Add shell_texture_cache_bind_pixbuf_property

This utility function is targeted for MetaWindow; we can create
a ClutterTexture which tracks the value of an "icon" property.

src/shell-texture-cache.c

@@ -770,6 +770,108 @@ out:
   g_free (data);
 }
 
+typedef struct {
+  ShellTextureCache *cache;
+  ClutterTexture *texture;
+  GObject *source;
+  guint notify_signal_id;
+  gboolean weakref_active;
+} ShellTextureCachePropertyBind;
+
+static void
+shell_texture_cache_reset_texture (ShellTextureCachePropertyBind *bind, const char *propname)
+{
+  GdkPixbuf *pixbuf;
+  CoglHandle texdata;
+
+  g_object_get (bind->source, propname, &pixbuf, NULL);
+
+  g_return_if_fail (pixbuf == NULL || GDK_IS_PIXBUF (pixbuf));
+
+  if (pixbuf != NULL)
+    {
+      texdata = pixbuf_to_cogl_handle (pixbuf);
+      g_object_unref (pixbuf);
+
+      clutter_texture_set_cogl_texture (bind->texture, texdata);
+      cogl_handle_unref (texdata);
+
+      clutter_actor_set_opacity (CLUTTER_ACTOR (bind->texture), 255);
+    }
+  else
+    clutter_actor_set_opacity (CLUTTER_ACTOR (bind->texture), 0);
+}
+
+static void
+shell_texture_cache_on_pixbuf_notify (GObject           *object,
+                                      GParamSpec        *paramspec,
+                                      gpointer           data)
+{
+  ShellTextureCachePropertyBind *bind = data;
+  shell_texture_cache_reset_texture (bind, paramspec->name);
+}
+
+static void
+shell_texture_cache_bind_weak_notify (gpointer     data,
+                                      GObject     *source_location)
+{
+  ShellTextureCachePropertyBind *bind = data;
+  bind->weakref_active = FALSE;
+  g_signal_handler_disconnect (bind->source, bind->notify_signal_id);
+}
+
+static void
+shell_texture_cache_free_bind (gpointer data)
+{
+  ShellTextureCachePropertyBind *bind = data;
+  if (bind->weakref_active)
+    g_object_weak_unref (G_OBJECT(bind->texture), shell_texture_cache_bind_weak_notify, bind);
+  g_free (bind);
+}
+
+/**
+ * shell_texture_cache_bind_pixbuf_property:
+ * @cache:
+ * @object: A #GObject with a property @property_name of type #GdkPixbuf
+ * @property_name: Name of a property
+ *
+ * Create a #ClutterTexture which tracks the #GdkPixbuf value of a GObject property
+ * named by @property_name.  Unlike other methods in ShellTextureCache, the underlying
+ * CoglHandle is not shared by default with other invocations to this method.
+ *
+ * If the source object is destroyed, the texture will continue to show the last
+ * value of the property.
+ *
+ * Return value: (transfer none): A new #ClutterActor
+ */
+ClutterActor *
+shell_texture_cache_bind_pixbuf_property (ShellTextureCache *cache,
+                                          GObject           *object,
+                                          const char        *property_name)
+{
+  ClutterTexture *texture;
+  gchar *notify_key;
+  ShellTextureCachePropertyBind *bind;
+
+  texture = CLUTTER_TEXTURE (clutter_texture_new ());
+
+  bind = g_new0 (ShellTextureCachePropertyBind, 1);
+  bind->cache = cache;
+  bind->texture = texture;
+  bind->source = object;
+  g_object_weak_ref (G_OBJECT (texture), shell_texture_cache_bind_weak_notify, bind);
+  bind->weakref_active = TRUE;
+
+  shell_texture_cache_reset_texture (bind, property_name);
+
+  notify_key = g_strdup_printf ("notify::%s", property_name);
+  bind->notify_signal_id = g_signal_connect_data (object, notify_key, G_CALLBACK(shell_texture_cache_on_pixbuf_notify),
+                                                  bind, (GClosureNotify)shell_texture_cache_free_bind, 0);
+  g_free (notify_key);
+
+  return CLUTTER_ACTOR(texture);
+}
+
 /**
  * shell_texture_cache_load_gicon:
  *

src/shell-texture-cache.h

@@ -40,6 +40,10 @@ GType shell_texture_cache_get_type (void) G_GNUC_CONST;
 
 ShellTextureCache* shell_texture_cache_get_default (void);
 
+ClutterActor *shell_texture_cache_bind_pixbuf_property (ShellTextureCache *cache,
+                                                        GObject           *object,
+                                                        const char        *property_name);
+
 ClutterActor *shell_texture_cache_load_icon_name (ShellTextureCache *cache,
                                                   const char        *name,
                                                   gint               size);