[Bug 96847] TearFree breaks when playing back videos in Firefox with GPU accelerated windows enabled in Firefox

[bugzilla-daemon at freedesktop.org]

https://bugs.freedesktop.org/show_bug.cgi?id=96847

nw9165-3201 at yahoo.com changed:

           What    |Removed                     |Added
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                 CC|                            |Michael at phoronix.com

--- Comment #6 from nw9165-3201 at yahoo.com ---
(In reply to Chris Wilson from comment #5)
> Absolutely, since I wrote the code, I had to explicitly disable TearFree
> when PresentPixmap is called because a client calling PresentPixmap can then
> treat that Pixmap as a front buffer and directly render into it bypassing X.

Maybe it should be noted in the man page then?

> > By the way, if you want to reproduce the issue:
> > 
> > As far as I can tell, the issue is triggered by switching the YouTube video
> > player to fullscreen.
> 
> Worksforme.

Have you set "layers.acceleration.force-enabled" to "true" in about:config
(https://bugzilla.mozilla.org/show_bug.cgi?id=594876) in Firefox?

You need to enable it to trigger the issue. I just recently came across this
setting ("layers.acceleration.force-enabled"), and when I enabled it, I noticed
that TearFree breakup. Setting "layers.acceleration.force-enabled" to "true"
results in a much better Firefox performance, especially on videos.

By the way, when the issue occurs, the video doesn't tear. But when moving
windows around on the screen, you can notice some tearing on the windows, which
usually is not there.

> Who said that DRI3 was meant to provide a TearFree experience? That's not
> what we put together in the specification or the code. Also note that DRI3
> *cannot* provide TearFree updates in a variety of configurations

But could you please explain to me why DRI=3 + TearFree=False is resulting in
tearing, whereas DRI=3 + TearFree=True is resulting in no tearing? Surely
TearFree must be doing something in that case?

> and due to
> many limitations in the current implementation is often inferior to DRI2
> (such as multi-monitor rendering).

Hm, yet even Intel has DRI3 enabled by default in Clear Linux and it also
appears to provide better performance:

http://www.phoronix.com/scan.php?page=article&item=clear-ubuntu-fedxf&num=1
http://www.phoronix.com/scan.php?page=article&item=intel-skylake-dri3&num=1
http://www.phoronix.com/scan.php?page=news_item&px=DRI3-Xubuntu-16.04-Extra

Regards

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