gdkframeclockidle: Don't permanently skew frame time

Since commit 3b2f9395, the frame time may be set into the future, so
only ensure monotonicity, and don't store the offset. This prevents the
frame time from becoming out of sync with g_get_monotonic_time().

Fixes #1612

diff --git a/gdk/gdkframeclockidle.c b/gdk/gdkframeclockidle.c
index 4a6ea108173af531caae67d6a12cb74cd7b59109..0e9bc3b1b7bb8ca4f1ebfc92c790f4df13fd9354 100644 (file)
--- a/gdk/gdkframeclockidle.c
+++ b/gdk/gdkframeclockidle.c
@@ -38,8 +38,6 @@
 
 struct _GdkFrameClockIdlePrivate
 {
-  /* timer_base is used to avoid ever going backward */
-  gint64 timer_base;
   gint64 frame_time;
   gint64 min_next_frame_time;
   gint64 sleep_serial;
@@ -160,22 +158,12 @@ compute_frame_time (GdkFrameClockIdle *idle)
 {
   GdkFrameClockIdlePrivate *priv = idle->priv;
   gint64 computed_frame_time;
-  gint64 elapsed;
 
-  elapsed = g_get_monotonic_time () + priv->timer_base;
-  if (elapsed < priv->frame_time)
-    {
-      /* clock went backward. adapt to that by forevermore increasing
-       * timer_base.  For now, assume we've gone forward in time 1ms.
-       */
-      /* hmm. just fix GTimer? */
+  computed_frame_time = g_get_monotonic_time ();
+
+  /* ensure monotonicity of frame time */
+  if (computed_frame_time <= priv->frame_time)
       computed_frame_time = priv->frame_time + 1;
-      priv->timer_base += (priv->frame_time - elapsed) + 1;
-    }
-  else
-    {
-      computed_frame_time = elapsed;
-    }
 
   return computed_frame_time;
 }