Re: 28th IUC paper - Tamil Unicode New

From: Richard Wordingham (richard.wordingham@ntlworld.com)
Date: Mon Aug 22 2005 - 18:48:22 CDT

  • Next message: Adam Twardoch: "Re: 28th IUC paper - Tamil Unicode New"

    Philippe Verdy wrote:

    > From: "Richard Wordingham"
    >> Adam Twardoch wrote:

    >>> GSUB tables don't handle the reordering in Indic languages. It's the
    >>> responsibility of the OpenType Layout processor, e.g. Uniscribe.
    >
    > How can an OpenType Layout processor correctly reorder glyphs, when all it
    > knows from a font is the binding of single (but whole) codepoints to
    > glyphs, and this does not work for characters that have composite glyphs
    > that must be reordered separately, and that don't have individual
    > codepoints assigned to each part?
    >
    > To work reliably, it would mean that the fonts have to be specially marked
    > so that the glyphs associated to each part are assigned predictable PUA
    > codepoints where they can be found in the font's codepoint-to-glyph table.

    Read the introduction to http://www.microsoft.com/typography/otspec/gsub.htm
    . Remember that the non-PostScript part of the font definitions works
    entirely in terms of glyph numbers; the relationship of glyph number to
    character code is (with a very few - three?- exceptions) peculiar to each
    font and is defined within it - the 'cmap' table.

    Richard.



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