(0.0, 1.0)*time*10.0 *0.4);
+
+  // Compute intensity, mostly on the bottom
+  float w = 2 * r * p.y;
+
+  // Smooth out left/right side and fade in at start
+  w /= smoothstep(0.0,0.1, xy.x)* smoothstep(0.0,0.1, 1.0-xy.x) *  smoothstep(0.0,0.4, time);
+
+  // Compute colors
+  vec3 c = vec3(1.0,.2,.05);
+  vec3 color = 1.0 / (w*w/c + 1.0);
+
+  // Mix in widget
+  vec4 widget = texture(u_source,uv);
+  fragColor = mix(vec4(color,1), widget, 1.0-color.x);
+}

demos/gtk-demo/glshader.c

@@ -0,0 +1,84 @@
+/* OpenGL/glshader
+ * #Keywords: OpenGL, shader
+ *
+ * Generate pixels using a custom fragment shader.
+ *
+ * The names of the uniforms are compatible with the shaders on shadertoy.com, so
+ * many of the shaders there work here too.
+ */
+#include <math.h>
+#include <gtk/gtk.h>
+#include "gtkshaderbin.h"
+
+static GtkWidget *demo_window = NULL;
+
+static void
+close_window (GtkWidget *widget)
+{
+  /* Reset the state */
+  demo_window = NULL;
+}
+
+static GtkWidget *
+fire_bin_new (void)
+{
+  GtkWidget *bin = gtk_shader_bin_new ();
+  GBytes *shader_b;
+  GskGLShader *shader;
+
+  shader_b = g_resources_lookup_data ("/glshader/fire.glsl", 0, NULL);
+  shader = gsk_glshader_new ((const char *)g_bytes_get_data (shader_b, NULL));
+  gtk_shader_bin_add_shader (GTK_SHADER_BIN (bin), shader, GTK_STATE_FLAG_PRELIGHT, GTK_STATE_FLAG_PRELIGHT);
+
+  return bin;
+}
+
+
+static GtkWidget *
+create_glshader_window (GtkWidget *do_widget)
+{
+  GtkWidget *window, *box, *button, *bin;
+
+  window = gtk_window_new ();
+  gtk_window_set_display (GTK_WINDOW (window),  gtk_widget_get_display (do_widget));
+  gtk_window_set_title (GTK_WINDOW (window), "glshader");
+  g_signal_connect (window, "destroy", G_CALLBACK (close_window), NULL);
+
+  box = gtk_box_new (GTK_ORIENTATION_VERTICAL, FALSE);
+  gtk_widget_set_margin_start (box, 12);
+  gtk_widget_set_margin_end (box, 12);
+  gtk_widget_set_margin_top (box, 12);
+  gtk_widget_set_margin_bottom (box, 12);
+  gtk_box_set_spacing (GTK_BOX (box), 6);
+  gtk_window_set_child (GTK_WINDOW (window), box);
+
+  bin = fire_bin_new ();
+  gtk_box_append (GTK_BOX (box), bin);
+
+  button = gtk_button_new_with_label ("Click me");
+  gtk_widget_set_receives_default (button, TRUE);
+  gtk_shader_bin_set_child (GTK_SHADER_BIN (bin), button);
+
+  bin = fire_bin_new ();
+  gtk_box_append (GTK_BOX (box), bin);
+
+  button = gtk_button_new_with_label ("Or me!");
+  gtk_widget_set_receives_default (button, TRUE);
+  gtk_shader_bin_set_child (GTK_SHADER_BIN (bin), button);
+
+  return window;
+}
+
+GtkWidget *
+do_glshader (GtkWidget *do_widget)
+{
+  if (!demo_window)
+    demo_window = create_glshader_window (do_widget);
+
+  if (!gtk_widget_get_visible (demo_window))
+    gtk_widget_show (demo_window);
+  else
+    gtk_window_destroy (GTK_WINDOW (demo_window));
+
+  return demo_window;
+}

demos/gtk-demo/gltransition.c

@@ -0,0 +1,113 @@
+/* OpenGL/Transitions
+ * #Keywords: OpenGL, shader
+ *
+ * Create transitions between pages using a custom fragment shader.
+ *
+ * The examples here are taken from gl-transitions.com.
+ */
+#include <math.h>
+#include <gtk/gtk.h>
+#include "gtkshaderstack.h"
+
+static GtkWidget *demo_window = NULL;
+
+static void
+close_window (GtkWidget *widget)
+{
+  /* Reset the state */
+  demo_window = NULL;
+}
+
+static GskGLShader *
+gsk_shader_new_from_resource (const char *resource_path)
+{
+  GBytes *shader_b;
+  GskGLShader *shader;
+
+  shader_b = g_resources_lookup_data (resource_path, 0, NULL);
+  shader = gsk_glshader_new ((const char *)g_bytes_get_data (shader_b, NULL));
+  g_bytes_unref (shader_b);
+
+  return shader;
+}
+
+static GtkWidget *
+make_shader_stack (const char *resource_path)
+{
+  GtkWidget *stack, *child;
+  GskGLShader *shader;
+
+  stack = gtk_shader_stack_new ();
+  shader = gsk_shader_new_from_resource (resource_path);
+  gtk_shader_stack_set_shader (GTK_SHADER_STACK (stack), shader);
+  g_object_unref (shader);
+
+  child = gtk_picture_new_for_resource ("/css_pixbufs/background.jpg");
+  gtk_picture_set_can_shrink (GTK_PICTURE (child), TRUE);
+  gtk_shader_stack_add_child (GTK_SHADER_STACK (stack), child);
+
+  child = gtk_picture_new_for_resource ("/transparent/portland-rose.jpg");
+  gtk_picture_set_can_shrink (GTK_PICTURE (child), TRUE);
+  gtk_shader_stack_add_child (GTK_SHADER_STACK (stack), child);
+
+  child = gtk_picture_new_for_resource ("/css_blendmodes/ducky.png");
+  gtk_picture_set_can_shrink (GTK_PICTURE (child), TRUE);
+  gtk_shader_stack_add_child (GTK_SHADER_STACK (stack), child);
+
+  return stack;
+}
+
+static GtkWidget *
+create_gltransition_window (GtkWidget *do_widget)
+{
+  GtkWidget *window, *grid;
+
+  window = gtk_window_new ();
+  gtk_window_set_display (GTK_WINDOW (window),  gtk_widget_get_display (do_widget));
+  gtk_window_set_title (GTK_WINDOW (window), "Transitions");
+  gtk_window_set_default_size (GTK_WINDOW (window), 400, 400);
+  g_signal_connect (window, "destroy", G_CALLBACK (close_window), NULL);
+
+  grid = gtk_grid_new ();
+  gtk_widget_set_halign (grid, GTK_ALIGN_CENTER);
+  gtk_widget_set_valign (grid, GTK_ALIGN_CENTER);
+  gtk_widget_set_margin_start (grid, 12);
+  gtk_widget_set_margin_end (grid, 12);
+  gtk_widget_set_margin_top (grid, 12);
+  gtk_widget_set_margin_bottom (grid, 12);
+  gtk_grid_set_row_spacing (GTK_GRID (grid), 6);
+  gtk_grid_set_column_spacing (GTK_GRID (grid), 6);
+  gtk_grid_set_row_homogeneous (GTK_GRID (grid), TRUE);
+  gtk_grid_set_column_homogeneous (GTK_GRID (grid), TRUE);
+
+  gtk_window_set_child (GTK_WINDOW (window), grid);
+
+  gtk_grid_attach (GTK_GRID (grid),
+                   make_shader_stack ("/gltransition/transition1.glsl"),
+                   0, 0, 1, 1);
+  gtk_grid_attach (GTK_GRID (grid),
+                   make_shader_stack ("/gltransition/transition2.glsl"),
+                   1, 0, 1, 1);
+  gtk_grid_attach (GTK_GRID (grid),
+                   make_shader_stack ("/gltransition/transition3.glsl"),
+                   0, 1, 1, 1);
+  gtk_grid_attach (GTK_GRID (grid),
+                   make_shader_stack ("/gltransition/transition4.glsl"),
+                   1, 1, 1, 1);
+
+  return window;
+}
+
+GtkWidget *
+do_gltransition (GtkWidget *do_widget)
+{
+  if (!demo_window)
+    demo_window = create_gltransition_window (do_widget);
+
+  if (!gtk_widget_get_visible (demo_window))
+    gtk_widget_show (demo_window);
+  else
+    gtk_window_destroy (GTK_WINDOW (demo_window));
+
+  return demo_window;
+}

demos/gtk-demo/gtkshaderbin.c

@@ -0,0 +1,219 @@
+#include "gtkshaderbin.h"
+
+typedef struct {
+  GskGLShader *shader;
+  GtkStateFlags state;
+  GtkStateFlags state_mask;
+} ShaderInfo;
+
+struct _GtkShaderBin
+{
+  GtkWidget parent_instance;
+  GtkWidget *child;
+  GskGLShader *active_shader;
+  GPtrArray *shaders;
+  guint tick_id;
+  float time;
+  gint64 first_frame_time;
+};
+
+struct _GtkShaderBinClass
+{
+  GtkWidgetClass parent_class;
+};
+
+G_DEFINE_TYPE (GtkShaderBin, gtk_shader_bin, GTK_TYPE_WIDGET)
+
+static void
+shader_info_free (ShaderInfo *info)
+{
+  g_object_unref (info->shader);
+  g_free (info);
+}
+
+static void
+gtk_shader_bin_finalize (GObject *object)
+{
+  GtkShaderBin *self = GTK_SHADER_BIN (object);
+
+  g_ptr_array_free (self->shaders, TRUE);
+
+  G_OBJECT_CLASS (gtk_shader_bin_parent_class)->finalize (object);
+}
+
+static void
+gtk_shader_bin_dispose (GObject *object)
+{
+  GtkShaderBin *self = GTK_SHADER_BIN (object);
+
+  g_clear_pointer (&self->child, gtk_widget_unparent);
+
+  G_OBJECT_CLASS (gtk_shader_bin_parent_class)->dispose (object);
+}
+
+static gboolean
+gtk_shader_bin_tick (GtkWidget     *widget,
+                     GdkFrameClock *frame_clock,
+                     gpointer       unused)
+{
+  GtkShaderBin *self = GTK_SHADER_BIN (widget);
+  gint64 frame_time;
+
+  frame_time = gdk_frame_clock_get_frame_time (gtk_widget_get_frame_clock (widget));
+  if (self->first_frame_time == 0)
+    self->first_frame_time = frame_time;
+  self->time = (frame_time - self->first_frame_time) / (float)G_USEC_PER_SEC;
+
+  gtk_widget_queue_allocate (widget);
+
+  return G_SOURCE_CONTINUE;
+}
+
+static void
+gtk_shader_bin_init (GtkShaderBin *self)
+{
+  self->shaders = g_ptr_array_new_with_free_func ((GDestroyNotify)shader_info_free);
+}
+
+void
+gtk_shader_bin_update_active_shader (GtkShaderBin *self)
+{
+  GtkStateFlags new_state = gtk_widget_get_state_flags (GTK_WIDGET (self));
+  GskGLShader *new_shader = NULL;
+
+  for (int i = 0; i < self->shaders->len; i++)
+    {
+      ShaderInfo *info = g_ptr_array_index (self->shaders, i);
+
+      if ((info->state_mask & new_state) == info->state)
+        {
+          new_shader = info->shader;
+          break;
+        }
+    }
+
+  if (self->active_shader == new_shader)
+    return;
+
+  self->active_shader = new_shader;
+  self->first_frame_time = 0;
+
+  if (self->active_shader)
+    {
+      if (self->tick_id == 0)
+        self->tick_id = gtk_widget_add_tick_callback (GTK_WIDGET (self),
+                                                      gtk_shader_bin_tick,
+                                                      NULL, NULL);
+    }
+  else
+    {
+      if (self->tick_id != 0)
+        {
+          gtk_widget_remove_tick_callback (GTK_WIDGET (self), self->tick_id);
+          self->tick_id = 0;
+        }
+    }
+
+  gtk_widget_queue_allocate (GTK_WIDGET (self));
+}
+
+static void
+gtk_shader_bin_state_flags_changed (GtkWidget        *widget,
+                                    GtkStateFlags     previous_state_flags)
+{
+  GtkShaderBin *self = GTK_SHADER_BIN (widget);
+
+  gtk_shader_bin_update_active_shader (self);
+}
+
+void
+gtk_shader_bin_add_shader (GtkShaderBin *self,
+                           GskGLShader  *shader,
+                           GtkStateFlags state,
+                           GtkStateFlags state_mask)
+{
+  ShaderInfo *info = g_new0 (ShaderInfo, 1);
+  info->shader = g_object_ref (shader);
+  info->state = state;
+  info->state_mask = state_mask;
+
+  g_ptr_array_add (self->shaders, info);
+
+  gtk_shader_bin_update_active_shader (self);
+}
+
+void
+gtk_shader_bin_set_child (GtkShaderBin *self,
+                          GtkWidget    *child)
+{
+
+  if (self->child == child)
+    return;
+
+  g_clear_pointer (&self->child, gtk_widget_unparent);
+
+  if (child)
+    {
+      self->child = child;
+      gtk_widget_set_parent (child, GTK_WIDGET (self));
+    }
+}
+
+GtkWidget *
+gtk_shader_bin_get_child   (GtkShaderBin *self)
+{
+  return self->child;
+}
+
+static void
+gtk_shader_bin_snapshot (GtkWidget   *widget,
+                         GtkSnapshot *snapshot)
+{
+  GtkShaderBin *self = GTK_SHADER_BIN (widget);
+  int width, height;
+
+  width = gtk_widget_get_width (widget);
+  height = gtk_widget_get_height (widget);
+
+  if (self->active_shader)
+    {
+      graphene_vec4_t args;
+      gtk_snapshot_push_glshader (snapshot, self->active_shader,
+                                  graphene_vec4_init (&args, self->time, 0, 0, 0),
+                                  &GRAPHENE_RECT_INIT(0, 0, width, height),
+                                  1);
+      gtk_widget_snapshot_child (widget, self->child, snapshot);
+      gtk_snapshot_pop (snapshot); /* Fallback */
+      gtk_widget_snapshot_child (widget, self->child, snapshot);
+      gtk_snapshot_pop (snapshot); /* Shader node child 1 */
+    }
+  else
+    {
+      gtk_widget_snapshot_child (widget, self->child, snapshot);
+    }
+}
+
+static void
+gtk_shader_bin_class_init (GtkShaderBinClass *class)
+{
+  GtkWidgetClass *widget_class = GTK_WIDGET_CLASS (class);
+  GObjectClass *object_class = G_OBJECT_CLASS (class);
+
+  object_class->finalize = gtk_shader_bin_finalize;
+  object_class->dispose = gtk_shader_bin_dispose;
+
+  gtk_widget_class_set_layout_manager_type (widget_class, GTK_TYPE_BIN_LAYOUT);
+
+  widget_class->snapshot = gtk_shader_bin_snapshot;
+  widget_class->state_flags_changed = gtk_shader_bin_state_flags_changed;
+}
+
+GtkWidget *
+gtk_shader_bin_new (void)
+{
+  GtkShaderBin *self;
+
+  self = g_object_new (GTK_TYPE_SHADER_BIN, NULL);
+
+  return GTK_WIDGET (self);
+}

