Re: Variation Selectors

From: Andrew West (
Date: Mon Mar 27 2006 - 07:12:09 CST

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    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.


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