visible glyphs for U+2062 and similar characters

From: Jungshik Shin (
Date: Fri May 09 2003 - 06:18:52 EDT

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    Recently I found some fonts have visible glyphs for invisible characters
    (that I _guess_ are supposed to have no visual effect) such as U+2062
    (the glyph for U+2062 is dotted 'x' inside a dotted box). With these
    kind of fonts present, a bit naive(??) approach of searching for glyphs
    in all the fonts on the system would turn the 'invisible' to the visible.
    For instance, the following MathML snippet was rendered with
    a visible glyph (⁢ == U+2062) by Mozilla.


    My questions are:

    (1) Is a font to blame for having visible glyphs for U+2062 and
    similar characters. I think U+2062 and similar characters are different
    from ZWJ/ZWNJ and other 'control' characters that do have visual effect
    in such context as Indic scripts, Arabic script and expressing authorial
    intent about ligature in Latin and other scripts)

    (2) What's the normative (if there's such a thing) rendering behavior
    of a sequence with U+2062-like characters? For instance,
    does '<U+0061><U+2062><U+0062>' have to be rendered exactly the same
    way as 'ab'? Perhaps, it'd better be left up to implementations.
    Some implementations (typographic tradition?) may use different
    kerning(?) or add a very thin space between 'a' and 'b'. Others would
    just treat them identically.

    (3) Is there any way (IF it's allowed) to express the authorial intent
    to render U+2062-like characters with visible glyphs?

    Thank you,


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