[Mesa-dev] [PATCH 2/2] mesa: enable ARB_gpu_shader5 in compat

[Benedikt Schemmer]

Am 18.05.2018 um 20:05 schrieb Ilia Mirkin:
> On Fri, May 18, 2018 at 1:54 PM, Benedikt Schemmer <ben at besd.de> wrote:
>> so the gll is ok?
>>
>> my idea with the glc is that this particular extension would no longer be advertised as soon as the app
>> request a context where the functionality is already part of it (ie OpenGL >= 4.0)
> 
> Why is this desirable? One could interpret that to mean that e.g.
> "#version 150; #extension GL_ARB_gpu_shader5: enable" wouldn't work...
> While legal, I doubt it'd go over well with applications.

I dont think any application would notice. They should just do #version 400 (or higher) and dont need GL_ARB_gpu_shader5 anymore
So less useless extensions to sift through.

> 
>> Do you think a minimum GLSL version could be added to this table (maybe replacing the year) so that
>> GLSL version overriding has a similar effect?
> 
> The minimum GL version seems to do that just fine...

This is of course very specific to this extension, although I do expect more have the same aspect.

I found an old (the) FXAA implementation from Nvidia that was used by retro (really really old) games
https://gist.github.com/kosua20/0c506b81b3812ac900048059d2383126

and it could use shader5 with GLSL 120. So it would be nice to have a way to enable that extension
even in cases where the requested OpenGL version is lower than specified but there is some justification
to it.

---

#ifndef FXAA_FAST_PIXEL_OFFSET
    //
    // Used for GLSL 120 only.
    //
    // 1 = GL API supports fast pixel offsets
    // 0 = do not use fast pixel offsets
    //
    #ifdef GL_EXT_gpu_shader4
        #define FXAA_FAST_PIXEL_OFFSET 1
    #endif
    #ifdef GL_NV_gpu_shader5
        #define FXAA_FAST_PIXEL_OFFSET 1
    #endif
    #ifdef GL_ARB_gpu_shader5
        #define FXAA_FAST_PIXEL_OFFSET 1
    #endif
    #ifndef FXAA_FAST_PIXEL_OFFSET
        #define FXAA_FAST_PIXEL_OFFSET 0
    #endif
#endif