1060573 - WebGL: gl_FragDepth not actually implemented

Status: RESOLVED INVALID

(Core :: Graphics: CanvasWebGL, defect)

Description

[David Koes]

Attachment: fragdepth.html

User Agent: Mozilla/5.0 (X11; Ubuntu; Linux x86_64; rv:31.0) Gecko/20100101 Firefox/31.0 (Beta/Release)
Build ID: 20140715214327

Steps to reproduce:

I tried to use gl_FragDepthEXT in a shader after calling gl.getExtension('EXT_frag_depth') to enable the extension.  I have attached a short example file.


Actual results:

I get an "extension is disabled" error.


Expected results:

I would expect gl_FragDepthEXT to work, or for it not to be listed as a supported extension.  In poking through the source code, the most likely source of this error message seems to be in the function extensionErrorCheck in
firefox/gfx/angle/src/compiler/translator/ParseContext.cpp
were the error is produced if the extension behavior is set to EBhUndefined.  In 
firefox/gfx/angle/src/compiler/translator/Initialize.cpp
several extensions, included GL_EXT_frag_depth, are set to have undefined behavior and I do not see how it would be possible for the behavior to change.

The ideal fix is to implement EXT_frag_depth.  If this isn't possible, it should not be listed as a supported extension.

Comment 1

[Francisco]

(In reply to David Koes from comment #0)
> Created attachment 8481563 [details]
> fragdepth.html
> 
> User Agent: Mozilla/5.0 (X11; Ubuntu; Linux x86_64; rv:31.0) Gecko/20100101
> Firefox/31.0 (Beta/Release)
> Build ID: 20140715214327
> 
> Steps to reproduce:
> 
> I tried to use gl_FragDepthEXT in a shader after calling
> gl.getExtension('EXT_frag_depth') to enable the extension.  I have attached
> a short example file.
> 
> 
> Actual results:
> 
> I get an "extension is disabled" error.
> 
> 
> Expected results:
> 
> I would expect gl_FragDepthEXT to work, or for it not to be listed as a
> supported extension.  In poking through the source code, the most likely
> source of this error message seems to be in the function extensionErrorCheck
> in
> firefox/gfx/angle/src/compiler/translator/ParseContext.cpp
> were the error is produced if the extension behavior is set to EBhUndefined.
> In 
> firefox/gfx/angle/src/compiler/translator/Initialize.cpp
> several extensions, included GL_EXT_frag_depth, are set to have undefined
> behavior and I do not see how it would be possible for the behavior to
> change.
> 
> The ideal fix is to implement EXT_frag_depth.  If this isn't possible, it
> should not be listed as a supported extension.

Have you tried placing this GLSL directive in your shader code?

#extension GL_EXT_frag_depth : enable

Comment 2

[David Koes]

That was the problem.