[XeTeX] Diacritics in color

[Khaled Hosny]

On Sat, Dec 03, 2011 at 08:45:24AM +0200, Tobias Schoel wrote:
> 
> 
> On 02.12.2011 21:48, Ross Moore wrote:
> >Hi Tobias,
> >
> >
> >On 03/12/2011, at 6:06, Tobias Schoel<liesdiedatei at googlemail.com>  wrote:
> >
> >>As a teacher I can think of some more Applications. Of course, these are pedagogical:
> >>
> >>Teaching scripts to beginners (learning to write a primary school, learning to write in a different script when learning another language (or even in the same language: Mongol?):
> >>
> >>You might want to color single parts of a glyph in order to highlight them. So, for example in a handwritten (see http://de.wikipedia.org/wiki/Schulausgangsschrift or english equivalents I haven't found in the time) "a" the beginning or end-strokes might be colored.
> >
> >Yes, but are these examples really requiring parts of the same whole character coloured differently?
> >
> >Presuming that the font did allow access to individual glyphs, as if separate characters, then would not all meaningful aspects be equally well (if not better) encoded by an overlay?
> The result would be mostly the same. I don't know if some software
> might treat a partially colored glyph and two overlaid glyphs
> distuinguishably differently.
> 
> Are overlaids encoded in a font and if yes, how are they accessible
> via XeTeX?

Dunno about XeTeX, but in ConTeXt (when used with LuaTeX), you can have
a sort of glyph color scheme that says glyph X takes color Y whenever it
appears in the document (where X is glyph name whether it is encoded or
not), if one wants to color, say the horizontal stroke of A, the font
can be built where A is first decomposed in the Lambda-like part and the
horizontal stroke, and then positioned together by some glyph
positioning rule (or even using negative side bearing for such a simple
case.) Someone can right something like that for LaTeX I think, but you
would still need LuaTeX (unless someone extends XeTeX of course.)

Regards,
 Khaled