Combining Class of Thai Nonspacing_Marks

[Gerriet M. Denkmann]

> On 4 Apr 2017, at 23:51,Richard Wordingham <richard.wordingham at ntlworld.com> wrote:
> 
> On Tue, 4 Apr 2017 09:39:57 +0700
> "Gerriet M. Denkmann" <gerrietm at icloud.com> wrote:
> 
>> So the rule should be:
>> 
>> A consonant may have zero or one tone/other marks and also zero or
>> one top/bottom vowels. Exceptions: 
>> 	NIKHAHIT + tone mark (no top/bottom vowel)
>> 	MAITAIKHU + tone mark (no top/bottom vowel)
> 
> This list is not exhaustive.  

> The order of MAITAIKHU and tone mark is significant - it should affect rendering.  
Most fonts disagree (exception: Tahoma and Microsoft Sans Serif). Are there minority languages where the order has really a semantic meaning?


Could one create a list of all possible combinations of non-spacing marks for Thai, minority languages and languages written using Thai characters (e.g. Pali, Sanskrit, Khmer, Burmese, etc.)?
Including cases, where the order of these marks has a semantical meaning.

The next step would then to agree on rules of normalisation.

For use in domain names, there probably need to be additional rules. This is not what I am concerned with.

The normalisation has (almost ?) nothing to do with the question of fonts.
E.g. กู้ in both variants (vowel + mark and mark + vowel) look identical in about a dozen Thai fonts - the only exception being Apple's Thonburi font, which refuses to show the non-normalised form correctly.

If a font can not correctly combine non-spacing marks, the font manufacturer should be notified.


Kind regards,

Gerriet.