What would be useful is the ability to select a clipping area, so that anything outside this area isn't displayed. This is somewhat different to viewports as a clipping area doesn't modify the current origin of graphics.
You can do this with POLYVECTOR. OK, it' not as easy as selecting a rect (or other shaped) area, but it's not that much harder.
VIEWPORT cant been used. Yes its does move x/y to its top corner on that VIEWPORT, but you can easy calculcate that.
Indeed, VIEWPORTS cant always be used as multiple overlapping viewports arent always allowed (OpenGL is very weird about that, although DirectX can be fine with it)
On a Tilemap?
You can draw a 1.000.000 tiles map with a simpl trick:
(btw. Old Code)
http://www.glbasic.com/forum/index.php?topic=966.msg5005#msg5005
simply draw things on the Screen not the outside one!
No, this is for objects on a pseudo 3d track, where multiple objects can overlay each other (which is why VIEWPORT wouldn't work).
I have been testing VIEWPORT, and another problem has cropped up with it, namely fractional parts (or rather a width or height < 1), mess up the positioning