[Mesa-users] GL_ACTIVE_UNIFORMS returns unexpected value

[Lascha Lagidse]

Hello :)

I am Lascha, new to linux and first time subscribing to a mailing list. 
I heard you were great guys ;)

So, I am currently in the process of porting the game Age of Wonders 3 
to Linux. The game is currently in open-beta on Steam, and people 
reported issues with the specifically the Mesa graphics driver. I had a 
look and it looks like this driver behaves differently on this driver 
when using glGetProgramiv and glGetActiveUniform.

The vertex shader (see bottom) is attached to a program. The program is 
then linked. Note: Only this vertex shader is attached to the program; 
there is no other shader attached. Now using glGetProgramiv with 
GL_ACTIVE_UNIFORMS will return 2, but I expect it to be 3 like on the 
other drivers. According to glGetActiveUniform it is the variable 'c24' 
which is missing. My guess is that it's optimized away, for some reason. 
If I also link the fragment shader, then 'c24' is listed correctly.

My goal is to retrieve the active uniforms from specifically the vertex 
shader. If I link both the vertex AND the fragment program, then there 
is no way to distinguish which uniforms belong to the vertex program and 
which belong to the fragment program (or is there?).

I can't think of a nice work-around; but since this is only 
initialization code the only work-around that comes to mind is to 
serialize the info I get from glGetActiveUniform on another driver and 
use that info instead of calling glGetActiveUniform at initialization.

#version 140
uniform mat4 c20;
uniform vec4 c24;
uniform vec4 c25;
in vec3 POSITION0;
in vec2 TEXCOORD0;
out vec2 xlv_TEXCOORD0;
void main ()
{
   vec4 PosWS_1;
   PosWS_1.xy = (c25.xy + (POSITION0.xy * c25.zw));
   PosWS_1.z = POSITION0.z;
   PosWS_1.w = 1.0;
   gl_Position = (c20 * PosWS_1);
   xlv_TEXCOORD0 = (c24.xy + (TEXCOORD0 * c24.zw));
}

Kind regards,
Lascha
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