Re: Script of U+0951 .. U+0954

Date: Wed Dec 04 2002 - 17:11:25 EST

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    On 12/03/2002 05:16:14 PM Antoine LECA wrote:

    >This issue is of relevance to the rendering engines. For example,
    >Microsoft's Uniscribe refuse to draw U+095x on top of any syllable
    >which is not Devanagari. I believe this behaviour is incorrect,
    >but the Script.txt file seems to assert MS position.

    I don't think the Script.txt file isn't intended to imply such
    implementation behaviours, though it's easy to imagine some implementers
    might treat it that way.

    There is a potential concern in Uniscribe/OpenType: substitution and
    positioning rules in OT are organised hierarchically by script then by
    individual writing system / typographic groups (the label used is
    languages, but the intent is really groups of writing systems that share
    common typographic behaviours). Thus, a rule that handles positioning of a
    glyph for 0950 (or whatever) relative to some member of some class of
    glyphs must be entered somewhere under some particular script. Now, there
    is nothing that prohibits a font developer from creating multiple
    positioning rules for 0950 with different classes of base glyphs and to
    have a different one placed in the hierarchy under several different
    scripts. But there may yet be an issue on the Uniscribe side: given a
    string of characters, which it will begin by mapping into a string of
    initial glyphs, it has to decide which script tag(s) to apply to portions
    of the string. What I don't know is whether it generally assumes combining
    marks belong to a specific script, or whether it allows combining marks to
    inherit their script from the base characters with which they combine.

    At least, that's my understanding of these technologies (which comes with
    no guarantees).

    - Peter

    Peter Constable

    Non-Roman Script Initiative, SIL International
    7500 W. Camp Wisdom Rd., Dallas, TX 75236, USA
    Tel: +1 972 708 7485

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