Date:	Wed, 1 Aug 2001 19:15:00 +0300 (IDT)
From:	Eli Zaretskii <eliz AT is DOT elta DOT co DOT il>
X-Sender:	eliz AT is
To:	"Mark E." <snowball3 AT bigfoot DOT com>
cc:	djgpp-workers AT delorie DOT com
Subject:	Re: djgpp: djgpp/src/libc/posix/termios/tmwrite.c
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On Wed, 1 Aug 2001, Mark E. wrote:

> I ran into a limitation I couldn't work around. I needed to scroll forward or 
> backward by n characters.

You mean, for the feature of readline where a long line is scrolled left 
or right to bring the cursor position into the view without wrapping the 
line?

> But the bios has no easy way to do this. It can be 
> done through bios, but it would require many calls to set the cursor, read 
> the character and attribute at the cursor, etc.

Yes, you need to do this manually.  However, I wonder: do curses and/or 
termcap support such operations on Unix systems?  If so, what primitives 
do you need to implement for that?  Anything beyond insert character and 
delete character?

> And if you or someone else could clue me in on what modes require a bios-only 
> solution, that would be a help.

All the modes up to 13h are supported by the standard BIOS.  Depending on 
the video adapter, more modes can also be supported.  ``Support'' here 
means mainly that the variables such as screen dimensions stored in the 
BIOS data area are consistent with the actual screen dimensions.

Graphics modes have one complications: the cursor is not visible.  But 
you could either ignore that, or (if you want to get fancy) emulate the 
cursor with a blinking underscore.  (I have code that I wrote for an 
unreleased port of UCB Logo which does all user interaction entirely 
through BIOS, and it includes the cursor emulation.)

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