From: Andrew West (andrewcwest@gmail.com)
Date: Mon Mar 27 2006 - 07:12:09 CST
On 3/25/2006 6:09 PM, Richard Wordingham wrote::
>
> Does anyone care to expound the theory of variation selectors?
>
I have a slightly different take on variation selectors compared with
Asmus, but I don't have time to expound my theory today (although it
would make a good blog topic). In summary, I feel that variation
selectors are used for two very different purposes, depending upon the
script that they are used with:
1. Bad Standardized Variants
For Mathematical operators and CJK ideographs variation selectors are
(or will be) used to select glyph variants that may or may not have
any semantic significance. My view is that if these differences are
not semantically significant they should be expressed using a higher
level protocol, and if they are then they should be encoded as
separate characters.
2. Good Standardized Variants
For Mongolian and Phags-pa (from 5.0) variation selectors are used to
select a contextual glyph form out of context. In these scripts the
glyph form taken by a particular character can vary according to
context, and under normal circumstances the rendering system will
select the correct glyph form according to its rendering rules without
any need for variation selectors. However, where context cannot be
determined by the rendering system (e.g. for Mongolian where
particular glyph forms may be used for writing foreign words) or where
the user needs to override the contextual rules (e.g. to display a
particular contextual glyph form in isolation), then the user needs to
explicitly select the desired glyph form by applying the appropriate
variation selector. As Asmus says, this usage is analogous to the use
of ZWJ and ZWNJ to select particular glyph forms in other scripts.
I think that the use of variation selectors in Mongolian and Phags-pa
is perfectly reasonable, and for these scripts it is definitely not "a
solution of last resort". For other scripts, using variation selectors
may be "pseudocoding" (as Michael terms it) and should best be
avoided. Nevertheless, I can think of scenarios where variation
selectors may be the optimal solution for dealing with non-contextual
glyph variants. Myanmar is definitely not one of these.
Andrew
This archive was generated by hypermail 2.1.5 : Mon Mar 27 2006 - 07:24:10 CST