incorrect extra ligatures in t1.etx for monowidth fonts?

Vladimir Volovich
Sun, 29 Aug 1999 09:14:08 -0400


t1.etx does not distinguish between monowidth and non-monowidth fonts
(unlike ot1.etx). As a result, it contains ligatures which are not
present in monowidth fonts. These are e.g. f-ligatures; their presence
usually does not cause any trouble because fontinst's etx files
provide slots with faked F-ligatures.

But there is also one extra ligature, "endash minus -> emdash" which
is present in roman T1-encoded fonts (ecrm1000) but is absent from
typewriter fonts (ectt1000). This results in _different typesetting_:

the sequence `----' will become

.\T1/cmtt/m/n/10 ^^U (ligature --)
.\T1/cmtt/m/n/10 ^^U (ligature --)

with ecrm1000: these are two minus signs, but with the corresponding
AE font aett10 we get another result:

.\T1/aett/m/n/10 ^^V (ligature ---)
.\T1/aett/m/n/10 -

these are three minus signs (two from ligature --- and one from -).
Therefore it seems that it is better to make fontinst more accurately
follow ligature setup of encodings (in particular, even remove
f-ligatures from typewriter fonts, etc).

	Best regards, -- Vladimir.