[XeTeX] Diacritics in color

[Tobias Schoel]

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?
> That is, position a coloured version of the required glyph over the full character in monochrome.
>
> In the pedagogical setting, you are presumably talking about the single stroke as a sub-part of the whole character, so it deserves to be placed as an entity in itself.
As a single stroke wouldn't be recognised as such, it should be shown in 
conjunction with the whole character. For example print the whole 
character in gray and the interesting stroke in brigt red.
> This is quite different to a colored diacritical mark modifying the meaning of a character.
Do you mean a technical difference or a semantic difference? Of course, 
the semantics differ. That's also the case with mathematical diacritics 
vs. text diacritics. The technical aspects should serve these semantics.
>
>>
>> Of course the font creator has to create sub-glyphs or other fancy stufff, but XeTeX should allow (re)composition of the glyph with different colors.
>>
>> bye
>>
>> Toscho
>
> Hope this helps,
>
>         Ross