Re: Combining marks with two letters

From: James Kass (
Date: Tue Feb 12 2008 - 05:08:39 CST

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    I wrote,

    > 2. If the CGJ function is only to prevent canonical re-ordering, then there
    > would never be a need for a rendering engine to use it as part of a font
    > look-up.
    > 3. T.U.S. 5.0 pages 540-541 does say that CGJ only blocks re-ordering.

    Oh, but wait...

    Quoting from T.U.S. 5.0 page 541,
    "The CGJ has no visible glyph and no other format effect on neighboring characters
    but simply blocks reodering of combining marks."

    Quoting from T.U.S. 5.0 page 542,
    "However, some older implementations may treat a sequence of grapheme clusters
    linked by combining grapheme joiners as a single unit for the application of
    combining enclosing marks."

    So, the statement on page 541 isn't true.

    And, if CGJs are used to actually join graphemes, as the character name implies
    and as it says on page 542, the rendering engines would be submitting CGJs
    as part of look-up strings and fonts would be including CGJ in GSUB look-ups.

    Best regards,

    James Kass

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