Python – Update display all at one time PyGame

pygamepython

Using PyGame, I get flickering things. Boxes, circles, text, it all flickers. I can reduce this by increasing the wait between my loop, but I though maybe I could eliminate it by drawing everything to screen at once, instead of doing everything individually. Here's a simple example of what happens to me:

    import pygame, time
    pygame.init()
    screen = pygame.display.set_mode((400, 300))
    loop = "yes"
    while loop=="yes":
        screen.fill((0, 0, 0), (0, 0, 400, 300))
        font = pygame.font.SysFont("calibri",40)
        text = font.render("TextA", True,(255,255,255))
        screen.blit(text,(0,0))
        pygame.display.update()

        font = pygame.font.SysFont("calibri",20)
        text = font.render("Begin", True,(255,255,255))
        screen.blit(text,(50,50))
        pygame.display.update()
        time.sleep(0.1)

The "Begin" button flickers for me. It could just be my slower computer, but is there a way to reduce or eliminate the flickers? In more complex things I'm working on, it gets really bad. Thanks!

Best Answer

I think part of the problem is you're calling 'pygame.display.update()' more then once. Try calling it only once during the mainloop.

Some other optimizations:

  • You could take the font creation code out of the main loop to speed things up
  • Do loop = True rather then loop = "yes"
  • To have a more consistent fps, you could use Pygame's clock class

So...

import pygame
pygame.init()

screen = pygame.display.set_mode((400, 300))
loop = True

# No need to re-make these again each loop.
font1 = pygame.font.SysFont("calibri",40)
font2 = pygame.font.SysFont("calibri",20)

fps = 30 
clock = pygame.time.Clock()

while loop:
    screen.fill((0, 0, 0), (0, 0, 400, 300))

    text = font1.render("TextA", True,(255,255,255))
    screen.blit(text,(0,0))

    text = font2.render("Begin", True,(255,255,255))
    screen.blit(text,(50,50))

    pygame.display.update()   # Call this only once per loop
    clock.tick(fps)     # forces the program to run at 30 fps.
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