demos/gtk-demo/gtkshaderbin.h

@@ -0,0 +1,22 @@
+#ifndef __GTK_SHADER_BIN_H__
+#define __GTK_SHADER_BIN_H__
+
+#include <gtk/gtk.h>
+
+G_BEGIN_DECLS
+
+#define GTK_TYPE_SHADER_BIN      (gtk_shader_bin_get_type ())
+G_DECLARE_FINAL_TYPE (GtkShaderBin, gtk_shader_bin, GTK, SHADER_BIN, GtkWidget)
+
+GtkWidget  *gtk_shader_bin_new        (void);
+void        gtk_shader_bin_add_shader (GtkShaderBin *self,
+                                       GskGLShader  *shader,
+                                       GtkStateFlags state,
+                                       GtkStateFlags state_mask);
+void       gtk_shader_bin_set_child   (GtkShaderBin *self,
+                                       GtkWidget    *child);
+GtkWidget *gtk_shader_bin_get_child   (GtkShaderBin *self);
+
+G_END_DECLS
+
+#endif /* __GTK_SHADER_BIN_H__ */

demos/gtk-demo/gtkshaderstack.c

@@ -0,0 +1,255 @@
+#include "gtkshaderstack.h"
+
+struct _GtkShaderStack
+{
+  GtkWidget parent_instance;
+
+  GskGLShader *shader;
+  GPtrArray *children;
+  int current;
+  int next;
+
+  guint tick_id;
+  float time;
+  float duration;
+  gint64 start_time;
+};
+
+struct _GtkShaderStackClass
+{
+  GtkWidgetClass parent_class;
+};
+
+
+G_DEFINE_TYPE (GtkShaderStack, gtk_shader_stack, GTK_TYPE_WIDGET)
+
+static void
+gtk_shader_stack_finalize (GObject *object)
+{
+  GtkShaderStack *self = GTK_SHADER_STACK (object);
+
+  g_object_unref (self->shader);
+
+  G_OBJECT_CLASS (gtk_shader_stack_parent_class)->finalize (object);
+}
+
+static gboolean
+transition_cb (GtkWidget     *widget,
+               GdkFrameClock *clock,
+               gpointer       unused)
+{
+  GtkShaderStack *self = GTK_SHADER_STACK (widget);
+  gint64 frame_time;
+
+  frame_time = gdk_frame_clock_get_frame_time (clock);
+
+  if (self->start_time == 0)
+    self->start_time = frame_time;
+
+  self->time = (frame_time - self->start_time) / (float)G_USEC_PER_SEC;
+
+  gtk_widget_queue_draw (widget);
+
+  if (self->time >= self->duration)
+    {
+      self->current = self->next;
+      self->next = -1;
+
+      return G_SOURCE_REMOVE;
+    }
+  else
+    return G_SOURCE_CONTINUE;
+}
+
+static void
+start_transition (GtkShaderStack *self)
+{
+  self->start_time = 0;
+  self->tick_id = gtk_widget_add_tick_callback (GTK_WIDGET (self),
+                                                transition_cb,
+                                                NULL, NULL);
+}
+
+static void
+stop_transition (GtkShaderStack *self)
+{
+  if (self->tick_id != 0)
+    {
+      gtk_widget_remove_tick_callback (GTK_WIDGET (self), self->tick_id);
+      self->tick_id = 0;
+    }
+
+  self->next = -1;
+}
+
+static void
+gtk_shader_stack_dispose (GObject *object)
+{
+  GtkShaderStack *self = GTK_SHADER_STACK (object);
+
+  stop_transition (self);
+
+  g_clear_pointer (&self->children, g_ptr_array_unref);
+
+  G_OBJECT_CLASS (gtk_shader_stack_parent_class)->dispose (object);
+}
+
+static void
+clicked_cb (GtkGestureClick *gesture,
+            guint            n_pressed,
+            double           x,
+            double           y,
+            gpointer         data)
+{
+  GtkShaderStack *self = GTK_SHADER_STACK (data);
+
+  stop_transition (self);
+
+  self->next = (self->current + 1) % self->children->len;
+
+  start_transition (self);
+}
+
+static void
+gtk_shader_stack_init (GtkShaderStack *self)
+{
+  GtkGesture *gesture;
+
+  self->children = g_ptr_array_new_with_free_func ((GDestroyNotify)gtk_widget_unparent);
+  self->current = -1;
+  self->next = -1;
+  self->duration = 1.0;
+
+  gesture = gtk_gesture_click_new ();
+  g_signal_connect (gesture, "pressed", G_CALLBACK (clicked_cb), self);
+  gtk_widget_add_controller (GTK_WIDGET (self), GTK_EVENT_CONTROLLER (gesture));
+}
+
+static void
+gtk_shader_stack_measure (GtkWidget      *widget,
+                          GtkOrientation  orientation,
+                          int             for_size,
+                          int            *minimum,
+                          int            *natural,
+                          int            *minimum_baseline,
+                          int            *natural_baseline)
+{
+  GtkShaderStack *self = GTK_SHADER_STACK (widget);
+  int i;
+
+  *minimum = 0;
+  *natural = 0;
+
+  for (i = 0; i < self->children->len; i++)
+    {
+      GtkWidget *child = g_ptr_array_index (self->children, i);
+      int child_min, child_nat;
+
+      if (gtk_widget_get_visible (child))
+        {
+          gtk_widget_measure (child, orientation, for_size, &child_min, &child_nat, NULL, NULL);
+
+          *minimum = MAX (*minimum, child_min);
+          *natural = MAX (*natural, child_nat);
+        }
+    }
+}
+
+static void
+gtk_shader_stack_size_allocate (GtkWidget *widget,
+                                int        width,
+                                int        height,
+                                int        baseline)
+{
+  GtkShaderStack *self = GTK_SHADER_STACK (widget);
+  GtkAllocation child_allocation;
+  GtkWidget *child;
+  int i;
+
+  child_allocation.x = 0;
+  child_allocation.y = 0;
+  child_allocation.width = width;
+  child_allocation.height = height;
+
+  for (i = 0; i < self->children->len; i++)
+    {
+      child = g_ptr_array_index (self->children, i);
+      if (gtk_widget_get_visible (child))
+        gtk_widget_size_allocate (child, &child_allocation, -1);
+    }
+}
+
+static void
+gtk_shader_stack_snapshot (GtkWidget   *widget,
+                           GtkSnapshot *snapshot)
+{
+  GtkShaderStack *self = GTK_SHADER_STACK (widget);
+  int width, height;
+  GtkWidget *current, *next;
+
+  width = gtk_widget_get_width (widget);
+  height = gtk_widget_get_height (widget);
+
+  current = g_ptr_array_index (self->children, self->current);
+
+  if (self->next == -1)
+    {
+      gtk_widget_snapshot_child (widget, current, snapshot);
+    }
+  else
+    {
+      graphene_vec4_t args;
+
+      next = g_ptr_array_index (self->children, self->next);
+
+      gtk_snapshot_push_glshader (snapshot, self->shader,
+                                  graphene_vec4_init (&args, self->time, self->time / self->duration, 0, 0),
+                                  &GRAPHENE_RECT_INIT(0, 0, width, height),
+                                  2);
+      gtk_widget_snapshot_child (widget, next, snapshot);
+      gtk_snapshot_pop (snapshot); /* Fallback */
+      gtk_widget_snapshot_child (widget, current, snapshot);
+      gtk_snapshot_pop (snapshot); /* current child */
+      gtk_widget_snapshot_child (widget, next, snapshot);
+      gtk_snapshot_pop (snapshot); /* next child */
+    }
+}
+
+static void
+gtk_shader_stack_class_init (GtkShaderStackClass *class)
+{
+  GtkWidgetClass *widget_class = GTK_WIDGET_CLASS (class);
+  GObjectClass *object_class = G_OBJECT_CLASS (class);
+
+  object_class->finalize = gtk_shader_stack_finalize;
+  object_class->dispose = gtk_shader_stack_dispose;
+
+  widget_class->snapshot = gtk_shader_stack_snapshot;
+  widget_class->measure = gtk_shader_stack_measure;
+  widget_class->size_allocate = gtk_shader_stack_size_allocate;
+}
+
+GtkWidget *
+gtk_shader_stack_new (void)
+{
+  return g_object_new (GTK_TYPE_SHADER_STACK, NULL);
+}
+
+void
+gtk_shader_stack_set_shader (GtkShaderStack *self,
+                             GskGLShader    *shader)
+{
+  g_set_object (&self->shader, shader);
+}
+
+void
+gtk_shader_stack_add_child (GtkShaderStack *self,
+                            GtkWidget      *child)
+{
+  g_ptr_array_add (self->children, child);
+  gtk_widget_set_parent (child, GTK_WIDGET (self));
+  gtk_widget_queue_resize (GTK_WIDGET (self));
+
+  if (self->current == -1)
+    self->current = 0;
+}

demos/gtk-demo/gtkshaderstack.h

@@ -0,0 +1,19 @@
+#ifndef __GTK_SHADER_STACK_H__
+#define __GTK_SHADER_STACK_H__
+
+#include <gtk/gtk.h>
+
+G_BEGIN_DECLS
+
+#define GTK_TYPE_SHADER_STACK     (gtk_shader_stack_get_type ())
+G_DECLARE_FINAL_TYPE (GtkShaderStack, gtk_shader_stack, GTK, SHADER_STACK, GtkWidget)
+
+GtkWidget * gtk_shader_stack_new          (void);
+void        gtk_shader_stack_set_shader   (GtkShaderStack *self,
+                                           GskGLShader    *shader);
+void        gtk_shader_stack_add_child    (GtkShaderStack *self,
+                                           GtkWidget      *child);
+
+G_END_DECLS
+
+#endif /* __GTK_SHADER_STACK_H__ */

demos/gtk-demo/meson.build

@@ -32,6 +32,8 @@ demos = files([
   'gears.c',
   'gestures.c',
   'glarea.c',
+  'glshader.c',
+  'gltransition.c',
   'headerbar.c',
   'hypertext.c',
   'iconscroll.c',
@@ -102,7 +104,9 @@ extra_demo_sources = files(['main.c',
                             'gtkfishbowl.c',
                             'fontplane.c',
                             'gtkgears.c',
+                            'gtkshaderbin.c',
                             'gtkshadertoy.c',
+                            'gtkshaderstack.c',
                             'puzzlepiece.c',
                             'bluroverlay.c',
                             'demoimage.c',

demos/gtk-demo/transition1.glsl

@@ -0,0 +1,32 @@
+float progress = u_args.y;
+
+vec4 getFromColor(vec2 uv) {
+  return texture(u_source, uv);
+}
+
+vec4 getToColor(vec2 uv) {
+  return texture(u_source2, uv);
+}
+
+
+// Source: https://gl-transitions.com/editor/wind
+// Author: gre
+// License: MIT
+
+uniform float size = 0.2;
+
+float rand(vec2 co) {
+  return fract(sin(dot(co.xy ,vec2(12.9898,78.233))) * 43758.5453);
+}
+
+vec4 transition(vec2 p) {
+  float r = rand(vec2(0, p.y));
+  float m = smoothstep(0.0, -size, p.x*(1.0-size) + size*r - (progress * (1.0 + size)));
+  return mix(getFromColor(p), getToColor(p), m);
+}
+
+
+void mainImage(out vec4 fragColor, in vec2 fragCoord, in vec2 resolution, in vec2 uv)
+{
+  fragColor = transition(uv);
+}

demos/gtk-demo/transition2.glsl

@@ -0,0 +1,33 @@
+float progress = u_args.y;
+
+vec4 getFromColor (vec2 uv) {
+  return texture(u_source, uv);
+}
+
+vec4 getToColor (vec2 uv) {
+  return texture(u_source2, uv);
+}
+
+
+// Source: https://gl-transitions.com/editor/Radial
+// License: MIT
+// Author: Xaychru
+
+uniform float smoothness = 1.0;
+
+const float PI = 3.141592653589;
+
+vec4 transition(vec2 p) {
+  vec2 rp = p*2.-1.;
+  return mix(
+    getToColor(p),
+    getFromColor(p),
+    smoothstep(0., smoothness, atan(rp.y,rp.x) - (progress-.5) * PI * 2.5)
+  );
+}
+
+
+void mainImage(out vec4 fragColor, in vec2 fragCoord, in vec2 resolution, in vec2 uv)
+{
+  fragColor = transition(uv);
+}

demos/gtk-demo/transition3.glsl

@@ -0,0 +1,26 @@
+float progress = u_args.y;
+
+vec4 getFromColor (vec2 uv) {
+  return texture(u_source, uv);
+}
+
+vec4 getToColor (vec2 uv) {
+  return texture(u_source2, uv);
+}
+
+
+// Source: https://gl-transitions.com/editor/crosswarp
+// Author: Eke Péter <peterekepeter@gmail.com>
+// License: MIT
+
+vec4 transition(vec2 p) {
+  float x = progress;
+  x=smoothstep(.0,1.0,(x*2.0+p.x-1.0));
+  return mix(getFromColor((p-.5)*(1.-x)+.5), getToColor((p-.5)*x+.5), x);
+}
+
+
+void mainImage(out vec4 fragColor, in vec2 fragCoord, in vec2 resolution, in vec2 uv)
+{
+  fragColor = transition(uv);
+}

demos/gtk-demo/transition4.glsl

@@ -0,0 +1,40 @@
+float progress = u_args.y;
+
+vec4 getFromColor (vec2 uv) {
+  return texture(u_source, uv);
+}
+
+vec4 getToColor (vec2 uv) {
+  return texture(u_source2, uv);
+}
+
+
+// Source: https://gl-transitions.com/editor/kaleidoscope
+// Author: nwoeanhinnogaehr
+// License: MIT
+
+uniform float speed = 1.0;
+uniform float angle = 1.0;
+uniform float power = 1.5;
+
+vec4 transition(vec2 uv) {
+  vec2 p = uv.xy / vec2(1.0).xy;
+  vec2 q = p;
+  float t = pow(progress, power)*speed;
+  p = p -0.5;
+  for (int i = 0; i < 7; i++) {
+    p = vec2(sin(t)*p.x + cos(t)*p.y, sin(t)*p.y - cos(t)*p.x);
+    t += angle;
+    p = abs(mod(p, 2.0) - 1.0);
+  }
+  abs(mod(p, 1.0));
+  return mix(
+    mix(getFromColor(q), getToColor(q), progress),
+    mix(getFromColor(p), getToColor(p), progress), 1.0 - 2.0*abs(progress - 0.5));
+}
+
+
+void mainImage(out vec4 fragColor, in vec2 fragCoord, in vec2 resolution, in vec2 uv)
+{
+  fragColor = transition(uv);
+}

gsk/broadway/gskbroadwayrenderer.c

@@ -272,6 +272,11 @@ collect_reused_child_nodes (GskRenderer *renderer,
 
       /* Bin nodes */
 
+    case GSK_GLSHADER_NODE:
+      collect_reused_node (renderer,
+                           gsk_glshader_node_get_fallback_child (node));
+      break;
+
     case GSK_SHADOW_NODE:
       collect_reused_node (renderer,
                            gsk_shadow_node_get_child (node));
@@ -792,6 +797,11 @@ gsk_broadway_renderer_add_node (GskRenderer *renderer,
         }
       return;
 
