general purpose bit blitter

[Hans Jespersen]

>From article <WJC.89Oct16104701 at hoswjc.hoswjc.ATT.COM>, by wjc at hoswjc.ATT.COM (Bill Carpenter):
> ...
> So, who has some nice, post-able, fairly general bitblt routine?
> Given that, I'd be able to post a UNIXpc version of the infamous
> "crabs" program.

I'm currently working on a dmd library to enable me to compile
and run programs written for the 5620/630/730 DMD environment.
The bitblt(3R) routine is just one of many necessary graphics
routines (ie. box(3R), circle(3L), ellipse(3L), etc.) as well as all
the font, and mouse manipulation routines. I started hoping that
I could simply map all the bitblt() parameters over to the
coresponding wrastop() parameters but the structure of Bitmap
is all backwards. Even provided the 630 bitplanes are 16 bit 
Words the bits are a mirror image of the bitplanes on the 3b1.
Therefore my bitblt() has to check the source and destination
bitplanes and if they are in display memory the Words have to
be flipped, otherwise you will get unrecognizable results.
Even with the bits flipped, the results can be disappointing
since the 630 has a nice 1:1 aspect ratio and the 3b1 has a
horribly scewed 7:3 (approx) ratio.

Getting bitblt() ported is a nice first step and will allow a
lot of 630 demo stuff to run ( should be enough for "crabs" )
but in order to use some of the REALLY neat stuff that the
labs are putting out for DMD terminals it would be advantageous
to have the complete DMD environment. Then the next step 
would be to get 'layers' up, perhaps through the use of the
existing window drivers.

-- 
Hans Jespersen                UUCP: uunet!attcan!hjespers
AT&T Canada Inc.                
Toronto, Ontario              

PS. The ultimate would be to get "gebaca" running on the 3b1.
    This has got to be one of the all time best arcade style
    games I've ever played but alas, it only runs on DMD terminals.