GdkWindowX11: start off with an odd frame-counter value

By starting with an odd frame counter value, we make the mapping
and initial paint of the window an atomic operation, avoiding
any visual artifacts from an unpainted window.

Possible improvement: start the frame when doing gdk_window_show(),
so that the same improvement occurs for windows that were previously
shown and are being mapped again.

https://bugzilla.gnome.org/show_bug.cgi?id=685460

diff --git a/gdk/x11/gdkwindow-x11.c b/gdk/x11/gdkwindow-x11.c
index f6af492277755ec917f7d6225d1cebc8964ea685..fbc13b56540aedb722fba3ac9f26e734328805db 100644 (file)
--- a/gdk/x11/gdkwindow-x11.c
+++ b/gdk/x11/gdkwindow-x11.c
@@ -226,10 +226,13 @@ gdk_x11_window_begin_frame (GdkWindow *window)
       impl->toplevel->extended_update_counter == None)
     return;
 
-  impl->toplevel->current_counter_value += 1;
-  set_sync_counter(GDK_WINDOW_XDISPLAY (impl->wrapper),
-                  impl->toplevel->extended_update_counter,
-                  impl->toplevel->current_counter_value);
+  if (impl->toplevel->current_counter_value % 2 == 0)
+    {
+      impl->toplevel->current_counter_value += 1;
+      set_sync_counter(GDK_WINDOW_XDISPLAY (impl->wrapper),
+                      impl->toplevel->extended_update_counter,
+                      impl->toplevel->current_counter_value);
+    }
 }
 
 static void
@@ -245,16 +248,19 @@ gdk_x11_window_end_frame (GdkWindow *window)
       impl->toplevel->extended_update_counter == None)
     return;
 
-  impl->toplevel->current_counter_value += 1;
-  set_sync_counter(GDK_WINDOW_XDISPLAY (impl->wrapper),
-                  impl->toplevel->extended_update_counter,
-                  impl->toplevel->current_counter_value);
-
-  if (gdk_x11_screen_supports_net_wm_hint (gdk_window_get_screen (window),
-                                           gdk_atom_intern_static_string ("_NET_WM_FRAME_DRAWN")))
+  if (impl->toplevel->current_counter_value % 2 == 1)
     {
-      impl->toplevel->frame_pending = TRUE;
-      gdk_frame_clock_freeze (gdk_window_get_frame_clock (window));
+      impl->toplevel->current_counter_value += 1;
+      set_sync_counter(GDK_WINDOW_XDISPLAY (impl->wrapper),
+                      impl->toplevel->extended_update_counter,
+                      impl->toplevel->current_counter_value);
+
+      if (gdk_x11_screen_supports_net_wm_hint (gdk_window_get_screen (window),
+                                              gdk_atom_intern_static_string ("_NET_WM_FRAME_DRAWN")))
+        {
+          impl->toplevel->frame_pending = TRUE;
+          gdk_frame_clock_freeze (gdk_window_get_frame_clock (window));
+        }
     }
 }
 
@@ -760,6 +766,9 @@ setup_toplevel_window (GdkWindow *window,
     gdk_x11_window_set_user_time (window, GDK_X11_DISPLAY (x11_screen->display)->user_time);
 
   ensure_sync_counter (window);
+
+  /* Start off in a frozen state - we'll finish this when we first paint */
+  gdk_x11_window_begin_frame (window);
 }
 
 static void