tk@cvl.UUCP (Tharakesh Siddalingaiah) (06/21/85)
Hello
Does anyone out there know how to make QuickDraw work with the
alternate screen buffer,i.e. is there a global that specifies the
starting address of screen memory? I want to do some smooth animation
and know how to cause the display hardware to switch between the
two different screens. I just have to get QuickDraw to work with
altternate screen buffer.
thanks
--
Tharakesh Siddalingaiah ---
University of Maryland Computer Vision Lab, (301) 454-4526
ARPA:tk@cvl CSNET:tk@cvl UUCP:{seismo,allegra,brl-bmd}!umcp-cs!cvl!tkbrian@ut-sally.UUCP (Brian H. Powell) (06/24/85)
> Does anyone out there know how to make QuickDraw work with the > alternate screen buffer,i.e. is there a global that specifies the > starting address of screen memory? I want to do some smooth animation > and know how to cause the display hardware to switch between the > two different screens. I just have to get QuickDraw to work with > alternate screen buffer. > > thanks > Tharakesh Siddalingaiah --- > University of Maryland Computer Vision Lab, (301) 454-4526 > ARPA:tk@cvl CSNET:tk@cvl UUCP:{seismo,allegra,brl-bmd}!umcp-cs!cvl!tk I don't think there is a global that tells you the address. Once you tell the segment loader which screen to use, you can get that information from quickdraw, so you won't have to have $72700 in your program as a constant. The way to get access to the alternate screen buffer is to tell the segment loader that you intend to use it. You have to use either Launch or Chain. There's apparently no way to have it happen from the finder. Probably you should write a small dummy application that launches your real application with the proper launch or chain command. See the segment loader part of Inside Mac for more info. Then your program has to tell the video hardware when to switch between the two buffers. To do this, set or clear bit 6 of address $EFFFFE. Set to 1 means use the default screen. Clear means use the alternate. To do this in a nice sort of manner, $EFFFFE comes from the base address of the VIA (found in the global "VIA" which turns out to be address $1D4 and it usually contains $EFE1FE) plus an offset 1E00. I don't think there's anything in Inside Mac to explain this. Brian H. Powell brian@ut-sally