import pyglet

window = pyglet.window.Window()

@window.event
def on_draw():
    window.clear()
    pyglet.graphics.draw(2, pyglet.gl.GL_QUADS,
                  ('v2i', (100,100,200,200)),
                  ('c3B', (255,0,0))
                  )

    label = pyglet.text.Label("There should also be a rectangle drawn")
    label.draw()

pyglet.app.run()