[pygame] Pygame alpha blits and self blitting

[Lenard Lindstrom <len-l@xxxxxxxxx>]

Hi everyone,

While checking out Mozilla bug 19 (*) I found that blitting a surface 
with colorkey to itself causes repetition of the source image. I have 
attached an example. This is a known problem with copy algorithms. SDL 
blits have special code to handle it. Pygame's blits do not. The 
concerns over self blits were discussed in the bug 19 related thread 
(**), but I could find no conclusion as to whether to support it or 
raise an exception and provide explicit scroll routines instead. Pygame 
has many special case blit loops to be considered.

Lenard

(*) http://pygame.motherhamster.org/bugzilla/show_bug.cgi?id=19
(**) http://thread.gmane.org/gmane.comp.python.pygame/15390/focus=15407

--
Lenard Lindstrom
<len-l@xxxxxxxxx>

Attachment: test.py
Description: application/python