[pdftex] "Grouping" glyphs

[Heiko Oberdiek]

On Thu, Mar 16, 2006 at 11:41:59AM -0500, Geoffrey Alan Washburn wrote:

> Hi everyone.  Consider the following contrived example where I am 
> creating a "new" mathematical symbol out of other glyphs.
> 
> \documentclass{article}
> \newcommand{\mysym}{\ensuremath{|\!\!=}}
> \begin{document}
> \[\mysym\]
> \end{document}
> 
> This works just fine visually, but it has the problem that \mysym is not 
> treated "atomically".  If I open the resulting PDF in Acrobat Reader and 
> search for "=" it will find the = that is part of my new "glyph". 
> Semantically it shouldn't be consider any "=" anymore, it is part of 
> some new "glyph".
> 
> Is there some pdfTeX magic that I can use to make \mysym appear to be 
> "atomic" to PDF searching?

In principle it is easy, use a real font that contains |= as glyph.
The difficulty is to find such a font.

Virtual TeX fonts will not work, because the resolution would
put two glyphs "|" and "=" into the pdf output. But in theory
a Type 3 font could be used that maps the two glyphs as one
glyph in the Type 3 font together. Also a mapping to Unicode
can be given, thus that the PDF Reader is able to detect the
new glyph by its Unicode. But I don't know, whether this approach
is possible with pdfTeX and how easy this would be.

Yours sincerely
  Heiko <oberdiek at uni-freiburg.de>
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