[luatex] callbacks in luatex 0.89

[Ulrike Fischer]

Am Thu, 11 Feb 2016 14:53:11 +0100 schrieb Hans Hagen:

>> Is there in context code which offers something similar to
>> \XeTeXinterchartoks? That means can one declare (unicode)
>> blocks/classes of characters and tokens (e.g. font switches,
>> language switches etc) which should be inserted between character of
>> different blocks?
>>
>> If yes, where is it?
> 
> No, because it's not the way context does things (or at least I never 
> needed it so I never bothered to look into writing it). I would probably 
> look into it when there was demand for some feature not supported yet. 
> Even then I'd probably not rely interpreting unicode characters but on 
> proper tagging because one never knows what the intended use/rendering 
> of some character at some point it.

Proper tagging is naturally always more reliable. But I can
understand that people who write e.g. a mix of chinese with some
english/ascii and need to switch fonts don't want to tag all the
time. That can get a bit tiring, also it is error prone.

The second case where \XeTeXinterchartoks is used is for spacing at
punctuation, e.g. in french. This can be done with attributes
(frenchb.ldf in latex uses it). The main difference is to the xetex
method is that almost every normal user can unterstand
\XeTeXinterchartoks and set it up, while the lua method needs more
knowledge. 


-- 
Ulrike Fischer 
http://www.troubleshooting-tex.de/