[Xy-pic] Conflict between unicode-math and xypic

[Will Robertson]

On 10/11/2010, at 6:46 AM, Ross Moore wrote:

>> Actually, since the patch for xypic is not needed when using xetex, I
>> surrounded it by \ifluatex ... \fi and I seem to get correct results
>> with both engines.
> 
>  ... but question whether this is the best fix.
> 
> The patch to Xy-pic coding seems to be about the use of
> \fontdimen22  to set alignment/positioning with respect to
> the baseline. It may also be setting the width of rules.

This is a currently-active area of the code at the moment. This xy-pic compatibility code was recently added but my plan is to remove it again soon.

As you can see, the current code patches routines within xy-pic that assume fontdimens for math according to TeX's traditional ideas for TFM fonts. These are not consistent with unicode-math fonts, which have a single set of math font dimens (rather than different font dimens according to which fam they're loaded in).

What the new code will do is patch the fonts in fams 2 and 3 to have fontdimens that are consistent with TeX's legacy ways of doing things. (And if you need the OpenType math font dimens, you'll need to use the fam for the last math font selected.) This should remove the need for any compatibility code in unicode-math, as the legacy interface will be backwards compatible.

I just haven't inserted the mapping between the fontdimens yet.

-- Will