[gtk+] wayland: Make subsurface desynchronized after first parent surface frame

[Jonas Ådahl <jadahl src gnome org>]

commit 7c4c8b90f0b1d5619b1a4e46420e09d9b3849684
Author: Jonas Ådahl <jadahl gmail com>
Date:   Thu Sep 10 17:42:21 2015 +0800

    wayland: Make subsurface desynchronized after first parent surface frame
    
    Initially the subsurface will be in synchronized mode and we will leave
    it like this until the first time the parent surface has been committed.
    The reason for this is because the subsurface position will be applied
    as part of the parent surface state, and we need to synchronize the
    initial position with the initial frame, so that we don't accidentally
    draw the subsurface at the default position (0, 0) which would happen in
    desynchronized mode if the subsurface content is committed before the
    next parent surface commit.
    
    https://bugzilla.gnome.org/show_bug.cgi?id=754839

 gdk/wayland/gdkwindow-wayland.c |   81 ++++++++++++++++++++++++++++++---------
 1 files changed, 63 insertions(+), 18 deletions(-)
---
diff --git a/gdk/wayland/gdkwindow-wayland.c b/gdk/wayland/gdkwindow-wayland.c
index 4c6f30c..ab7f384 100644
--- a/gdk/wayland/gdkwindow-wayland.c
+++ b/gdk/wayland/gdkwindow-wayland.c
@@ -37,6 +37,14 @@
 #include <string.h>
 #include <errno.h>
 
+enum {
+  COMMITTED,
+
+  LAST_SIGNAL
+};
+
+static guint signals[LAST_SIGNAL];
+
 #define WINDOW_IS_TOPLEVEL_OR_FOREIGN(window) \
   (GDK_WINDOW_TYPE (window) != GDK_WINDOW_CHILD &&   \
    GDK_WINDOW_TYPE (window) != GDK_WINDOW_OFFSCREEN)
@@ -431,6 +439,8 @@ on_frame_clock_after_paint (GdkFrameClock *clock,
   wl_surface_commit (impl->surface);
   if (_gdk_wayland_is_shm_surface (impl->cairo_surface))
     _gdk_wayland_shm_surface_set_busy (impl->cairo_surface);
+
+  g_signal_emit (impl, signals[COMMITTED], 0);
 }
 
 static void
@@ -860,6 +870,19 @@ static const struct wl_surface_listener surface_listener = {
 };
 
 static void
+on_parent_surface_committed (GdkWindowImplWayland *parent_impl,
+                             GdkWindow            *window)
+{
+  GdkWindowImplWayland *impl = GDK_WINDOW_IMPL_WAYLAND (window->impl);
+
+  g_signal_handlers_disconnect_by_func (parent_impl,
+                                        (gpointer) on_parent_surface_committed,
+                                        window);
+
+  wl_subsurface_set_desync (impl->subsurface);
+}
+
+static void
 gdk_wayland_window_create_subsurface (GdkWindow *window)
 {
   GdkWindowImplWayland *impl, *parent_impl = NULL;
@@ -886,7 +909,14 @@ gdk_wayland_window_create_subsurface (GdkWindow *window)
         wl_subcompositor_get_subsurface (display_wayland->subcompositor,
                                          impl->surface, parent_impl->surface);
       wl_subsurface_set_position (impl->subsurface, window->x, window->y);
-      wl_subsurface_set_desync (impl->subsurface);
+
+      /* In order to synchronize the initial position with the initial frame
+       * content, wait with making the subsurface desynchronized until after
+       * the parent was committed.
+       */
+      g_signal_connect_object (parent_impl, "committed",
+                               G_CALLBACK (on_parent_surface_committed),
+                               window, 0);
       gdk_window_request_transient_parent_commit (window);
     }
 }
@@ -1295,6 +1325,23 @@ gdk_wayland_window_show (GdkWindow *window,
 }
 
 static void
+unmap_subsurface (GdkWindow *window)
+{
+  GdkWindowImplWayland *impl = GDK_WINDOW_IMPL_WAYLAND (window->impl);
+  GdkWindowImplWayland *parent_impl;
+
+  g_return_if_fail (impl->subsurface);
+  g_return_if_fail (impl->transient_for);
+
+  parent_impl = GDK_WINDOW_IMPL_WAYLAND (impl->transient_for->impl);
+  wl_subsurface_destroy (impl->subsurface);
+  g_signal_handlers_disconnect_by_func (parent_impl,
+                                        (gpointer) on_parent_surface_committed,
+                                        window);
+  impl->subsurface = NULL;
+}
+
+static void
 gdk_wayland_window_hide_surface (GdkWindow *window)
 {
   GdkWaylandDisplay *display_wayland = GDK_WAYLAND_DISPLAY (gdk_window_get_display (window));
@@ -1338,10 +1385,7 @@ gdk_wayland_window_hide_surface (GdkWindow *window)
         }
 
       if (impl->subsurface)
-        {
-          wl_subsurface_destroy (impl->subsurface);
-          impl->subsurface = NULL;
-        }
+        unmap_subsurface (window);
 
       if (impl->awaiting_frame)
         {
@@ -1793,24 +1837,18 @@ static void
 gdk_wayland_window_set_transient_for (GdkWindow *window,
                                       GdkWindow *parent)
 {
-  GdkWindowImplWayland *impl;
+  GdkWindowImplWayland *impl = GDK_WINDOW_IMPL_WAYLAND (window->impl);
+
+  if (impl->subsurface)
+    unmap_subsurface (window);
 
-  impl = GDK_WINDOW_IMPL_WAYLAND (window->impl);
   impl->transient_for = parent;
 
   gdk_wayland_window_sync_parent (window);
 
-  if (GDK_WINDOW_TYPE (window) == GDK_WINDOW_SUBSURFACE)
-    {
-      if (impl->subsurface)
-        {
-          wl_subsurface_destroy (impl->subsurface);
-          impl->subsurface = NULL;
-        }
-
-      if (parent && gdk_window_is_visible (window))
-        gdk_wayland_window_create_subsurface (window);
-    }
+  if (GDK_WINDOW_TYPE (window) == GDK_WINDOW_SUBSURFACE &&
+      parent && gdk_window_is_visible (window))
+    gdk_wayland_window_create_subsurface (window);
 }
 
 static void
@@ -2392,6 +2430,13 @@ _gdk_window_impl_wayland_class_init (GdkWindowImplWaylandClass *klass)
   impl_class->show_window_menu = gdk_wayland_window_show_window_menu;
   impl_class->create_gl_context = gdk_wayland_window_create_gl_context;
   impl_class->invalidate_for_new_frame = gdk_wayland_window_invalidate_for_new_frame;
+
+  signals[COMMITTED] = g_signal_new ("committed",
+                                     G_TYPE_FROM_CLASS (object_class),
+                                     G_SIGNAL_RUN_LAST,
+                                     0,
+                                     NULL, NULL, NULL,
+                                     G_TYPE_NONE, 0);
 }
 
 void