[tex-live] Latin Modern bug in lm-texnansi-os.enc

Taco Hoekwater taco at elvenkind.com
Thu May 24 17:56:50 CEST 2007

bop at bop.com.pl wrote:
> Hi,
>> On the ConTeXT mailing list, Idris posted some messages because he was
>> trying to use oldstyle numerals in the latest Latin Modern release,
>> and was experiencing two pretty big problems:
>>    * really bad kerning around the oldstyle numerals
> We would be grateful if we could get more details (which font, which tfm,
> which encoding, pdftex or tex/dvips, on the screen or on the paper, etc.)
> My first guess is that proportional figures were used with tabular metrics...

Yes, but see explanation below.

>> The implementation of 'automatic' oldstyle numbers in ConTeXt uses a
>> set of encoding files that used to ship with LM (lm-xxxxxx-os.enc).
>> By way of a map file fragment, this allows to switch the fonts
>> 'en masse' from lining to oldstyle (and back) without the need for
>> special metric files, which is a pretty nice feature.
> Don't understand -- the vertical oldstyle digits, in general, have different
> metric data (tabular digits differ only with respect to vertical dimensions).
> So, the replacement of the encoding implies the replacement of TFMs. Or I
> misundersood something.

How it used to work:

   The tabular lining figures are replaced by oldstyle figures by
   means of an encoding file only. This worked fine (because the
   oldstyle figures were tabular as well).

The height and depth are normally not all that important to TeX,
and with the widths the same, there was no need for a different
metrics file, just a single encoding file is enough to give all the
LM fonts oldstyle (tabular) figures instead of lining figures.

This trick broke when the tabular oldstyle figures were renamed
and proportional oldstyle figures were added (to the non-typewriter
fonts. Both problems Idris had came directly from that the fact
that these changes make the encoding file invalid:

* the perceived kerning is wrong because the actual proportional glyphs
   have different sidebearings, and
* the monospace fonts gave an error because the glyphs were renamed,
   so the requested glyphs were no longer existent at all.

>> While writing a bug report, I noticed that these encoding files are no
>> longer in the font distribution
> No. We have a lot enough of TFMs and I'd be reluctant to add more. The only
> resort I can see is to use OTFs...
>> Is this trick to get oldstyle now officially unsupported?
> Rather not, I've just learned about it. ;-)

Yes, I understand that now. Well, can you please consider starting to
support it then? ;-)

>> because there are no oldstyle-using TFM files in the LM
>> distribution either ...
> There are. As I mentioned, ts1 encoding contains oldstyle tabular figures.
> Perhaps accessing them needs other tricks, but as long as 256-glyph fonts are
> to be used, some glyphs must be accessed clumsily. e.g., proportional digits
> (normal and oldstyle).

I know there are way to many TFM  files already, I don't want you to
ship dozens (hundreds?) of new ones. But from a user's point of view,
having to switch to a different encoding for each number is not what
I consider 'supporting oldstyle digits'.

The trick I explained above works surprisingly well (even if the figures
are tabular, not proportional). If I had realized that those encoding
files were not created by you yourself, I would not have bothered you
at all, as it was not your problem to begin with. But that's life ...

Cheers, Taco

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