documentation of \pdfgentounicode

Ulrike Fischer news3 at
Wed May 27 12:54:43 CEST 2020

When using \pdfgentounicode=1 without loading glyphtounicode.tex or
setting up some mapping with `\pdfglyphtounicode` one gets a warning

`pdfTeX warning: pdflatex-dev.exe: no GlyphToUnicode entry has been
inserted yet

and no cmap resource with ToUnicode entries in the pdf. That is what
I expected from the documentation.

Not quite expected was what happened when I added one nonsense


In this case one get a cmap resources *and* this resources is
populated with lots of entries that pdftex seems to guess from the

Looking at texk/web2c/pdftexdir/tounicode.c I found that the rules
seem to be that 

 /* s is a multiple value of form "uniXXXX" */
 /* s matched an entry with numeric value in the
    database, or a value derived from "uXXXX" */

That is quite nice and means that for example the libertine math
font gets quite good tounicode values as it uses the uXXXX-syntax. 

Imho this should be better documented.






Ulrike Fischer

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