Re: Control picture glyphs

From: James Kass (
Date: Tue Sep 04 2007 - 10:41:00 CDT

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    Quoting from

         "All combinations not listed in StandardizedVariants.txt are
         unspecified and are reserved for future standardization;
         no conformant process may interpret them as standardized

    Displaying invalid sequences using visible control pictures in plain-text
    editing environments is conformant.

    Not highlighting invalid sequences in some fashion means that they are
    being treated/interpreted exactly as though they were valid
    standardized variant sequences.

    If, by providing control picture glyphs for VS characters, a font
    developer enables an otherwise conformant application, like Notepad,
    to remain conformant, where's the harm?

    Suppose, in plain-text, I wanted to point out something about VS characters
    and standardized sequences, like:

    ∩ + ︀ = ∩︀

    In order to get a sensible display, we'd need to be able to display that
    character in isolation. That's really all that the control picture is doing.

    Perhaps one of the most common uses on the web right now for VS
    characters is to populate Unicode HTML charts. Again, this calls for
    a control character to be displayed in isolation. How to display these
    characters in isolation is up to the combination of the browser, the
    rendering engine, and the selected font.

    (Some web pages do not use an NCR to provide a display glyph for the
    VS characters, but some pages do.)

    If we find the above example on a web page and open the web page source
    in Notepad, we might see something like:
    &#8745; + &#65024; = &#8745;&#65024;

    Why should the display make *less* sense if we convert the NCRs to UTF-8?

    Best regards,

    James Kass

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