1541396 - WebGL 2 Transform Feedback Broken (generic bind point blocking non-TF use)

Status: VERIFIED FIXED

(Core :: Graphics: CanvasWebGL, defect, P1)

Description

[tareksherif]

User Agent: Mozilla/5.0 (Windows NT 10.0; Win64; x64; rv:66.0) Gecko/20100101 Firefox/66.0

Steps to reproduce:

Go to this page: https://tsherif.github.io/webgl2bugs/firefox/transform-feedback-unbind.html

Actual results:

Point doesn't animate

Expected results:

Point should animate.

The problem seems to be that when a buffer is bound to TRANSFORM_FEEDBACK_BUFFER it gets bound to the current transform feedback object as well as the default one. The TRANSFORM_FEEDBACK_BUFFER on the default transform feedback object then has to be explicitly unbound. See comments in the source code for details: https://github.com/tsherif/webgl2bugs/blob/master/firefox/transform-feedback-unbind.html

Broken on both Windows 10 and Ubuntu 16.04. Works in Chrome on both.

Comment 1

[Aria Beingessner [:Gankra]]

ni?jgilbert to confirm we're misimplementing semantics here

Comment 2

[Kelsey Gilbert [:jgilbert]]

(In reply to tareksherif from comment #0)

User Agent: Mozilla/5.0 (Windows NT 10.0; Win64; x64; rv:66.0) Gecko/20100101 Firefox/66.0

Steps to reproduce:

Go to this page: https://tsherif.github.io/webgl2bugs/firefox/transform-feedback-unbind.html

Actual results:

Point doesn't animate

Expected results:

Point should animate.

The problem seems to be that when a buffer is bound to TRANSFORM_FEEDBACK_BUFFER it gets bound to the current transform feedback object as well as the default one. The TRANSFORM_FEEDBACK_BUFFER on the default transform feedback object then has to be explicitly unbound. See comments in the source code for details: https://github.com/tsherif/webgl2bugs/blob/master/firefox/transform-feedback-unbind.html

Broken on both Windows 10 and Ubuntu 16.04. Works in Chrome on both.

The TF Buffer object is probably still bound to the TRANSFORM_FEEDBACK_BUFFER non-indexed bind point, which Firefox still treats as "bound for transform feedback".

A workaround is to call bindBuffer(TRANSFORM_FEEDBACK_BUFFER, null) after bindBufferBase/Range(TRANSFORM_FEEDBACK_BUFFER, ...).

Comment 3

[Kelsey Gilbert [:jgilbert]]

Attachment: Bug 1541396 - Refactor (non-)transform-feedback binding/use checks.

• Remove WebGLBuffer::SetSlot
• Make most bindBuffer calls lazy.
• Replace nsTArray with std::vector in WebGLVertexArray.

Comment 5

[Kelsey Gilbert [:jgilbert]]

Attachment: Bug 1541396 - Raise INVALID_VALUE for BindBufferRange, size>buffer.size.

This lets us dodge an "unexpected GL error" assert due to differences in handling
between GLES3 and GL410 and below. (macOS)

Comment 6

[Kelsey Gilbert [:jgilbert]]

Attachment: Bug 1541396 - Raise INVALID_VALUE for BindBufferRange, size>buffer.size.

This lets us dodge an "unexpected GL error" assert due to differences in handling
between GLES3 and GL410 and below. (macOS)

Comment 7

[Kelsey Gilbert [:jgilbert]]

Attachment: Bug 1541396 - Add GLBuffer prebind workaround.

BindBufferBase/Range will fail (on some drivers) if the buffer name has never been bound.
(GenBuffers makes a name, but BindBuffer initializes that name as a real buffer object)

Comment 8

[Pulsebot]

Pushed by [e-mail]:
https://hg.mozilla.org/integration/autoland/rev/0c28fedb2c6a
Refactor (non-)transform-feedback binding/use checks. r=lsalzman
https://hg.mozilla.org/integration/autoland/rev/979f1395a70c
Add GLBuffer prebind workaround. r=lsalzman

Comment 9

[Andreea Pavel [:apavel]]

https://hg.mozilla.org/mozilla-central/rev/0c28fedb2c6a
https://hg.mozilla.org/mozilla-central/rev/979f1395a70c

Comment 10

[Negritas Sergiu, Desktop QA]

Following the STR from the description, I reproduced this issue using Fx 68.0a1(2018-04-03) on Ubuntu 18.04 LTS and on Windows 10 using the same Fx version. I can confirm that this issue is fixed using Fx 69.0b13 on the same environments.

Comment 11

[Cristian Comorasu, QA [:ccomorasu], Releae Desktop QA - Please contact [e-mail]]

Thank you, Sergiu!