[Xy-pic] \vbox and xypic

[Ross Moore]

Hello Raymond,

On 17 Jan 2020, at 7:02 pm, Raymond Boute <raymond.boute at pandora.be<mailto:raymond.boute at pandora.be>> wrote:

Dear fellow xy-pic users,

It seems that, for an \xymatrix, \vbox has the same effect as \vtop,
rather than aligning the reference point with the last line of the
\xymatrix.

Um, no;
because the \xymatrix  has created its own nested boxes for containing complicated material.
So both \vbox and \vtop see only a single vertical mode entry.
Thus they have no separate decision to make:  alignment is at the base of that single entry.

Why do you want alignment on the last line of the  vmatrix?
Why not the baseline of the first, or third, or any particular row of a large matrix?

Kris (RIP) and I discussed this issue and could not see any reasonable way
to specify how alignments on particular rows could work reliably.
It was left as a possible extension to be encoded some time in the future.

But in any case, if you are wanting to adjust the vertical positions of different \xymatrix  structures
along a common baseline, then consider using the  \xygraph  construction,
with !M{…}  escape objects to capture the \xymatrix-like structures.
Within  \xygraph  it is much easier to adjust positions, using the usual !C !U !D  etc.
  <object modifier>s, with numerical arguments:  e.g.  !D(.7) .


 On the other hand, \vcenter works as expected.
Is there a way to overcome the problem with \vbox?

\vcenter on the other hand, creates a new box aligned on the centre of its contents.
Any alignment that those contents would naturally have had is disregarded.


With best regards,

Raymond Boute



Hope this helps.


Dr Ross Moore
Department of Mathematics and Statistics
12 Wally’s Walk, Level 7, Room 734
Macquarie University, NSW 2109, Australia
T: +61 2 9850 8955  |  F: +61 2 9850 8114
M:+61 407 288 255  |  E: ross.moore at mq.edu.au<mailto:ross.moore at mq.edu.au>
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