alpha: Don't use the GClosure to compute the alpha when possible

Setting up the call and calling the GClosure was showing up in profiles
and seemed an easy one to remove.

Instead of calling the closure, let's remember the alpha func and the
user_data when possible (ie set_mode() and set_func()) and use it in
get_alpha().

https://bugzilla.gnome.org/show_bug.cgi?id=654727

clutter/clutter-alpha.c

@@ -131,6 +131,10 @@ struct _ClutterAlphaPrivate
 
   GClosure *closure;
 
+  ClutterAlphaFunc func;
+  gpointer user_data;
+  GDestroyNotify notify;
+
   gulong mode;
 };
 
@@ -216,7 +220,9 @@ clutter_alpha_finalize (GObject *object)
 {
   ClutterAlphaPrivate *priv = CLUTTER_ALPHA (object)->priv;
 
-  if (priv->closure)
+  if (priv->notify != NULL)
+    priv->notify (priv->user_data);
+  else if (priv->closure != NULL)
     g_closure_unref (priv->closure);
 
   G_OBJECT_CLASS (clutter_alpha_parent_class)->finalize (object);
@@ -415,7 +421,11 @@ clutter_alpha_get_alpha (ClutterAlpha *alpha)
 
   priv = alpha->priv;
 
-  if (G_LIKELY (priv->closure))
+  if (G_LIKELY (priv->func))
+    {
+      return priv->func (alpha, priv->user_data);
+    }
+  else if (priv->closure)
     {
       GValue params = { 0, };
       GValue result_value = { 0, };
@@ -455,9 +465,18 @@ clutter_alpha_set_closure_internal (ClutterAlpha *alpha,
 {
   ClutterAlphaPrivate *priv = alpha->priv;
 
-  if (priv->closure)
+  if (priv->notify != NULL)
+    priv->notify (priv->user_data);
+  else if (priv->closure != NULL)
     g_closure_unref (priv->closure);
 
+  priv->func = NULL;
+  priv->user_data = NULL;
+  priv->notify = NULL;
+
+  if (closure == NULL)
+    return;
+
   /* need to take ownership of the closure before sinking it */
   priv->closure = g_closure_ref (closure);
   g_closure_sink (closure);
@@ -520,17 +539,28 @@ clutter_alpha_set_func (ClutterAlpha    *alpha,
                         GDestroyNotify   destroy)
 {
   ClutterAlphaPrivate *priv;
-  GClosure *closure;
 
   g_return_if_fail (CLUTTER_IS_ALPHA (alpha));
   g_return_if_fail (func != NULL);
 
   priv = alpha->priv;
 
-  closure = g_cclosure_new (G_CALLBACK (func), data, (GClosureNotify) destroy);
+  if (priv->notify != NULL)
-  clutter_alpha_set_closure_internal (alpha, closure);
+    {
+      priv->notify (priv->user_data);
+    }
+  else if (priv->closure != NULL)
+    {
+      g_closure_unref (priv->closure);
+      priv->closure = NULL;
+    }
+
+  priv->func = func;
+  priv->user_data = data;
+  priv->notify = destroy;
 
   priv->mode = CLUTTER_CUSTOM_MODE;
+
   g_object_notify_by_pspec (G_OBJECT (alpha), obj_props[PROP_MODE]);
 }
 
@@ -1243,7 +1273,8 @@ clutter_alpha_set_mode (ClutterAlpha *alpha,
     }
   else if (mode < CLUTTER_ANIMATION_LAST)
     {
-      GClosure *closure;
+      if (priv->mode == mode)
+        return;
 
       /* sanity check to avoid getting an out of sync
        * enum/function mapping
@@ -1251,10 +1282,11 @@ clutter_alpha_set_mode (ClutterAlpha *alpha,
       g_assert (animation_modes[mode].mode == mode);
       g_assert (animation_modes[mode].func != NULL);
 
-      closure = g_cclosure_new (G_CALLBACK (animation_modes[mode].func),
+      clutter_alpha_set_closure_internal (alpha, NULL);
-                                NULL,
+
-                                NULL);
+      priv->func = animation_modes[mode].func;
-      clutter_alpha_set_closure_internal (alpha, closure);
+      priv->user_data = NULL;
+      priv->notify = NULL;
 
       priv->mode = mode;
     }
@@ -1263,6 +1295,9 @@ clutter_alpha_set_mode (ClutterAlpha *alpha,
       AlphaData *alpha_data = NULL;
       gulong real_index = 0;
 
+      if (priv->mode == mode)
+        return;
+
       if (G_UNLIKELY (clutter_alphas == NULL))
         {
           g_warning ("No alpha functions defined for ClutterAlpha to use. "
@@ -1285,12 +1320,11 @@ clutter_alpha_set_mode (ClutterAlpha *alpha,
         clutter_alpha_set_closure (alpha, alpha_data->closure);
       else
         {
-          GClosure *closure;
+          clutter_alpha_set_closure_internal (alpha, NULL);
 
-          closure = g_cclosure_new (G_CALLBACK (alpha_data->func),
+          priv->func = alpha_data->func;
-                                    alpha_data->data,
+          priv->user_data = alpha_data->data;
-                                    NULL);
+          priv->notify = NULL;
-          clutter_alpha_set_closure_internal (alpha, closure);
         }
 
       priv->mode = mode;