WIP: clutter/stage-cogl: Factor in pending_swaps to next_presentation_time [performance]
get_update_time
was returning -1
in some cases even if schedule_update
was called prior. So the master clock was overshooting the correct update
time and missing some frames. This seems to be happening most under moderate
CPU load (gnome-shell#1411 (closed)), but not so high a load as to justify the frame
skips that were occurring.
The reason for get_update_time
returning -1
in these cases was because
it was considered impossible to calculate the next update time while
pending_swaps > 0
. That's not completely true. We know if
pending_swaps == 1
then schedule_update
should schedule one frame later.
So just factor pending_swaps
into schedule_update
. Now get_update_time
won't return -1
in these cases so we're more likely to render the next
frame (or move the cursor) at the correct time.
Closes: gnome-shell#1411 (closed)
Prerequisite (just FYI for backporters): !216 (merged)