[GRASS5] Polygons slow when zoomed in

[Jens Oberender]

Hi

> I think I know why it is slow, I could reproduce it. 
> When coordinates of the polygon are recalculated from map units to display
> (canvas) units it may happen (if you zoom out) that some values overflow
> integer maximum value. Result in the display is (known) mess:
> http://mpa.itc.it/radim/qgis/poly-zoom-out.png (should be only filled by blue)
> 
> I guess that this also makes rendering (on X side) slow, because X has to render 
> very complex (wrong, more or less random) polygons.
> 
> Just now, I don't know how to solve this, because any pre-clipping would be slow?
> Anybody has idea?

I hope it doesn't sound dumb but why not use doubles instead of integer to circumvent this?
It would need much more memory but we are on the save side then.

Ciao,
	Jens