Re: Control picture glyphs (was Re: Apostrophes at

From: Asmus Freytag (
Date: Sun Aug 26 2007 - 14:22:30 CDT

  • Next message: James Kass: "Re: Control picture glyphs (was Re: Apostrophes at"


    imagine you are the programmer writing an editor that, as one of its
    features, has a 'Reveal Special Characters' mode. Your users are free to
    use this editor with *any* font, but they expect that *all* the special
    characters can be shown at all times. Finally, your boss is aware of the
    fact that users want the screenshots in the help files to accurately
    reflect what they will be seeing, and that any unexplained 'weird'
    looking symbols will generate calls to support.

    Your choices of how to meet these requirements are very limited. If you
    rely on each font to carry visible renditions of all these special
    characters, you will face two problems: fonts will not only vary the
    symbols based on basic font style (that would be OK), but there will be
    no agreement between fonts on how to represent certain special
    characters - in the worst case, two fonts might use the same symbol for
    two different special characters. Clearly, even if you can trap the use
    of the .notdef glyph, your boss will be very concerned with that solution.

    You could decide to use as symbols only characters that also occur with
    standard semantics, and which are guaranteed to be in each font. Or that
    occur in an ever-present suite of system fonts. Many editors do that
    when showing spaces, tabs and end of paragraph, but there is the
    inevitable risk of confusion when you encounter a legitimate use of one
    of these characters, and the repertoire of usable, yet guaranteed to be
    available, shapes is limited. The upside is a nice typographic
    correspondence between text and special symbols. If your goal was
    limited support, you'd be done.

    If you want to cover all special characters in Unicode, the easiest
    solution is to ship your own font with glyphs for all the special
    characters. That way, you are in charge of the choice of representation,
    you won't ever get a .notdef glyph, and so forth. You give up having the
    symbols match the type style of the surrounding text, but your
    user-experience will be predictable, and your boss will be happy.

    If the Reveal Special Characters mode is disabled, you would not pass
    any of the special character codes to the rendering engine, unless that
    engine guarantees not to show it, or would consume it, e.g. in rendering
    a variation sequence.

    Variation selectors have no business being visible - unless you are in a
    special mode. The whole idea behind them is that they can (and should)
    be ignored when the resources to act on them (variant glyphs) are not


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