window-actor: Make it clearer that the surface actor doesn't change

The way code was structured made it easy to misunderstand things as the
surface actor of a window actor could change over time. So is not the
case, however, the intention of the corresponding "update" function was
so that a surface actor could be assigned to a window actor as soon as
the X11 window was associated with its corresponding wl_surface, if the
window in question came from Xwayland.

Restructure the code and internal API a bit to make it clear that a
window actor only once gets a surface actor assigned to it, and that it
after that point never changes.

https://gitlab.gnome.org/GNOME/mutter/merge_requests/659

src/compositor/compositor.c

@@ -778,18 +778,6 @@ meta_compositor_window_opacity_changed (MetaCompositor *compositor,
   meta_window_actor_update_opacity (window_actor);
 }
 
-void
-meta_compositor_window_surface_changed (MetaCompositor *compositor,
-                                        MetaWindow     *window)
-{
-  MetaWindowActor *window_actor;
-  window_actor = META_WINDOW_ACTOR (meta_window_get_compositor_private (window));
-  if (!window_actor)
-    return;
-
-  meta_window_actor_update_surface (window_actor);
-}
-
 /**
  * meta_compositor_process_event: (skip)
  * @compositor:

src/compositor/meta-window-actor-private.h

@@ -17,8 +17,8 @@ struct _MetaWindowActorClass
                           ClutterFrameInfo *frame_info,
                           int64_t           presentation_time);
 
-  void (*set_surface_actor) (MetaWindowActor  *actor,
-                             MetaSurfaceActor *surface);
+  void (*assign_surface_actor) (MetaWindowActor  *actor,
+                                MetaSurfaceActor *surface_actor);
 
   void (*queue_frame_drawn) (MetaWindowActor *actor,
                              gboolean         skip_sync_delay);
@@ -73,7 +73,10 @@ void meta_window_actor_effect_completed (MetaWindowActor  *actor,
                                          MetaPluginEffect  event);
 
 MetaSurfaceActor *meta_window_actor_get_surface (MetaWindowActor *self);
-void meta_window_actor_update_surface (MetaWindowActor *self);
+
+void meta_window_actor_assign_surface_actor (MetaWindowActor  *self,
+                                             MetaSurfaceActor *surface_actor);
+
 MetaWindowActor *meta_window_actor_from_window (MetaWindow *window);
 
 #endif /* META_WINDOW_ACTOR_PRIVATE_H */

src/compositor/meta-window-actor-x11.c

@@ -329,32 +329,19 @@ meta_window_actor_x11_frame_complete (MetaWindowActor  *actor,
 }
 
 static void
-meta_window_actor_x11_set_surface_actor (MetaWindowActor  *actor,
-                                         MetaSurfaceActor *surface)
+meta_window_actor_x11_assign_surface_actor (MetaWindowActor  *actor,
+                                            MetaSurfaceActor *surface_actor)
 {
   MetaWindowActorClass *parent_class =
     META_WINDOW_ACTOR_CLASS (meta_window_actor_x11_parent_class);
   MetaWindowActorX11 *actor_x11 = META_WINDOW_ACTOR_X11 (actor);
-  MetaSurfaceActor *old_surface;
 
-  old_surface = meta_window_actor_get_surface (actor);
+  parent_class->assign_surface_actor (actor, surface_actor);
 
-  if (old_surface)
-    {
-      g_signal_handler_disconnect (old_surface,
-                                   actor_x11->repaint_scheduled_id);
-      actor_x11->repaint_scheduled_id = 0;
-    }
-
-  parent_class->set_surface_actor (actor, surface);
-
-  if (surface)
-    {
   actor_x11->repaint_scheduled_id =
-        g_signal_connect (surface, "repaint-scheduled",
+    g_signal_connect (surface_actor, "repaint-scheduled",
                       G_CALLBACK (surface_repaint_scheduled),
                       actor_x11);
-    }
 }
 
 static void
@@ -503,10 +490,19 @@ static void
 meta_window_actor_x11_dispose (GObject *object)
 {
   MetaWindowActorX11 *actor_x11 = META_WINDOW_ACTOR_X11 (object);
+  MetaSurfaceActor *surface_actor;
 
   if (actor_x11->send_frame_messages_timer != 0)
     remove_frame_messages_timer (actor_x11);
 
