title: How to efficiently paint two QGLWidget?
body: <p>I have two different <code>QGLWidget</code>, and they all have their own shaders.</p>
  
  <p>In case of performance, shall I use two different shaders or I shall write two shaders into one shader and use a uniform value to trigger which shader I should use now?</p>
  
  <p>If So, how can I use one shader in different <code>QGLWidgets</code>?</p>