[mutter] clutter/frame-clock: Ignore missing presentation timestamps

[Georges Basile Stavracas Neto <gbsneto src gnome org>]

commit b4fff403b89f516ce239f9fc39d526deaee1eb17
Author: Dor Askayo <dor askayo gmail com>
Date:   Sun Jun 26 11:19:18 2022 +0300

    clutter/frame-clock: Ignore missing presentation timestamps
    
    In some hardware configurations, presentation timestamps could be
    missing from some page flip events, leading to a temporary loss of
    vblank synchronization.
    
    This occurs at least with AMD GPUs for atomic commits that only update
    the cursor plane. [0]
    
    In those cases, it's better to calculate the next update time
    according to the last valid presentation timestamp instead of relying
    on the dispatch lateness.
    
    [0] https://gitlab.freedesktop.org/drm/amd/-/issues/2030
    
    Part-of: <https://gitlab.gnome.org/GNOME/mutter/-/merge_requests/2481>

 clutter/clutter/clutter-frame-clock.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)
---
diff --git a/clutter/clutter/clutter-frame-clock.c b/clutter/clutter/clutter-frame-clock.c
index ad306225c8..cf740adc3b 100644
--- a/clutter/clutter/clutter-frame-clock.c
+++ b/clutter/clutter/clutter-frame-clock.c
@@ -270,7 +270,8 @@ clutter_frame_clock_notify_presented (ClutterFrameClock *frame_clock,
     }
 #endif
 
-  frame_clock->last_presentation_time_us = frame_info->presentation_time;
+  if (frame_info->presentation_time > 0)
+    frame_clock->last_presentation_time_us = frame_info->presentation_time;
 
   frame_clock->got_measurements_last_frame = FALSE;