[pygame] Sprite group drawing with offset

[Thiago Chaves <shundread@xxxxxxxxx>]

Hi,

I just had a conversation with some people at #pygame on IRC, and it
seems that at least me and unlucky777 agree that it would be cool to
be able to pass an offset value to the drawing function on pygame
sprite groups. The idea is that people who think about a "camera" (or
when writing games have something more natural to work with).

Anyway, unlucky777 came up wth some modified renderUpdates sprite
group to solve a scrolling problem, while I caught myself putting
offset information on the update method of my sprite classes so I
could deal with the same problem (but apparently in an uglier way).

I'm attaching unlycky777's relevant piece of code, and also what I
came up with. Personally, I like unlucky's idea better.

Any thoughts?

-Thiago

#from the sprite (module?)     class RenderUpdates(Group):

def draw(self, surface, offset):
	spritedict = self.spritedict
	surface_blit = surface.blit
	dirty = self.lostsprites
	self.lostsprites = []
	dirty_append = dirty.append
	for s in self.sprites():
		r = spritedict[s]
		newrect = surface_blit(s.image, s.rect.move(offset))
		if r is 0:
			dirty_append(newrect)
		else:
			if newrect.colliderect(r):
				dirty_append(newrect.union(r))
			else:
				dirty_append(newrect)
				dirty_append(r)
		spritedict[s] = newrect
	return dirty