+    case GSK_GLSHADER_NODE:
+      gsk_broadway_renderer_add_node (renderer,
+                                      gsk_glshader_node_get_fallback_child (node), offset_x, offset_y, clip_bounds);
+      return;
+
       /* Generic nodes */
 
     case GSK_CONTAINER_NODE:

gsk/gl/gskglrenderer.c

@@ -64,6 +64,11 @@
                               glGetUniformLocation(program_ptr->id, "u_" #uniform_basename);\
               }G_STMT_END
 
+static Program *gsk_gl_renderer_lookup_custom_program (GskGLRenderer  *self,
+                                                       GskGLShader *shader);
+static Program *gsk_gl_renderer_create_custom_program (GskGLRenderer  *self,
+                                                       GskGLShader *shader);
+
 typedef enum
 {
   FORCE_OFFSCREEN  = 1 << 0,
@@ -130,6 +135,13 @@ print_render_node_tree (GskRenderNode *root, int level)
         print_render_node_tree (gsk_shadow_node_get_child (root), level + 1);
         break;
 
+      case GSK_GLSHADER_NODE:
+        g_print ("%*s GLShader\n", level * INDENT, " ");
+        print_render_node_tree (gsk_glshader_node_get_fallback_child (root), level + 1);
+        for (i = 0; i < gsk_glshader_node_get_n_children (root); i++)
+          print_render_node_tree (gsk_glshader_node_get_child (root, i), level + 1);
+        break;
+
       case GSK_TEXTURE_NODE:
         g_print ("%*s Texture %p\n", level * INDENT, " ", gsk_texture_node_get_texture (root));
         break;
@@ -495,6 +507,40 @@ struct _GskGLRendererClass
 
 G_DEFINE_TYPE (GskGLRenderer, gsk_gl_renderer, GSK_TYPE_RENDERER)
 
+static void
+init_shader_builder (GskGLRenderer       *self,
+                     GskGLShaderBuilder  *shader_builder)
+{
+#ifdef G_ENABLE_DEBUG
+  if (GSK_RENDERER_DEBUG_CHECK (GSK_RENDERER (self), SHADERS))
+    shader_builder->debugging = TRUE;
+#endif
+
+  if (gdk_gl_context_get_use_es (self->gl_context))
+    {
+      gsk_gl_shader_builder_set_glsl_version (shader_builder, SHADER_VERSION_GLES);
+      shader_builder->gles = TRUE;
+    }
+  else if (gdk_gl_context_is_legacy (self->gl_context))
+    {
+      int maj, min;
+
+      gdk_gl_context_get_version (self->gl_context, &maj, &min);
+
+      if (maj == 3)
+        gsk_gl_shader_builder_set_glsl_version (shader_builder, SHADER_VERSION_GL3_LEGACY);
+      else
+        gsk_gl_shader_builder_set_glsl_version (shader_builder, SHADER_VERSION_GL2_LEGACY);
+
+      shader_builder->legacy = TRUE;
+        }
+  else
+    {
+      gsk_gl_shader_builder_set_glsl_version (shader_builder, SHADER_VERSION_GL3);
+      shader_builder->gl3 = TRUE;
+    }
+}
+
 static void G_GNUC_UNUSED
 add_rect_ops (RenderOpBuilder       *builder,
               const graphene_rect_t *r)
@@ -1006,6 +1052,101 @@ render_texture_node (GskGLRenderer       *self,
     }
 }
 
+static inline void
+render_glshader_node (GskGLRenderer       *self,
+                      GskRenderNode       *node,
+                      RenderOpBuilder     *builder)
+{
+  GskGLShader *shader = gsk_glshader_node_get_shader (node);
+  Program *program = gsk_gl_renderer_lookup_custom_program (self, shader);
+  GskRenderNode *fallback = gsk_glshader_node_get_fallback_child (node);
+  int n_children = gsk_glshader_node_get_n_children (node);
+
+  if (program == NULL)
+    {
+      GskGLShaderBuilder shader_builder;
+      const char *shader_source;
+      GError *error = NULL;
+
+     program = gsk_gl_renderer_create_custom_program (self, shader);
+     shader_source = gsk_glshader_peek_source (shader);
+
+      gsk_gl_shader_builder_init (&shader_builder,
+                                  "/org/gtk/libgsk/glsl/preamble.glsl",
+                                  "/org/gtk/libgsk/glsl/preamble.vs.glsl",
+                                  "/org/gtk/libgsk/glsl/preamble.fs.glsl");
+
+      init_shader_builder (self, &shader_builder);
+
+      program->id = gsk_gl_shader_builder_create_program (&shader_builder,
+                                                          "/org/gtk/libgsk/glsl/custom.glsl",
+                                                          shader_source,
+                                                          &error);
+
+      if (program->id >= 0)
+        {
+          INIT_COMMON_UNIFORM_LOCATION (program, alpha);
+          INIT_COMMON_UNIFORM_LOCATION (program, source);
+          INIT_COMMON_UNIFORM_LOCATION (program, clip_rect);
+          INIT_COMMON_UNIFORM_LOCATION (program, viewport);
+          INIT_COMMON_UNIFORM_LOCATION (program, projection);
+          INIT_COMMON_UNIFORM_LOCATION (program, modelview);
+          program->glshader.size_location = glGetUniformLocation(program->id, "u_size");
+          program->glshader.args_location = glGetUniformLocation(program->id, "u_args");
+          program->glshader.extra_source_locations[0] = glGetUniformLocation(program->id, "u_source2");
+          program->glshader.extra_source_locations[1] = glGetUniformLocation(program->id, "u_source3");
+          program->glshader.extra_source_locations[2] = glGetUniformLocation(program->id, "u_source4");
+        }
+      else
+        {
+          g_warning ("Failed to compile gl shader: %s\n", error->message);
+          g_error_free (error);
+        }
+
+      gsk_gl_shader_builder_finish (&shader_builder);
+    }
+
+  if (program->id >= 0 && n_children <= 4)
+    {
+      graphene_vec4_t args;
+      graphene_vec2_t size;
+      TextureRegion regions[4];
+      gboolean is_offscreen[4];
+
+      for (guint i = 0; i < n_children; i++)
+        {
+          GskRenderNode *child = gsk_glshader_node_get_child (node, i);
+          if (!add_offscreen_ops (self, builder,
+                                  &node->bounds,
+                                  child,
+                                  &regions[i], &is_offscreen[i],
+                                  FORCE_OFFSCREEN | RESET_CLIP | RESET_OPACITY))
+            {
+              if (fallback)
+                gsk_gl_renderer_add_render_ops (self, fallback, builder);
+              return;
+            }
+        }
+
+      gsk_glshader_node_get_args (node, &args);
+      ops_set_program (builder, program);
+
+      graphene_vec2_init (&size, node->bounds.size.width, node->bounds.size.height);
+      ops_set_glshader_args (builder, &size, &args);
+      if (n_children >= 0)
+        ops_set_texture (builder, regions[0].texture_id);
+      for (guint i = 1; i < n_children; i++)
+        ops_set_extra_texture (builder, regions[i].texture_id, i-1);
+
+      load_offscreen_vertex_data (ops_draw (builder, NULL), node, builder);
+    }
+  else
+    {
+      if (fallback)
+        gsk_gl_renderer_add_render_ops (self, fallback, builder);
+    }
+}
+
 /* Returns TRUE is applying transform to bounds
  * yields an axis-aligned rectangle
  */
@@ -2671,6 +2812,18 @@ apply_source_texture_op (const Program   *program,
   glBindTexture (GL_TEXTURE_2D, op->texture_id);
 }
 
+static inline void
+apply_source_extra_texture_op (const Program        *program,
+                               const OpExtraTexture *op)
+{
+  g_assert(op->texture_id != 0);
+  OP_PRINT (" -> New extra texture %d: %d", op->idx, op->texture_id);
+  /* Use texture unit 1 + op->idx for the source */
+  glUniform1i (program->glshader.extra_source_locations[op->idx], 1 + op->idx);
+  glActiveTexture (GL_TEXTURE0 + 1 + op->idx);
+  glBindTexture (GL_TEXTURE_2D, op->texture_id);
+}
+
 static inline void
 apply_color_matrix_op (const Program       *program,
                        const OpColorMatrix *op)
@@ -2815,6 +2968,16 @@ apply_border_op (const Program  *program,
   glUniform4fv (program->border.outline_rect_location, 3, (float *)&op->outline.bounds);
 }
 
+static inline void
+apply_glshader_args_op (const Program  *program,
+                        const OpGLShader *op)
+{
+  OP_PRINT (" -> Custom Args");
+
+  glUniform2fv (program->glshader.size_location, 1, op->size);
+  glUniform4fv (program->glshader.args_location, 1, op->args);
+}
+
 static inline void
 apply_border_width_op (const Program  *program,
                        const OpBorder *op)
@@ -2886,6 +3049,28 @@ gsk_gl_renderer_dispose (GObject *gobject)
   G_OBJECT_CLASS (gsk_gl_renderer_parent_class)->dispose (gobject);
 }
 
+static void
+program_init (Program *program)
+{
+  program->index = -1;
+  program->state.opacity = 1.0f;
+}
+
+static void
+program_finalize (Program *program)
+{
+  if (program->id > 0)
+    glDeleteProgram (program->id);
+  gsk_transform_unref (program->state.modelview);
+}
+
+static void
+program_free (Program *program)
+{
+  program_finalize (program);
+  g_free (program);
+}
+
 static GskGLRendererPrograms *
 gsk_gl_renderer_programs_new (void)
 {
@@ -2895,9 +3080,11 @@ gsk_gl_renderer_programs_new (void)
   programs = g_new0 (GskGLRendererPrograms, 1);
   programs->ref_count = 1;
   for (i = 0; i < GL_N_PROGRAMS; i ++)
-    {
-      programs->state[i].opacity = 1.0f;
-    }
+    program_init (&programs->programs[i]);
+
+  /* We use direct hash for performance, not string hash on the source, because we assume each caller
+   * reuses a single GskGLShader for all uses and different callers will use different source content. */
+  programs->custom_programs = g_hash_table_new_full (g_direct_hash, g_direct_equal, (GDestroyNotify)g_object_unref, (GDestroyNotify)program_free);
 
   return programs;
 }
@@ -2918,15 +3105,33 @@ gsk_gl_renderer_programs_unref (GskGLRendererPrograms *programs)
   if (programs->ref_count == 0)
     {
       for (i = 0; i < GL_N_PROGRAMS; i ++)
-        {
-          if (programs->programs[i].id > 0)
-            glDeleteProgram (programs->programs[i].id);
-          gsk_transform_unref (programs->state[i].modelview);
-        }
+        program_finalize (&programs->programs[i]);
+
+      g_hash_table_destroy (programs->custom_programs);
       g_free (programs);
     }
 }
 
+static Program *
+gsk_gl_renderer_lookup_custom_program (GskGLRenderer  *self,
+                                       GskGLShader *shader)
+{
+  return g_hash_table_lookup (self->programs->custom_programs, shader);
+}
+
+static Program *
+gsk_gl_renderer_create_custom_program (GskGLRenderer  *self,
+                                       GskGLShader *shader)
+{
+  Program *program = g_new0 (Program, 1);
+
+  program_init (program);
+
+  g_hash_table_insert (self->programs->custom_programs, g_object_ref (shader), program);
+
+  return program;
+}
+
 static GskGLRendererPrograms *
 gsk_gl_renderer_create_programs (GskGLRenderer  *self,
                                  GError        **error)
@@ -2961,35 +3166,7 @@ gsk_gl_renderer_create_programs (GskGLRenderer  *self,
 
   g_assert (G_N_ELEMENTS (program_definitions) == GL_N_PROGRAMS);
 
-#ifdef G_ENABLE_DEBUG
-  if (GSK_RENDERER_DEBUG_CHECK (GSK_RENDERER (self), SHADERS))
-    shader_builder.debugging = TRUE;
-#endif
-
-  if (gdk_gl_context_get_use_es (self->gl_context))
-    {
-
-      gsk_gl_shader_builder_set_glsl_version (&shader_builder, SHADER_VERSION_GLES);
-      shader_builder.gles = TRUE;
-    }
-  else if (gdk_gl_context_is_legacy (self->gl_context))
-    {
-      int maj, min;
-
-      gdk_gl_context_get_version (self->gl_context, &maj, &min);
-
-      if (maj == 3)
-        gsk_gl_shader_builder_set_glsl_version (&shader_builder, SHADER_VERSION_GL3_LEGACY);
-      else
-        gsk_gl_shader_builder_set_glsl_version (&shader_builder, SHADER_VERSION_GL2_LEGACY);
-
-      shader_builder.legacy = TRUE;
-    }
-  else
-    {
-      gsk_gl_shader_builder_set_glsl_version (&shader_builder, SHADER_VERSION_GL3);
-      shader_builder.gl3 = TRUE;
-    }
+  init_shader_builder (self, &shader_builder);
 
   programs = gsk_gl_renderer_programs_new ();
 
