Hi !
> GGI - as far as I know - has only a notion of a rectangular clipping
> rectangle being valid for all subsequent primitive drawing calls.
Yes. This is due to the fact, that there are only two methods I have seen to
do clipping in Hardware:
1. a single rectangle (eventually invertible, i.e. you can only draw _outside_)
2. a Z-Buffer, stencil-buffer or windowID-buffer. That is with 2. you can
decide for every pixel, if it can be drawn to or not.
> Well, what, if I have a clipping region, like X does, which I can
> subdivide into an enumeration/array of rectangles?
I would try to use 2. (which is more in the scope of LibGGI3D than plain
LibGGI) or emulating that.
> Do I have to repeat a single e.g. line drawing call,
I cannot recommend that, unless you have a very very powerful accelerator and
a very very weak CPU or are low on RAM.
If not, I'd draw the window (which is what you are hinting at - right ?) into
RAM and then blit over only the visible portion, which can be done by just
crossblitting the clipping rectangles.
This also provides backbuffering, which is usually a nice thing to have anyway,
as you can redraw contents without application help, which is useful for stuff
like opaque window moves.
> after having reset the clipping rectangle each time or is there a
> (maybe private, but stable) function / shortcut??
No. As said, LibGGI3D should have such functions as Method 2. falls into its
scope, but unfortunately LibGGI3D is not in a useable state right now AFAIK.
CU, ANdy
--
Andreas Beck | Email : <[EMAIL PROTECTED]>
