[XeTeX] Devanagari rendering with XeTeX - a comparision

[Deepak Jois]

Hi All

I have been using XeTeX to test the rendering of Devanagari using
different fonts and layout engines. Here is a sample containing
multiple renderings of a word from the Rig Veda.

Sample Rendering :
http://farm3.static.flickr.com/2755/4250942627_469615ffbc_o.png

TeX source : http://gist.github.com/270468

The first four are using OpenType fonts (Nakula, Sahadeva, Akshar and
Gargi respectively). The last one uses Devanagari MT. In my (not so
expert) opinion, the Devangari MT/AAT rendering while not perfect, is
superior to the OpenType rendering by a fair stretch. I am mailing
this list to get some insights about the rendering process, and see if
anything can be done to improve it for OpenType fonts. Specifically :

1. Why is the OpenType/ICU rendering bad, compared to AAT. Is it the
font, or is it the layout engine, or both? My limited understanding is
that the Devangari MT font contains glyph layout information within
itself, as opposed to the OpenType fonts which rely more on software
to layout the glyphs. Is there an inherent advantage in the font
containing the layout information, or can software be made to
replicate a similar quality?

2. What can be done to improve this? Are there better fonts? Does a
later version of ICU (i believe XeTeX uses ICU 4.0) contain any
enhancements?

3. Can anyone tell if Uniscribe on Windows Vista does a better job. I
would appreciate a sample, since I dont have a Windows system here to
test it out myself.

Thanks
Deepak