Make process_all_updates draw synchronously

By calling XSync in _gdk_x11_display_after_process_all_updates we
effectively make gdk rendering sync, which avoids problems with the
client animations running faster than the Xserver rendering, thus
filling up the X rendering pipes and essentially "locking up" the
Xserver (i.e. you can't even close the offending window because the
WM is starved too).

I verified this worked by making GtkSpinner paint multiple times on my
intel driver (which has some issue making this rendering slow atm),
and without this patch i get severe lag where even window dragging
stops for 5 seconds when i drag the mouse around. However, with the
patch everything is smooth.

https://bugzilla.gnome.org/show_bug.cgi?id=684639

diff --git a/gdk/x11/gdkwindow-x11.c b/gdk/x11/gdkwindow-x11.c
index 4ef6f46f8a76ff08bebd4188f938d788040a125b..e4b880f6b3c7e1690f01a04919e2adddd3edcd75 100644 (file)
--- a/gdk/x11/gdkwindow-x11.c
+++ b/gdk/x11/gdkwindow-x11.c
@@ -4858,6 +4858,11 @@ _gdk_x11_display_before_process_all_updates (GdkDisplay *display)
 void
 _gdk_x11_display_after_process_all_updates (GdkDisplay *display)
 {
+  /* Sync after all drawing, otherwise the client can get "ahead" of
+     the server rendering during animations, such that we fill up
+     the Xserver pipes with sync rendering ops not letting other
+     clients (including the VM) do anything. */
+  XSync (GDK_DISPLAY_XDISPLAY (display), FALSE);
 }
 
 static Bool