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

From: Kenneth Whistler (kenw@sybase.com)
Date: Mon Aug 04 2003 - 20:36:28 EDT

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    Peter Kirk asked:

    > A similar issue which is not Hebrew related would be a (mythical)
    > requirement to display a diacritic like 0315, 031B or 0322 in isolation.
    > It would not always be appropriate to use a space or NBSP as a base
    > character as this would indent the glyph from the beginning of a line in
    > a way which might not be wanted. What would be the recommended encoding
    > if one wanted to display one of these characters with no leading white
    > space?

    If you just want to display a nonspacing mark in isolation, then
    you apply it to a SPACE (or NO-BREAK SPACE) and typically let the
    metrics of the font then handle how the mark is going to appear
    "floating in space" as it were.

    If you want to display some character like U+0315 COMBINING COMMA
    ABOVE RIGHT *and* you want to do it is isolation *and* you want
    it to occur at the beginning of a line *and* you want there to
    be no display width between the margin and the left edge of the
    display bits of the glyph, then you have stepped over the boundaries
    of what is reasonable to expect plain text to convey. Feel free
    to make use of the higher-level capabilities of your word
    processor or page layout program to individually adjust the
    positioning of particular glyphs displayed in particular fonts.

    More generally, however, when the issue of the relative
    position of a non-spacing mark with respect to its base
    glyph is what is in question, the standard recommends
    (and uses) the convention of displaying the non-spacing
    mark on a dotted circle as a base. This makes it clear that
    we are talking about the non-spacing mark itself, but also
    makes clear the positional differences between left, centered,
    and right forms, for example.


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