Mail Archives: djgpp/1998/12/21/10:20:48
Tobias Nygren writes:
> I am writing a program that uses VESA mode 10F, 320x200x16.8M.
Are you aware that 0x10F is not a standard VESA mode number? If you
just hardcode this value, your program may not work on other machines
that use different drivers. For a reliable mode set, you need to
scan through the list of available modes as reported by the VESA
driver, until you find one that matches your requirements. Also
the 320x200x24 modes are not supported by many drivers, so if you
use this resolution, many people won't be able to run your code at
all! It is a lot more reliable to use only 8 bit lowres modes, and
go to 640x480 if you want truecolor graphics.
> I want the modeinfo.physbaseptr into an
> unsigned char *bigbuffer;
You can do that using the routines from <sys/nearptr.h>, which are
described in the info docs ("info libc alpha __djgpp_nearptr_enable").
I can't say that I recommend this method, though: many people seem
to like it because it is very easy to program, but IMHO it is much
better to use farptr routines: they are just as fast when used
properly, maintain proper memory protection, and are far more
reliable when used on different platforms like Windows NT or
Linux DOSEMU, where the nearptr hack won't work at all.
> I know it has got something to do with
> __dpmi_physical_address_mapping()...
Yes indeed. This subject is too big to cover by email, but look in
the djgpp FAQ and the User's Guide on www.delorie.com, where you
can find both lengthy explanations and example code.
Shawn Hargreaves.
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