Re: Display of Isolated Nonspacing Marks (was Re: Questions on ZWNBS...)

From: Peter Kirk (
Date: Sat Aug 09 2003 - 17:07:48 EDT

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    On 09/08/2003 13:23, Noah Levitt wrote:

    >According to the docs at
    >uniscribe renders combining marks in isolation when they are
    >applied to SPACE + ZWJ. (Without the ZWJ, it uses a dotted
    >circle.) Perhaps this is an acceptable solution to the
    >people calling for a new character.
    > Combining marks and signs that appear in text not in
    > conjunction with a valid consonant base are considered
    > invalid. Uniscribe displays these marks using the fallback
    > rendering mechanism defined in the Unicode Standard
    > (section 5.12, 'Rendering Non-Spacing Marks' of the
    > Unicode Standard 3.1), i.e. positioned on a dotted circle.
    > Please note that to render a sign standalone (in apparent
    > isolation from any base) one should apply it on a space
    > (see section 2.5 'Combining Marks' of the Unicode
    > Standard). Uniscribe requires a ZWJ to be placed between
    > the space and a mark for them to combine into a standalone
    > sign.
    This is a clear demonstration that Microsoft also has problems with the
    mechanism which has been defined in the standard for ten years, that
    space followed by diacritic is legal and should be rendered as the
    isolated diacritic. But the alternative mechanism which they have
    implemented is non-standard and apparently a defective combining
    sequence, as ZWJ (if I remember correctly) is not a base character. The
    best way to fix this situation is to define a new character with the
    correct properties.

    Peter Kirk (personal) (work)

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