[texhax] Unicode Replacement Character in Standard TeX

Karl Berry karl at freefriends.org
Thu Jan 15 00:30:38 CET 2015

Hi Doug,

    Is there a font, available to -all- TeX users

Do you mean "available in theory", or "available in practice in all TeX

If the latter, no: it's not in Computer Modern -> not available to all
users.  There's not even a filled black diamond (never mind the reverse
video question mark) in cmsy.

Now, if you're willing to load a font that's not built into the formats,
there are filled black diamonds (e.g., mathabx -- see
http://ctan.org/pkg/comprehensive), but I don't see U+FFFD itself in
that doc.

I suppose it must exist in the big OpenType fonts like DejaVu that are
also used as system fonts.  Many of these are part of TeX Live, but a
random document couldn't rely on them being present.  (XeTeX won't
magically give it to you either, by the way.  You would still have to
select some font with it.)

    Inserting TikZ commands?  Raw PostScript?

If you can't rely on random font xxx to be present, you certainly can't
rely on tikz to be present, either.

Raw PostScript would prevent creation of PDF.  Maybe it could be done
directly in PDF too, but I don't have a recipe.  Just inserting a
question mark glyph in either PS or PDF seems potentially problematic to
me, starting from a bare environment.  These days, I don't think you can
count on even /Times-Roman to be present.

    Right now, for lack of a better solution, I'm using a \textbullet,
    simply because it's the boldest/blackest glyph I can think of, and
    it's available in most standard fonts.

Indeed, it is in cmsy10.  An even "blacker" glyph is \clubsuit.
Of course, using any real character looks problematic.

    unless (perhaps) it can be done automatically and on the fly when
    processing the document each time.

In practice, no, that wouldn't be workable.

Hmm.  I don't seem to have a good answer.  Sorry.  What's the context?


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