Re: New FAQ page

From: James Kass (thunder-bird@earthlink.net)
Date: Thu Oct 11 2007 - 00:27:58 CDT

  • Next message: Doug Ewell: "Re: Emoticons"

    Exasperated sigh.

    >
    > http://www.unicode.org/faq/unsup_char.html
    >

    > Q: How should characters be displayed if the rendering system
    > doesn't fully support them?

    The correct answer is that it depends on the operating system and the
    font(s) in use. Display issues such as these are beyond the scope of a character encoding standard. Suggestions are fine, defining expected
    behavior is not.

    > A: There are three main options, depending on the type of
    > character involved. Some should not display at all (zero-width
    > invisible characters); some should display as a visible (but blank)
    > space; and some should be displayed with one or more generic
    > glyphs, often referred to as "missing glyphs" or a ".notdef glyph".

    The appearance of the "missing glyph" in a font is completely under
    the control of the font developer. Many developers use a hollow
    rectangle, but some developers use their own logos. Even some
    mainstream fonts, like MingLiU, have a spacing glyph with no
    contours for the missing glyph. (No contours means that, in
    such fonts, the missing glyph will display as a space. Take any
    blank sheet of paper, it matches MingLiU's display of any Canadian
    Syllabics text, for instance.)

    > Where a font is being designed for a rendering system that does
    > not handle invisible characters (such as variation selectors), then
    > the best glyph for them — in the absence of other support — is a
    > zero-width invisible glyph.

    Fonts are built to the font specs and should be cross-platform. In
    the unlikely event that a developer targets a rendering system which
    doesn't handle so-called invisible characters, the font developer has
    a slim chance of knowing if and when the rendering system might
    be updated. Savvy font developers hew to the line, and let the chips
    fall where they may.

    The attached graphic "2229VS1.GIF" shows the display of the same
    text in two different fonts. What do the authors of this FAQ
    consider "broken" in this picture? One font? Both fonts? The
    operating system? The rendering system? The application?

    The correct answer is that the operating system, both the fonts,
    the rendering system, and the application are behaving correctly
    and as expected.

    Here's the text string used in the graphic: ∩ + ︀ = ∩︀

    Best regards,

    James Kass

    P.S. - I doubt if 'how to display unsupported characters' is really
    asked frequently and wonder what criteria determines the
    frequency of FAQs on the Unicode site. If it *is* a FAQ, then
    it should be asked on the OpenType list rather than at the
    consortium.


    2229VS1.GIF

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