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.
Eric.
On 2/2/2020 11:43 AM, Mark Davis ☕️ via Unicode wrote:
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.
Eric.
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
On Sun, Feb 2, 2020 at 10:09 AM Richard Wordingham via Unicode <unicode@unicode.org> wrote:
On Sun, 2 Feb 2020 07:51:56 -0800
Ken Whistler via Unicode <unicode@unicode.org> wrote:
> What it comes down to is avoidance of conundrums involving canonical
> reordering for normalization. The effect of variation selectors is
> defined in terms of an immediate adjacency. If you allowed variation
> selectors to be defined for combining marks of ccc!=0, then
> normalization of sequences could, in principle, move the two apart.
> That would make implementation of the intended rendering much more
> difficult.
I can understand that for non-starters. However, a lot of non-spacing
combining marks are starters (i.e. ccc=0), so they would not be a
problem. <starter, variation selector> is an unbreakable block in
canonical equivalence-preserving changes. Is this restriction therefore
just a holdover from when canonical equivalence could be corrected?
Richard.
