clutter/blur-effect: Switch to create_pipeline vfunc

The blur pipeline is still cached on ClutterBlurEffect, and we
simply update the uniforms when asked to create the pipeline.

Now that ClutterOffscreenEffect will use the blur pipeline, it
doesn't need to override the paint_target() vfunc anymore.

Part-of: <https://gitlab.gnome.org/GNOME/mutter/-/merge_requests/1355>

clutter/clutter/clutter-blur-effect.c

@@ -81,9 +81,6 @@ struct _ClutterBlurEffect
 
   gint pixel_step_uniform;
 
-  gint tex_width;
-  gint tex_height;
-
   CoglPipeline *pipeline;
 };
 
@@ -98,20 +95,41 @@ G_DEFINE_TYPE (ClutterBlurEffect,
                clutter_blur_effect,
                CLUTTER_TYPE_OFFSCREEN_EFFECT);
 
+static CoglPipeline *
+clutter_blur_effect_create_pipeline (ClutterOffscreenEffect *effect,
+                                     CoglTexture            *texture)
+{
+  ClutterBlurEffect *blur_effect = CLUTTER_BLUR_EFFECT (effect);
+
+  if (blur_effect->pixel_step_uniform > -1)
+    {
+      float pixel_step[2];
+      int tex_width, tex_height;
+
+      tex_width = cogl_texture_get_width (texture);
+      tex_height = cogl_texture_get_height (texture);
+
+      pixel_step[0] = 1.0f / tex_width;
+      pixel_step[1] = 1.0f / tex_height;
+
+      cogl_pipeline_set_uniform_float (blur_effect->pipeline,
+                                       blur_effect->pixel_step_uniform,
+                                       2, /* n_components */
+                                       1, /* count */
+                                       pixel_step);
+    }
+
+  cogl_pipeline_set_layer_texture (blur_effect->pipeline, 0, texture);
+
+  return cogl_object_ref (blur_effect->pipeline);
+}
+
 static gboolean
 clutter_blur_effect_pre_paint (ClutterEffect       *effect,
                                ClutterPaintContext *paint_context)
 {
-  ClutterBlurEffect *self = CLUTTER_BLUR_EFFECT (effect);
   ClutterEffectClass *parent_class;
 
-  if (!clutter_actor_meta_get_enabled (CLUTTER_ACTOR_META (effect)))
-    return FALSE;
-
-  self->actor = clutter_actor_meta_get_actor (CLUTTER_ACTOR_META (effect));
-  if (self->actor == NULL)
-    return FALSE;
-
   if (!clutter_feature_available (CLUTTER_FEATURE_SHADERS_GLSL))
     {
       /* if we don't have support for GLSL shaders then we
@@ -125,59 +143,7 @@ clutter_blur_effect_pre_paint (ClutterEffect       *effect,
     }
 
   parent_class = CLUTTER_EFFECT_CLASS (clutter_blur_effect_parent_class);
-  if (parent_class->pre_paint (effect, paint_context))
+  return parent_class->pre_paint (effect, paint_context);
-    {
-      ClutterOffscreenEffect *offscreen_effect =
-        CLUTTER_OFFSCREEN_EFFECT (effect);
-      CoglHandle texture;
-
-      texture = clutter_offscreen_effect_get_texture (offscreen_effect);
-      self->tex_width = cogl_texture_get_width (texture);
-      self->tex_height = cogl_texture_get_height (texture);
-
-      if (self->pixel_step_uniform > -1)
-        {
-          gfloat pixel_step[2];
-
-          pixel_step[0] = 1.0f / self->tex_width;
-          pixel_step[1] = 1.0f / self->tex_height;
-
-          cogl_pipeline_set_uniform_float (self->pipeline,
-                                           self->pixel_step_uniform,
-                                           2, /* n_components */
-                                           1, /* count */
-                                           pixel_step);
-        }
-
-      cogl_pipeline_set_layer_texture (self->pipeline, 0, texture);
-
-      return TRUE;
-    }
-  else
-    return FALSE;
-}
-
-static void
-clutter_blur_effect_paint_target (ClutterOffscreenEffect *effect,
-                                  ClutterPaintContext    *paint_context)
-{
-  ClutterBlurEffect *self = CLUTTER_BLUR_EFFECT (effect);
-  CoglFramebuffer *framebuffer =
-    clutter_paint_context_get_framebuffer (paint_context);
-  guint8 paint_opacity;
-
-  paint_opacity = clutter_actor_get_paint_opacity (self->actor);
-
-  cogl_pipeline_set_color4ub (self->pipeline,
-                              paint_opacity,
-                              paint_opacity,
-                              paint_opacity,
-                              paint_opacity);
-
-  cogl_framebuffer_draw_rectangle (framebuffer,
-                                   self->pipeline,
-                                   0, 0,
-                                   self->tex_width, self->tex_height);
 }
 
 static gboolean
@@ -229,7 +195,7 @@ clutter_blur_effect_class_init (ClutterBlurEffectClass *klass)
   effect_class->modify_paint_volume = clutter_blur_effect_modify_paint_volume;
 
   offscreen_class = CLUTTER_OFFSCREEN_EFFECT_CLASS (klass);
-  offscreen_class->paint_target = clutter_blur_effect_paint_target;
+  offscreen_class->create_pipeline = clutter_blur_effect_create_pipeline;
 }
 
 static void