[Xy-pic] Re: What are the default entry modifiers in xygraph, xymatrix, and xymatrix@1?

Alexander Perlis alexanderperlis@yahoo.com
Mon, 26 Aug 2002 15:19:27 -0700 (PDT)

I found the answer to my earlier question and wanted to share it for
the benefit of others facing a similar issue.

The Xy-pic Reference Manual (pp. 50--51) fails to completely document
the behavior of \xymatrix@1{...}. Using it in place of \xymatrix{...}
affects not only alignment but also margins. As explained in the
Reference Manual (see also Ross's explanation in this thread),
alignment is affected by inserting a math strut (zero-width left
parenthesis) into each entry. Undocumented is how margins are
affected, but the Xy-pic source code gives it away: they are set to
exactly 1 pt. Thus the following two pieces of code produce identical

  \xymatrix@1{ ... }

  \xymatrix@M=1pt{ ... }

Thus, if you only want one or the other of the two effects of
\xymatrix@1{...}, you should now see what to do.

Finally, the situation that brought this up in the first place: If a
complicated \xymatrix@1{...} construction forces you to escape to
Xy-pic kernel code, to maintain consistency in the appearance of your
drops, use the form: *+1pt{\vphantom( ...}

I hope this helps someone.

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