But glgetuniformlocation always returns the-1 uniform.

This is because the uniform is not used.

It is used not only to say that you have used it, but also to say that it has an effect on the output.

That is to say, only the shader function uses its value. The used state of the uniform is false.

For example, halotex

// Fp
Uniform sampler2d halotex;
Uniform vec4 halorect;
Void Main ( Void )
{

Gl_fragcolor = vec4 ( 0 , 1 ,0 , 1 );

Float X = gl_fragcoord.x;
Float Y = gl_fragcoord.y;

If (X> halorect. X & x Y> halorect. Y & Y {

Float Width = halorect. Z-halorect. X;
Float Height = halorect. W-halorect. Y;

Float Coordx = (X-halorect. X)/width;
Float Coordy = (Y-halorect. Y)/height;

Vec4 texcolor = texture2d (halotex, vec2 (coordx, coordy ));

Gl_fragcolor.rgba = vec4 ( 0 , 0 , 1 , 0.5 );
}

}