@@ -3000,7 +3177,7 @@ gsk_gl_renderer_create_programs (GskGLRenderer  *self,
       prog->index = i;
       prog->id = gsk_gl_shader_builder_create_program (&shader_builder,
                                                        program_definitions[i].resource_path,
-                                                       error);
+                                                       NULL, error);
       if (prog->id < 0)
         {
           g_clear_pointer (&programs, gsk_gl_renderer_programs_unref);
@@ -3445,6 +3622,10 @@ gsk_gl_renderer_add_render_ops (GskGLRenderer   *self,
       render_repeat_node (self, node, builder);
     break;
 
+    case GSK_GLSHADER_NODE:
+      render_glshader_node (self, node, builder);
+    break;
+
     case GSK_REPEATING_LINEAR_GRADIENT_NODE:
     case GSK_REPEATING_RADIAL_GRADIENT_NODE:
     case GSK_CAIRO_NODE:
@@ -3727,6 +3908,10 @@ gsk_gl_renderer_render_ops (GskGLRenderer *self)
           apply_source_texture_op (program, ptr);
           break;
 
+        case OP_CHANGE_EXTRA_SOURCE_TEXTURE:
+          apply_source_extra_texture_op (program, ptr);
+          break;
+
         case OP_CHANGE_CROSS_FADE:
           g_assert (program == &self->programs->cross_fade_program);
           apply_cross_fade_op (program, ptr);
@@ -3773,6 +3958,10 @@ gsk_gl_renderer_render_ops (GskGLRenderer *self)
           apply_repeat_op (program, ptr);
           break;
 
+        case OP_CHANGE_GLSHADER_ARGS:
+          apply_glshader_args_op (program, ptr);
+          break;
+
         case OP_DRAW:
           {
             const OpDraw *op = ptr;

gsk/gl/gskglrenderops.c

@@ -60,7 +60,7 @@ get_current_program_state (RenderOpBuilder *builder)
   if (!builder->current_program)
     return NULL;
 
-  return &builder->programs->state[builder->current_program->index];
+  return &builder->current_program->state;
 }
 
 void
@@ -218,10 +218,10 @@ ops_free (RenderOpBuilder *builder)
 
 void
 ops_set_program (RenderOpBuilder *builder,
-                 const Program   *program)
+                 Program   *program)
 {
   OpProgram *op;
-  ProgramState *program_state;
+  ProgramState *program_state = NULL;
 
   if (builder->current_program == program)
     return;
@@ -231,7 +231,7 @@ ops_set_program (RenderOpBuilder *builder,
 
   builder->current_program = program;
 
-  program_state = &builder->programs->state[program->index];
+  program_state = &program->state;
 
   if (memcmp (&builder->current_projection, &program_state->projection, sizeof (graphene_matrix_t)) != 0)
     {
@@ -558,6 +558,18 @@ ops_set_texture (RenderOpBuilder *builder,
   builder->current_texture = texture_id;
 }
 
+void
+ops_set_extra_texture (RenderOpBuilder *builder,
+                       int              texture_id,
+                       int              idx)
+{
+  OpExtraTexture *op;
+
+  op = ops_begin (builder, OP_CHANGE_EXTRA_SOURCE_TEXTURE);
+  op->texture_id = texture_id;
+  op->idx = idx;
+}
+
 int
 ops_set_render_target (RenderOpBuilder *builder,
                        int              render_target_id)
@@ -621,6 +633,26 @@ ops_set_color (RenderOpBuilder *builder,
   op->rgba = color;
 }
 
+void
+ops_set_glshader_args (RenderOpBuilder       *builder,
+                       const graphene_vec2_t *size,
+                       const graphene_vec4_t *args)
+{
+  ProgramState *current_program_state = get_current_program_state (builder);
+  OpGLShader *op;
+
+  if (graphene_vec2_equal (size, &current_program_state->custom.size) &&
+      graphene_vec4_equal (args, &current_program_state->custom.args))
+    return;
+
+  current_program_state->custom.size = *size;
+  current_program_state->custom.args = *args;
+
+  op = ops_begin (builder, OP_CHANGE_GLSHADER_ARGS);
+  graphene_vec4_to_float (args, &op->args[0]);
+  graphene_vec2_to_float (size, &op->size[0]);
+}
+
 void
 ops_set_color_matrix (RenderOpBuilder         *builder,
                       const graphene_matrix_t *matrix,

gsk/gl/gskglrenderopsprivate.h

@@ -31,6 +31,61 @@ typedef struct
   OpsMatrixMetadata metadata;
 } MatrixStackEntry;
 
+typedef struct
+{
+  GskTransform *modelview;
+  GskRoundedRect clip;
+  graphene_matrix_t projection;
+  int source_texture;
+  graphene_rect_t viewport;
+  float opacity;
+  /* Per-program state */
+  union {
+    GdkRGBA color;
+    struct {
+      graphene_matrix_t matrix;
+      graphene_vec4_t offset;
+    } color_matrix;
+    struct {
+      float widths[4];
+      GdkRGBA color;
+      GskRoundedRect outline;
+    } border;
+    struct {
+      GskRoundedRect outline;
+      float dx;
+      float dy;
+      float spread;
+      GdkRGBA color;
+    } inset_shadow;
+    struct {
+      GskRoundedRect outline;
+      float dx;
+      float dy;
+      float spread;
+      GdkRGBA color;
+    } unblurred_outset_shadow;
+    struct {
+      int n_color_stops;
+      GskColorStop color_stops[MAX_GRADIENT_STOPS];
+      float start_point[2];
+      float end_point[2];
+    } linear_gradient;
+    struct {
+      int n_color_stops;
+      GskColorStop color_stops[MAX_GRADIENT_STOPS];
+      float center[2];
+      float start;
+      float end;
+      float radius[2]; /* h/v */
+    } radial_gradient;
+    struct {
+      graphene_vec2_t size;
+      graphene_vec4_t args;
+    } custom;
+  };
+} ProgramState;
+
 struct _Program
 {
   int index;        /* Into the renderer's program array */
@@ -108,59 +163,15 @@ struct _Program
       int child_bounds_location;
       int texture_rect_location;
     } repeat;
+    struct {
+      int size_location;
+      int args_location;
+      int extra_source_locations[3];
+    } glshader;
   };
-};
 
-typedef struct
-{
-  GskTransform *modelview;
-  GskRoundedRect clip;
-  graphene_matrix_t projection;
-  int source_texture;
-  graphene_rect_t viewport;
-  float opacity;
-  /* Per-program state */
-  union {
-    GdkRGBA color;
-    struct {
-      graphene_matrix_t matrix;
-      graphene_vec4_t offset;
-    } color_matrix;
-    struct {
-      float widths[4];
-      GdkRGBA color;
-      GskRoundedRect outline;
-    } border;
-    struct {
-      GskRoundedRect outline;
-      float dx;
-      float dy;
-      float spread;
-      GdkRGBA color;
-    } inset_shadow;
-    struct {
-      GskRoundedRect outline;
-      float dx;
-      float dy;
-      float spread;
-      GdkRGBA color;
-    } unblurred_outset_shadow;
-    struct {
-      int n_color_stops;
-      GskColorStop color_stops[MAX_GRADIENT_STOPS];
-      float start_point[2];
-      float end_point[2];
-    } linear_gradient;
-    struct {
-      int n_color_stops;
-      GskColorStop color_stops[MAX_GRADIENT_STOPS];
-      float center[2];
-      float start;
-      float end;
-      float radius[2]; /* h/v */
-    } radial_gradient;
-  };
-} ProgramState;
+  ProgramState state;
+};
 
 typedef struct {
   int ref_count;
@@ -183,13 +194,13 @@ typedef struct {
       Program unblurred_outset_shadow_program;
     };
   };
-  ProgramState state[GL_N_PROGRAMS];
+  GHashTable *custom_programs; /* GskGLShader -> Program* */
 } GskGLRendererPrograms;
 
 typedef struct
 {
   GskGLRendererPrograms *programs;
-  const Program *current_program;
+  Program *current_program;
   int current_render_target;
   int current_texture;
 
@@ -236,7 +247,7 @@ void              ops_pop_modelview      (RenderOpBuilder         *builder);
 float             ops_get_scale          (const RenderOpBuilder   *builder);
 
 void              ops_set_program        (RenderOpBuilder         *builder,
-                                          const Program           *program);
+                                          Program                 *program);
 
 void              ops_push_clip          (RenderOpBuilder         *builder,
                                           const GskRoundedRect    *clip);
@@ -255,6 +266,9 @@ graphene_rect_t   ops_set_viewport       (RenderOpBuilder         *builder,
 
 void              ops_set_texture        (RenderOpBuilder         *builder,
                                           int                      texture_id);
+void              ops_set_extra_texture  (RenderOpBuilder         *builder,
+                                          int                      texture_id,
+                                          int                      idx);
 
 int               ops_set_render_target  (RenderOpBuilder         *builder,
                                           int                      render_target_id);
@@ -281,6 +295,9 @@ void              ops_set_inset_shadow   (RenderOpBuilder         *self,
                                           const GdkRGBA           *color,
                                           float                    dx,
                                           float                    dy);
+void              ops_set_glshader_args  (RenderOpBuilder         *builder,
+                                          const graphene_vec2_t   *size,
+                                          const graphene_vec4_t   *args);
 void              ops_set_unblurred_outset_shadow   (RenderOpBuilder         *self,
                                                      const GskRoundedRect     outline,
                                                      float                    spread,

gsk/gl/gskglshaderbuilder.c

@@ -47,7 +47,9 @@ check_shader_error (int     shader_id,
   int log_len;
   char *buffer;
   int code_len;
-  char *code;
+  int line;
+  char *code, *p;
+  GString *s;
 
   glGetShaderiv (shader_id, GL_COMPILE_STATUS, &status);
 
@@ -62,11 +64,29 @@ check_shader_error (int     shader_id,
   code = g_malloc0 (code_len + 1);
   glGetShaderSource (shader_id, code_len, NULL, code);
 
+  s = g_string_new ("");
+  p = code;
+  line = 1;
+  while (*p)
+    {
+      char *end = strchr (p, '\n');
+      if (end)
+        end = end + 1; /* Include newline */
+      else
+        end = p + strlen (p);
+
+      g_string_append_printf (s, "%3d| ", line++);
+      g_string_append_len (s, p, end - p);
+
+      p = end;
+    }
+
   g_set_error (error, GDK_GL_ERROR, GDK_GL_ERROR_COMPILATION_FAILED,
                "Compilation failure in shader.\nError message: %s\n\nSource code:\n%s\n\n",
                buffer,
-               code);
+               s->str);
 
+  g_string_free (s, TRUE);
   g_free (buffer);
   g_free (code);
 
@@ -76,6 +96,7 @@ check_shader_error (int     shader_id,
 int
 gsk_gl_shader_builder_create_program (GskGLShaderBuilder  *self,
                                       const char          *resource_path,
+                                      const char          *extra_fragment_snippet,
                                       GError             **error)
 {
 
@@ -136,7 +157,7 @@ gsk_gl_shader_builder_create_program (GskGLShaderBuilder  *self,
     }
 
   fragment_id = glCreateShader (GL_FRAGMENT_SHADER);
-  glShaderSource (fragment_id, 8,
+  glShaderSource (fragment_id, 9,
                   (const char *[]) {
                     version_buffer,
                     self->debugging ? "#define GSK_DEBUG 1\n" : "",
@@ -145,7 +166,8 @@ gsk_gl_shader_builder_create_program (GskGLShaderBuilder  *self,
                     self->gles ? "#define GSK_GLES 1\n" : "",
                     g_bytes_get_data (self->preamble, NULL),
                     g_bytes_get_data (self->fs_preamble, NULL),
-                    fragment_shader_start
+                    fragment_shader_start,
+                    extra_fragment_snippet ? extra_fragment_snippet : ""
                   },
                   (int[]) {
                     -1,
@@ -156,6 +178,7 @@ gsk_gl_shader_builder_create_program (GskGLShaderBuilder  *self,
                     -1,
                     -1,
                     -1,
+                    -1,
                   });
   glCompileShader (fragment_id);
 
@@ -188,6 +211,7 @@ gsk_gl_shader_builder_create_program (GskGLShaderBuilder  *self,
       g_free (buffer);
 
       glDeleteProgram (program_id);
+      program_id = -1;
 
       goto out;
     }

gsk/gl/gskglshaderbuilderprivate.h

@@ -33,6 +33,7 @@ void   gsk_gl_shader_builder_set_glsl_version (GskGLShaderBuilder  *self,
 
 int    gsk_gl_shader_builder_create_program   (GskGLShaderBuilder  *self,
                                                const char          *resource_path,
+                                               const char          *extra_fragment_snippet,
                                                GError             **error);
 
 G_END_DECLS

gsk/gl/opbuffer.c

@@ -31,6 +31,8 @@ static guint op_sizes[OP_LAST] = {
   sizeof (OpDebugGroup),
   0,
   sizeof (OpBlend),
+  sizeof (OpGLShader),
+  sizeof (OpExtraTexture),
 };
 
 void

gsk/gl/opbuffer.h

@@ -39,6 +39,8 @@ typedef enum
   OP_PUSH_DEBUG_GROUP                  = 25,
   OP_POP_DEBUG_GROUP                   = 26,
   OP_CHANGE_BLEND                      = 27,
+  OP_CHANGE_GLSHADER_ARGS              = 28,
+  OP_CHANGE_EXTRA_SOURCE_TEXTURE       = 29,
   OP_LAST
 } OpKind;
 
@@ -124,6 +126,12 @@ typedef struct
   int texture_id;
 } OpTexture;
 
+typedef struct
+{
+  int texture_id;
+  int idx;
+} OpExtraTexture;
+
 typedef struct
 {
   gsize vao_offset;
@@ -198,6 +206,12 @@ typedef struct
   float texture_rect[4];
 } OpRepeat;
 
+typedef struct
+{
+  float size[2];
+  float args[4];
+} OpGLShader;
+
 void     op_buffer_init            (OpBuffer *buffer);
 void     op_buffer_destroy         (OpBuffer *buffer);
 void     op_buffer_clear           (OpBuffer *buffer);

gsk/gskenums.h

@@ -75,7 +75,8 @@ typedef enum {
   GSK_CROSS_FADE_NODE,
   GSK_TEXT_NODE,
   GSK_BLUR_NODE,
-  GSK_DEBUG_NODE
+  GSK_DEBUG_NODE,
+  GSK_GLSHADER_NODE
 } GskRenderNodeType;
 
