wayland: Move tree updating to the shell surface role

The shell surface role is the one where subsurfaces may exist, and it
has direct relation to the MetaWindowActorWayland which currently has
the subsurface stacking logic.

Instead of directly finding the window actor when dealing with
subsurfaces, notify the parent surface that the subsurface state
changed, so that it can outsource the application of this information to
the role. For subsurface roles, this simply means forward upward to the
parent; for shell surface roles, this means regenerate the surface actor
layering.

This allows us to move away from accessing the window directly from the
surface, which in turn allows us to change the ownership structure of
windows.

https://gitlab.gnome.org/GNOME/mutter/merge_requests/835

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

@@ -91,17 +91,6 @@ meta_window_actor_wayland_rebuild_surface_tree (MetaWindowActor *actor)
                    actor);
 }
 
-MetaWindowActor *
-meta_window_actor_wayland_from_surface (MetaWaylandSurface *surface)
-{
-  if (surface->window)
-    return meta_window_actor_from_window (surface->window);
-  else if (surface->sub.parent)
-    return meta_window_actor_wayland_from_surface (surface->sub.parent);
-  else
-    return NULL;
-}
-
 static void
 meta_window_actor_wayland_assign_surface_actor (MetaWindowActor  *actor,
                                                 MetaSurfaceActor *surface_actor)

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

@@ -33,6 +33,5 @@ G_DECLARE_FINAL_TYPE (MetaWindowActorWayland,
                       MetaWindowActor)
 
 void meta_window_actor_wayland_rebuild_surface_tree (MetaWindowActor *actor);
-MetaWindowActor * meta_window_actor_wayland_from_surface (MetaWaylandSurface *surface);
 
 #endif /*META_WINDOW_ACTOR_WAYLAND_H */

src/wayland/meta-wayland-shell-surface.c

@@ -24,6 +24,7 @@
 #include "wayland/meta-wayland-shell-surface.h"
 
 #include "compositor/meta-surface-actor-wayland.h"
+#include "compositor/meta-window-actor-wayland.h"
 #include "wayland/meta-wayland-actor-surface.h"
 #include "wayland/meta-wayland-buffer.h"
 #include "wayland/meta-wayland-subsurface.h"
@@ -165,6 +166,22 @@ meta_wayland_shell_surface_surface_apply_state (MetaWaylandSurfaceRole  *surface
     meta_wayland_surface_get_height (surface) * geometry_scale;
 }
 
+static void
+meta_wayland_shell_surface_notify_subsurface_state_changed (MetaWaylandSurfaceRole *surface_role)
+{
+  MetaWaylandSurface *surface =
+    meta_wayland_surface_role_get_surface (surface_role);
+  MetaWindow *window;
+  MetaWindowActor *window_actor;
+
+  window = surface->window;
+  if (!window)
+    return;
+
+  window_actor = meta_window_actor_from_window (window);
+  meta_window_actor_wayland_rebuild_surface_tree (window_actor);
+}
+
 static double
 meta_wayland_shell_surface_get_geometry_scale (MetaWaylandActorSurface *actor_surface)
 {
@@ -246,6 +263,8 @@ meta_wayland_shell_surface_class_init (MetaWaylandShellSurfaceClass *klass)
 
   surface_role_class->apply_state =
     meta_wayland_shell_surface_surface_apply_state;
+  surface_role_class->notify_subsurface_state_changed =
+    meta_wayland_shell_surface_notify_subsurface_state_changed;
 
   actor_surface_class->get_geometry_scale =
     meta_wayland_shell_surface_get_geometry_scale;

src/wayland/meta-wayland-subsurface.c

@@ -139,7 +139,6 @@ meta_wayland_subsurface_parent_state_applied (MetaWaylandSubsurface *subsurface)
     {
       GSList *it;
       MetaWaylandSurface *parent;
-      MetaWindowActor *window_actor;
 
       parent = surface->sub.parent;
 
@@ -184,9 +183,7 @@ meta_wayland_subsurface_parent_state_applied (MetaWaylandSubsurface *subsurface)
       g_slist_free (surface->sub.pending_placement_ops);
       surface->sub.pending_placement_ops = NULL;
 
-      window_actor = meta_window_actor_wayland_from_surface (surface);
-      if (window_actor)
-        meta_window_actor_wayland_rebuild_surface_tree (window_actor);
+      meta_wayland_surface_notify_subsurface_state_changed (parent);
     }
 
   if (is_surface_effectively_synchronized (surface))
@@ -258,6 +255,16 @@ meta_wayland_subsurface_should_cache_state (MetaWaylandSurfaceRole *surface_role
   return TRUE;
 }
 
