[XeTeX] LaTeX Font Warning: Encoding `OT1' has changed to `U' for symbol font

[Will Robertson]

On 13/05/2006, at 5:53 , William Adams wrote:
> On May 12, 2006, at 2:43 PM, Will Robertson wrote:
>
>> No, this is going down the wrong track.
>
> I would beg to differ given that....

:)
Sorry, I was a bit curt there.

>> I think the current Mac XeTeX installer must include an older version
>> of fontspec -- I fixed this annoying warning up (well, hid it) in the
>> last released version.
>
> Rather than hiding it, wouldn't doing a proper utfenc.def file fix
> it? Would it afford any other advantages? Perhaps address some other
> of the encoding difficulties we've been having?

I haven't pushed for the creation of our very own font encoding for  
XeTeX+fontspec for the reason that "font encoding" doesn't mean the  
same thing when you're using unicode fonts. In LaTeX proper, I font  
encoding is supposed to mean (although doesn't always, to their  
chagrin) that the font contains *exactly* some set of glyphs. Then,  
if a character is requested that cannot be typeset with this font,  
corrective measures are taken.

But consider what this means: every non-ascii character is active and  
assigned a "LaTeX Input Character Representation" (or something,  
can't ever remember what the acronym stands for). E.g. "é" -> \eacute  
-> slot XXX in font with encoding YYY. With XeTeX, we know we're  
always using unicode fonts. So this step is largely unnecessary. "é"  
in the source will be typeset directly by XeTeX.

In order to fulfil the LaTeX paradigm, we'd need to set up a mapping  
for every character in unicode to a control sequence, back to a glyph  
in a unicode font. We'd then need to start representing fonts by  
which subset of unicode they contain, and this will never be fully  
consistent across fonts.

In the scheme above, you could perform error checking in the stage  
from going from command name to unicode glyph, but it would be  
terribly inefficient (consider that Jonathan Kew hasn't wanted to  
implement this *in the source*. This would be much slower.)

Finally :) this wouldn't fix the stupid warning that LaTeX gives when  
changing the encoding of the maths fonts. You can see Robin  
Fairbairn's thoughts on the matter here:
   <http://groups.google.com/group/comp.text.tex/msg/7b80060bf862de20>

It happens whenever you change this stuff :(

All the best,
Will Robertson