1316310 - WebGL 2.0 sample http://webglsamples.org/WebGL2Samples/#draw_primitive_restart is not working

Status: RESOLVED FIXED

(Core :: Graphics: CanvasWebGL, defect, P3)

Description

[Mihai Boldan, Desktop QA [:mboldan]]

[Affected versions]:
- Firefox 51.0a2(2016-11-08), Firefox 52.0a1(2016-11-08)

[Affected platforms]:
- Windows 10x64, Mac OS X 10.11.6, Ubuntu 16.04x64

[Steps to reproduce]:
1. Launch Firefox.
2. Open http://webglsamples.org/WebGL2Samples/.
3. Select the sample draw_primitive_restart, or the sample transform_feedback_separated_2.   

[Expected result]:
- Both samples are correctly displayed.

[Actual result]:
- A black screen is displayed.

[Regression range]:
- This is not a regression.

[Additional notes]:
- Here are the errors thrown in the Browser console -  http://pastebin.com/eE7z7NUL
- Note that the samples are correctly displayed on Chrome Canary.

Comment 3

[Petruta Horea [:phorea]]

Comment 0 mentions 2 samples that weren't working. Only one of them was fixed in bug 1320500.

http://webglsamples.org/WebGL2Samples/#draw_primitive_restart is still affected, reopening.

Comment 4

[Kelsey Gilbert [:jgilbert]]

With my local changes, there are now two differing tests:
* fbo_blit (which actually seems to work fine in Nightly!)
* texture_vertex (Chrome Canary has flickering, Nightly has a moire artifact instead)

draw_primitive_restart is I think fixed by bug 1324972.

Comment 5

[Kelsey Gilbert [:jgilbert]]

fbo_blit looks different on Chrome+Win, but the same on all of [Firefox Win/OSX, Chrome OSX]. Calling that a likely Chrome+Win bug.

Comment 6

[Kelsey Gilbert [:jgilbert]]

After much debugging, the difference in behavior on "texture_vertex" between Firefox+ANGLE and everything else (even Firefox+Win+GL) turns out to be our choice for depth format for {depth:true, stencil:false} contexts.

Adding stencil:true to the context creation attribs causes the behavior of Firefox+ANGLE to match everything else. Of course, there's still some flickering, and that's because it looks like the depth buffer isn't cleared properly. I believe the reason it seems to render at all is that we clear depth every time we Present the webgl buffer.

Link to PR:
https://github.com/WebGLSamples/WebGL2Samples/pull/137

Tomorrow's Nightly should have all the patches to fix this. (at least "draw_primitive_restart" is still broken)