human
I wrote the below code

    n_check = 3
    app = use_app()
    with Canvas(app=app, size=_win_size, title='same_0') as c0:
        with Canvas(app=app, size=_win_size, title='same_1') as c1:
            ct = [0, 0]
            @c0.events.draw.connect
            def draw0(event):
                ct[0] += 1
                c0.update()
            @c1.events.draw.connect
            def draw1(event):
                ct[1] += 1
                c1.update()
            c0.show()
            c1.show()
            c0.update()
            c1.update()
            timeout = (time() + 2.0)
            while (((ct[0] < n_check) or (ct[1] < n_check)) and (time() < timeout)):
                app.process_events()
            print (ct, n_check)
            assert (n_check <= ct[0] <= (n_check + 2))
            assert (n_check <= ct[1] <= (n_check + 2))
            global timer_ran
            timer_ran = False
            def on_timer(_):
                global timer_ran
                timer_ran = True
            t = Timer(0.1, app=app, connect=on_timer, iterations=1, start=True)
            app.process_events()
            sleep(0.5)
            app.process_events()
            app.process_events()
            assert timer_ran
    if (app.backend_name.lower() == 'wx'):
        raise SkipTest('wx    fails    test    #2')
    kwargs = dict(app=app, autoswap=False, size=_win_size, show=True)
    with Canvas(title='0', **kwargs) as c0:
        with Canvas(title='1', **kwargs) as c1:
            bgcolors = ([None] * 2)
            @c0.events.draw.connect
            def draw00(event):
                print '        {0:7}:    {1}'.format('0', bgcolors[0])
                if (bgcolors[0] is not None):
                    gl.glViewport(0, 0, *list(_win_size))
                    gl.glClearColor(*bgcolors[0])
                    gl.glClear(gl.GL_COLOR_BUFFER_BIT)
                    gl.glFinish()
            @c1.events.draw.connect
            def draw11(event):
                print '        {0:7}:    {1}'.format('1', bgcolors[1])
                if...

What's a good function header?
 What is a Python program to print (ct, n_check)?
assistant
#Here is Python program to print (ct, n_check)
.

@requires_application()
def test_multiple_canvases():