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

[Ross Moore]

Hi Daniel, Kris and Will

On 10/11/2010, at 8:49 AM, Daniel Müllner wrote:

> Hi Ross and all others,
> 
> xypdf indeed uses a \fontdimen parameter: \fontdimen8\textfont3 for the default line width. Besides, it relies on other parameters calculated by Xy-pic, like \xydashl@ for the dash length and \xydashh@ for the separation of multiple strokes.

The patches in  unicode-math.sty  are related to 
  \fontdimen22 \textfont\tw@ .

This token sequence occurs in several places within the
various  xy*.tex  files.
That fact alone suggests that the token sequence should
be replaced by a macro.

As well as being superior (from the functional programming
point of view) it would make it easier to maintain; especially 
for the situation in which  \fontdimen22  doesn't exist.
You would just need to replace a single macro expansion with
something else that produces the desired value.

It might be even more efficient to use a dimension-register to 
store the appropriate value. However, doing this might well require 
that this register be checked to indeed hold the correct value; 
e.g., if the font-size or face changes, then so would this value.
So staying with a macro may well be best.

> 
> If unusual math font setups cannot provide these parameters, a patch should supply these. If there are better or more future-compatible ways of getting the math font parameters, please tell me so that I can adapt the methods in xypdf.

Indeed.
This is consistent with shifting any code that refers to specific 
font parameters out of the main  xy*.tex  application and 
extension files, and into another file whose purpose is more 
like that of a driver.


Now supposing we have such a macro  \xyfontxxii  say,
with default expansion  \fontdimen22 \textfont\tw@  ,
the questions become: 
   How is this to be patched?
   When should it be patched?

Is having  unicode-math.sty  loaded sufficient to require
the macro be patched?   Surely not. 
There also needs to be an instance of  \setmathfont ,
because a package should be able to be loaded, 
without actually using its features.

Now there is the possibility that \setmathfont  is used within 
a group; so that some of the maths could be in older TeX style,
while some is done in unicode-math style.

Thus the patched expansion of  \xyfontxxii  needs to include
a test for the kind of mathematics support being used; or rather
the type of font being used. Slightly messy; but I'm confident
that the benefits will be worth it.

Similar arguments apply to any other place where Xy-pic (or xypdf)
needs to access font properties.

> 
> Best,
> 
> Daniel


So it looks like an Xy-pic 3.8.4 is on the horizon.


Cheers,

	Ross

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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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