title: Pygame screen.blit black after mode change
body: <p>I want to show different <code>pygame</code> surfaces in different modes. My first mode works but the surfaces in the subsequent ones are black. I don't understand why.</p>
  
  <pre><code>import pygame
  import pygame.gfxdraw
  
  screenWidth = 800
  screenHeight = 800
  
  path = (r"C:\Users\eeifler\Pictures\code drawings\35\trace.PNG")
  
  imageFile = pygame.image.load(path)
  imageFile = pygame.transform.scale(imageFile, (screenWidth,screenHeight))
  
  pygame.init()
  
  screen = pygame.display.set_mode((screenWidth, screenHeight))
  
  running = True
  quadrent = 1
  
  while running:
      screen.blit(imageFile, (0,0))
      cropped = pygame.Surface((screenWidth//2, screenHeight//2))      
  
  
      if quadrent == 1:
          cropped.blit(screen, (0,0), pygame.Rect( 0, 0, screenWidth//2, screenHeight//2))
  
          bottomLeft = pygame.transform.flip(cropped, False, True)
          screen.blit(bottomLeft, pygame.Rect(0,screenHeight//2,screenWidth//2,screenHeight//2))
  
          topRight = pygame.transform.flip(cropped,True,False)
          screen.blit(topRight, pygame.Rect(screenWidth//2,0,screenWidth//2, screenHeight//2))
  
          bottomRight = pygame.transform.flip(cropped, True, True)
          screen.blit(bottomRight, pygame.Rect(screenWidth//2,screenHeight//2, screenWidth//2, screenHeight//2))
  
      if quadrent == 2:
          cropped.blit(screen, (screenWidth//2,screenHeight//2), pygame.Rect( screenWidth//2, 0, screenWidth//2, screenHeight//2))
  
          topLeft = pygame.transform.flip(cropped, False, True)
          screen.blit(topLeft, pygame.Rect( 0, 0, screenWidth//2, screenHeight//2))
  
          bottomLeft = pygame.transform.flip(cropped, True, True)
          screen.blit(bottomLeft, pygame.Rect(0,screenHeight//2,screenWidth//2,screenHeight//2))
  
          bottomRight = pygame.transform.flip(cropped, True, True)
          screen.blit(bottomRight, pygame.Rect(screenWidth//2,screenHeight//2, screenWidth//2, screenHeight//2))
  
  
  
      #if quadrent == 3:
          #cropped.blit(screen, (0,0), pygame.Rect( 0, screenHeight//2, screenWidth//2, screenHeight//2))
      #if quadrent == 4:
          #cropped.blit(screen, (0,0), pygame.Rect(screenWidth//2,screenHeight//2, screenWidth, screenHeight))
  
      key = pygame.key.get_pressed()
  
      if key[pygame.K_a]:
          quadrent = 1
      if key[pygame.K_s]:
          quadrent = 2
      if key[pygame.K_d]:
          quadrent = 3
      if key[pygame.K_f]:
          quadrent = 4
  
      for event in pygame.event.get():
          if event.type == pygame.QUIT:
              running = False
  
      pygame.display.flip()
  </code></pre>