[mutter] clutter/stage-cogl: Protect against extremely high refresh rates

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

commit 1dbf25afa15779d922ed66ddfb8bcda205ae7494
Author: Georges Basile Stavracas Neto <georges stavracas gmail com>
Date:   Fri Jun 7 12:12:55 2019 -0300

    clutter/stage-cogl: Protect against extremely high refresh rates
    
    After 4faeb12731b8, the maximum time allowed for an update to happen
    is calculated as:
    
      max_render_time_allowed = refresh_interval - 1000 * sync_delay;
    
    However, extremely small refresh intervals -- that come as consequence
    to extremely high refresh rates -- may fall into an odd numerical range
    when refresh_interval < 1000 * sync_delay. That would give us a negative
    time.
    
    To be extra cautious about it, add another sanity check for this case.
    
    Change suggested by Jasper St. Pierre.
    
    https://gitlab.gnome.org/GNOME/mutter/merge_requests/363

 clutter/clutter/cogl/clutter-stage-cogl.c | 11 +++++++++++
 1 file changed, 11 insertions(+)
---
diff --git a/clutter/clutter/cogl/clutter-stage-cogl.c b/clutter/clutter/cogl/clutter-stage-cogl.c
index 03f067267..5b6eeb8bf 100644
--- a/clutter/clutter/cogl/clutter-stage-cogl.c
+++ b/clutter/clutter/cogl/clutter-stage-cogl.c
@@ -199,6 +199,17 @@ clutter_stage_cogl_schedule_update (ClutterStageWindow *stage_window,
   min_render_time_allowed = refresh_interval / 2;
   max_render_time_allowed = refresh_interval - 1000 * sync_delay;
 
+  /* Be robust in the case of incredibly bogus refresh rate */
+  if (max_render_time_allowed <= 0)
+    {
+      g_warning ("Unsupported monitor refresh rate detected. "
+                 "(Refresh rate: %.3f, refresh interval: %ld)",
+                 refresh_rate,
+                 refresh_interval);
+      stage_cogl->update_time = now;
+      return;
+    }
+
   if (min_render_time_allowed > max_render_time_allowed)
     min_render_time_allowed = max_render_time_allowed;