[Groff] hyphenation differences between fonts

[Steve Izma]

I have an Adobe Type 1 font, Minion-Regular, that doesn't
hyphenate the way my other fonts do. For testing, I created a
test file with a line length of 1P (I don't know of another way
of testing hyphenation) like this:

.ll 1P
.fam T
foreground
.br
.fam MIN
foreground
.br
.fam GA
foreground
.br

Running this through troff, I get this intermediate output:

x T ps
x res 72000 1 1
x init
p1
x font 21 TR
f21
s10000
V12000
H72000
md
DFd
tfore
Chy
h3330
n12000 0
V24000
H72000
tground
n12000 0
x font 52 MINR
f52
V36000
H72000
tf
H74920
to
H80060
tr
H83610
te
h40
tg
h110
tr
H96050
tound
n12000 0
x font 53 GAR
f53
V48000
H72000
tfore
Chy
h3660
n12000 0
V60000
H72000
tground
n12000 0
x trailer
V792000
x stop

You'll note that both Times (TR) and Garamond (GAR) produce two
lines "fore-" and "ground", but the same word in the MINR font
doesn't break at all. I've tried this with many different words,
and I think it has something to do with kerning pairs. The Minion
font has tons of kern pairs in its AFM file, and one of them is
"e g". The above output shows that the "e" and the "g" are kerned
by 40 units (which is the value in the AFM file multiplied by
10). Neither the Times or the Garamond have a "e g" kerning pair,
and in fact Minion seems unusual in that it has a vastly larger
number of kern pairs for lower-case letters. One would think that
good font design would make most of them unnecessary.

But why should pair kerning matter in the hyphenation procedure?
Or am I missing something here?

        -- Steve
-- 
Steve Izma
-
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Work: Wilfrid Laurier University Press p:519-884-0710 ext. 6125
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A: Because it messes up the order in which people normally read text.
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