As originally intended, a Type 1 SEAC charstring would be used for
an accented glyph (like `acaron' or `uumlaut'), where the advance
width of the SEAC glyph is the same as that of the `base' glyph
(like `a' or `u'). In this case it is not uncommon for the SEAC
glyph to not use an (H)SBW opcode of its own but to rely on the
value from the base glyph.
However, out-of-spec fonts also use SEAC glyphs for ligatures (like
`oe' or `fi'), and in those cases the overall advance width is
greater than that of the `base' glyph. For this reason we have to
allow that the SEAC glyph can have an (H)SBW value of its own, and
if it has, retain this value, rather than the one from the base
glyph.
* src/psaux/psintrp.c (cf2_interpT2CharString) <cf2_escSEAC>:
Implement it.
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