[gtk: 3/8] frame clock: Use compositor refresh rate info even if presentation time not set

[Alexander Larsson <alexl src gnome org>]

commit f1215d2d776dd44e389b7c141eaac3f72942deae
Author: Alexander Larsson <alexl redhat com>
Date:   Fri May 22 15:30:05 2020 +0200

    frame clock: Use compositor refresh rate info even if presentation time not set
    
    On my X11 + nvidia setup gnome-shell doesn't report presentation times.
    However it does report refresh rate. We were mostly using this in our
    calculation except when computing predicted presentation time, were
    it fell back on the default 60Hz.

 gdk/gdkframeclock.c | 25 +++++++++++++++----------
 1 file changed, 15 insertions(+), 10 deletions(-)
---
diff --git a/gdk/gdkframeclock.c b/gdk/gdkframeclock.c
index fc0fbe6b8c..04dfd93c7b 100644
--- a/gdk/gdkframeclock.c
+++ b/gdk/gdkframeclock.c
@@ -599,16 +599,12 @@ gdk_frame_clock_get_refresh_info (GdkFrameClock *frame_clock,
                                   gint64        *presentation_time_return)
 {
   gint64 frame_counter;
+  gint64 default_refresh_interval = DEFAULT_REFRESH_INTERVAL;
 
   g_return_if_fail (GDK_IS_FRAME_CLOCK (frame_clock));
 
   frame_counter = gdk_frame_clock_get_frame_counter (frame_clock);
 
-  if (presentation_time_return)
-    *presentation_time_return = 0;
-  if (refresh_interval_return)
-    *refresh_interval_return = DEFAULT_REFRESH_INTERVAL;
-
   while (TRUE)
     {
       GdkFrameTimings *timings = gdk_frame_clock_get_timings (frame_clock, frame_counter);
@@ -616,19 +612,21 @@ gdk_frame_clock_get_refresh_info (GdkFrameClock *frame_clock,
       gint64 refresh_interval;
 
       if (timings == NULL)
-        return;
+        break;
 
       refresh_interval = timings->refresh_interval;
       presentation_time = timings->presentation_time;
 
+      if (refresh_interval == 0)
+        refresh_interval = default_refresh_interval;
+      else
+        default_refresh_interval = refresh_interval;
+
       if (presentation_time != 0)
         {
           if (presentation_time > base_time - MAX_HISTORY_AGE &&
               presentation_time_return)
             {
-              if (refresh_interval == 0)
-                refresh_interval = DEFAULT_REFRESH_INTERVAL;
-
               if (refresh_interval_return)
                 *refresh_interval_return = refresh_interval;
 
@@ -637,13 +635,20 @@ gdk_frame_clock_get_refresh_info (GdkFrameClock *frame_clock,
 
               if (presentation_time_return)
                 *presentation_time_return = presentation_time;
+
+              return;
             }
 
-          return;
+          break;
         }
 
       frame_counter--;
     }
+
+  if (presentation_time_return)
+    *presentation_time_return = 0;
+  if (refresh_interval_return)
+    *refresh_interval_return = default_refresh_interval;
 }
 
 void