1229946 - [Skia-update branch] GrClipMaskManager.cpp:406: failed assertion "result"

Status: RESOLVED FIXED

(Core :: Graphics, defect)

Description

[Jesse Ruderman]

Attachment: testcase

Using the Mac build from https://treeherder.mozilla.org/#/jobs?repo=try&revision=91dc4f334fc5

(This does NOT reproduce on mozilla-central because bug 1082598 has not landed yet.)

gfx/skia/skia/src/gpu/GrClipMaskManager.cpp:406: failed assertion "result"

Comment 1

[Jesse Ruderman]

Attachment: stack

Comment 2

[Lee Salzman [:lsalzman]]

I was not able to reproduce this on Linux. We should check after the Skia update if this is OS X specific.

Comment 3

[Daniel Veditz [:dveditz]]

Jesse: does this still reproduce?

Comment 4

[Milan Sreckovic [:milan] (needinfo for best results)]

I can reproduce it on OS X.  The comment around the assertion is "If createAlphaClipMask fails it means useSWOnlyPath has a bug"

Comment 5

[Lee Salzman [:lsalzman]]

I still can't get this one to reproduce here, so it is somehow localized to OS X and not just SkiaGL.

Mason, do you want to take a look into this one since it should be easy for you to pinpoint?

Comment 6

[Lee Salzman [:lsalzman]]

Attachment: report GL_ARB_texture_rg extension to SkiaGL to avoid using GL_ALPHA render targets

So after investigation with Mason, we found this bug is a result of the SkiaGL backend creating clip masks using a GL_ALPHA8 render target.

The problem is the FBO spec is somewhat "nebulous" on this, or at least confusing, and while the spec says ALPHA8 should be color-renderable in compatibility contexts, OS X is still reporting framebuffer incompleteness when trying to use them (there is potentially room for this in the "implementation-dependent" get-out-of-jail-free clause). So it could be Skia is wrong to assume this, or that the OS X implementation of legacy compatibility contexts is not quite right.

In any case, we have a workaround in that Skia will use GL_RED8 instead of GL_ALPHA8 so long as we report GL_ARB_texture_rg in the extension string.

This patch detects the GL_ARB_texture_rg extension and also adds a feature entry for it, since an implementation may only report it via GL version and not via extension (as OS X does). This should pretty much always be present if the context if 3.0+ or GL_ARB_framebuffer_object is present on OS X.

With this, Skia uses GL_RED8 for the clip mask and all is well.

Comment 7

[Lee Salzman [:lsalzman]]

Try run: https://treeherder.mozilla.org/#/jobs?repo=try&revision=f895173ce18e

Comment 8

[Pulsebot]

https://hg.mozilla.org/integration/mozilla-inbound/rev/39a20fcf9976

Comment 9

[Wes Kocher (:KWierso) (Not reading bugmail; email directly if needed)]

https://hg.mozilla.org/mozilla-central/rev/39a20fcf9976