Date:	Mon, 3 May 1993 23:13 EST
From:	"Wonkoo Kim, EE, U. of Pittsburgh" <WKIM AT vms DOT cis DOT pitt DOT edu>
Subject:	Problem with 256-color mode in LIBGRX/BCC2GRX/ATI-VGA-Wonder
To:	djgpp AT sun DOT soe DOT clarkson DOT EDU
Cc:	phc27 AT rz DOT uni-kiel DOT dbp DOT DE

Dear Csaba Biegl:

I encountered trouble with 256 color mode with LIBGRX 1.02 when I execute the 
demo programs that came with the library package.  My system is 
486/25MHz/8MB/msdos 5.0/qemm with ATI VGA Wonder(ROM BIOS ver V5M-1.00/512KB).
When I test LIBGRX demo programs, 256 color mode graphics screens have errors 
around top one 3rd and bottom of screen.  16 color mode seems to be okay.

I found this error when I installed BCC2GRX library package and executed a demo
program bccbgi.c supplied with BCC2GRX.  The demo program have many graphics
screens.  In 256 color mode using ativga.grn driver of LIBGRX, the demo
graphics screens are not cleared between the graphics screens, so several
screens are overlapped. Drawing each demo graphics screen is almost correct,
but there some glitches at around top portion(1/3) and bottom line of the
screen. 

I tested LIBGRX test programs with both the old libgrx.a from LIBGRX 1.02 and
the new libgrx.a from BCC2GRX 1.0 package, but I got the same error.

This error occurs also for stdvga.grn, so it seems that the problem is not in 
ativga.grn.  The error remains even if I use the old style ati.grd driver.
So, any of the following settings gave the error:
	set go32=ansi driver d:\gcc\drivers\ativga.grn gw 640 gh 480 nc 256
	set go32=ansi driver d:\gcc\drivers\ativga.grn gw 320 gh 200 nc 256
	set go32=ansi driver d:\gcc\drivers\stdvga.grn gw 320 gh 200 nc 256
	set go32=ansi driver d:\gcc\drivers\ati.grd gw 640 gh 480
For 16 color mode by setting nc 16 using ativga.grn or stdvga.grn drivers, 
there is no problem.

I discussed with Hartmut Schirmer (author of BCC2GRX) about this problem.
Now I think the problem is rather in LIBGRX + graphics driver part.
(HP2XX program(djgpp-compiled) displayed graphics screen correctly without any 
error(with "nc 256" setting for .grn in go32 variable), but I don.t know if it 
tells something.)

Any help?
Thanks.

Best regards,

Wonkoo Kim
EE, U. of Pittsburgh
wkim AT vms DOT cis DOT pitt DOT edu

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