+static void
+meta_wayland_subsurface_notify_subsurface_state_changed (MetaWaylandSurfaceRole *surface_role)
+{
+  MetaWaylandSurface *surface =
+    meta_wayland_surface_role_get_surface (surface_role);
+  MetaWaylandSurface *parent = surface->sub.parent;
+
+  return meta_wayland_surface_notify_subsurface_state_changed (parent);
+}
+
 static double
 meta_wayland_subsurface_get_geometry_scale (MetaWaylandActorSurface *actor_surface)
 {
@@ -313,6 +320,8 @@ meta_wayland_subsurface_class_init (MetaWaylandSubsurfaceClass *klass)
 
   surface_role_class->get_toplevel = meta_wayland_subsurface_get_toplevel;
   surface_role_class->should_cache_state = meta_wayland_subsurface_should_cache_state;
+  surface_role_class->notify_subsurface_state_changed =
+    meta_wayland_subsurface_notify_subsurface_state_changed;
 
   actor_surface_class->get_geometry_scale =
     meta_wayland_subsurface_get_geometry_scale;
@@ -519,7 +528,6 @@ wl_subcompositor_get_subsurface (struct wl_client   *client,
   MetaWaylandSurface *surface = wl_resource_get_user_data (surface_resource);
   MetaWaylandSurface *parent = wl_resource_get_user_data (parent_resource);
   MetaWindow *toplevel_window;
-  MetaWindowActor *window_actor;
 
   if (surface->wl_subsurface)
     {
@@ -564,9 +572,7 @@ wl_subcompositor_get_subsurface (struct wl_client   *client,
   g_node_append (parent->subsurface_branch_node,
                  surface->subsurface_branch_node);
 
-  window_actor = meta_window_actor_wayland_from_surface (surface);
-  if (window_actor)
-    meta_window_actor_wayland_rebuild_surface_tree (window_actor);
+  meta_wayland_surface_notify_subsurface_state_changed (parent);
 }
 
 static const struct wl_subcompositor_interface meta_wayland_subcompositor_interface = {

src/wayland/meta-wayland-surface.c

@@ -1843,6 +1843,24 @@ meta_wayland_surface_should_cache_state (MetaWaylandSurface *surface)
   return meta_wayland_surface_role_should_cache_state (surface->role);
 }
 
+static void
+meta_wayland_surface_role_notify_subsurface_state_changed (MetaWaylandSurfaceRole *surface_role)
+{
+  MetaWaylandSurfaceRoleClass *klass;
+
+  klass = META_WAYLAND_SURFACE_ROLE_GET_CLASS (surface_role);
+  g_return_if_fail (klass->notify_subsurface_state_changed);
+
+  klass->notify_subsurface_state_changed (surface_role);
+}
+
+void
+meta_wayland_surface_notify_subsurface_state_changed (MetaWaylandSurface *surface)
+{
+  if (surface->role)
+    meta_wayland_surface_role_notify_subsurface_state_changed (surface->role);
+}
+
 MetaWaylandSurface *
 meta_wayland_surface_role_get_surface (MetaWaylandSurfaceRole *role)
 {

src/wayland/meta-wayland-surface.h

@@ -62,6 +62,7 @@ struct _MetaWaylandSurfaceRoleClass
                                      MetaLogicalMonitor     *logical_monitor);
   MetaWaylandSurface * (*get_toplevel) (MetaWaylandSurfaceRole *surface_role);
   gboolean (*should_cache_state) (MetaWaylandSurfaceRole *surface_role);
+  void (*notify_subsurface_state_changed) (MetaWaylandSurfaceRole *surface_role);
 };
 
 struct _MetaWaylandSurfaceState
@@ -325,6 +326,8 @@ MetaSurfaceActor *  meta_wayland_surface_get_actor (MetaWaylandSurface *surface)
 
 void                meta_wayland_surface_notify_geometry_changed (MetaWaylandSurface *surface);
 
+void                meta_wayland_surface_notify_subsurface_state_changed (MetaWaylandSurface *surface);
+
 int                 meta_wayland_surface_get_width (MetaWaylandSurface *surface);
 int                 meta_wayland_surface_get_height (MetaWaylandSurface *surface);