742460 - ANGLE fails to validate a seemingly valid shader

Status: RESOLVED INVALID

(Core :: Graphics: CanvasWebGL, defect)

Description

[(no longer active)]

The shader source is here: https://gist.github.com/2304593

Disabling webgl.shader_validator makes the shader compile successfully.  According to Behdad this also happens in Chrome, which makes it very likely to be an Angle bug.

Comment 1

[Behdad Esfahbod]

So, the shader is buggy in that it doesn't have a precision for float as the first thing in the code.  However, the fact that the error message doesn't make it out is a bug.  I found this by testing the shader at:

  http://www.iquilezles.org/apps/shadertoy/

Comment 2

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

Looked at it with Ehsan; there is no ANGLE bug here. precision qualifiers are mandatory in GLSL ES fragment shader, fixed by adding:

  precision mediump float;

The other errors relate to usage of standard derivatives, which are an extension in OpenGL ES and in WebGL, and WebGL extensions must be explicitly enabled. WebGL's version of that extension also requires shaders using this feature to start with
#extension GL_OES_standard_derivatives : enable

See:
http://www.khronos.org/registry/webgl/extensions/OES_standard_derivatives/

Comment 3

[Behdad Esfahbod]

Well, as I said, the error is that with angle enabled, these errors are NOT reported back to the user through the shader log API.  But Ehsan said he'll open another bug for that.

Comment 4

[(no longer active)]

Filed bug 724490.

Comment 5

[Behdad Esfahbod]

(In reply to Ehsan Akhgari [:ehsan] from comment #4)
> Filed bug 724490.

Wrong number?  bug 742490 perhaps?

Comment 6

[(no longer active)]

(In reply to Behdad Esfahbod from comment #5)
> (In reply to Ehsan Akhgari [:ehsan] from comment #4)
> > Filed bug 724490.
> 
> Wrong number?  bug 742490 perhaps?

Yep.