window: track when resize is pending via new flag

For Xwayland clients, resizing is an asynchronous operation.  First, the
window manager part of mutter resizes the frame and client window, then
Xwayland waits for damage from the client, and commits a new surface to
the display server part of mutter.

In order to prevent flicker, we need to know when an initiated resize
operation has fully come out the other end of that multi-step process as
a new surface.

This commit lays the plumbing work for preventing the aforementioned
flicker problem, by adding a new resize_pending flag (and associated
accessors), and setting the flag appropriately based on when a resize
is started and subsequently when a new surface is attached.

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

@@ -125,6 +125,17 @@ meta_surface_actor_wayland_get_window (MetaSurfaceActor *actor)
   return surface->window;
 }
 
+static void
+meta_surface_actor_wayland_size_changed (MetaSurfaceActor *actor)
+{
+  MetaWindow *window;
+
+  window = meta_surface_actor_wayland_get_window (actor);
+
+  if (window)
+    meta_window_set_resize_pending (window, FALSE);
+}
+
 static void
 meta_surface_actor_wayland_get_preferred_width  (ClutterActor *actor,
                                                  gfloat        for_height,
@@ -237,6 +248,8 @@ meta_surface_actor_wayland_class_init (MetaSurfaceActorWaylandClass *klass)
   surface_actor_class->set_frozen = meta_surface_actor_wayland_set_frozen;
   surface_actor_class->get_window = meta_surface_actor_wayland_get_window;
 
+  surface_actor_class->size_changed = meta_surface_actor_wayland_size_changed;
+
   object_class->dispose = meta_surface_actor_wayland_dispose;
 }
 

src/compositor/meta-surface-actor.c

@@ -135,8 +135,8 @@ meta_surface_actor_class_init (MetaSurfaceActorClass *klass)
 
   signals[SIZE_CHANGED] = g_signal_new ("size-changed",
                                         G_TYPE_FROM_CLASS (object_class),
-                                        G_SIGNAL_RUN_LAST,
-                                        0,
+                                        G_SIGNAL_RUN_FIRST,
+                                        G_STRUCT_OFFSET (MetaSurfaceActorClass, size_changed),
                                         NULL, NULL, NULL,
                                         G_TYPE_NONE, 0);
 

src/compositor/meta-surface-actor.h

@@ -40,6 +40,8 @@ struct _MetaSurfaceActorClass
                                   gboolean          is_frozen);
 
   MetaWindow *(* get_window)      (MetaSurfaceActor *actor);
+
+  void     (* size_changed)      (MetaSurfaceActor *actor);
 };
 
 struct _MetaSurfaceActor

src/core/window-private.h

@@ -407,6 +407,9 @@ struct _MetaWindow
   /* whether or not the window is from a program running on another machine */
   guint is_remote : 1;
 
+  /* if TRUE, the X server hasn't yet committed a new buffer following resize of the frame/client window */
+  guint resize_pending : 1;
+
   /* if non-NULL, the bounds of the window frame */
   cairo_region_t *frame_bounds;
 
@@ -781,6 +784,9 @@ void meta_window_move_resize_internal (MetaWindow          *window,
                                        MetaMoveResizeFlags  flags,
                                        int                  gravity,
                                        MetaRectangle        frame_rect);
+void meta_window_set_resize_pending (MetaWindow *window,
+                                     gboolean    is_resize_pending);
+gboolean meta_window_resize_is_pending (MetaWindow  *window);
 
 void meta_window_grab_op_began (MetaWindow *window, MetaGrabOp op);
 void meta_window_grab_op_ended (MetaWindow *window, MetaGrabOp op);

src/core/window.c

@@ -6311,6 +6311,19 @@ meta_window_update_resize (MetaWindow *window,
   update_resize (window, snap, x, y, force);
 }
 
+void
+meta_window_set_resize_pending (MetaWindow *window,
+                                gboolean    is_resize_pending)
+{
+  window->resize_pending = is_resize_pending;
+}
+
+gboolean
+meta_window_resize_is_pending (MetaWindow  *window)
+{
+  return window->resize_pending;
+}
+
 static void
 end_grab_op (MetaWindow *window,
              const ClutterEvent *event)

src/wayland/meta-wayland-surface.c

@@ -1102,6 +1102,7 @@ meta_wayland_surface_set_window (MetaWaylandSurface *surface,
                                "position-changed",
                                G_CALLBACK (window_position_changed),
                                surface, 0);
+      meta_window_set_resize_pending (window, FALSE);
     }
 }
 

src/wayland/meta-window-xwayland.c

@@ -71,6 +71,20 @@ meta_window_xwayland_shortcuts_inhibited (MetaWindow         *window,
   return meta_wayland_compositor_is_shortcuts_inhibited (compositor, source);
 }
 
+static void
+meta_window_xwayland_move_resize_internal (MetaWindow                *window,
+                                           int                        gravity,
+                                           MetaRectangle              unconstrained_rect,
+                                           MetaRectangle              constrained_rect,
+                                           MetaMoveResizeFlags        flags,
+                                           MetaMoveResizeResultFlags *result)
+{
+  META_WINDOW_CLASS (meta_window_xwayland_parent_class)->move_resize_internal (window, gravity, unconstrained_rect, constrained_rect, flags, result);
+
+  if (*result & META_MOVE_RESIZE_RESULT_RESIZED)
+    meta_window_set_resize_pending (window, TRUE);
+}
+
 static void
 meta_window_xwayland_get_property (GObject    *object,
                                    guint       prop_id,
@@ -117,6 +131,7 @@ meta_window_xwayland_class_init (MetaWindowXwaylandClass *klass)
 
   window_class->force_restore_shortcuts = meta_window_xwayland_force_restore_shortcuts;
   window_class->shortcuts_inhibited = meta_window_xwayland_shortcuts_inhibited;
+  window_class->move_resize_internal = meta_window_xwayland_move_resize_internal;
 
   gobject_class->get_property = meta_window_xwayland_get_property;
   gobject_class->set_property = meta_window_xwayland_set_property;