[Mesa-dev] [PATCH] mesa: set GLSL 1.20 for the fixed-function fragment shader

[Roland Scheidegger]

Am 07.01.2017 um 19:11 schrieb Marek Olšák:
> On Sat, Jan 7, 2017 at 5:23 PM, Roland Scheidegger <sroland at vmware.com> wrote:
>> Am 07.01.2017 um 15:51 schrieb Marek Olšák:
>>> From: Marek Olšák <marek.olsak at amd.com>
>>>
>>> This fixes broken depth texturing after:
>>>
>>> commit 22639a6e19f95902aef23474ad672bf489231ea7
>>> Author: Timothy Arceri <timothy.arceri at collabora.com>
>>> Date:   Mon Nov 21 00:29:29 2016 +1100
>>>
>>>     st/mesa: get Version from gl_program rather than gl_shader_program
>>> ---
>>>  src/mesa/main/ff_fragment_shader.cpp | 3 ++-
>>>  1 file changed, 2 insertions(+), 1 deletion(-)
>>>
>>> diff --git a/src/mesa/main/ff_fragment_shader.cpp b/src/mesa/main/ff_fragment_shader.cpp
>>> index 48b84e8..a13a5de 100644
>>> --- a/src/mesa/main/ff_fragment_shader.cpp
>>> +++ b/src/mesa/main/ff_fragment_shader.cpp
>>> @@ -1215,21 +1215,22 @@ create_new_program(struct gl_context *ctx, struct state_key *key)
>>>     p.shader_program = _mesa_new_shader_program(0);
>>>
>>>     /* Tell the linker to ignore the fact that we're building a
>>>      * separate shader, in case we're in a GLES2 context that would
>>>      * normally reject that.  The real problem is that we're building a
>>>      * fixed function program in a GLES2 context at all, but that's a
>>>      * big mess to clean up.
>>>      */
>>>     p.shader_program->SeparateShader = GL_TRUE;
>>>
>>> -   state->language_version = 130;
>>> +   /* Don't use 1.30, because depth texturing behaves differently there. */
>> Could you elaborate on this?
> 
> Yeah it wasn't a completely accurate statement. IIRC (off the top of
> my head), the legacy GLSL shadow functions follow the depth texture
> mode and return vec4. The GLSL 1.30 shadow functions return float and
> ignore the depth texture mode. That's a shader and state dependency
> that's difficult to deal with. st/mesa uses a simple but not
> completely correct solution: if the shader declares GLSL >= 1.30 and
> the depth texture mode is GL_ALPHA (000X), it sets the XXXX swizzle
> instead. Thus, the GLSL 1.30 shadow function will get the result in .x
> and legacy shadow functions will get it in .w as expected. It's an
> acceptable deviation from the spec considering how rare the GL_ALPHA
> setting is, but one piglit test checking GL_ALPHA showed an obvious
> failure there.
> 

Ah yes, that makes sense. With an updated comment,

Reviewed-by: Roland Scheidegger <sroland at vmware.com>