cssimage: Make image transition a vfunc

gtk/gtkcssimage.c

@@ -69,6 +69,15 @@ gtk_css_image_real_compute (GtkCssImage             *image,
   return g_object_ref (image);
 }
 
+GtkCssImage *
+gtk_css_image_real_transition (GtkCssImage *start,
+                               GtkCssImage *end,
+                               guint        property_id,
+                               double       progress)
+{
+  return _gtk_css_image_cross_fade_new (start, end, progress);
+}
+
 static void
 _gtk_css_image_class_init (GtkCssImageClass *klass)
 {
@@ -76,6 +85,7 @@ _gtk_css_image_class_init (GtkCssImageClass *klass)
   klass->get_height = gtk_css_image_real_get_height;
   klass->get_aspect_ratio = gtk_css_image_real_get_aspect_ratio;
   klass->compute = gtk_css_image_real_compute;
+  klass->transition = gtk_css_image_real_transition;
 }
 
 static void
@@ -143,6 +153,36 @@ _gtk_css_image_compute (GtkCssImage             *image,
   return klass->compute (image, property_id, provider, values, parent_values, dependencies);
 }
 
+GtkCssImage *
+_gtk_css_image_transition (GtkCssImage *start,
+                           GtkCssImage *end,
+                           guint        property_id,
+                           double       progress)
+{
+  GtkCssImageClass *klass;
+
+  g_return_val_if_fail (start == NULL || GTK_IS_CSS_IMAGE (start), NULL);
+  g_return_val_if_fail (end == NULL || GTK_IS_CSS_IMAGE (end), NULL);
+
+  progress = CLAMP (progress, 0.0, 1.0);
+
+  if (start == NULL)
+    {
+      if (end == NULL)
+        return NULL;
+      else
+        {
+          start = end;
+          end = NULL;
+          progress = 1.0 - progress;
+        }
+    }
+
+  klass = GTK_CSS_IMAGE_GET_CLASS (start);
+
+  return klass->transition (start, end, property_id, progress);
+}
+
 void
 _gtk_css_image_draw (GtkCssImage        *image,
                      cairo_t            *cr,

gtk/gtkcssimagecrossfade.c

@@ -114,6 +114,9 @@ gtk_css_image_cross_fade_draw (GtkCssImage        *image,
 
           cairo_push_group (cr);
 
+          /* performance trick */
+          cairo_reset_clip (cr);
+
           _gtk_css_image_draw (cross_fade->start, cr, width, height);
 
           cairo_push_group (cr);

gtk/gtkcssimageprivate.h

@@ -61,6 +61,11 @@ struct _GtkCssImageClass
                                                     GtkCssComputedValues       *values,
                                                     GtkCssComputedValues       *parent_values,
                                                     GtkCssDependencies         *dependencies);
+  /* transition between start and end image (end may be NULL), returns new reference */
+  GtkCssImage *(* transition)                      (GtkCssImage                *start,
+                                                    GtkCssImage                *end,
+                                                    guint                       property_id,
+                                                    double                      progress);
 
   /* draw to 0,0 with the given width and height */
   void         (* draw)                            (GtkCssImage                *image,
@@ -90,6 +95,10 @@ GtkCssImage *  _gtk_css_image_compute              (GtkCssImage                *
                                                     GtkCssComputedValues       *values,
                                                     GtkCssComputedValues       *parent_values,
                                                     GtkCssDependencies         *dependencies);
+GtkCssImage *  _gtk_css_image_transition           (GtkCssImage                *start,
+                                                    GtkCssImage                *end,
+                                                    guint                       property_id,
+                                                    double                      progress);
 
 void           _gtk_css_image_draw                 (GtkCssImage                *image,
                                                     cairo_t                    *cr,

gtk/gtkcssimagevalue.c

@@ -72,13 +72,14 @@ gtk_css_value_image_transition (GtkCssValue *start,
                                 guint        property_id,
                                 double       progress)
 {
-  GtkCssImage *fade;
+  GtkCssImage *transition;
 
-  fade = _gtk_css_image_cross_fade_new (_gtk_css_image_value_get_image (start),
+  transition = _gtk_css_image_transition (_gtk_css_image_value_get_image (start),
                                           _gtk_css_image_value_get_image (end),
+                                          property_id,
                                           progress);
       
-  return _gtk_css_image_value_new (fade);
+  return _gtk_css_image_value_new (transition);
 }
 
 static void