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[ft-devel] Re: Really serious FT bug

From: Werner LEMBERG
Subject: [ft-devel] Re: Really serious FT bug
Date: Sat, 25 Jun 2005 09:27:43 +0200 (CEST)

> > According to the docs, we have
> >   pp1 = xMin - lsb
> >   pp2 = pp1 + aw
> > Most fonts have xMin = lsb so that pp1 is zero normally.  The
> > gotyk font has
> >     xMin = 188
> >     lsb   = 28
> > which means that the whole outline is shifted, causing wrong
> > results.
> Um, I wouldn't leap to that conclusion.  There is some very weird
> stuff in the ttf spec regarding the difference between min & lsb
> (which I never understood).  And shifting phantom point one around
> is a way of translating the entire glyph.

Yes, but actually translating the glyph is wrong IMHO.  I think the
proper action is to recompute lsb and aw after pp1 and pp2 have
changed and nothing more -- the hinting process already shifts the
outline points to the right places.

> I wouldn't be surprised if this weren't correct behavior.  ff does
> not look at that level of tt behavior so my analysis missed all
> that.

Well, if you translate the whole glyph, the global values of lsb and
aw (from the `hmtx' table which should be device independent) become
completely wrong, and this can't be correct.


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