Re: Ligatures, kerning, ZWNJ & OpenType

From: Marcin 'Qrczak' Kowalczyk (
Date: Sun Jul 15 2007 - 14:43:24 CDT

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    Dnia 15-07-2007, N o godzinie 10:17 -0700, John Hudson napisał(a):

    > I believe ZWNJ should *not* inhibit kerning,

    This is what I thought.

    Pango inhibits kerning at ZWNJ too.

    > In the OT Layout GSUB table, include a lookup that either substitutes
    > the base letters for these duplicates in context of a following ZWNJ:

    Thank you for the suggestion. It didn't work out of the box, but it
    worked with XeTeX when I made such ligatures with ".null" (mapped at
    U+0000). ICU does treat ZWNJ somewhat specially, it doesn't put ZWNJ
    glyphs in the output stream, and it seems that it replaces them with
    ".null" glyphs at some stage.

    I knew to try to use ".null" because when I did not have a ".null" glyph
    in my font, XeTeX replaced ZWNJ with a regular space. This is definitely
    an ICU-specific hack, nobody said that ZWNJ should become ".null"...
    It doesn't work with Pango, neither do ligatures with ZWNJ.

       __("<         Marcin Kowalczyk

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