From: John H. Jenkins (email@example.com)
Date: Mon Aug 17 2009 - 18:17:29 CDT
在 Aug 17, 2009 12:37 PM 時， Julian Bradfield 寫到：
> Incidentally, Wikipedia currently says (under "OpenType") that
> Opentype has no font-internal support for complex script shaping. If
> that's not the case, perhaps you could correct it?
> If it is the case, then what's so different from doing client-side
> script-shaping with bitmapped fonts, which you could also do?
The statement in Wikipedia is correct. Kind of.
OpenType splits complex rendering into two hunks of data. The
rendering engine has all the data needed to do the basic operations
common to any font for a given script (reordering, insertion, bidi
algorithm, and so on). The font contains the data needed to resolve
cases pertinent to the font.
To use a trivial case, the OpenType rendering engine knows that Latin
letters are laid out one-by-one, left-to-right across each line. The
fonts, on the other hand, hold the information on which ligatures (if
any) the font supports, and so on.
The fact that there are font-specific aspects to rendering any script
(yes, even Han) is what underlies Unicode's predisposition towards
complex rendering. For example, monospaced fonts on the Mac will
generally have ﬁ and ﬂ ligatures, even though it makes no
typographic sense and text that uses them looks really ugly. They
have them because the two ligatures are characters in MacRoman.
From a technical standpoint, there's no reason that script-shaping
can't be done just as easily with bitmap fonts as with outline fonts.
I don't know to what extend this is actually the case, because I know
very little about text rendering on X11. I do know that there's been
a fair amount of work extending TeX and Metafont for Unicode support.
John H. Jenkins
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