[luatex] Please document units_per_em

[luigi scarso]

On Tue, Dec 8, 2020 at 1:39 PM Patrick Gundlach <patrick at gundla.ch> wrote:

> Hello all,
>
> I could not find the key units_per_em in the font table (6.1 The font
> tables), I assume this is just an oversight. Perhaps this could be
> documented?
>
> Thank you
>
>   Patrick
>
>
>
I think so.  Iirc, It should be related to the unusual em-size:

* There is a new <tfmtable> key: 'units_per_em' (defaults to 0).
  This is part of a fix for bug #200 (Problem with CFF fonts having
  em-size other than 1000): there is a special correction to the
  embedded cff font itself and the font scale if the font to be output
  is opentype or type1 in unicode encoding and the 'units_per_em
  differs' from zero.
  <tfmtable>.units_per_em has to be passed back to luatex from
  the lua font loading code for this to work.

-- 
luigi
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