Karl Koehler wrote on 2000-11-14 13:02 UTC:
> I have a question regarding the arabic presentation forms in
> the standard fixed width fonts:
> Lam-Alef in occupies one code position only. For xterm,
> it would be nicer if it could be also split into two code positions;
> that is, Lam-Alef would be actually two characters wich would
> be always drawn beside each other, but could be inserted and deleted
> one char at a time. A terminal-emulator ( e.g. xterm ) could use
> these special characters to shape the Ligature without loosing space.
> ( At the moment, xterm does not substitute the ligature form; I suppose
> the extra space would look even worse than the U-shaped
> Lam-Alif-nonligatured combination. )
>
> Would it be OK to add such characters
> ( Lam -Alef,-Alef-Madda,-Alef-Hamza ) in a private unicode-region
> to the fonts 10x20, 9x15, 9x15bold ?
> If so, where would they be added ?
There is a far simpler solution to get the same effect, which I suggested
in:
http://mail.nl.linux.org/linux-utf8/2000-09/msg00137.html
You can declare these Arabic ligatures to be double-width characters,
just like all the CJK ideographs. You then just have to put suitable
glyphs into the corresponding double-width font (e.g. 18x18 for 9x18,
etc.). If you want to have a go at it, we can easily add a 20x20 font to
the fixed collection. There is no need to mess around with private
characters. There is also no need to make any changes to xterm, except
for its wcwidth() function, which determines whether a character should
come from the normal or from the corresponding doublewidth font.
We will eventually have to sit down and write a more formal standard than
http://www.cl.cam.ac.uk/~mgk25/ucs/wcwidth.c
that says what wcwidth should be for a VT100 UTF-8 terminal emulator
(something like an RFC, Unicode TR, or ECMA standard), in order to
ensure wcwidth interoperability between systems (in the light of telnet,
ssh, etc.). It might well be a good idea to give the ALEF LAM ligatures
a wcwidth() == 2 in such a spec, so we should definitely play around
with the idea and add the necessary glyphs to at least some of the
terminal emulator fonts.
Markus
--
Markus G. Kuhn, Computer Laboratory, University of Cambridge, UK
Email: mkuhn at acm.org, WWW: <http://www.cl.cam.ac.uk/~mgk25/>
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Linux-UTF8: i18n of Linux on all levels
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