[prev in list] [next in list] [prev in thread] [next in thread] 

List:       freedos-dev
Subject:    Re: [fd-dev] DISPLAY  CON?=
From:       Matthias Paul <Matthias.Paul () post ! rwth-aachen ! de>
Date:       2002-12-04 17:02:03
[Download RAW message or body]

On 2002-12-04, Tom Ehlert wrote:

>>  DEVICE=DISPLAY.SYS co80:=(ega,437,(6,3)) bw80:=(mono,(437,161),0)
>
> AFAIK, there is no possibility to change the fonts on BW80 =HGC ?
> and so there is no need for display to do anything to BW80.

For illustration purposes I assumed an Arabic HGC clone card, which
has two hardware fonts (codepages 437, 161), no software fonts (0),
here. Actually, using codepage 161 ("Arabic") was a bad example,
because this particular one is usually provided as a software
codepage in VIDEO.CPI, but there are similar hardware codepages
or fontpages like codepage 151 ("Nafitha Arabic (EPROM fontpage)").

For the common HGC and CGA clone cards as we know them over here,
you're right. But I have at least seen cards with more than one
font switchable by a jumper (easy to make this software configurable
by a little user modification) - not the same as the rare HGC/RAMFONT,
which provides a font RAM to store fonts.

Anyway, a tiny TSR providing a small API in INT 10h, INT 15h, or
INT 2Fh, could solve the problem, when DISPLAY.SYS would talk to
this interface when it attempts to switch hardware codepages.

In fact, a similar facility exists in Arabic and Hebrew issues
of MS-DOS at INT 2Fh/AX=AD4xh, although they don't actually use
console drivers named DISPLAY.SYS, but ARABIC.COM/HEBREW.COM,
SK_HGC.COM, and a bunch of others. Most probably there is
a lower-lever API as well, but I'm certainly no expert on
Arabic/Hebrew DOS. Anyone?

Maybe "MONO" should be replaced by "AMONO" or "HMONO" to better
distinguish between them? 

Greetings,

 Matthias

On 2002-12-04, Aitor Santamarķa Merino wrote:

> The : I assume it's optional.... Many times it appears, many
> others it doesn't.

That's right.

> Hey, now that I notice, I'll have to review in the documentation
> (possibly in your long messages about internationalisation) what is
> meant by (437,161).... At a first sight, the device to be replaced is
> single, the codepage should be single too (?).

Sorry, I don't comprehend. You can prepare up to a total of 12
concurrent codepages, so you could easily switch between them
without having to prepare the desired target codepage all the
time. Of course, this would require lot's of memory for the
font buffers, that's why some issues of DISPLAY.SYS (of
PC DOS 7/2000, for example) store the currently unused fonts
in XMS memory. Some earlier issues of MS-DOS/PC DOS DISPLAY.SYS
seem to have had a facility to store them in the HMA, but I'm
not completely sure about that. I have never observed this to
happen. The DR-DOS DISPLAY.SYS does not currently support
storing the fonts in the HMA or XMS, unfortunately.

Greetings,

 Matthias

-- 
<mailto:Matthias.Paul@post.rwth-aachen.de>; <mailto:mpaul@drdos.org>
http://www.uni-bonn.de/~uzs180/mpdokeng.html; http://mpaul.drdos.org

"Programs are poems for computers."

----------
list options/archives/etc.: http://www.topica.com/lists/fd-dev
unsubscribe: send blank email to: fd-dev-unsubscribe@topica.com

==^^===============================================================
This email was sent to: freedos-dev@progressive-comp.com

EASY UNSUBSCRIBE click here: http://topica.com/u/?bz8Rv5.bbTs7X.ZnJlZWRv
Or send an email to: fd-dev-unsubscribe@topica.com

T O P I C A -- Register now to manage your mail!
http://www.topica.com/partner/tag02/register
==^^===============================================================

[prev in list] [next in list] [prev in thread] [next in thread]