Combining Marks and Variation Selectors

[Richard Wordingham via Unicode]

On Sun, 2 Feb 2020 16:20:07 -0800
Eric Muller via Unicode <unicode at unicode.org> wrote:

> That would imply some coordination among variations sequences on
> different code points, right?
> 
> E.g. <0B48> ≡ <0B47, 0B56>, so a variation sequence on 0B56 (Mn,
> ccc=0) would imply the existence of a variation sequence on 0B48 with
> the same variation selector, and the same effect.

That particular case oughtn't to be impossible, as in NFD everything in
sight has ccc=0.  However TUS 12.0 Section 23.4 does contain an
additional prohibition against meaningfully applying a variation
selector to a 'canonical decomposable character'. (Scare quotes because
'ly' seems to be missing from the phrase.)

Richard.

> On 2/2/2020 11:43 AM, Mark Davis ☕️ via Unicode wrote:
> I don't think there is a technical reason for disallowing variation
> selectors after any starters (ccc=000); the normalization algorithm
> doesn't care about the general category of characters.
> 
> Mark