opengl.cpp

String fragmentShader =     "uniform vec4 Color1;" NEW_LINE
                                "uniform vec4 Color2;" NEW_LINE
                                "uniform vec2 ScreenBounds;" NEW_LINE
                                "void main(void)" NEW_LINE
                                "{" NEW_LINE
                                "   " //juce is ARGB, GL is RGBA. Destination is xyzw
                                "   " NEW_LINE
    /*
     gl_FragCoord is in window coords.  so, 1024 x 768 or whtaever
     */
                                "vec2 pos = gl_FragCoord.xy / ScreenBounds.xy;" NEW_LINE
                                "gl_FragColor = vec4(mix(Color1, Color2, pos.y));" NEW_LINE
                                "}" NEW_LINE;

//

    auto r = getLocalBounds().toFloat();
    shaderProgram->setUniform("ScreenBounds",
                              r.getWidth(),
                              r.getHeight(),
                              0.f,
                              0.f);