[SDL] correct way of map scrolling

[Scott Harper]

> If you're doing a true tiling system (say, 32x32 tiles or similar),  
> then ya might consider just recreating the background every frame.   
> You'll undoubtedly be animating EVERY tile, so you'll have to  
> redraw it anyway...

For me, since I use SDL as a cheap way to set up and OpenGL context  
on whatever platform, I'm pretty sure I have to redraw all the tiles  
each frame anyway, as a result of using 3D acceleration for drawing.   
It should be relatively easy, however, to figure out what is on- 
screen or not (test bounds) so you don't have to draw EVERYTHING...   
Though with OGL, I recall that if something's offscreen it'll PROCESS  
the vertices you give it, but won't waste time drawing if nothing  
shows on-screen...  My general idea is to break larger maps down into  
smaller map segments, and do hit-testing on them for if they're near  
the screen edges, that way I may lose SOME cycles each redraw to  
wasted tiles drawn, but probably not as many as would be wasted with  
small hit-checks on each tile.  Kind of like a hand-made quad-tree,  
only without the even breaks.

Wow, that was scatterbrained! >.<  Sorry for the unintelligible  
response! =)

-- Scott