Basic framework for support of the OES_standard_derivatives.

[bhouston]

So I've done a bit of the work to support the OES_standard_derivates extension, but it is not complete. I am missing how to integrate it with ANGLE. I notice in the angle code base there is extensions.standardDerivates but I do not see how it is set:

I would appreciate some guidance or some existing example code to follow. Maybe I should be looking at the Chromium source code?

If we could figure out how to do this glue to ANGLE we can likely support a ton of extensions quite quickly.

Thanks for any help.

[mikolalysenko]

Extra semicolon

[mikolalysenko]

In order to enable the extension we'll need to stick the following preprocessor directive in the head of each shader:

#extension GL_OES_standard_derivatives : enable

I think the right way to do this would be to have the WebGL context track a list of all shader extensions, then when it is enabled prepend it to all future created shaders when enabled. We should also use the #line directive to make sure that source maps don't get screwed up. So in shaderSource we'd do something like prepend the lines:

#extension GL_OES_standard_derivatives : enable
// ... and any other extensions ...
#line 1

[bhouston]

I know that if you want to use this in WebGL, you need to start your share with:

#extension GL_OES_standard_derivatives : enable

I sort of figured that this WebGL glsl directive was converted automatically into OpenGL via the ANGLE project? Or am I mistaken. I guess I keep expecting it to work easily because ANGLE already supports this extension (as well as quite a few others.)

[mikolalysenko]

Yeah, disregard that last remark, I was confused. I think you should just be able to query the extension from ANGLE and load it directly. Can't dig into it right now, my attention is split a bit.

[bhouston]

@mikolalysenko, Okay I understand. Let me know if you wanted compensation for your time to help make this library better. We can offer some.

[mhirsch]

What's the status of this? Does it work? Can it be merged? Wouldn't this approach work for other extensions?