Re: [Indic-computing-standards] Hi All!

[Dr. U.B. P. <pav...@vi...>]

> Mahesh T Pai <pai...@vs...> wrote:
>
> Personally, I feel that a large number of characters in malayalam
> deserve to be added to the unicode standard.  Example are the
> characters, unicode ED15 to ED55 in malayalam.ttf, from
> http://malayalamlinux.sourceforge.net/fonts/1.1/malayalam.ttf;  ie.
> glyph characters 174 to 230 in that file. ( I had sought guidance on
> some lists about unicode coding for these characters, and have no
> reply. 
>  hence, I presume that these characters are not covered by unicode).

There is big difference between TrueType (TTF) fonts normally 
used by 8-bit ASCII (or ISCII) based encoding system and the 
OpenType (OTF/TTF) fonts used by 16-bit Uniocde based encoding 
systems. This diffenerce is prominent in case of Indic scripts 
where glyph positioning and glyph substitution matters.

Consider the first case where TTF fonts are used. Here the 
font will be having all the glyphs that are needed to make the 
characters and character combinations. Since the font is based 
on 8-bit system, there is a limit of maximum number of glyphs. 
The glyph id has to be between 32 and 255 (ASCII). Some glyph 
numbers can not be used in this range as they are used 
internally by the system. In case of Kannada we are able to 
manage with 142 glyphs. As you type the keys, the keyboard 
driver keeps adding and/or changing the glyphs depending on 
the context.

In the second case where you use a 16-bit Unicode system, 
OpenType fonts are used. There is no limit on the number 
glyphs. Hence you can have glyphs for almost all combinations. 
Here the glyph substitution and glyph positioning logic is 
built into the font (details are available at Microsoft's 
Typography site, www.microsoft.com/typography). There is a 
rendering engine in Windows 2000 and XP called Uniscribe 
(usp10.dll) which does the rendering of the font as per the 
tables built into the font /1/. Hence there is no need of 
encoding every glyph present in the font. I suggest you to 
download VOLT from Microsoft site, study the tutorial and 
documents, and then create your Opentype font for Malayalam.

Regards,
Pavanaja

Footnote:
/1/ Latest Pango/Gtk are supposed to be having the rendering 
capability of Indic Opentype fonts. Karunakar can throw more 
lights on this.-----------------------------------------------
------
Dr. U.B. Pavanaja
Editor, Vishva Kannada
World's first Internet magazine in Kannada
http://www.vishvakannada.com/

Note: I don't worry about pselling mixtakes