Re: [Freefont-bugs] Sinhala engine for Uniscribe

[Primoz PETERLIN]

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Hello Mettavihari,

On Thu, 10 Apr 2003 address@hidden wrote:

> Hi list members,
> I am forwarding something that might interest you on the list
> I do not fully understand this myself.
> Perhaps someone else will understand this better.
> and would like to explain it a bit.
> A number of the Sinhala letters will have to be placed in the private area
> so I presume that is what the driver is for.

It's good to have an expert for Sinhalese on the list! :)

ISO 10646/Unicode encodes characters rather than glyphs. While there were
some questionable decisions on what exactly qualifies for a character, the
Indian standard committee (from where ISO 10646/Unicode coding originates
in this part) decided that characters are either vocals (a, aa, ae, i,
ii...) or consonant forms with inherent -a ending (ka, kha, ga, gha, nga,
ca...). This certainly doesn't cover all the neccessary *glyphs* for
typesetting text in any of the South-Asian language (I have absolutely no
information on Sinhalese, but I presume the situation is similar to the
one with South Indian languages).

There are several ways to solve this problem. One is to devise an ad-hoc
"standard" for encoding the un-encoded glyphs. I would instead propose to
use the solutions provided by Unicode and OpenType: the glyph substitution
tables. Using this, you can get the glyph for the 'ke' sound by typing an
alpapraana kayanna (U+0d9a) followed by a kombuva (u+0dd9), and the
rendering software will ask the font if there is a ligature for an u+0d9a
char followed by a u+0dd9 char, and if such a ligature exists (it does not
need a code for itself), it will be substituted and rendered on your
screen or printer.

What we do need is a list of all glyphs neccessary to render Sinhalese. In
theory this means 41 consonants x 18 vowels, which equals 738 glyphs. From
my experience with south Indic languages, most of these glyphs mean simply
prefixing or suffixing by a wovel sign, but for some wovels it might mean
an entirely separate glyph.

> We use a special keyboard layout for typing sinhala (Wijayasekera keyboard)
> You find a layout of the keyboard layout at
> http://metta.lk/fonts/
> when you download the fonts it should also have a keyboard layout..

Actually, if you decide to follow standards, the fonts issue can be
detached from the keyboard issue - somebody can take care of correctly
rendering Sinhalese text from a stream of ISO10646 characters, and another
one can take care of transforming key strokes into a stream of ISO 10646
characters.

With kind regards, Primoz

- --
Primož Peterlin,   Inštitut za biofiziko, Med. fakulteta, Univerza v Ljubljani
Lipičeva 2, SI-1000 Ljubljana, Slovenija.  address@hidden
Tel +386-1-5437632, fax +386-1-4315127,  http://biofiz.mf.uni-lj.si/~peterlin/
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