[luatex] Using the token_filter callback only for 'some tokens'

[Joseph Wright]

On 07/02/2014 09:02, Khaled Hosny wrote:
> On Fri, Feb 07, 2014 at 08:54:59AM +0000, Joseph Wright wrote:
>> what's the correct approach?
> 
> Personally, I’d just work on node lists before font layout is done (so
> that they are char nodes) and use attributes to mark what nodes I’m
> interested in from the TeX side. This way I don’t need to worry about
> macro expansion at all, and I can control where to apply the case
> transformation without enabling/disabling the callback all the time.
> 
> Regards,
> Khaled

To be clear, that's using the properties of the font not the character,
yes (so at the TeX end the characters are unchanged)? Does that work
reliably for all fonts (most obviously CM)?

I guess my worry is that this is not transparent to the 'user': they've
asked the case to change but if they examine the TeX material it's not
actually happened.
-- 
Joseph Wright