nanogui: Bogl changes & Nano-X-0.5
Subject:
RE: Bogl changes & Nano-X-0.5
From:
Alex Holden ####@####.####
Date:
18 May 1999 23:06:38 -0000
Message-Id: <Pine.LNX.4.04.9905182346090.16616-100000@hyperspace>
On Tue, 18 May 1999, Greg Haerr wrote:
> There are considerable changes that need to be made to use unmodified bogl libraries.
> The first major issue is that all the bogl entry points need to have code added
> to support drawing in AND, OR and XOR modes, in addition to SET, which is
> already implemented.
After thinking about this, and looking at the code, isn't the best way to
do this for the graphics screen to be mirrored in main memory, and do the
processing on that then copy only the altered areas out to the buffer on
the graphics card? That way, you aren't shipping large amounts of data
over a PCI or ISA bus... I seem to recall Allegro had about five different
ways of dealing with this problem though, so there probably isn't one
answer which is best for all situations. It doesn't seem that reading from
the frame buffer, performing an operation on it, and writing it back out
again is going to be a very good idea, and I couldn't see any obvious way
to use the hardware capabilities of the graphics card to do it with the
Linux Framebuffer interface (maybe you can do it with the accelerated ones
though).
BTW, I've just switched the newest bogl library in place of the old one.
Very few changes at all were needed, though I didn't copy the readpixel()
stuff (as I said above, I don't think reading it from the framebuffer
itself is the best way to do it anyway) so you can "rub out" the screen by
waving the mouse over it. The Map program looks good in VGA16 mode, but on
the NetWinder it's just a mess of random lines (structure alignment
problems, no doubt).
--------------- Linux- the choice of a GNU generation. --------------
: Alex Holden (M1CJD)- Caver, Programmer, Land Rover nut, Radio Ham :
-------------------- http://www.linuxhacker.org/ --------------------
