From: Hartmut Schirmer <hsc AT techfak DOT uni-kiel DOT de>
Newsgroups: comp.os.msdos.djgpp
Subject: Re: libgrx20: Graphics / Textmode
Date: Tue, 21 Oct 1997 08:07:17 +0200
Organization: Technische Fakultaet, University of Kiel, Germany
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Andreas Bierhals wrote:
> 
> Hi!
> 
> I wrote a couple of small routines using the library GRX 2.0,
> which was no problem, yet. Only a few thinks do annoy me a little
> bit: first, at the end of the program, I usually change back
> from graphics to textmode (from 'GR_default_graphics' to
> 'GR_default_text'). However, when the program stops, all the text
> on the screen (including runtime error messages etc.) is cleared.
> This also happens, if I press Ctrl&C while running a program
> in 'GR_default_text' (maybe this is NOT the same textmode which
> is originally used by DOS?!).

It can be different, if you don't use 80x25. Use the GRX20DRV
environment variable to define eg.
grx20drv=th 80 tw 43 tc 16 
for 80x43 text with 16 colors as default value
Try GR_NC_default_text instead of GR_default_text (NC: do not clear)

> Another little problem is, that when running a program in a
> DOS box under Windows, changing from text to graphics mode always
> causes the DOS box to rise to full screen mode. Pressing
> Alt&Enter shrinks it back (this happens under Windows as well
> as under Win95) and the programm proceeds its execution.
> Does anyone of you have an idea how to circumvent these
> 'effects'? Thanks for any help in advance...

GRX requests a video mode change from the VGA/SVGA/VESA bios. If your
Windows video driver is clever, this switch will be detected and full
screen dos box is enabled. Normally this is the only way to use graphics
(at least SVGA) in a dos box. Check your graphics cards documentation if
this feature can be disabled.

Hartmut
-- 
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