SwapBitsRastPortClipRect

Swap bits between common bitmap and obscured ClipRect

Support routine useful for those that need to do some operations not done by the layer library. Allows programmer to swap the contents of a small BitMap with a subsection of the display. This is accomplished without using extra memory. The bits in the display RastPort are exchanged with the bits in the ClipRect's BitMap.

Note:

the ClipRect structures which the layer library allocates are

actually a little bigger than those described in the graphics/clip.h include file. So be warned that it is not a good idea to have instances of cliprects in your code.

rp

pointer to rastport

cr

pointer to cliprect to swap bits with

Because the blit operation started by this function is done asynchronously, it is imperative that a WaitBlit() be performed before releasing or using the processor to modify any of the associated structures.

Note, too, that this call is slow on RTG screens as it uses a double-XOR to exchange graphics between the ClipRect and the RastPort.

If possible, other means of exchanging bits should be used. At the time of writing, the only operating system use of this function is intuition, for menu rendering in low memory situations. If memory permits, intuition uses a second buffer. It is recommended that user programs follow a similar strategy and avoid this function if memory permits.

<graphics/clip.h>, <graphics/rastport.h>, <graphics/clip.h>