//vertex shader
#version 140
in int p; //dummy input
out vec2 t; //finicky output
void main() {
    p;    // line in question
    vec2 pos;
    vec4 st = vec4(-2.5, 2.5, 0.0, 5);  //const values
    if (gl_VertexID == 0)       { pos.x = st.x; pos.y = st.z; t.x = 1; t.y = 1;}
    else if (gl_VertexID == 1)  { pos.x = st.x; pos.y = st.w; t.x = 1; t.y = 0;}
    else if (gl_VertexID == 2)  { pos.x = st.y; pos.y = st.z; t.x = 0; t.y = 1;}
    else if (gl_VertexID == 3)  { pos.x = st.y; pos.y = st.w; t.x = 0; t.y = 0;}
    gl_Position = gl_ModelViewProjectionMatrix * vec4( pos, 0.0, 1.0 );
}
//fragment shader
#version 140
uniform sampler2D tex;
in vec2 t;
void main() {
    gl_FragColor = texture2D(tex, t);
}