[Xy-pic] Problem with skewing(?)

[Ross Moore]

Hi Richard,

On 28/03/2004, at 11:41 AM, Ross Moore wrote:

> Thirdly:
>
>   the \xybox  does not allow control over *where*,
> inside the <object> that it builds,
> the reference point is to be located.
>
> Accordingly, I've just devised a variant that builds
> the same kind of compound <object>, but also sets
> its reference-point to be at the <coord> of the
> last <POS> within the box; i.e., the <coord> for
> the <object> that has been built is at the current
> <POS> when the Xy-pic parsing has been completed.
> The LRUD extents are the size of the complete box;
> i.e., *not* the extents of the final <POS>.


I've now managed to trace the reason that this (and
the previous efforts) didn't work with some of your
examples, but generated infinite looping.
Some control-sequence names associated with constructing
arrows/paths need to be re-initialised.
Appropriate coding is given below.

>
> Here is coding that should go in your document's
> preamble -- eventually it should be added to  xy.tex
>
>
> ---------  start of new Xy-pic definitions  -------
>
> \makeatletter   % adjust the \catcode of @

% this is a better definition for the new  \xyobjbox

   \xydef@\xyobjbox#1{\xy
     \let \PATHafterPOS\PATHafterPOS at default
     \let \arsavedPATHafterPOS@@\relax
     \let\afterar@@\relax
     \POS#1\endxyobj\Edge at c={\rectangleEdge}\computeLeftUpness@}

> \xydef@\endxyobj{\if\inxy@\else\xyerror@{Unexpected \string\endxy}{}\fi
>  \relax
>   \dimen@=\Y at max \advance\dimen at -\Y at min
>   \ifdim\dimen@<\z@ \dimen@=\z@ \Y at min=\z@ \Y at max=\z@ \fi
>   \dimen@=\X at max \advance\dimen at -\X at min
>   \ifdim\dimen@<\z@ \dimen@=\z@ \X at min=\z@ \X at max=\z@ \fi
>   \edef\tmp@{\egroup
>     \setboxz at h{\kern-\the\X at min \boxz@}%
>     \ht\z@=\the\Y at max \dp\z@=-\the\Y at min \wdz@=\the\dimen@
>     \noexpand\maybeunraise@ \raise\dimen@\boxz@
>     \noexpand\recoverXyStyle@ \egroup \noexpand\xy at end
>     \U at c=\the\Y at max \advance\U at c-\the\Y at c
>     \D at c=-\the\Y at min \advance\D at c\the\Y at c
>     \L at c=-\the\X at min  \advance\L at c\the\X at c
>     \R at c=\the\X at max  \advance\R at c-\the\X at c
>    }\tmp@}
>
> \makeatother   % revert \catcode of @
>
> ---------  end of new Xy-pic definitions  -------
>
>>
>> %%% This one gives an infinite loop
>> %% \xygraph{!Z{3cm}{3cm}
>> %%   !S{11111111}23 (?:[r] !S{1}{222222}{3},
>> %%                   ?:[d] !S{1}{2}{333333})
>> %% }

This example now works as expected.


> Hmm.
> This is hard to trace.
> I'm still working on it.
>
>>
>> %%% This one also runs forever
>> %% \xygraph{!Z{3cm}{3cm}
>> %%   !S{11111111}{2}{3}="start"
>> %%   "start":[r] !S{1}{222222}{3}
>> %%   "start":[d] !S{1}{2}{333333}
>> %% }

   ... and this one too.


Best regards,

	Ross


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