Pygame error: display surface quit: Why?

Question

Can anyone tell me why my app quits with:

pygame error: display Surface quit.

Answer 1

I had a similar problem in a very simple piece of code:

    import sys, pygame
    pygame.init()

    size = width, height = 640, 480
    speed = [2, 2]
    black = 0, 0, 0

    screen = pygame.display.set_mode(size)
    ball = pygame.image.load("Golfball.png")
    ballrect = ball.get_rect()
    while 1:
        event = pygame.event.poll()
        if event.type == pygame.QUIT:
                pygame.quit()

        ballrect = ballrect.move(speed)
        if ballrect.left < 0 or ballrect.right > width:
            speed[0] = -speed[0]
        if ballrect.top < 0 or ballrect.bottom > height:
            speed[1] = -speed[1]
        screen.fill(black)
        screen.blit(ball, ballrect)
        pygame.display.flip()
        pygame.time.delay(5)

Error message was:

    Traceback (most recent call last):
      File "", line 1, in 
      File "bounce.py", line 22, in 
        screen.fill(black)
    pygame.error: display Surface quit

So I put

    import pdb

at the top after

    pygame.init()

and used

    pdb.set_trace()

after the line with

    pygame.quit()

Now I ran the program, clicked to close the window and was actually a bit surprised to see that I fell into the debugger (after all, I expected the quit to completely take me out immediately). So I concluded that the quit doesn't actually stop everything at that point. Looked like the program was continuing beyond the quit, was reaching

    screen.fill(black)

and this was causing the problem. So I added

    break

after the

    pygame.quit()

and all works happily now.

[ Added later: It occurs to me now that

    pygame.quit()

is quitting the module, and not the program that is running, so you need the break to get out of this simple program. ]

Just for the record, this means the good version is

    import sys, pygame
    pygame.init()

    size = width, height = 640, 480
    speed = [2, 2]
    black = 0, 0, 0

    screen = pygame.display.set_mode(size)
    ball = pygame.image.load("Golfball.png")
    ballrect = ball.get_rect()
    while 1:
        event = pygame.event.poll()
        if event.type == pygame.QUIT:
                pygame.quit()
                break

        ballrect = ballrect.move(speed)
        if ballrect.left < 0 or ballrect.right > width:
            speed[0] = -speed[0]
        if ballrect.top < 0 or ballrect.bottom > height:
            speed[1] = -speed[1]
        screen.fill(black)
        screen.blit(ball, ballrect)
        pygame.display.flip()
        pygame.time.delay(5)