On 14/11/2011 06:00, Will Robertson wrote:
>> 3.	(I accept that you might consider this one a bit cheeky; I don't even
>> know if it's possible): for coffins containing text, provide a means of
>> defining left and right poles that align with the glyph outlines,
>> excluding sidebearings. I realise this is quite challenging even to
>> specify --- what to do, for example, when a glyph's ink protrudes into
>> the sidebearing. I can also accept, up front, that this has nothing to
>> do with xcoffin per se; but it would be a very useful feature.
> 
> This isn't so cheeky when you consider the use case. Lining up glyphs by their ink would definitely be a feature when designing titlepages and the like.
> 
> I'm going to go out on a limb and suggest this won't be provided in the medium-term by the base package for one main reason: calculating side-bearings is only possible in XeTeX and LuaTeX, so pdfTeX would not be able to support this feature. (Although graceful degradation *could* be an option here.)
> 
> I'm not actually aware of a user-friendly way to access side-bearings in LuaTeX, but it would be easy to imagine a package that provided such facilities for both unicode engines and then a hook into the coffins code to allow these poles to be calculated somewhat automatically.

As Will says, this seems to be somewhat outside the core competence of
xcoffins, at least at the moment. We've not really begun to get a real
feel for how to handle stuff that pdfTeX simply cannot do. This one is
worth noting so I'll open an issue in the database so we don't loose it!
-- 
Joseph Wright