[tlbuild] Problems with xdvipdmfx (at least) and some fonts

[Reinhard Kotucha]

On 2015-08-25 at 19:17:46 +0200, Fabian Greffrath wrote:

 > Remains the (probably Debian-specific) problem that occurs when two
 > fonts with the same /FontName but different glyph coverage are
 > installed into fontconfig's search path and then apparently get
 > mixed up by XeTeX. Do you think there is anything that can be done
 > about that?

Hi Fabian,
I can at least assure you that the problem is definitely *not*
Debian-specific.  The modified fonts are ubiquitous.

Problems occur if you create a graphics file with references to these
fonts instead of embedding them.  Many programs (like Xfig) rely on
Ghostscript in order to embed the fonts.  PDFTeX tries to create a
common subset of fonts used in the document and external graphics and
the result is unpredictable if there are two different fonts involved
with the same /FontName.

There is no simple solution.  The best thing one could do is to extend
these programs in order to allow users to use TeX Gyre fonts instead.

TeX Gyre fonts were derived from and are metric compatible with the
original URW fonts.  They are certainly a better choice.  However,
unfortunately they don't cover Cyrillic.  AFAIR supporting Cyrillic
had been considered but had to be dropped because TeX Gyre developers
were unable to contact Valek Filippov at that time.

As far as Ghostscript is concerned, I once explained in detail on a
mailing list why it was a bad idea to provide a modified font without
changing /FontName and also explained the impact on TeX.  Someone
forwarded my mail to the Ghostscript development team.  The result is
that Ghostscript is even more unpredictable now.  They said that the
whole purpose of these fonts is to provide a replacement for Adobe
fonts built into PostScript printers.  Hence they created another
subset which contains even less glyphs than the original URW fonts
(and added at least one additional glyph to the Symbol font) and
compiled these subsets into the binary.  Now it makes a significant
difference whether you have the external fonts installed or, if not,
you are are using the built-in fonts.

Ghostscript does by far not provide the reliability we need in the TeX
world in respect of URW fonts.  However, apart from URW fonts,
Ghostscript is quite reliable.

Sadly, the only reasonable solution is to avoid these modified fonts.
It's a pity because it would have been so easy to change /FontName
appropriately.  But it's far too late now.

Regards,
  Reinhard

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