[comp.sys.mac.programmer] Rolling your own 32-bit offscreen pixmaps -- magic incantations?

tim@efi.com (Tim Maroney) (07/24/90)

I am working on an application that requires offscreen pixmaps in which
the baseAddr field gets changed frequently to point to pixel buffers
the application is managing.  Offscreen pixmap support in 32-bit
Quickdraw does not let you control the baseAddr field, and I imagine
that if I change it, I will be incompatible with graphics acceleration
hardware that intercepts the offscreen pixmap calls.  So, I am trying
to roll my own offscreen pixmaps.  I started with the code from the
old FracApp, but it only does 8-bit pixmaps, where I need 32-bit pixmaps.

So, I made changes as recommended, including such annoyances as creating
an empty color table.  Problem is, after some intensive debugging effort,
peeking at all the fields of the CGrafPort, GDevice, and PixMapHandle
with Lightsbug, and going over my code with a fine-toothed comb, I still
crash during the initial EraseRect.  Is there some magic wand I have to
wave to get a 32-bit offscreen pixmap to work?