 /**

gsk/gskrendernode.h

@@ -53,6 +53,11 @@ struct _GskShadow
   float radius;
 };
 
+#define GSK_TYPE_GLSHADER (gsk_glshader_get_type ())
+
+GDK_AVAILABLE_IN_ALL
+G_DECLARE_FINAL_TYPE (GskGLShader, gsk_glshader, GSK, GLSHADER, GObject)
+
 /**
  * GskParseErrorFunc:
  * @section: the #GtkCssSection where the error occurred
@@ -72,6 +77,12 @@ GType                   gsk_render_node_get_type                (void) G_GNUC_CO
 GDK_AVAILABLE_IN_ALL
 GQuark                  gsk_serialization_error_quark           (void);
 
+
+GDK_AVAILABLE_IN_ALL
+GskGLShader *           gsk_glshader_new                        (const char   *source);
+GDK_AVAILABLE_IN_ALL
+const char *            gsk_glshader_peek_source                (GskGLShader  *shader);
+
 GDK_AVAILABLE_IN_ALL
 GskRenderNode *         gsk_render_node_ref                     (GskRenderNode *node);
 GDK_AVAILABLE_IN_ALL
@@ -122,6 +133,7 @@ GskRenderNode *         gsk_render_node_deserialize             (GBytes
 #define GSK_TYPE_CROSS_FADE_NODE                (gsk_cross_fade_node_get_type())
 #define GSK_TYPE_TEXT_NODE                      (gsk_text_node_get_type())
 #define GSK_TYPE_BLUR_NODE                      (gsk_blur_node_get_type())
+#define GSK_TYPE_GLSHADER_NODE                  (gsk_glshader_node_get_type())
 
 typedef struct _GskDebugNode                    GskDebugNode;
 typedef struct _GskColorNode                    GskColorNode;
@@ -146,6 +158,7 @@ typedef struct _GskBlendNode                    GskBlendNode;
 typedef struct _GskCrossFadeNode                GskCrossFadeNode;
 typedef struct _GskTextNode                     GskTextNode;
 typedef struct _GskBlurNode                     GskBlurNode;
+typedef struct _GskGLShaderNode                 GskGLShaderNode;
 
 GDK_AVAILABLE_IN_ALL
 GType                   gsk_debug_node_get_type                 (void) G_GNUC_CONST;
@@ -451,6 +464,29 @@ GskRenderNode *         gsk_blur_node_get_child                 (GskRenderNode
 GDK_AVAILABLE_IN_ALL
 float                   gsk_blur_node_get_radius                (GskRenderNode            *node);
 
+GDK_AVAILABLE_IN_ALL
+GType                   gsk_glshader_node_get_type              (void) G_GNUC_CONST;
+GDK_AVAILABLE_IN_ALL
+GskRenderNode *         gsk_glshader_node_new                   (GskGLShader              *shader,
+                                                                 const graphene_vec4_t    *args,
+                                                                 const graphene_rect_t    *bounds,
+                                                                 GskRenderNode            *fallback,
+                                                                 GskRenderNode           **children,
+                                                                 int                       n_children);
+GDK_AVAILABLE_IN_ALL
+GskRenderNode *         gsk_glshader_node_get_fallback_child    (GskRenderNode            *node);
+GDK_AVAILABLE_IN_ALL
+guint                   gsk_glshader_node_get_n_children        (GskRenderNode            *node);
+GDK_AVAILABLE_IN_ALL
+GskRenderNode *         gsk_glshader_node_get_child             (GskRenderNode            *node,
+                                                                 int                       idx);
+GDK_AVAILABLE_IN_ALL
+void                    gsk_glshader_node_get_args              (GskRenderNode            *node,
+                                                                 graphene_vec4_t          *out_args);
+GDK_AVAILABLE_IN_ALL
+GskGLShader *           gsk_glshader_node_get_shader            (GskRenderNode            *node);
+
+
 G_END_DECLS
 
 #endif /* __GSK_RENDER_NODE_H__ */

gsk/gskrendernodeimpl.c

@@ -4470,6 +4470,323 @@ gsk_debug_node_get_message (GskRenderNode *node)
   return self->message;
 }
 
+/*** GSK_GLSHADER_NODE ***/
+struct _GskGLShader
+{
+  GObject parent_instance;
+  char *source;
+};
+
+G_DEFINE_TYPE (GskGLShader, gsk_glshader, G_TYPE_OBJECT)
+
+enum {
+  GLSHADER_PROP_0,
+  GLSHADER_PROP_SOURCE,
+  GLSHADER_N_PROPS
+};
+static GParamSpec *gsk_glshader_properties[GLSHADER_N_PROPS];
+
+static void
+gsk_glshader_get_property (GObject    *object,
+                           guint       prop_id,
+                           GValue     *value,
+                           GParamSpec *pspec)
+{
+  GskGLShader *shader = GSK_GLSHADER (object);
+
+  switch (prop_id)
+    {
+    case GLSHADER_PROP_SOURCE:
+      g_value_set_string (value, shader->source);
+      break;
+
+    default:
+      g_assert_not_reached ();
+    }
+}
+
+static void
+gsk_glshader_set_property (GObject      *object,
+                           guint         prop_id,
+                           const GValue *value,
+                           GParamSpec   *pspec)
+{
+  GskGLShader *shader = GSK_GLSHADER (object);
+
+  switch (prop_id)
+    {
+    case GLSHADER_PROP_SOURCE:
+      g_free (shader->source);
+      shader->source = g_value_dup_string (value);
+      break;
+
+    default:
+      g_assert_not_reached ();
+    }
+}
+
+static void
+gsk_glshader_finalize (GObject *object)
+{
+  GskGLShader *shader = GSK_GLSHADER (object);
+
+  g_free (shader->source);
+
+  G_OBJECT_CLASS (gsk_glshader_parent_class)->finalize (object);
+}
+
+static void
+gsk_glshader_class_init (GskGLShaderClass *klass)
+{
+   GObjectClass *object_class = G_OBJECT_CLASS (klass);
+
+  object_class->get_property = gsk_glshader_get_property;
+  object_class->set_property = gsk_glshader_set_property;
+  object_class->finalize = gsk_glshader_finalize;
+
+  /**
+   * GskGLShader:source:
+   *
+   * The source code for the shader.
+   */
+  gsk_glshader_properties[GLSHADER_PROP_SOURCE] =
+    g_param_spec_string ("source",
+                         "Source",
+                         "The source code for the shader",
+                         NULL,
+                         G_PARAM_READWRITE |
+                         G_PARAM_CONSTRUCT_ONLY |
+                         G_PARAM_STATIC_STRINGS);
+
+  g_object_class_install_properties (object_class, GLSHADER_N_PROPS, gsk_glshader_properties);
+}
+
+static void
+gsk_glshader_init (GskGLShader *shader)
+{
+}
+
+GskGLShader *
+gsk_glshader_new (const char *source)
+{
+   GskGLShader *shader = g_object_new (GSK_TYPE_GLSHADER,
+                                       "source", source,
+                                       NULL);
+   return shader;
+}
+
+const char *
+gsk_glshader_peek_source (GskGLShader *shader)
+{
+  return shader->source;
+}
+
+struct _GskGLShaderNode
+{
+  GskRenderNode render_node;
+
+  GskGLShader *shader;
+  graphene_vec4_t args;
+  GskRenderNode *fallback;
+  guint n_children;
+  GskRenderNode **children;
+};
+
+static void
+gsk_glshader_node_finalize (GskRenderNode *node)
+{
+  GskGLShaderNode *self = (GskGLShaderNode *) node;
+  GskRenderNodeClass *parent_class = g_type_class_peek (g_type_parent (GSK_TYPE_GLSHADER_NODE));
+
+  for (guint i = 0; i < self->n_children; i++)
+    gsk_render_node_unref (self->children[i]);
+  g_free (self->children);
+
+  gsk_render_node_unref (self->fallback);
+
+  g_object_unref (self->shader);
+
+  parent_class->finalize (node);
+}
+
+static void
+gsk_glshader_node_draw (GskRenderNode *node,
+                        cairo_t       *cr)
+{
+  GskGLShaderNode *self = (GskGLShaderNode *) node;
+
+  gsk_render_node_draw (self->fallback, cr);
+}
+
+static void
+gsk_glshader_node_diff (GskRenderNode  *node1,
+                        GskRenderNode  *node2,
+                        cairo_region_t *region)
+{
+  GskGLShaderNode *self1 = (GskGLShaderNode *) node1;
+  GskGLShaderNode *self2 = (GskGLShaderNode *) node2;
+
+  if (graphene_rect_equal (&node1->bounds, &node2->bounds) &&
+      self1->shader == self2->shader &&
+      graphene_vec4_equal (&self1->args, &self2->args) &&
+      self1->n_children == self2->n_children)
+    {
+      gsk_render_node_diff (self1->fallback, self2->fallback, region);
+
+      for (guint i = 0; i < self1->n_children; i++)
+        {
+          if (self1->children[i] != self2->children[i])
+            {
+              gsk_render_node_diff_impossible (node1, node2, region);
+              break;
+            }
+        }
+    }
+  else
+    {
+      gsk_render_node_diff_impossible (node1, node2, region);
+    }
+}
+
+/**
+ * gsk_glshader_node_new:
+ * @shader: the shader glsl code
+ * @args: a vec4 argument to the shader
+ * @bounds: the rectangle to render the glshader into
+ * @fallback: Render node to use if OpenGL is not supported
+ * @children: List of child nodes, these will be rendered to textures and used as input.
+ * @n_children: Length of @children (currenly the GL backend only supports max 4 children)
+ *
+ * Creates a #GskRenderNode that will render the given @gl_program into the area given by @bounds.
+ *
+ * Returns: (transfer full) (type GskGLShaderNode): A new #GskRenderNode
+ */
+GskRenderNode *
+gsk_glshader_node_new (GskGLShader           *shader,
+                       const graphene_vec4_t *args,
+                       const graphene_rect_t *bounds,
+                       GskRenderNode         *fallback,
+                       GskRenderNode        **children,
+                       int                    n_children)
+{
+  GskGLShaderNode *self;
+  GskRenderNode *node;
+
+  g_return_val_if_fail (bounds != NULL, NULL);
+
+  self = gsk_render_node_alloc (GSK_GLSHADER_NODE);
+  node = (GskRenderNode *) self;
+
+  graphene_rect_init_from_rect (&node->bounds, bounds);
+  self->shader = g_object_ref (shader);
+  self->args = *args;
+
+  self->fallback = gsk_render_node_ref (fallback);
+
+  self->n_children = n_children;
+  if (n_children > 0)
+    {
+      self->children = g_malloc_n (n_children, sizeof (GskRenderNode *));
+      for (guint i = 0; i < n_children; i++)
+        self->children[i] = gsk_render_node_ref (children[i]);
+    }
+
+  return node;
+}
+
+/**
+ * gsk_glshader_node_get_fallback_child:
+ * @node: (type GskGLShaderNode): a #GskRenderNode for a gl shader
+ *
+ * Gets the fallback child node
+ *
+ * Returns: (transfer none): The fallback node
+ */
+GskRenderNode *
+gsk_glshader_node_get_fallback_child (GskRenderNode *node)
+{
+  GskGLShaderNode *self = (GskGLShaderNode *) node;
+
+  g_return_val_if_fail (GSK_IS_RENDER_NODE_TYPE (node, GSK_GLSHADER_NODE), NULL);
+
+  return self->fallback;
+}
+
+/**
+ * gsk_glshader_node_get_n_children:
+ * @node: (type GskGLShaderNode): a #GskRenderNode for a gl shader
+ *
+ * Returns the number of (non-fallback) children
+ *
+ * Returns: The number of children
+ */
+guint
+gsk_glshader_node_get_n_children (GskRenderNode *node)
+{
+  GskGLShaderNode *self = (GskGLShaderNode *) node;
+
+  g_return_val_if_fail (GSK_IS_RENDER_NODE_TYPE (node, GSK_GLSHADER_NODE), 0);
+
+  return self->n_children;
+}
+
+/**
+ * gsk_glshader_node_get_child:
+ * @node: (type GskGLShaderNode): a #GskRenderNode for a gl shader
+ * @idx: the position of the child to get
+ *
+ * Gets one of the (non-fallback) children.
+ *
+ * Returns: (transfer none): the @idx'th child of @node
+ */
+GskRenderNode *
+gsk_glshader_node_get_child (GskRenderNode *node,
+                             int            idx)
+{
+  GskGLShaderNode *self = (GskGLShaderNode *) node;
+
+  g_return_val_if_fail (GSK_IS_RENDER_NODE_TYPE (node, GSK_GLSHADER_NODE), NULL);
+  g_return_val_if_fail (idx < self->n_children, NULL);
+
+  return self->children[idx];
+}
+
+/**
+ * gsk_glshader_node_get_shader:
+ * @node: (type GskGLShaderNode): a #GskRenderNode for a gl shader
+ *
+ * Gets shader code for the node.
+ *
+ * Returns: (transfer none): the #GskGLShader shader
+ */
+GskGLShader *
+gsk_glshader_node_get_shader (GskRenderNode *node)
+{
+  GskGLShaderNode *self = (GskGLShaderNode *) node;
+
+  g_return_val_if_fail (GSK_IS_RENDER_NODE_TYPE (node, GSK_GLSHADER_NODE), 0);
+
+  return self->shader;
+}
+
+/**
+ * gsk_glshader_node_get_args:
+ * @node: (type GskGLShaderNode): a #GskRenderNode for a gl shader
+ * @out_args: Location to write results to.
+ *
+ * Gets args for the node.
+ */
+void
+gsk_glshader_node_get_args (GskRenderNode   *node,
+                            graphene_vec4_t *out_args)
+{
+  GskGLShaderNode *self = (GskGLShaderNode *) node;
+
+  g_return_if_fail (GSK_IS_RENDER_NODE_TYPE (node, GSK_GLSHADER_NODE));
+
+  *out_args = self->args;
+}
+
 GType gsk_render_node_types[GSK_RENDER_NODE_TYPE_N_TYPES];
 
