[tex-live] Re: [Fontforge-devel] Re: UTF8 and (La)TeX backend?

Vladimir Volovich vvv at vsu.ru
Wed Jan 5 14:56:13 CET 2005

"GW" == George Williams writes:

 >> Then they have to be there in the CFF separately. The H/D can be
 >> different from the outlines, eg. due to overshoot.
 GW> What do you mean by overshoot?

 GW> Remember tfm metrics are not perfect. There are only 16 possible
 GW> values for depth or height, and one of these is required to be
 GW> 0. So in a font with many different glyph sizes the tfm file has
 GW> already done some kind of grouping operation which can lose a lot
 GW> of information.

 GW> All the information about the glyph's shape is contained in its
 GW> outline.  It's going to be far more accurate than a rounded tfm
 GW> value.

No, the glyph height, for example, is used by TeX to put calculate
accent positioning over the glyph. And by design, some glyphs like "o"
have small "overshoots", which should not lead to a change in
caculated accent position. So having glyph dimentions as separate
entities (rather than obtained from glyph outline) seems the right
thing to do.

(added Cc to tex-fonts at math.utah.edu, as this discussion is most
relevant to that list).


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