Re: [pygame] sprite engine

[Kamilche <klachemin@xxxxxxxxxxx>]

DR0ID wrote:
> Brian Fisher schrieb:

> > For example, what happens when the ghost moves behind the tree? In
> > that case, the ghost didn't dirty any part of the tree 
> Huh? When the Gohst moves or changes layer (!)....


I think I see what's going on here. Some people appear to be confusing a 
'dirty sprite' (one that needs repainting) with a 'dirty screen 
rectangle)' (an area of the screen that needs to be redrawn.) 
Internally, I don't call the sprite flag 'dirty' - i call it 'paint.' If 
a graphic needs to be recreated because of size, appearance, or text 
changes, the 'paint' flag is turned on.

Maybe the following pseudocode will make the order of events clear.

For each dirty rectangle
   For each sprite
      If the sprite needs painting (paint flag is on)
         paint it (will add another rect to the dirty rects list)
         clear the paint flag
      If the sprite intersects the dirty rectangle
         draw it

Note that the dirty rectangle list is potentially modified as you 
iterate over it. Because of it, you shouldn't just 'clear the 
dirtyrects' at the end because you'll eat your newly-added rects! You 
should do a loop something like:

while len(dirtyrects) > 0:
   do proper stuff with dirtyrect[0]
   del dirtyrects[0]

This will repaint the existing dirty rectangles, and any new ones that 
got added during the iteration. And going through it this way is a good 
sanity check - if your program is looping endlessly, it's a sign you've 
put in an extra 'SetRect' where you don't need it, and the list never 
gets clear.


--Kamilche