User Guide

perhaps you want to link the left sidebearing of “B” to “D,
E, F, H, I, K, L, M, N, P, R, and U.” Many other characters
share a similar right sidebearing.
Once you have set up all the equivalence classes
imaginable, you probably won’t want to do so again. That’s
why there is the big “Save to file” button.
Of course, the real power of equivalence classes lies in the
fact that once set up, you can change the values of the base
characters. Therefore, if you really get into it, it is possible
to set up enough classes so that you can completely
determine the widths and sidebearings of the entire font by
manually setting those characteristics for some small set of
base characters.
Removing equivalence classes is quite straightforward:
simply select the base character, delete it, and click “OK.”
If you open the dialog again, you will see that the class has
been erased.
Sometimes you will see constructs like this: “a d-m z” in
the “Apply to these characters” field. This happens when
you had originally entered something like “adefghijklmz”.
Fontographer will detect contiguous characters, and
abbreviate them with a hyphen. This can frequently save
some space, because sets
like “abcdefghijklmnopqrstuvwxyz” appear much shorter
as “a-z.” If you want, you may also use the “a-z”
convention when entering characters.
The same base character can be involved in different
classes. For instance, one class might connect the left
sidebearing of the “A” with a bunch of other characters,
while another class could connect the width of the “A” to
some different characters. If you need to connect “A”
with more characters than will fit in the “Apply to these
characters” field, it is perfectly legal to make another class,
with the same base character and same characteristics, to
continue the first class. Of course, base characters for
some classes can be included in the “Apply to these
characters” parts of other classes, but watch out—this can
get confusing really fast.
If you include the base character in the “Apply to these
characters” field of that same class, it will be recognized as
a circular reference, and automatically removed when the
Fontographer User's Manual
5: Metrics: Spacing and Kerning Page #24