 #ifndef I_
@@ -4506,6 +4823,7 @@ GSK_DEFINE_RENDER_NODE_TYPE (gsk_blend_node, GSK_BLEND_NODE)
 GSK_DEFINE_RENDER_NODE_TYPE (gsk_cross_fade_node, GSK_CROSS_FADE_NODE)
 GSK_DEFINE_RENDER_NODE_TYPE (gsk_text_node, GSK_TEXT_NODE)
 GSK_DEFINE_RENDER_NODE_TYPE (gsk_blur_node, GSK_BLUR_NODE)
+GSK_DEFINE_RENDER_NODE_TYPE (gsk_glshader_node, GSK_GLSHADER_NODE)
 GSK_DEFINE_RENDER_NODE_TYPE (gsk_debug_node, GSK_DEBUG_NODE)
 
 static void
@@ -4863,6 +5181,22 @@ gsk_render_node_init_types_once (void)
     gsk_render_node_types[GSK_BLUR_NODE] = node_type;
   }
 
+  {
+    const GskRenderNodeTypeInfo node_info =
+    {
+      GSK_GLSHADER_NODE,
+      sizeof (GskGLShaderNode),
+      NULL,
+      gsk_glshader_node_finalize,
+      gsk_glshader_node_draw,
+      NULL,
+      gsk_glshader_node_diff,
+    };
+
+    GType node_type = gsk_render_node_type_register_static (I_("GskGLShaderNode"), &node_info);
+    gsk_render_node_types[GSK_GLSHADER_NODE] = node_type;
+  }
+
   {
     const GskRenderNodeTypeInfo node_info =
     {

gsk/gskrendernodeparser.c

@@ -1089,6 +1089,15 @@ parse_inset_shadow_node (GtkCssParser *parser)
   return gsk_inset_shadow_node_new (&outline, &color, dx, dy, spread, blur);
 }
 
+
+static GskRenderNode *
+parse_glshader_node (GtkCssParser *parser)
+{
+  /* TODO */
+  gtk_css_parser_error_syntax (parser, "glshader node parsing not implemented yet");
+  return NULL;
+}
+
 static GskRenderNode *
 parse_border_node (GtkCssParser *parser)
 {
@@ -1603,6 +1612,7 @@ parse_node (GtkCssParser *parser,
     { "text", parse_text_node },
     { "texture", parse_texture_node },
     { "transform", parse_transform_node },
+    { "glshader", parse_glshader_node },
   };
   GskRenderNode **node_p = out_node;
   guint i;
@@ -1837,6 +1847,19 @@ append_point (GString                *str,
   string_append_double (str, p->y);
 }
 
+static void
+append_string (GString    *str,
+               const char *value)
+{
+  char *escaped = g_strescape (value, NULL);
+
+  g_string_append_c (str, '"');
+  g_string_append (str, escaped);
+  g_string_append_c (str, '"');
+
+  g_free (escaped);
+}
+
 static void
 append_vec4 (GString               *str,
              const graphene_vec4_t *v)
@@ -1914,6 +1937,18 @@ append_point_param (Printer                *p,
   g_string_append_c (p->str, '\n');
 }
 
+static void
+append_string_param (Printer    *p,
+                     const char *param_name,
+                     const char *value)
+{
+  _indent (p);
+  g_string_append_printf (p->str, "%s: ", param_name);
+  append_string (p->str, value);
+  g_string_append_c (p->str, ';');
+  g_string_append_c (p->str, '\n');
+}
+
 static void
 append_vec4_param (Printer               *p,
                    const char            *param_name,
@@ -2441,6 +2476,27 @@ render_node_print (Printer       *p,
       }
       break;
 
+    case GSK_GLSHADER_NODE:
+      {
+        start_node (p, "glshader");
+
+        GskGLShader *shader = gsk_glshader_node_get_shader (node);
+        append_string_param (p, "shader", gsk_glshader_peek_source (shader));
+        graphene_vec4_t args;
+        gsk_glshader_node_get_args (node, &args);
+        append_vec4_param (p, "args", &args);
+        append_node_param (p, "fallback", gsk_glshader_node_get_fallback_child (node));
+        for (guint i = 0; i < gsk_glshader_node_get_n_children (node); i ++)
+          {
+            GskRenderNode *child = gsk_glshader_node_get_child (node, i);
+            _indent (p);
+            render_node_print (p, child);
+          }
+
+        end_node (p);
+      }
+      break;
+
     case GSK_REPEAT_NODE:
       {
         GskRenderNode *child = gsk_repeat_node_get_child (node);

gsk/gskrendernodeprivate.h

@@ -13,7 +13,7 @@ typedef struct _GskRenderNodeClass GskRenderNodeClass;
  * We don't add an "n-types" value to avoid having to handle
  * it in every single switch.
  */
-#define GSK_RENDER_NODE_TYPE_N_TYPES    (GSK_DEBUG_NODE + 1)
+#define GSK_RENDER_NODE_TYPE_N_TYPES    (GSK_GLSHADER_NODE + 1)
 
 extern GType gsk_render_node_types[];
 

gsk/meson.build

@@ -16,6 +16,7 @@ gsk_private_gl_shaders = [
   'resources/glsl/cross_fade.glsl',
   'resources/glsl/blend.glsl',
   'resources/glsl/repeat.glsl',
+  'resources/glsl/custom.glsl',
 ]
 
 gsk_public_sources = files([

gsk/resources/glsl/blend.glsl

@@ -267,8 +267,8 @@ luminosity (vec4 Cs, vec4 Cb)
 }
 
 void main() {
-  vec4 bottom_color = Texture(u_source, vUv);
-  vec4 top_color = Texture(u_source2, vUv);
+  vec4 bottom_color = GskTexture(u_source, vUv);
+  vec4 top_color = GskTexture(u_source2, vUv);
 
   vec4 result;
   if (u_mode == 0)
@@ -306,5 +306,5 @@ void main() {
   else
     discard;
 
-  setOutputColor(result * u_alpha);
+  gskSetOutputColor(result * u_alpha);
 }

gsk/resources/glsl/blit.glsl

@@ -7,7 +7,7 @@ void main() {
 
 // FRAGMENT_SHADER:
 void main() {
-  vec4 diffuse = Texture(u_source, vUv);
+  vec4 diffuse = GskTexture(u_source, vUv);
 
-  setOutputColor(diffuse * u_alpha);
+  gskSetOutputColor(diffuse * u_alpha);
 }

gsk/resources/glsl/blur.glsl

@@ -39,14 +39,14 @@ void main() {
   vec3 incrementalGaussian = initial_gaussian;
 
   float coefficientSum = 0.0;
-  vec4 sum = Texture(u_source, vUv) * incrementalGaussian.x;
+  vec4 sum = GskTexture(u_source, vUv) * incrementalGaussian.x;
   coefficientSum += incrementalGaussian.x;
   incrementalGaussian.xy *= incrementalGaussian.yz;
 
   vec2 p = pixel_step;
   for (int i = 1; i <= int(pixels_per_side); i++) {
-    sum += Texture(u_source, vUv - p) * incrementalGaussian.x;
-    sum += Texture(u_source, vUv + p) * incrementalGaussian.x;
+    sum += GskTexture(u_source, vUv - p) * incrementalGaussian.x;
+    sum += GskTexture(u_source, vUv + p) * incrementalGaussian.x;
 
     coefficientSum += 2.0 * incrementalGaussian.x;
     incrementalGaussian.xy *= incrementalGaussian.yz;
@@ -54,5 +54,5 @@ void main() {
     p += pixel_step;
   }
 
-  setOutputColor(sum / coefficientSum);
+  gskSetOutputColor(sum / coefficientSum);
 }

gsk/resources/glsl/border.glsl

@@ -4,37 +4,37 @@ uniform vec4 u_widths;
 uniform vec4[3] u_outline_rect;
 
 _OUT_ vec4 final_color;
-_OUT_ _ROUNDED_RECT_UNIFORM_ transformed_outside_outline;
-_OUT_ _ROUNDED_RECT_UNIFORM_ transformed_inside_outline;
+_OUT_ _GSK_ROUNDED_RECT_UNIFORM_ transformed_outside_outline;
+_OUT_ _GSK_ROUNDED_RECT_UNIFORM_ transformed_inside_outline;
 
 void main() {
   gl_Position = u_projection * u_modelview * vec4(aPosition, 0.0, 1.0);
 
-  final_color = premultiply(u_color) * u_alpha;
+  final_color = gsk_premultiply(u_color) * u_alpha;
 
-  RoundedRect outside = create_rect(u_outline_rect);
-  RoundedRect inside = rounded_rect_shrink (outside, u_widths);
+  GskRoundedRect outside = gsk_create_rect(u_outline_rect);
+  GskRoundedRect inside = gsk_rounded_rect_shrink (outside, u_widths);
 
-  rounded_rect_transform(outside, u_modelview);
-  rounded_rect_transform(inside, u_modelview);
+  gsk_rounded_rect_transform(outside, u_modelview);
+  gsk_rounded_rect_transform(inside, u_modelview);
 
-  rounded_rect_encode(outside, transformed_outside_outline);
-  rounded_rect_encode(inside, transformed_inside_outline);
+  gsk_rounded_rect_encode(outside, transformed_outside_outline);
+  gsk_rounded_rect_encode(inside, transformed_inside_outline);
 }
 
 // FRAGMENT_SHADER:
 uniform vec4[3] u_outline_rect;
 
 _IN_ vec4 final_color;
-_IN_ _ROUNDED_RECT_UNIFORM_ transformed_outside_outline;
-_IN_ _ROUNDED_RECT_UNIFORM_ transformed_inside_outline;
+_IN_ _GSK_ROUNDED_RECT_UNIFORM_ transformed_outside_outline;
+_IN_ _GSK_ROUNDED_RECT_UNIFORM_ transformed_inside_outline;
 
 void main() {
-  vec2 frag = get_frag_coord();
+  vec2 frag = gsk_get_frag_coord();
 
-  float alpha = clamp(rounded_rect_coverage(decode_rect(transformed_outside_outline), frag) -
-                      rounded_rect_coverage(decode_rect(transformed_inside_outline), frag),
+  float alpha = clamp(gsk_rounded_rect_coverage(gsk_decode_rect(transformed_outside_outline), frag) -
+                      gsk_rounded_rect_coverage(gsk_decode_rect(transformed_inside_outline), frag),
                       0.0, 1.0);
 
-  setOutputColor(final_color * alpha);
+  gskSetOutputColor(final_color * alpha);
 }

gsk/resources/glsl/color.glsl

@@ -6,13 +6,13 @@ _OUT_ vec4 final_color;
 void main() {
   gl_Position = u_projection * u_modelview * vec4(aPosition, 0.0, 1.0);
 
-  final_color = premultiply(u_color) * u_alpha;
+  final_color = gsk_premultiply(u_color) * u_alpha;
 }
 
 // FRAGMENT_SHADER:
 _IN_ vec4 final_color;
 
 void main() {
-  setOutputColor(final_color);
+  gskSetOutputColor(final_color);
 }
 

gsk/resources/glsl/color_matrix.glsl

@@ -10,7 +10,7 @@ uniform mat4 u_color_matrix;
 uniform vec4 u_color_offset;
 
 void main() {
-  vec4 color = Texture(u_source, vUv);
+  vec4 color = GskTexture(u_source, vUv);
 
   // Un-premultilpy
   if (color.a != 0.0)
@@ -21,5 +21,5 @@ void main() {
 
   color.rgb *= color.a;
 
-  setOutputColor(color * u_alpha);
+  gskSetOutputColor(color * u_alpha);
 }

gsk/resources/glsl/coloring.glsl

@@ -8,7 +8,7 @@ void main() {
 
   vUv = vec2(aUv.x, aUv.y);
 
-  final_color = premultiply(u_color) * u_alpha;
+  final_color = gsk_premultiply(u_color) * u_alpha;
 }
 
 // FRAGMENT_SHADER:
@@ -16,7 +16,7 @@ void main() {
 _IN_ vec4 final_color;
 
 void main() {
-  vec4 diffuse = Texture(u_source, vUv);
+  vec4 diffuse = GskTexture(u_source, vUv);
 
-  setOutputColor(final_color * diffuse.a);
+  gskSetOutputColor(final_color * diffuse.a);
 }

gsk/resources/glsl/cross_fade.glsl

@@ -10,11 +10,11 @@ uniform float u_progress;
 uniform sampler2D u_source2;
 
 void main() {
-  vec4 source1 = Texture(u_source, vUv);  // start child
-  vec4 source2 = Texture(u_source2, vUv); // end child
+  vec4 source1 = GskTexture(u_source, vUv);  // start child
+  vec4 source2 = GskTexture(u_source2, vUv); // end child
 
   float p_start = (1.0 - u_progress) * u_alpha;
   float p_end = u_progress * u_alpha;
   vec4 color = (p_start * source1) + (p_end * source2);
-  setOutputColor(color);
+  gskSetOutputColor(color);
 }

gsk/resources/glsl/custom.glsl

@@ -0,0 +1,20 @@
+// VERTEX_SHADER:
+void main() {
+  gl_Position = u_projection * u_modelview * vec4(aPosition, 0.0, 1.0);
+  vUv = vec2(aUv.x, aUv.y);
+}
+
+// FRAGMENT_SHADER:
+// The shader supplies:
+void mainImage(out vec4 fragColor, in vec2 fragCoord, in vec2 resolution, in vec2 uv);
+
+uniform vec2 u_size;
+uniform vec4 u_args;
+uniform sampler2D u_source2;
+
+void main() {
+  vec4 fragColor;
+  vec2 fragCoord = vec2(vUv.x * u_size.x, (1.0-vUv.y) * u_size.y);
+  mainImage(fragColor, fragCoord, u_size, vUv);
+  gskSetOutputColor(fragColor);
+}

gsk/resources/glsl/inset_shadow.glsl

@@ -5,8 +5,8 @@ uniform vec2 u_offset;
 uniform vec4[3] u_outline_rect;
 
 _OUT_ vec4 final_color;
-_OUT_ _ROUNDED_RECT_UNIFORM_ transformed_outside_outline;
-_OUT_ _ROUNDED_RECT_UNIFORM_ transformed_inside_outline;
+_OUT_ _GSK_ROUNDED_RECT_UNIFORM_ transformed_outside_outline;
+_OUT_ _GSK_ROUNDED_RECT_UNIFORM_ transformed_inside_outline;
 
 void main() {
   gl_Position = u_projection * u_modelview * vec4(aPosition, 0.0, 1.0);
@@ -15,29 +15,29 @@ void main() {
   final_color.rgb *= final_color.a;
   final_color *= u_alpha;
 
