[require]
GLSL >= 1.10

[vertex shader]
uniform vec4 a;
uniform vec4 b;
uniform vec4 c;
uniform vec4 d;

void main()
{
   gl_Position = gl_ModelViewProjectionMatrix * gl_Vertex;

   /* This constructor should result in the following matrix (GLSL matrices are
    * column-major):
    *
    *     0.0  a.w  b.z  c.y
    *     a.x  0.0  b.w  c.z
    *     a.y  b.x  0.0  c.w
    *     a.z  b.y  c.x  0.0
    */
   mat4 m = mat4(0.0, a, 0.0, b, 0.0, c, 0.0);
   gl_FrontColor = m * d;
}

[fragment shader file]
glsl-color.frag

[test]
uniform vec4 a 1.0 0.0 0.0 0.3
uniform vec4 b 1.0 0.0 0.4 0.0
uniform vec4 c 1.0 0.3 0.0 0.0
uniform vec4 d 0.8 0.8 0.8 0.8

clear color 0.2 0.2 0.2 1.0
clear
ortho
draw rect 10 10 10 10
probe rgb 15 15 0.8 0.8 0.8