[PATCH weston v2 10/11] [RFC] Account for very large repaint window misses

Daniel Stone daniels at collabora.com
Wed Mar 1 11:34:09 UTC 2017

At the bottom of weston_output_finish_frame(), code exists to account
for flips which have missed the repaint window, by shifting them to lock
on to the next repaint window rather than repainting immediately.

This code only accounted for flips which missed their target by one
repaint window. If they miss by multiples of the repaint window, adjust
them until the next repaint timestamp is in the future.

I was unable to find from discussion of the original development whether
or not this is desirable; I can see an argument both ways. Hence, RFC

Signed-off-by: Daniel Stone <daniels at collabora.com>
Cc: Pekka Paalanen <pekka.paalanen at collabora.co.uk>
Cc: Mario Kleiner <mario.kleiner.de at gmail.com>
 libweston/compositor.c | 11 ++++++++---
 1 file changed, 8 insertions(+), 3 deletions(-)

v2: New in this revision. Unsure if necessary or not.

diff --git a/libweston/compositor.c b/libweston/compositor.c
index a64e695..511f85a 100644
--- a/libweston/compositor.c
+++ b/libweston/compositor.c
@@ -2485,9 +2485,14 @@ weston_output_finish_frame(struct weston_output *output,
 	 * the deadline given by repaint_msec? In that case we delay until
 	 * the deadline of the next frame, to give clients a more predictable
 	 * timing of the repaint cycle to lock on. */
-	if (presented_flags == WP_PRESENTATION_FEEDBACK_INVALID && msec_rel < 0)
-		timespec_add_nsec(&output->next_repaint, &output->next_repaint,
-				  refresh_nsec);
+	if (presented_flags == WP_PRESENTATION_FEEDBACK_INVALID &&
+	    msec_rel < 0) {
+		while (timespec_sub_to_nsec(&output->next_repaint, &now) < 0) {
+			timespec_add_nsec(&output->next_repaint,
+					  &output->next_repaint,
+					  refresh_nsec);
+		}
+	}
 	output->repaint_status = REPAINT_SCHEDULED;

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