-  RoundedRect outside = create_rect(u_outline_rect);
-  RoundedRect inside = rounded_rect_shrink(outside, vec4(u_spread));
+  GskRoundedRect outside = gsk_create_rect(u_outline_rect);
+  GskRoundedRect inside = gsk_rounded_rect_shrink(outside, vec4(u_spread));
 
-  rounded_rect_offset(inside, u_offset);
+  gsk_rounded_rect_offset(inside, u_offset);
 
-  rounded_rect_transform(outside, u_modelview);
-  rounded_rect_transform(inside, u_modelview);
+  gsk_rounded_rect_transform(outside, u_modelview);
+  gsk_rounded_rect_transform(inside, u_modelview);
 
-  rounded_rect_encode(outside, transformed_outside_outline);
-  rounded_rect_encode(inside, transformed_inside_outline);
+  gsk_rounded_rect_encode(outside, transformed_outside_outline);
+  gsk_rounded_rect_encode(inside, transformed_inside_outline);
 }
 
 // FRAGMENT_SHADER:
 _IN_ vec4 final_color;
-_IN_ _ROUNDED_RECT_UNIFORM_ transformed_outside_outline;
-_IN_ _ROUNDED_RECT_UNIFORM_ transformed_inside_outline;
+_IN_ _GSK_ROUNDED_RECT_UNIFORM_ transformed_outside_outline;
+_IN_ _GSK_ROUNDED_RECT_UNIFORM_ transformed_inside_outline;
 
 void main() {
-  vec2 frag = get_frag_coord();
+  vec2 frag = gsk_get_frag_coord();
 
-  float alpha = clamp(rounded_rect_coverage(decode_rect(transformed_outside_outline), frag) -
-                      rounded_rect_coverage(decode_rect(transformed_inside_outline), frag),
+  float alpha = clamp(gsk_rounded_rect_coverage(gsk_decode_rect(transformed_outside_outline), frag) -
+                      gsk_rounded_rect_coverage(gsk_decode_rect(transformed_inside_outline), frag),
                       0.0, 1.0);
 
-  setOutputColor(final_color * alpha);
+  gskSetOutputColor(final_color * alpha);
 }

gsk/resources/glsl/linear_gradient.glsl

@@ -25,10 +25,10 @@ void main() {
 
   for (int i = 0; i < u_num_color_stops; i ++) {
     color_offsets[i] = u_color_stops[(i * 5) + 0];
-    color_stops[i] = premultiply(vec4(u_color_stops[(i * 5) + 1],
-                                      u_color_stops[(i * 5) + 2],
-                                      u_color_stops[(i * 5) + 3],
-                                      u_color_stops[(i * 5) + 4]));
+    color_stops[i] = gsk_premultiply(vec4(u_color_stops[(i * 5) + 1],
+                                          u_color_stops[(i * 5) + 2],
+                                          u_color_stops[(i * 5) + 3],
+                                          u_color_stops[(i * 5) + 4]));
   }
 }
 
@@ -49,7 +49,7 @@ _IN_ float color_offsets[8];
 
 void main() {
   // Position relative to startPoint
-  vec2 pos = get_frag_coord() - startPoint;
+  vec2 pos = gsk_get_frag_coord() - startPoint;
 
   // Current pixel, projected onto the line between the start point and the end point
   // The projection will be relative to the start point!
@@ -66,5 +66,5 @@ void main() {
     }
   }
 
-  setOutputColor(color * u_alpha);
+  gskSetOutputColor(color * u_alpha);
 }

gsk/resources/glsl/outset_shadow.glsl

@@ -3,31 +3,31 @@ uniform vec4 u_color;
 uniform vec4[3] u_outline_rect;
 
 _OUT_ vec4 final_color;
-_OUT_ _ROUNDED_RECT_UNIFORM_ transformed_outline;
+_OUT_ _GSK_ROUNDED_RECT_UNIFORM_ transformed_outline;
 
 void main() {
   gl_Position = u_projection * u_modelview * vec4(aPosition, 0.0, 1.0);
 
   vUv = vec2(aUv.x, aUv.y);
 
-  final_color = premultiply(u_color) * u_alpha;
+  final_color = gsk_premultiply(u_color) * u_alpha;
 
-  RoundedRect outline = create_rect(u_outline_rect);
-  rounded_rect_transform(outline, u_modelview);
-  rounded_rect_encode(outline, transformed_outline);
+  GskRoundedRect outline = gsk_create_rect(u_outline_rect);
+  gsk_rounded_rect_transform(outline, u_modelview);
+  gsk_rounded_rect_encode(outline, transformed_outline);
 }
 
 // FRAGMENT_SHADER:
 _IN_ vec4 final_color;
-_IN_ _ROUNDED_RECT_UNIFORM_ transformed_outline;
+_IN_ _GSK_ROUNDED_RECT_UNIFORM_ transformed_outline;
 
 void main() {
-  vec2 frag = get_frag_coord();
+  vec2 frag = gsk_get_frag_coord();
 
-  float alpha = Texture(u_source, vUv).a;
-  alpha *= (1.0 -  clamp(rounded_rect_coverage(decode_rect(transformed_outline), frag), 0.0, 1.0));
+  float alpha = GskTexture(u_source, vUv).a;
+  alpha *= (1.0 -  clamp(gsk_rounded_rect_coverage(gsk_decode_rect(transformed_outline), frag), 0.0, 1.0));
 
   vec4 color = final_color * alpha;
 
-  setOutputColor(color);
+  gskSetOutputColor(color);
 }

gsk/resources/glsl/preamble.fs.glsl

@@ -16,17 +16,17 @@ _IN_ vec2 vUv;
 
 
 
-RoundedRect decode_rect(_ROUNDED_RECT_UNIFORM_ r)
+GskRoundedRect gsk_decode_rect(_GSK_ROUNDED_RECT_UNIFORM_ r)
 {
 #if defined(GSK_GLES) || defined(GSK_LEGACY)
-  return RoundedRect(r[0], r[1], r[2]);
+  return GskRoundedRect(r[0], r[1], r[2]);
 #else
   return r;
 #endif
 }
 
 float
-ellipsis_dist (vec2 p, vec2 radius)
+gsk_ellipsis_dist (vec2 p, vec2 radius)
 {
   if (radius == vec2(0, 0))
     return 0.0;
@@ -38,14 +38,14 @@ ellipsis_dist (vec2 p, vec2 radius)
 }
 
 float
-ellipsis_coverage (vec2 point, vec2 center, vec2 radius)
+gsk_ellipsis_coverage (vec2 point, vec2 center, vec2 radius)
 {
-  float d = ellipsis_dist (point - center, radius);
+  float d = gsk_ellipsis_dist (point - center, radius);
   return clamp (0.5 - d, 0.0, 1.0);
 }
 
 float
-rounded_rect_coverage (RoundedRect r, vec2 p)
+gsk_rounded_rect_coverage (GskRoundedRect r, vec2 p)
 {
   if (p.x < r.bounds.x || p.y < r.bounds.y ||
       p.x >= r.bounds.z || p.y >= r.bounds.w)
@@ -61,10 +61,10 @@ rounded_rect_coverage (RoundedRect r, vec2 p)
   vec2 ref_br = r.corner_points2.xy;
   vec2 ref_bl = r.corner_points2.zw;
 
-  float d_tl = ellipsis_coverage(p, ref_tl, rad_tl);
-  float d_tr = ellipsis_coverage(p, ref_tr, rad_tr);
-  float d_br = ellipsis_coverage(p, ref_br, rad_br);
-  float d_bl = ellipsis_coverage(p, ref_bl, rad_bl);
+  float d_tl = gsk_ellipsis_coverage(p, ref_tl, rad_tl);
+  float d_tr = gsk_ellipsis_coverage(p, ref_tr, rad_tr);
+  float d_br = gsk_ellipsis_coverage(p, ref_br, rad_br);
+  float d_bl = gsk_ellipsis_coverage(p, ref_bl, rad_bl);
 
   vec4 corner_coverages = 1.0 - vec4(d_tl, d_tr, d_br, d_bl);
 
@@ -76,7 +76,7 @@ rounded_rect_coverage (RoundedRect r, vec2 p)
   return 1.0 - dot(vec4(is_out), corner_coverages);
 }
 
-vec4 Texture(sampler2D sampler, vec2 texCoords) {
+vec4 GskTexture(sampler2D sampler, vec2 texCoords) {
 #if defined(GSK_GLES) || defined(GSK_LEGACY)
   return texture2D(sampler, texCoords);
 #else
@@ -88,7 +88,7 @@ vec4 Texture(sampler2D sampler, vec2 texCoords) {
 layout(origin_upper_left) in vec4 gl_FragCoord;
 #endif
 
-vec2 get_frag_coord() {
+vec2 gsk_get_frag_coord() {
   vec2 fc = gl_FragCoord.xy;
 
 #ifdef GSK_GL3
@@ -101,15 +101,15 @@ vec2 get_frag_coord() {
   return fc;
 }
 
-void setOutputColor(vec4 color) {
-  vec2 f = get_frag_coord();
+void gskSetOutputColor(vec4 color) {
+  vec2 f = gsk_get_frag_coord();
 
   // We do *NOT* transform the clip rect here since we already
   // need to do that on the CPU.
 #if defined(GSK_GLES) || defined(GSK_LEGACY)
-  gl_FragColor = color * rounded_rect_coverage(create_rect(u_clip_rect), f);
+  gl_FragColor = color * gsk_rounded_rect_coverage(gsk_create_rect(u_clip_rect), f);
 #else
-  outputColor = color * rounded_rect_coverage(create_rect(u_clip_rect), f);
+  outputColor = color * gsk_rounded_rect_coverage(gsk_create_rect(u_clip_rect), f);
 #endif
   /*outputColor = color;*/
 }

gsk/resources/glsl/preamble.glsl

@@ -5,15 +5,15 @@ precision highp float;
 #if defined(GSK_GLES) || defined(GSK_LEGACY)
 #define _OUT_ varying
 #define _IN_ varying
-#define _ROUNDED_RECT_UNIFORM_ vec4[3]
+#define _GSK_ROUNDED_RECT_UNIFORM_ vec4[3]
 #else
 #define _OUT_ out
 #define _IN_ in
-#define _ROUNDED_RECT_UNIFORM_ RoundedRect
+#define _GSK_ROUNDED_RECT_UNIFORM_ GskRoundedRect
 #endif
 
 
-struct RoundedRect
+struct GskRoundedRect
 {
   vec4 bounds;
   // Look, arrays can't be in structs if you want to return the struct
@@ -22,9 +22,9 @@ struct RoundedRect
   vec4 corner_points2; // xy = bottom right, zw = bottom left
 };
 
-// Transform from a GskRoundedRect to a RoundedRect as we need it.
-RoundedRect
-create_rect(vec4[3] data)
+// Transform from a C GskRoundedRect to what we need.
+GskRoundedRect
+gsk_create_rect(vec4[3] data)
 {
   vec4 bounds = vec4(data[0].xy, data[0].xy + data[0].zw);
 
@@ -33,9 +33,9 @@ create_rect(vec4[3] data)
   vec4 corner_points2 = vec4(bounds.zw + (data[2].xy * vec2(-1, -1)),
                              bounds.xw + vec2(data[2].zw * vec2(1, -1)));
 
-  return RoundedRect(bounds, corner_points1, corner_points2);
+  return GskRoundedRect(bounds, corner_points1, corner_points2);
 }
 
-vec4 premultiply(vec4 c) {
+vec4 gsk_premultiply(vec4 c) {
   return vec4(c.rgb * c.a, c.a);
 }

gsk/resources/glsl/preamble.vs.glsl

@@ -13,8 +13,8 @@ _OUT_ vec2 vUv;
 #endif
 
 // amount is: top, right, bottom, left
-RoundedRect
-rounded_rect_shrink (RoundedRect r, vec4 amount)
+GskRoundedRect
+gsk_rounded_rect_shrink (GskRoundedRect r, vec4 amount)
 {
   vec4 new_bounds = r.bounds + vec4(1.0,1.0,-1.0,-1.0) * amount.wxyz;
   vec4 new_corner_points1 = r.corner_points1;
@@ -25,11 +25,11 @@ rounded_rect_shrink (RoundedRect r, vec4 amount)
   if (r.corner_points2.xy == r.bounds.zw) new_corner_points2.xy = new_bounds.zw;
   if (r.corner_points2.zw == r.bounds.xw) new_corner_points2.zw = new_bounds.xw;
 
-  return RoundedRect (new_bounds, new_corner_points1, new_corner_points2);
+  return GskRoundedRect (new_bounds, new_corner_points1, new_corner_points2);
 }
 
 void
-rounded_rect_offset(inout RoundedRect r, vec2 offset)
+gsk_rounded_rect_offset(inout GskRoundedRect r, vec2 offset)
 {
   r.bounds.xy += offset;
   r.bounds.zw += offset;
@@ -39,7 +39,7 @@ rounded_rect_offset(inout RoundedRect r, vec2 offset)
   r.corner_points2.zw += offset;
 }
 
-void rounded_rect_transform(inout RoundedRect r, mat4 mat)
+void gsk_rounded_rect_transform(inout GskRoundedRect r, mat4 mat)
 {
   r.bounds.xy = (mat * vec4(r.bounds.xy, 0.0, 1.0)).xy;
   r.bounds.zw = (mat * vec4(r.bounds.zw, 0.0, 1.0)).xy;
@@ -53,9 +53,9 @@ void rounded_rect_transform(inout RoundedRect r, mat4 mat)
 
 #if defined(GSK_LEGACY)
 // Can't have out or inout array parameters...
-#define rounded_rect_encode(r, uni) uni[0] = r.bounds; uni[1] = r.corner_points1; uni[2] = r.corner_points2;
+#define gsk_rounded_rect_encode(r, uni) uni[0] = r.bounds; uni[1] = r.corner_points1; uni[2] = r.corner_points2;
 #else
-void rounded_rect_encode(RoundedRect r, out _ROUNDED_RECT_UNIFORM_ out_r)
+void gsk_rounded_rect_encode(GskRoundedRect r, out _GSK_ROUNDED_RECT_UNIFORM_ out_r)
 {
 #if defined(GSK_GLES)
   out_r[0] = r.bounds;

gsk/resources/glsl/radial_gradient.glsl

@@ -21,10 +21,10 @@ void main() {
 
   for (int i = 0; i < u_num_color_stops; i ++) {
     color_offsets[i] = u_color_stops[(i * 5) + 0];
-    color_stops[i] = premultiply(vec4(u_color_stops[(i * 5) + 1],
-                                      u_color_stops[(i * 5) + 2],
-                                      u_color_stops[(i * 5) + 3],
-                                      u_color_stops[(i * 5) + 4]));
+    color_stops[i] = gsk_premultiply(vec4(u_color_stops[(i * 5) + 1],
+                                          u_color_stops[(i * 5) + 2],
+                                          u_color_stops[(i * 5) + 3],
+                                          u_color_stops[(i * 5) + 4]));
   }
 }
 
