728361 - WebGL getParameter(DEPTH_BITS) returns 0 on some platforms

Status: RESOLVED WORKSFORME

(Core :: Graphics: CanvasWebGL, defect)

Description

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

Just try it in the Web Console:

var ctx = document.createElement('canvas').getContext('experimental-webgl');
ctx.getParameter(ctx.DEPTH_BITS);

returns 0.

The impl is just forwarding this call to the GL. What might be happening is that since we're not using the main framebuffer of that GL context at all, we don't bother requiring a depth buffer for it at all. So this could be a regression from the switch to FBOs. But really we should keep track of these variables manually, not rely on the GL for that.

Comment 1

[Kelsey Gilbert [:jgilbert]]

GL will get the bits based on the current bound framebuffer.
This was probably a regression from when we were binding to 0 most of the time. However, now, we are properly bound to the correct buffers all the time.

Testing on linux (GLX only uses FBOs) with trunk, I get proper behavior.

bjacob, can you repro this anywhere? Also, this is marked as blocking conformance. Which test is hitting this? Is that test passing or failing now?

Comment 2

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

Indeed, I can't reproduce anymore.

IIRC this was not hit by a conformance test (whence the webgl-tests-needed).

Comment 3

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

Conformance tests added:

default framebuffer:
https://cvs.khronos.org/svn/repos/registry/trunk/public/webgl/sdk/tests/conformance/context/context-attributes-alpha-depth-stencil-antialias.html
(note that we fail this one!)

framebuffer objects:
https://cvs.khronos.org/svn/repos/registry/trunk/public/webgl/sdk/tests/conformance/renderbuffers/framebuffer-object-attachment.html