Re: Control picture glyphs (was Re: Apostrophes at

From: John Hudson (
Date: Fri Aug 24 2007 - 17:05:27 CDT

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    When we're making OT fonts for complex scripts in which control characters such as
    ZWJ/ZWNJ or directionality control marks are expected to be encountered in text, we do
    include visible glyphs for these characters, and our expectation is that the application
    will control whether these display or not depending on user-settings. Ideally, these
    glyphs are zero-width but with visible indicators above the text, so that they are easily
    visible. There are a few visual conventions for the display of common control characters,
    mostly intuitive.

    Some apps have problems with these visible glyphs, because they have not figured out that
    they need to suppress display unless the user wants them for editing purposes. Usually, if
    this is pointed out to them they understand how the fonts are designed to work, and there
    seem to be enough such fonts on the market to drive app developers to work according to
    this model.

    This is not to say that it is the best possible model. I can imagine a model in which
    control character glyphs would always be zero-width blank glyphs, and in which editing
    mode in applications would provide their own visualisation of control characters.

    John Hudson

    Tiro Typeworks
    Gulf Islands, BC
    Do not begin to paddle unless you intend always to paddle.
              - St Jean de BrΓ©beuf, instructions for missionaries, 1637

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