Skip to content

Fix frameclock going backwards

Alexander Larsson requested to merge alexl/gtk:fix-frameclock-going-backwards into master

When we run the frameclock RUN_FLUSH_IDLE idle before the paint, then gdk_frame_clock_flush_idle() sets

  priv->phase = GDK_FRAME_CLOCK_PHASE_BEFORE_PAINT

at the end if there is a paint comming.

But, before doing the paint cycle it may handle other X events, and during that time the phase is set to BEFORE_PAINT. This means that the current check on whether we're inside a paint is wrong:

  if (priv->phase != GDK_FRAME_CLOCK_PHASE_NONE &&
     priv->phase != GDK_FRAME_CLOCK_PHASE_FLUSH_EVENTS)
    return priv->smoothed_frame_time_base;

This caused us to sometimes use this smoothed_frame_time_base even though we previously reported a later value during PHASE_NONE, thus being non-monotonic.

We can't just additionally check for the BEGIN_PAINT phase though, becasue if we are in the paint loop actually doing that phase we should use the time base. Instead we check for !(BEFORE_PAINT && in_paint_idle).

Merge request reports