[Mesa-dev] [PATCH 1/2] glsl: always enable OES_standard_derivatives features if supported

[Timothy Arceri]

On 16/05/18 22:09, Ilia Mirkin wrote:
> On Wed, May 16, 2018 at 8:04 AM, Timothy Arceri <tarceri at itsqueeze.com> wrote:
>>
>>
>> On 16/05/18 21:12, Ilia Mirkin wrote:
>>>
>>>   From the spec,
>>>
>>> """
>>>       The built-in derivative functions dFdx, dFdy, and fwidth are
>>> optional, and
>>>       must be enabled by
>>>
>>>       #extension GL_OES_standard_derivatives : enable
>>>
>>>       before being used.
>>> """
>>>
>>> Sounds like you need an application override?
>>
>>
>> The ES spec has no such wording is simply states:
>>
>> "dFdx(), dFdy(), and fwidth() are made optional."
> 
> That is under the heading of "Changes from Revision 59 of the OpenGL
> Shading Language specification:", i.e. desktop GLSL.
> 
> There isn't a single other reference to those functions anywhere else
> in https://www.khronos.org/files/opengles_shading_language.pdf . The
> "optional" is in reference to it being moved out to an extension
> rather than being part of the core language.

Well it's not very clear either way. If it is as you suspect it seems 
odd that none of the conformance suites test for it. They are normally 
pretty good at this type of testing.

> 
>    -ilia
>