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clutter/frame-clock: Apply error diffusion (dithering) to dispatch times

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But only the dispatch times used when `last_presentation_time_us == 0`
(Nvidia + Xorg).

This ensures the average dispatch interval is always precisely equal
to the refresh interval, regardless of any jitter in the mainloop.

Fixes: https://gitlab.gnome.org/GNOME/mutter/-/issues/1751,
       https://gitlab.gnome.org/GNOME/mutter/-/issues/1758,
       https://gitlab.gnome.org/GNOME/mutter/-/issues/1870

Part-of: <https://gitlab.gnome.org/GNOME/mutter/-/merge_requests/1826>
This commit is contained in:
Daniel van Vugt 2021-04-15 20:30:31 +08:00
parent ba1490ec9c
commit 0555a5bbc1
1 changed files with 14 additions and 1 deletions
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15
clutter/clutter/clutter-frame-clock.c
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@ -86,6 +86,7 @@ struct _ClutterFrameClock
ClutterFrameClockState state;
int64_t last_dispatch_time_us;
int64_t last_dispatch_lateness_us;
int64_t last_presentation_time_us;
gboolean is_next_presentation_time_valid;
@ -378,7 +379,8 @@ calculate_next_update_time_us (ClutterFrameClock *frame_clock,
{
*out_next_update_time_us =
frame_clock->last_dispatch_time_us ?
frame_clock->last_dispatch_time_us + refresh_interval_us :
((frame_clock->last_dispatch_time_us -
frame_clock->last_dispatch_lateness_us) + refresh_interval_us) :
now_us;
*out_next_presentation_time_us = 0;
@ -613,9 +615,20 @@ clutter_frame_clock_dispatch (ClutterFrameClock *frame_clock,
{
int64_t frame_count;
ClutterFrameResult result;
int64_t ideal_dispatch_time_us, lateness_us;
COGL_TRACE_BEGIN_SCOPED (ClutterFrameClockDispatch, "Frame Clock (dispatch)");
ideal_dispatch_time_us = (frame_clock->last_dispatch_time_us -
frame_clock->last_dispatch_lateness_us) +
frame_clock->refresh_interval_us;
lateness_us = time_us - ideal_dispatch_time_us;
if (lateness_us < 0 || lateness_us >= frame_clock->refresh_interval_us)
frame_clock->last_dispatch_lateness_us = 0;
else
frame_clock->last_dispatch_lateness_us = lateness_us;
frame_clock->last_dispatch_time_us = time_us;
g_source_set_ready_time (frame_clock->source, -1);