[BRLTTY] FWD: Re: A dos character problem

[Lars Bjørndal]

Hi Dave!

Could you read the forwarded message. I've problem reading some
characters under Dosemu with BRLTTY. The characters that I cannot
read, is displayed as '?' on the braille display. If I use 'setfont
iso01.16', a control character is displayed on the screen, but just a
question mark on the braille display. 'setfont lat1-16' gives the box
drawing char on screen, but also question mark on my display. Why
isn't BRLTTY able to interpret this character? I use no-h braille table.

Lars

From: Bart Oldeman <bartoldeman at gmail.com>
Subject: Re: A dos character problem
In-reply-to: <m3d51a43co.fsf at fox.lamasti.net>
To: Lars Bj.ANxrndal <lars.bjorndal at broadpark.no>
Cc: linux-msdos <linux-msdos at vger.kernel.org>
Message-id: <c3d607cc0705091146t7f2663eaj49854ceee16fd831 at mail.gmail.com>
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$(C&"&"(B

On 5/9/07, Lars Bj$(C)*(Brndal <lars.bjorndal at broadpark.no> wrote:

> Thanks for clarifying. It's however difficult to understand why doing
> alt-179 under dosemu running under the screen program with terminal
> type set to linux doesn't work, and not if dosemu is started under the
> standard console. Without dosemu rinning, Alt-179 works fine, both
> with and without screen running.

The difference is mostly in the raw keyboard setting. I didn't think
of the keyboard before, but now I understand.

First of all:
Character 179 in DOS (cp437, cp850, etc) is BOX DRAWINGS LIGHT
VERTICAL ($(C&"(B) which is something else than | (VERTICAL LINE, ASCII
124).
Character 179 in ISO-8859-1 is on the other hand SUPERSCRIPT THREE ($(C)x(B).
The superscript 3 is also present in cp850, at position 252.

Without rawkeyboard (and dosemu in screen, as you have discovered,
can't use the raw keyboard; this is something dosemu can't do anything
about), when you type alt-179, all that dosemu sees, incoming, is the
character 179. This is interpreted as a superscript 3 (external
encoding, iso-8859-1), translated to cp850 character 252, and then
translated back on to 179, to display as superscript 3.

DOS programs however, will only see the 252, not the 179, and the 252
is what will be stored in files.

With rawkeyboard on, something else happens. DOSEMU sees you typing
alt-down 1-down 1-up 7-down 7-up 9-down 9-up alt-up.
And interpretes that as real DOS would, as *CP850* character 179.
So, then, if you want a superscript 3 instead you need to type alt-252!

Now, how CP850 character 179 is displayed depends a lot on the font,
terminal setting etc, as I explained in the previous mail; you can
create a file in Linux using
cat > file
(now type alt-179, <enter>, <ctrl>-d)
and "type" it in DOS.
With setfont iso01.f16 I see nothing (no box drawings with mc either),
but with setfont lat1-16 I see the vertical box drawing. You should
get the same as when you type alt-179 with raw keyboard enabled.

Bart