Wrap shader stack into private functions

The shader stack held by ClutterMainContext should only be accessed
using functions, and not directly.

Since it's a stack, we can use stack-like operations: push, pop and
peek.

clutter/clutter-actor.c

@@ -9544,15 +9544,12 @@ clutter_actor_shader_pre_paint (ClutterActor *actor,
 {
   ShaderData *shader_data;
   ClutterShader *shader;
-  ClutterMainContext *context;
 
   shader_data = g_object_get_qdata (G_OBJECT (actor), quark_shader_data);
   if (shader_data == NULL)
     return;
 
-  context = _clutter_context_get_default ();
   shader = shader_data->shader;
-
   if (shader != NULL)
     {
       clutter_shader_set_is_enabled (shader, TRUE);
@@ -9560,7 +9557,7 @@ clutter_actor_shader_pre_paint (ClutterActor *actor,
       g_hash_table_foreach (shader_data->value_hash, set_each_param, shader);
 
       if (!repeat)
-        context->shaders = g_slist_prepend (context->shaders, actor);
+        _clutter_context_push_shader_stack (actor);
     }
 }
 
@@ -9569,28 +9566,27 @@ clutter_actor_shader_post_paint (ClutterActor *actor)
 {
   ShaderData *shader_data;
   ClutterShader *shader;
-  ClutterMainContext *context;
 
   shader_data = g_object_get_qdata (G_OBJECT (actor), quark_shader_data);
   if (shader_data == NULL)
     return;
 
-  context = _clutter_context_get_default ();
   shader = shader_data->shader;
-
   if (shader != NULL)
     {
+      ClutterActor *head;
+
       clutter_shader_set_is_enabled (shader, FALSE);
 
-      context->shaders = g_slist_remove (context->shaders, actor);
-      if (context->shaders)
-        {
-          /* call pre-paint again, this time with the second argument being
-           * TRUE, indicating that we are reapplying the shader and thus
-           * should not be prepended to the stack
-           */
-          clutter_actor_shader_pre_paint (context->shaders->data, TRUE);
-        }
+      /* remove the actor from the shaders stack; if there is another
+       * actor inside it, then call pre-paint again to set its shader
+       * but this time with the second argument being TRUE, indicating
+       * that we are re-applying an existing shader and thus should it
+       * not be prepended to the stack
+       */
+      head = _clutter_context_pop_shader_stack (actor);
+      if (head != NULL)
+        clutter_actor_shader_pre_paint (head, TRUE);
     }
 }
 

clutter/clutter-main.c

@@ -3276,3 +3276,32 @@ _clutter_context_get_pick_mode (void)
 
   return context->pick_mode;
 }
+
+void
+_clutter_context_push_shader_stack (ClutterActor *actor)
+{
+  ClutterMainContext *context = _clutter_context_get_default ();
+
+  context->shaders = g_slist_prepend (context->shaders, actor);
+}
+
+ClutterActor *
+_clutter_context_peek_shader_stack (void)
+{
+  ClutterMainContext *context = _clutter_context_get_default ();
+
+  if (context->shaders != NULL)
+    return context->shaders->data;
+
+  return NULL;
+}
+
+ClutterActor *
+_clutter_context_pop_shader_stack (ClutterActor *actor)
+{
+  ClutterMainContext *context = _clutter_context_get_default ();
+
+  context->shaders = g_slist_remove (context->shaders, actor);
+
+  return _clutter_context_peek_shader_stack ();
+}

clutter/clutter-private.h

@@ -127,7 +127,7 @@ struct _ClutterMainContext
   ClutterActor *pointer_grab_actor;
   ClutterActor *keyboard_grab_actor;
 
-  /* stack of overridden shaders during paint */
+  /* stack of actors with shaders during paint */
   GSList *shaders;
 
   /* fb bit masks for col<->id mapping in picking */
@@ -170,12 +170,15 @@ typedef struct
 gboolean _clutter_threads_dispatch      (gpointer data);
 void     _clutter_threads_dispatch_free (gpointer data);
 
-#define CLUTTER_CONTEXT()	(_clutter_context_get_default ())
+#define CLUTTER_CONTEXT()       (_clutter_context_get_default ())
 ClutterMainContext *    _clutter_context_get_default            (void);
 gboolean                _clutter_context_is_initialized         (void);
 PangoContext *          _clutter_context_create_pango_context   (void);
 PangoContext *          _clutter_context_get_pango_context      (void);
 ClutterPickMode         _clutter_context_get_pick_mode          (void);
+void                    _clutter_context_push_shader_stack      (ClutterActor *actor);
+ClutterActor *          _clutter_context_pop_shader_stack       (ClutterActor *actor);
+ClutterActor *          _clutter_context_peek_shader_stack      (void);
 
 #define CLUTTER_PARAM_READABLE  (G_PARAM_READABLE | G_PARAM_STATIC_STRINGS)
 #define CLUTTER_PARAM_WRITABLE  (G_PARAM_WRITABLE | G_PARAM_STATIC_STRINGS)

clutter/clutter-texture.c

@@ -468,27 +468,26 @@ update_fbo (ClutterActor *self)
 {
   ClutterTexture        *texture = CLUTTER_TEXTURE (self);
   ClutterTexturePrivate *priv = texture->priv;
-  ClutterMainContext    *context;
+  ClutterActor          *head;
   ClutterShader         *shader = NULL;
   ClutterActor          *stage = NULL;
   CoglMatrix             projection;
   CoglColor              transparent_col;
 
-  context = _clutter_context_get_default ();
+  head = _clutter_context_peek_shader_stack ();
+  if (head != NULL)
+    shader = clutter_actor_get_shader (head);
 
-  if (context->shaders)
-    shader = clutter_actor_get_shader (context->shaders->data);
-
-  /* Temporarily turn off the shader on the top of the context's shader stack,
-   * to restore the GL pipeline to it's natural state.
+  /* Temporarily turn off the shader on the top of the context's
+   * shader stack, to restore the GL pipeline to it's natural state.
    */
-  if (shader)
+  if (shader != NULL)
     clutter_shader_set_is_enabled (shader, FALSE);
 
   /* Redirect drawing to the fbo */
   cogl_push_framebuffer (priv->fbo_handle);
 
-  if ((stage = clutter_actor_get_stage (self)))
+  if ((stage = clutter_actor_get_stage (self)) != NULL)
     {
       gfloat stage_width, stage_height;
       ClutterActor *source_parent;
@@ -554,7 +553,7 @@ update_fbo (ClutterActor *self)
   cogl_pop_framebuffer ();
 
   /* If there is a shader on top of the shader stack, turn it back on. */
-  if (shader)
+  if (shader != NULL)
     clutter_shader_set_is_enabled (shader, TRUE);
 }