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

Ross Moore ross.moore at mq.edu.au
Tue Nov 9 21:16:42 CET 2010

Hi Rémy, Will, Kris, Daniel, Khaled, and others

On 09/11/2010, at 7:52 PM, Rémy Oudompheng wrote:

> On 2010/11/9 Rémy Oudompheng <remyoudompheng at gmail.com> wrote:
>> It seems that the patch for xypic that is included in unicode-math
>> assumes that xypdf is loaded, which is not true when using xelatex. By
>> the way, are these patches backwards-compatible with older engines
>> like tex and pdftex? I was wondering whether they could be included in
>> xypic main codebase.
>> By the way I'm encountering an apparently unrelated error:
>> ! Font \nullfont has only 7 fontdimen parameters.
>> \um_font_dimen:Nnnnn ...criptfont:D }}}}}}}\c_two

Yes, I confirm this problem ...

> 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.

One has to ask whether that patch has been done correctly, 
since it can result (using XeTeX without xypdf) in code blocks 
being invoked while the \font is \nullfont, so cannot have 
the required \fontdimen  parameters.

This also begs the question of whether the patch really belongs
in  unicode-math.sty  or within Xy-pic itself, and whether or
not it is really needed only when xypdf.sty has been loaded
 --- I suspect not, but would like the clarification.

Could someone who worked on this coding please send a report
to Kris Rose and myself, through the Xypic mailing list.

this \fontdimen  stuff is critical, as the OpenType Math fonts
that are appearing do not need to have the same parameters as
Knuth's original math fonts. This is something that may need
to be adjusted in even more places within Xy-pic.

> -- 
> Rémy.



Ross Moore                                       ross.moore at mq.edu.au 
Mathematics Department                           office: E7A-419      
Macquarie University                             tel: +61 (0)2 9850 8955
Sydney, Australia  2109                          fax: +61 (0)2 9850 8114

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