Re: U+25CC and fonts

From: John Hudson (
Date: Sat Jun 16 2007 - 19:49:08 CDT

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    Samuel Thibault wrote:

    > Ok, but my question is: should it have an entry for U+200D, or should
    > the font engine know that U+200D doesn't render anything and thus not
    > having an entry for it is fine (and avoids displaying .notdef)?

    Ah. At least from Microsoft's perspective, the font should contain glyphs for U+200D and
    other control characters even though these glyphs will not be displayed most of the time.
    For editing purposes, it can be useful to turn on display of such control characters, and
    programs like MS Word allow this in the options setting. So fonts should actually contain
    zero-width but visible and distinguishable glyphs for these control characters, even
    though the display of these glyphs is suppressed unless the user turns them on.

    The suppression of control character glyph display is something that happens after font
    layout processing, in case the glyphs are used in glyph substitution lookups as sometimes
    happens. This means they are actively suppressed and not simply ignored for display
    purposes. So the moment at which the application determines that the font is missing a
    cmap entry for the control character occurs long before a decision about whether to
    display the glyph.

    John Hudson

    Tiro Typeworks
    Gulf Islands, BC
    We say our understanding measures how things are,
    and likewise our perception, since that is how we
    find our way around, but in fact these do not measure.
    They are measured.   -- Aristotle, Metaphysics

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