1464679 - Only use _NET_WM_BYPASS_COMPOSITOR hint with Basic compositor

Status: RESOLVED FIXED

(Core :: Graphics, enhancement, P3)

Description

[Ryan Hendrickson [rhendric on GitLab, GitHub]]

I see from bug 1134077 that the _NET_WM_BYPASS_COMPOSITOR hint was added to Firefox windows to resolve video tearing; however, on versions of Firefox prior to 60, I didn't have any issues with fullscreen videos (I am admittedly voiding my warranty with media.hardware-video-decoding.force-enabled, which on my hardware is the only way I've found to get decent video performance at all). Since upgrading to 60, however, fullscreen videos have more latency and the video lags behind the audio, and I only just figured out that this change was to blame—when I remove that hint, video goes back to its pre-60 performance.

Can you please make this hint controllable with an about:config preference? I'm fine with the hint being present by default, since it seems like you have a logical justification for setting it, but at least for me (and I would assume some other power users as well), having the ability to disable it is necessary to make videos watchable on Firefox.

Comment 1

[Ryan Hendrickson [rhendric on GitLab, GitHub]]

Attachment: Bug 1464679 - X11: Only use _NET_WM_BYPASS_COMPOSITOR hint with Basic compositor. r?karlt

Comment 2

[Karl Tomlinson (:karlt)]

What is "Compositing" in about:support?

If it is not "Basic", then framebuffer updates probably are aligned with vblank, in which case _NET_WM_BYPASS_COMPOSITOR should not be set.
It would be better to do this automatically than to require an additional preference to be set.

Comment 3

[Ryan Hendrickson [rhendric on GitLab, GitHub]]

I have OpenGL for Compositing, so that sounds like a good idea to me!

Comment 4

[Pulsebot]

Pushed by [e-mail]:
https://hg.mozilla.org/integration/autoland/rev/a0315e4606c7
X11: Only use _NET_WM_BYPASS_COMPOSITOR hint with Basic compositor. r=karlt

Comment 5

[Daniel Varga [:dvarga]]

https://hg.mozilla.org/mozilla-central/rev/a0315e4606c7