[XeTeX] LuaTeX et al

[Jonathan Kew]

On 11 Aug 2006, at 2:52 am, Will Robertson wrote:
>>
>>  Does that imply that it can also access uninstalled
>> OpenType fonts directly?
>
> That would be better answered by Jonathan Kew; at this stage, no,  
> XeTeX still relies on font-config to find the fonts installed.  
> There have been requests for access to "uninstalled" fonts, however.

Right; currently fonts have to be "installed" in the sense of "known  
to fontconfig" (or installed in the traditional tex way with tfms and  
map files and all that, of course). There's no technical barrier to  
using "uninstalled" fonts, specified by filename (or path) in the tex  
source, and located via kpathsearch; it'll just require a little  
extra checking in xetex and xdvipdfmx, to allow for this usage. (All  
fontconfig does, in effect, is map from a "real" font name, as known  
by the user, to a font file on disk, which xetex then uses. So we  
could go directly to the font file by path/name instead.)

>
>>> This is through its use of the ICU OpenType rendering library; I
>>> can't see any reason here to want to reinvent the wheel. Of course,
>>> it's only a component of the system you're discussing.
>>
>> IIRC, ICU does not support the microtypography already present in
>> pdfTeX (font expansion, hanging punctuation). But if it does, or if
>> it is likely that it will start doing so in the very near future,
>> than it is definately worth looking into (so please let me know).
>
> The OpenType format supports margin kerning, but no fonts that  
> anyone's heard of actually includes that data. I guess the problem  
> for you guys is that ICU is for *OpenType fonts* and you still want  
> to provide backwards compatibility support -- and it would be nice  
> to have font expansion and hanging punctuation no matter what font  
> format is used.

Yes, of course it would. But I see this as being a different level  
from the basic OpenType layout processing that is required to apply  
OT typographic features or to provide linguistically correct  
rendering for complex scripts. ICU provides this, and I don't see any  
benefit in re-inventing that particular wheel.

The pdftex microtypography features would be a layer underneath this,  
but I haven't attempted to add this to xetex yet.

JK