+  surface_actor = meta_window_actor_get_surface (META_WINDOW_ACTOR (actor_x11));
+  if (surface_actor)
+    {
+      g_signal_handler_disconnect (surface_actor,
+                                   actor_x11->repaint_scheduled_id);
+      actor_x11->repaint_scheduled_id = 0;
+    }
+
   G_OBJECT_CLASS (meta_window_actor_x11_parent_class)->dispose (object);
 }
 
@@ -528,7 +524,7 @@ meta_window_actor_x11_class_init (MetaWindowActorX11Class *klass)
   MetaWindowActorClass *window_actor_class = META_WINDOW_ACTOR_CLASS (klass);
 
   window_actor_class->frame_complete = meta_window_actor_x11_frame_complete;
-  window_actor_class->set_surface_actor = meta_window_actor_x11_set_surface_actor;
+  window_actor_class->assign_surface_actor = meta_window_actor_x11_assign_surface_actor;
   window_actor_class->queue_frame_drawn = meta_window_actor_x11_queue_frame_drawn;
   window_actor_class->pre_paint = meta_window_actor_x11_pre_paint;
   window_actor_class->post_paint = meta_window_actor_x11_post_paint;

src/compositor/meta-window-actor.c

@@ -137,12 +137,13 @@ static void meta_window_actor_get_property (GObject      *object,
                                             GValue       *value,
                                             GParamSpec   *pspec);
 
+static void meta_window_actor_real_assign_surface_actor (MetaWindowActor  *self,
+                                                         MetaSurfaceActor *surface_actor);
+
 static void meta_window_actor_paint (ClutterActor *actor);
 
 static gboolean meta_window_actor_get_paint_volume (ClutterActor       *actor,
                                                     ClutterPaintVolume *volume);
-static void set_surface (MetaWindowActor  *actor,
-                         MetaSurfaceActor *surface);
 
 static gboolean meta_window_actor_has_shadow (MetaWindowActor *self);
 
@@ -159,13 +160,6 @@ G_DEFINE_ABSTRACT_TYPE_WITH_CODE (MetaWindowActor, meta_window_actor, CLUTTER_TY
                                   G_IMPLEMENT_INTERFACE (META_TYPE_CULLABLE, cullable_iface_init)
                                   G_IMPLEMENT_INTERFACE (META_TYPE_SCREEN_CAST_WINDOW, screen_cast_window_iface_init));
 
-static void
-meta_window_actor_real_set_surface_actor (MetaWindowActor  *actor,
-                                          MetaSurfaceActor *surface)
-{
-  set_surface (actor, surface);
-}
-
 static void
 meta_window_actor_class_init (MetaWindowActorClass *klass)
 {
@@ -181,7 +175,7 @@ meta_window_actor_class_init (MetaWindowActorClass *klass)
   actor_class->paint = meta_window_actor_paint;
   actor_class->get_paint_volume = meta_window_actor_get_paint_volume;
 
-  klass->set_surface_actor = meta_window_actor_real_set_surface_actor;
+  klass->assign_surface_actor = meta_window_actor_real_assign_surface_actor;
 
   /**
    * MetaWindowActor::first-frame:
@@ -365,26 +359,18 @@ meta_window_actor_thaw (MetaWindowActor *self)
 }
 
 static void
-set_surface (MetaWindowActor  *self,
-             MetaSurfaceActor *surface)
+meta_window_actor_real_assign_surface_actor (MetaWindowActor  *self,
+                                             MetaSurfaceActor *surface_actor)
 {
   MetaWindowActorPrivate *priv =
     meta_window_actor_get_instance_private (self);
 
-  if (priv->surface)
-    {
-      g_signal_handler_disconnect (priv->surface, priv->size_changed_id);
-      clutter_actor_remove_child (CLUTTER_ACTOR (self), CLUTTER_ACTOR (priv->surface));
-      g_object_unref (priv->surface);
-    }
+  g_assert (!priv->surface);
 
