From: Asmus Freytag (firstname.lastname@example.org)
Date: Mon Nov 24 2008 - 13:21:18 CST
On 11/23/2008 9:36 PM, John Hudson wrote:
> Karl Pentzlin wrote:
>> At least, this. This can be accomplished by an algorithm...
> An algorithmic approach to mark positioning is certainly a desirable
> fallback when a font does not contain specific anchor positioning data
> for the base+mark sequence. This, of course, means that the layout
> engine will need to query whether the font contains anchor positioning
> for the glyph sequence -- a blind check for the presence of e.g. a
> <mark> layout feature in an OpenType font is not sufficient, since such
> a feature may support e.g. Latin+mark combinations but not Cyrillic+mark
> --, and if not then apply the algorithm.
> There are, of course, things that the algorithmic approach won't be able
> to handle reliably: marks that attach to the base in different
> horizontal positions depending on the shape of base (e.g. ogonek), marks
> that are by design not centred but e.g. above the right side of the
> lettter, and the substitution of flatter accent forms above capital and
> ascending letters.
I think that an algorithm could have generic tables that capture some
aspects of typical ink distribution for certain characters. For example,
the generic fact that the typical A is trigonal, whereas O or U etc.
typically touch the base only in the center. Having some canned
information like that beats having information for each individual pair.
If this info fails for any specific font - well, it's intended as a
I also think that if such algorithms were more widely deployed, it would
be advantageous if there was a way for font suppliers to create and make
accessible generic flattened forms of diacritics. That's still cheaper
than designing all the specific combinations.
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