[luatex] How to color unicode combinging characters.

[Paul Isambert]

Le 18/03/2011 03:21, Khaled Hosny a écrit :
> On Fri, Mar 18, 2011 at 03:39:50AM +0200, Khaled Hosny wrote:
>> On Thu, Mar 17, 2011 at 10:25:11PM +0200, Simo Ojala wrote:
>>> Hi,
>>>
>>> I am really just taking my first steps in TeX world, so forgive me
>>> my ignorance. However I already have this quite advanced coloring
>>> problem and I have read and been told that LuaTeX might be able to
>>> solve this kind of stuff. So thats why I try to ask this here,
>>> hopefully found the right place to post this kind of problem...
>>>
>>> I am trying to create some ancient hebrew inflection charts and the
>>> problem is to be able to paint vowels (and other diacritics) without
>>> changing color of the consonants they are combined with. (The vowels
>>> are unicode combining characters which are positioned according to
>>> and combined with consonants.) I already have got some suggestions
>>> that I could do some thing like this:
>>>
>>> \textcolor{red}{a}\textcolor{blue}{b} % where 'a' represents a
>>> consonant and 'b' a vowel
>>>
>>> However this leads to situation where the characters are not
>>> actually combined, but just placed separately to the document. That
>>> it turn leads to positioning problems and other bad stuff.
>> You don't provide any sample files, so one can only guess.
>>
>> I think the problem is related to pdfliteral whatsits used to implement
>> color, so using luacolor package (check its documentation) in LaTeX or
>> using ConTeXt would help, either would get rid of whatsits in favour of
>> attributes. But again, without a test file one can only guess.
>>
>> ConTeXt have even more "goodies" to automatically color certain glyphs
>> without manually inserted color commands, but I never used it, though.
> Looks like luacolor is not compatible with luaotfload so opentype
> features (needed for mark positioning) will not work.

Just a question: wouldn't it be simpler to create a virtual font? 
(Virtual fonts are illustrated in luatexref with colors, precisely).

Best,
Paul