-  priv->surface = surface;
-
-  if (priv->surface)
-    {
-      g_object_ref_sink (priv->surface);
+  priv->surface = g_object_ref_sink (surface_actor);
   priv->size_changed_id = g_signal_connect (priv->surface, "size-changed",
-                                                G_CALLBACK (surface_size_changed), self);
+                                            G_CALLBACK (surface_size_changed),
+                                            self);
   clutter_actor_add_child (CLUTTER_ACTOR (self), CLUTTER_ACTOR (priv->surface));
 
   meta_window_actor_update_shape (self);
@@ -393,28 +379,35 @@ set_surface (MetaWindowActor  *self,
     meta_surface_actor_set_frozen (priv->surface, TRUE);
   else
     meta_window_actor_sync_thawed_state (self);
-    }
 }
 
 void
-meta_window_actor_update_surface (MetaWindowActor *self)
+meta_window_actor_assign_surface_actor (MetaWindowActor  *self,
+                                        MetaSurfaceActor *surface_actor)
+{
+  META_WINDOW_ACTOR_GET_CLASS (self)->assign_surface_actor (self,
+                                                            surface_actor);
+}
+
+static void
+init_surface_actor (MetaWindowActor *self)
 {
   MetaWindowActorPrivate *priv =
     meta_window_actor_get_instance_private (self);
   MetaWindow *window = priv->window;
   MetaSurfaceActor *surface_actor;
 
-#ifdef HAVE_WAYLAND
-  if (window->surface)
-    surface_actor = meta_wayland_surface_get_actor (window->surface);
-  else
-#endif
   if (!meta_is_wayland_compositor ())
     surface_actor = meta_surface_actor_x11_new (window);
+#ifdef HAVE_WAYLAND
+  else if (window->surface)
+    surface_actor = meta_wayland_surface_get_actor (window->surface);
+#endif
   else
     surface_actor = NULL;
 
-  META_WINDOW_ACTOR_GET_CLASS (self)->set_surface_actor (self, surface_actor);
+  if (surface_actor)
+    meta_window_actor_assign_surface_actor (self, surface_actor);
 }
 
 static void
@@ -430,7 +423,7 @@ meta_window_actor_constructed (GObject *object)
   /* Hang our compositor window state off the MetaWindow for fast retrieval */
   meta_window_set_compositor_private (window, object);
 
-  meta_window_actor_update_surface (self);
+  init_surface_actor (self);
 
   meta_window_actor_update_opacity (self);
 
@@ -476,7 +469,13 @@ meta_window_actor_dispose (GObject *object)
 
   g_clear_object (&priv->window);
 
-  META_WINDOW_ACTOR_GET_CLASS (self)->set_surface_actor (self, NULL);
+  if (priv->surface)
+    {
+      g_signal_handler_disconnect (priv->surface, priv->size_changed_id);
+      clutter_actor_remove_child (CLUTTER_ACTOR (self),
+                                  CLUTTER_ACTOR (priv->surface));
+      g_clear_object (&priv->surface);
+    }
 
   G_OBJECT_CLASS (meta_window_actor_parent_class)->dispose (object);
 }

src/meta/compositor.h

@@ -82,10 +82,6 @@ META_EXPORT
 void meta_compositor_window_opacity_changed (MetaCompositor *compositor,
                                              MetaWindow     *window);
 
-META_EXPORT
-void meta_compositor_window_surface_changed (MetaCompositor *compositor,
-                                             MetaWindow     *window);
-
 META_EXPORT
 gboolean meta_compositor_process_event (MetaCompositor *compositor,
                                         XEvent         *event,

src/wayland/meta-xwayland.c

@@ -40,6 +40,7 @@
 #include <X11/Xauth.h>
 
 #include "compositor/meta-surface-actor-wayland.h"
+#include "compositor/meta-window-actor-private.h"
 #include "meta/main.h"
 #include "wayland/meta-wayland-actor-surface.h"
 
@@ -74,6 +75,7 @@ meta_xwayland_associate_window_with_surface (MetaWindow          *window,
                                              MetaWaylandSurface  *surface)
 {
   MetaDisplay *display = window->display;
+  MetaWindowActor *window_actor;
 
   /* If the window has an existing surface, like if we're
    * undecorating or decorating the window, then we need
@@ -102,7 +104,14 @@ meta_xwayland_associate_window_with_surface (MetaWindow          *window,
                  xwayland_surface_signals[XWAYLAND_SURFACE_WINDOW_ASSOCIATED],
                  0);
 
-  meta_compositor_window_surface_changed (display->compositor, window);
+  window_actor = meta_window_actor_from_window (window);
+  if (window_actor)
+    {
+      MetaSurfaceActor *surface_actor;
+
+      surface_actor = meta_wayland_surface_get_actor (surface);
+      meta_window_actor_assign_surface_actor (window_actor, surface_actor);
+    }
 
   /* Now that we have a surface check if it should have focus. */
   meta_display_sync_wayland_input_focus (display);