@@ -51,17 +51,17 @@ float abs_offset(float offset)  {
 }
 
 void main() {
-  vec2 pixel = get_frag_coord();
+  vec2 pixel = gsk_get_frag_coord();
   vec2 rel = (center - pixel) / (u_radius);
   float d = sqrt(dot(rel, rel));
 
   if (d < abs_offset (color_offsets[0])) {
-    setOutputColor(color_stops[0] * u_alpha);
+    gskSetOutputColor(color_stops[0] * u_alpha);
     return;
   }
 
   if (d > end) {
-    setOutputColor(color_stops[u_num_color_stops - 1] * u_alpha);
+    gskSetOutputColor(color_stops[u_num_color_stops - 1] * u_alpha);
     return;
   }
 
@@ -80,5 +80,5 @@ void main() {
     }
   }
 
-  setOutputColor(color * u_alpha);
+  gskSetOutputColor(color * u_alpha);
 }

gsk/resources/glsl/repeat.glsl

@@ -35,7 +35,7 @@ void main() {
   tp.x = u_texture_rect.x + (wrapped_x * tw);
   tp.y = u_texture_rect.y + (wrapped_y * th);
 
-  vec4 diffuse = Texture(u_source, tp);
+  vec4 diffuse = GskTexture(u_source, tp);
 
-  setOutputColor(diffuse * u_alpha);
+  gskSetOutputColor(diffuse * u_alpha);
 }

gsk/resources/glsl/unblurred_outset_shadow.glsl

@@ -5,8 +5,8 @@ uniform vec2 u_offset;
 uniform vec4[3] u_outline_rect;
 
 _OUT_ vec4 final_color;
-_OUT_ _ROUNDED_RECT_UNIFORM_ transformed_outside_outline;
-_OUT_ _ROUNDED_RECT_UNIFORM_ transformed_inside_outline;
+_OUT_ _GSK_ROUNDED_RECT_UNIFORM_ transformed_outside_outline;
+_OUT_ _GSK_ROUNDED_RECT_UNIFORM_ transformed_inside_outline;
 
 void main() {
   gl_Position = u_projection * u_modelview * vec4(aPosition, 0.0, 1.0);
@@ -15,30 +15,30 @@ void main() {
   final_color.rgb *= final_color.a;
   final_color *= u_alpha;
 
-  RoundedRect inside = create_rect(u_outline_rect);
-  RoundedRect outside = rounded_rect_shrink(inside, vec4(- u_spread));
+  GskRoundedRect inside = gsk_create_rect(u_outline_rect);
+  GskRoundedRect outside = gsk_rounded_rect_shrink(inside, vec4(- u_spread));
 
-  rounded_rect_offset(outside, u_offset);
+  gsk_rounded_rect_offset(outside, u_offset);
 
-  rounded_rect_transform(outside, u_modelview);
-  rounded_rect_transform(inside, u_modelview);
+  gsk_rounded_rect_transform(outside, u_modelview);
+  gsk_rounded_rect_transform(inside, u_modelview);
 
-  rounded_rect_encode(outside, transformed_outside_outline);
-  rounded_rect_encode(inside, transformed_inside_outline);
+  gsk_rounded_rect_encode(outside, transformed_outside_outline);
+  gsk_rounded_rect_encode(inside, transformed_inside_outline);
 }
 
 // FRAGMENT_SHADER:
 _IN_ vec4 final_color;
-_IN_ _ROUNDED_RECT_UNIFORM_ transformed_outside_outline;
-_IN_ _ROUNDED_RECT_UNIFORM_ transformed_inside_outline;
+_IN_ _GSK_ROUNDED_RECT_UNIFORM_ transformed_outside_outline;
+_IN_ _GSK_ROUNDED_RECT_UNIFORM_ transformed_inside_outline;
 
 void main() {
-  vec2 frag = get_frag_coord();
+  vec2 frag = gsk_get_frag_coord();
 
-  float alpha = clamp(rounded_rect_coverage(decode_rect(transformed_outside_outline), frag) -
-                      rounded_rect_coverage(decode_rect(transformed_inside_outline), frag),
+  float alpha = clamp(gsk_rounded_rect_coverage(gsk_decode_rect(transformed_outside_outline), frag) -
+                      gsk_rounded_rect_coverage(gsk_decode_rect(transformed_inside_outline), frag),
                       0.0, 1.0);
 
-  setOutputColor(final_color * alpha);
+  gskSetOutputColor(final_color * alpha);
 }
 

gsk/vulkan/gskvulkanrenderpass.c

@@ -539,6 +539,10 @@ gsk_vulkan_render_pass_add_node (GskVulkanRenderPass           *self,
       }
       return;
 
+    case GSK_GLSHADER_NODE:
+     gsk_vulkan_render_pass_add_node (self, render, constants, gsk_glshader_node_get_fallback_child (node));
+      return;
+
     case GSK_DEBUG_NODE:
       gsk_vulkan_render_pass_add_node (self, render, constants, gsk_debug_node_get_child (node));
       return;

gtk/gtksnapshot.c

@@ -91,6 +91,14 @@ struct _GtkSnapshotState {
     struct {
       graphene_rect_t bounds;
     } clip;
+    struct {
+      GskGLShader *shader;
+      graphene_vec4_t args;
+      graphene_rect_t bounds;
+      int n_children;
+      int node_idx;
+      GskRenderNode **nodes;
+    } glshader;
     struct {
       GskRoundedRect bounds;
     } rounded_clip;
@@ -812,6 +820,122 @@ gtk_snapshot_push_clip (GtkSnapshot           *snapshot,
   gtk_graphene_rect_scale_affine (bounds, scale_x, scale_y, dx, dy, &state->data.clip.bounds);
 }
 
+static GskRenderNode *
+maybe_clip (GskRenderNode         *node,
+            const graphene_rect_t *bounds)
+{
+  if (node &&
+      !graphene_rect_contains_rect (bounds, &node->bounds))
+    {
+      return gsk_clip_node_new (node, bounds);
+    }
+
+  return gsk_render_node_ref (node);
+}
+
+static GskRenderNode *
+gtk_snapshot_collect_glshader (GtkSnapshot      *snapshot,
+                               GtkSnapshotState *state,
+                               GskRenderNode   **nodes,
+                               guint             n_nodes)
+{
+  GskRenderNode *shader_node = NULL, *child_node;
+  GdkRGBA transparent = { 0, 0, 0, 0 };
+
+  child_node = gtk_snapshot_collect_default (snapshot, state, nodes, n_nodes);
+
+  if (child_node == NULL)
+    child_node = gsk_color_node_new (&transparent, &state->data.glshader.bounds);
+
+  state->data.glshader.nodes[state->data.glshader.node_idx] = child_node;
+
+  if (state->data.glshader.node_idx != state->data.glshader.n_children)
+    return NULL; /* Not last */
+
+  /* This is the last pop */
+
+  shader_node = NULL;
+
+  if (state->data.glshader.bounds.size.width != 0 &&
+      state->data.glshader.bounds.size.height != 0)
+    {
+      GskRenderNode *fallback_node = maybe_clip (state->data.glshader.nodes[0],
+                                  &state->data.glshader.bounds);
+      shader_node = gsk_glshader_node_new (state->data.glshader.shader,
+                                           &state->data.glshader.args,
+                                           &state->data.glshader.bounds,
+                                           fallback_node,
+                                           &state->data.glshader.nodes[1],
+                                           state->data.glshader.n_children);
+      gsk_render_node_unref (fallback_node);
+    }
+
+  g_object_unref (state->data.glshader.shader);
+  for (guint i = 0; i  < state->data.glshader.n_children + 1; i++)
+    gsk_render_node_unref (state->data.glshader.nodes[i]);
+  g_free (state->data.glshader.nodes);
+
+  return shader_node;
+}
+
+/**
+ * gtk_snapshot_push_glshader:
+ * @snapshot: a #GtkSnapshot
+ * @shader: The code to run
+ * @args: A vec4 argument given to the shader
+ * @bounds: the rectangle to render into
+ * @n_children: The number of extra nodes given as argument to the shader as textures.
+ *
+ * Renders a rectagle with output from a GLSL shader. If shaders are not supported
+ * the fallback will be used instead. The fallback is pushed to the snapshot
+ * until the first call to gtk_snapshot_pop(). After that the extra nodes
+ * pushed, and @n_children mode gtk_snapshot_pop() calls are expected for
+ * these.
+ */
+void
+gtk_snapshot_push_glshader (GtkSnapshot           *snapshot,
+                            GskGLShader           *shader,
+                            const graphene_vec4_t  *args,
+                            const graphene_rect_t *bounds,
+                            int                    n_children)
+{
+  GtkSnapshotState *state;
+  float scale_x, scale_y, dx, dy;
+  GskRenderNode **nodes;
+  int node_idx;
+  graphene_rect_t transformed_bounds;
+
+  gtk_snapshot_ensure_affine (snapshot, &scale_x, &scale_y, &dx, &dy);
+
+  state = gtk_snapshot_push_state (snapshot,
+                                   gtk_snapshot_get_current_state (snapshot)->transform,
+                                   gtk_snapshot_collect_glshader);
+  gtk_graphene_rect_scale_affine (bounds, scale_x, scale_y, dx, dy, &transformed_bounds);
+  state->data.glshader.bounds = transformed_bounds;
+  state->data.glshader.shader = g_object_ref (shader);
+  if (args)
+    state->data.glshader.args = *args;
+  else
+    graphene_vec4_init (&state->data.glshader.args, 0, 0, 0, 0);
+  state->data.glshader.n_children = n_children;
+  nodes = g_new0 (GskRenderNode *, n_children + 1);
+  node_idx = n_children; /* We pop in reverse order */
+
+  state->data.glshader.node_idx = node_idx--;
+  state->data.glshader.nodes = nodes;
+
+  for (int i = 0; i  < n_children; i++)
+    {
+      state = gtk_snapshot_push_state (snapshot,
+                                       gtk_snapshot_get_current_state (snapshot)->transform,
+                                       gtk_snapshot_collect_glshader);
+      state->data.glshader.node_idx = node_idx--;
+      state->data.glshader.n_children = n_children;
+      state->data.glshader.nodes = nodes;
+      state->data.glshader.bounds = transformed_bounds;
+    }
+}
+
 static GskRenderNode *
 gtk_snapshot_collect_rounded_clip (GtkSnapshot      *snapshot,
                                    GtkSnapshotState *state,

gtk/gtksnapshot.h

@@ -99,6 +99,12 @@ GDK_AVAILABLE_IN_ALL
 void            gtk_snapshot_push_cross_fade            (GtkSnapshot            *snapshot,
                                                          double                  progress);
 GDK_AVAILABLE_IN_ALL
+void            gtk_snapshot_push_glshader              (GtkSnapshot            *snapshot,
+                                                         GskGLShader            *shader,
+                                                         const graphene_vec4_t  *args,
+                                                         const graphene_rect_t  *bounds,
+                                                         int                     n_children);
+GDK_AVAILABLE_IN_ALL
 void            gtk_snapshot_pop                        (GtkSnapshot            *snapshot);
 
 GDK_AVAILABLE_IN_ALL

gtk/inspector/recorder.c

@@ -171,6 +171,25 @@ create_list_model_for_render_node (GskRenderNode *node)
       return create_render_node_list_model ((GskRenderNode *[2]) { gsk_cross_fade_node_get_start_child (node),
                                                                    gsk_cross_fade_node_get_end_child (node) }, 2);
 
+    case GSK_GLSHADER_NODE:
+      {
+        GListStore *store = G_LIST_STORE (create_render_node_list_model ((GskRenderNode *[1]) { gsk_glshader_node_get_fallback_child (node) }, 1));
+
+        for (guint i = 0; i < gsk_glshader_node_get_n_children (node); i++)
+          {
+            GskRenderNode *child = gsk_glshader_node_get_child (node, i);
+            graphene_rect_t bounds;
+            GdkPaintable *paintable;
+
+            gsk_render_node_get_bounds (child, &bounds);
+            paintable = gtk_render_node_paintable_new (child, &bounds);
+            g_list_store_append (store, paintable);
+            g_object_unref (paintable);
+          }
+
+        return G_LIST_MODEL (store);
+      }
+
     case GSK_CONTAINER_NODE:
       {
         GListStore *store;
@@ -270,6 +289,8 @@ node_type_name (GskRenderNodeType type)
       return "Text";
     case GSK_BLUR_NODE:
       return "Blur";
+    case GSK_GLSHADER_NODE:
+      return "GLShader";
     }
 }
 
@@ -301,6 +322,7 @@ node_name (GskRenderNode *node)
     case GSK_CROSS_FADE_NODE:
     case GSK_TEXT_NODE:
     case GSK_BLUR_NODE:
+    case GSK_GLSHADER_NODE:
       return g_strdup (node_type_name (gsk_render_node_get_node_type (node)));
 
     case GSK_DEBUG_NODE:
@@ -521,6 +543,20 @@ add_float_row (GtkListStore  *store,
   g_free (text);
 }
 
+static void
+add_vec4_row (GtkListStore    *store,
+              const char      *name,
+              graphene_vec4_t *value)
+{
+  char *text = g_strdup_printf ("[%.2f, %.2f, %.2f, %.2f]",
+                                graphene_vec4_get_x (value),
+                                graphene_vec4_get_y (value),
+                                graphene_vec4_get_z (value),
+                                graphene_vec4_get_w (value));
+  add_text_row (store, name, text);
+  g_free (text);
+}
+
 static void
 populate_render_node_properties (GtkListStore  *store,
                                  GskRenderNode *node)
@@ -759,6 +795,14 @@ populate_render_node_properties (GtkListStore  *store,
       add_float_row (store, "Radius", gsk_blur_node_get_radius (node));
       break;
 
+    case GSK_GLSHADER_NODE:
+      {
+        graphene_vec4_t args;
+        gsk_glshader_node_get_args (node, &args);
+        add_vec4_row (store, "Args", &args);
+      }
+      break;
+
     case GSK_INSET_SHADOW_NODE:
       {
         const GdkRGBA *color = gsk_inset_shadow_node_peek_color (node);