gistfile1.cpp

void renderScene() {
  // do all your normal rendering here
  
  ...

  // Render the latency test color if required
  renderLatencyTestSquare();
}

void renderLatencyTestSquare() {
  OVR::Color colorToDisplay;
  // If this returns a non-0 value, we're performing a latency
  // test and must render a colored square underneath the tester 
  // (On the lens axis)
  if (ovrLatencyTest.DisplayScreenColor(colorToDisplay)) {
    latencyTestProgram->use();
    latencyTestProgram->setUniform("Color", Rift::fromOvr(colorToDisplay));

    gl::MatrixStack & mv = gl::Stacks::modelview();
    glDisable(GL_DEPTH_TEST);
    mv.with_push([&]{
      mv.identity().translate(glm::vec3(0, 0, -0.1f)).scale(0.005f);
      GlUtils::renderGeometry(latencyTestQuad, latencyTestProgram);
    });
    glEnable(GL_DEPTH_TEST);
  }
}