At 05:33 PM 8/3/2004, "Richard Wordingham"
<richard.wordingham@...> wrote:

>The Thai script is a South Indian script in origin, and presents the
>same issues as Tamil. Pre-Unicode practice (TIS-620) has been
>adopted for Unicode - Thai is entered in the order it is typed on a
>manual typewriter. (Thai codepoints are TIS-620 codes + 0D60.) Lao
>followed suit, but phonetic order seems to have been imposed on the
>Unicode representation of other Tai scripts.

IIRC, legacy Tamil and other Indic scripts were also
visually-linear-inputted. With recent Unicode advances in technology,
phonetic implementation, spurred largely by needs for proper sorting and
compatibility issues, has come to the fore.

>Limitation:
>Thai characters ro ru and lo lu are actually 'independent vowels',
>but may be used as though dependent. Notepad will allow vowels to
>be applied to them, but the Thai version of Word 2002 does not allow
>vowels to be added to them. If other software also prevents these
>combinations, they cannot be used as consonants, and more arbitrary
>encodings will be required.

Because <character ru> and <character lu> are inherently _vocalic_
(historically syllabic r and l, respectively in Indic sources), the only
"vowel" character that can be gramamtically/properly added to these is the
lengthening character (which looks similar to <sara aa>). Forcing other
vowels onto these two glyphs in applications that are not fully uniscribe
happy just goes to show that non-native elements will accrue in
spelling/typesetting.

cheers,
-Patrick