unique id for wayland objects

Pekka Paalanen ppaalanen at gmail.com
Sat May 12 15:17:14 UTC 2018

On Thu, 10 May 2018 12:53:49 +0800
zou lan <nancy.lan.zou at gmail.com> wrote:

> Hi pekka
> I test presentation on my side. The presentation results is not accurate
> because our pageflip event send last frame's timestamp every time. So
> weston_output_finish_frame send last frame's present tine
> to current frame's feedback. For this situation, I just delay one frame to
> send present event. Does this get the right c2p time? Thank you.

Hi Nancy,

I think your driver needs to get fixed, so that it provides the
correct timestamp instead of an outdated one. If this is a kernel
DRM driver, then the behaviour you describe is clearly a bug. The
timestamp of the pageflip event signifies the time the new frame
starts transmitting out of the connector. I believe there should be
DRM driver API documentation stating that.

This is also what weston_output_finish_frame() expects. Anything
else will cause the frame scheduling to misbehave.

It may be possible to work around the bug as you suggest, but that
will make the compositor incorrect on any other driver, and it may
cause other subtle breakage (the timestamp may be correct, but the
time the event gets sent is now wrong and might even be delayed
indefinitely if nothing causes a repaint).

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