719986 - (blacklist-xrender) Blacklist XRender on machines where it's not useful

Status: RESOLVED WONTFIX

(Core :: Graphics, defect)

Description

[Jeff Muizelaar [:jrmuizel]]

There are lots of places where XRender is worse than software. We should use software in those cases.

Comment 1

[Benoit Jacob [:bjacob] (mostly away)]

If we have a choice, we should probably never use XRender, if only because it's at least blocking us from upgrading the NVIDIA driver on linux slaves (bug 684165) which is a blocker for enabling GL layers acceleration. Also, if we could not use X pixmaps at all that would allow us to avoid bad interaction with GL which is likely a blocker for GL layers too (see blockers of bug 594876).

I hope that Skia would give us that, but if you know a quick way to do that with Cairo, by all means do it.

Comment 2

[Jeff Muizelaar [:jrmuizel]]

(In reply to Benoit Jacob [:bjacob] from comment #1)
> If we have a choice, we should probably never use XRender, if only because
> it's at least blocking us from upgrading the NVIDIA driver on linux slaves
> (bug 684165) which is a blocker for enabling GL layers acceleration. Also,
> if we could not use X pixmaps at all that would allow us to avoid bad
> interaction with GL which is likely a blocker for GL layers too (see
> blockers of bug 594876).
> 
> I hope that Skia would give us that, but if you know a quick way to do that
> with Cairo, by all means do it.

Yes. We can just use cairo image surfaces. There are no problems that Skia solves here beyond some extra performance in some situations.

Comment 3

[Benoit Jacob [:bjacob] (mostly away)]

The problem that skia solves is that there are people working on the patch in bug 702158.

If it's easy to switch cairo to the image backend, please do it.

Comment 4

[Karl Tomlinson (:karlt)]

Blacklisting XRender where there are serious problems makes sense, and perhaps even on platforms where XRender uses software it may be a win.

(In reply to Benoit Jacob [:bjacob] from comment #3)
> If it's easy to switch cairo to the image backend, please do it.

It's easy to switch, but hard to make it fast.

Any advantages of switching off XRender have to be weighed against the disadvantages of turning off 2D acceleration and having to read back GTK2 themes from VRAM.

http://www.hackermusings.com/2012/05/firefoxs-graphics-performance-on-x11/