vec4 unionJack(void)
{
    // first lets mirror the tcoord
    vec2 tc = TexCoord0;
    vec4 retCol = vec4(1.0, 1.0, 1.0, 1.0);
    bool flipx = false, flipy=false;
    if (tc.x > 0.5) 
    {
       tc.x = 1.0 - tc.x;
       flipx = true;
    }
    if (tc.y > 0.5) 
    {
       tc.y = 1.0 - tc.y;
       flipy = true;
    }
    
    // england- st george
    bool george =   (tc.x > 0.45) || (tc.y > 0.39);
    
    // scotland- st andrew
    bool andrew =   (tc.x + 0.112 < tc.y ) || (tc.x - 0.112 > tc.y);
    // clipping filter
    bool andrewfilter =   (tc.x < 0.41) && (tc.y < 0.32);
    
    // ireland- st paddy split into 2 parts
    bool patrick1 = (tc.x - 0.08 < tc.y ) && (tc.x > tc.y) && andrewfilter;
    bool patrick2 = (tc.x + 0.08 > tc.y) && (tc.x < tc.y) && andrewfilter;
    // only show part of paddy depending on which corner we're in
    bool patrick =     (flipy && flipx && patrick1)
                    || (flipy && !flipx && patrick2)
                    || (!flipy && flipx && patrick2)
                    || (!flipy && !flipx && patrick1);
  
    // red
    if (george || patrick)
       retCol = vec4(1.0, 0.0, 0.0, 1.0);
  
    // blue
    if (andrew && andrewfilter)
       retCol = vec4(0.0, 0.0, 1.0, 1.0);
       
    // white
    return retCol;
}