[Xy-pic] large arrow tips?

[Ross Moore]

Hi Peter,

On 15/05/2006, at 10:53 AM, Peter Selinger wrote:

> Hi,
>
> I would appreciate some help with the following problem.
>
> When using Xy-pic with SliTeX, the various arrow heads don't scale
> with the size of the font of the rest of the document. I tried using
> the \SelectTips command to change their size, but this has no visible
> effect.

No, that won't help much.

>
> How can I get larger arrow heads? The below file is a simple example.
> On a slide show on an LCD projector, the arrow heads will be virtually
> invisible to the audience, and in particular, the difference between A
> and B will not be visible from the back of the room.

Make sure the rotation/scaling extension is loaded ...

\usepackage[all,rotate]{xy}
\xyoption{ps}
\xyoption{dvips}


Then use the [thicker] modifier and/or scale the
size of the whole diagram; e.g. as follows:

\begin{slide}
   \[
   \let\labelstyle\objectstyle
   \vcenter{%
  \xy*[*3][thicker]\xybox{\tiny
%^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
   \xymatrix{
       A \ar@{-}[rr]^<>(.5){\rm id}
       \ar@{}[rr]|<>(.5)/.3ex/{\dir2{>}}&&A
       \\
       B \ar@{-}[rr]^<>(.5){\rm id}
       \ar@{}[rr]|<>(.5)/-.3ex/{\dir2{<}}&&B
       \\
       C \ar[r]^{f} & C
       }}\endxy
        ^^^^^^^
      }%  end of \vcenter
   \]
   \[
   \SelectTips{cm}{10}
    \xy*[*3][thicker][thicker]\xybox{\tiny\POS*{} \ar
%  ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
    @{*{\UseTips\dir_{<<}}-*{\UseTips\dir{>}}}
    (20,5)*{}}\endxy
             ^^^^^^^
   \]

\end{slide}


Note the \xybox{...} enclosure, which is treated
as a single <object>, so that the scaling and thickness
modifiers can be applied consistently.

Also, the use of \tiny is to partially counteract the
fact that the scaling in PostScript is applied to all
of the ordinary text and mathematical symbols as well
as to the Xy-pic parts of the diagram layouts.


Alter the <num> scale-factor in   \xy*[*<num>]\xybox{
to match the text/math-font symbols to the Xy-pic bits,
according to your own tastes.

>
> Note that the file below also includes the example from the Xy-pic
> reference manual, section 10. However, for "family=cm" and
> "family=eu", I can only change the "size" to 10,11,12, with the
> changes in the output being almost imperceptible. Any larger size
> leads to font errors.

Exactly.
These fonts are only available at the specified sizes.
But using the PostScript back-end, there is no need
for fonts at all. Everything is done with vector-graphics,
which can be scaled arbitrarily.

> For "family=xy", the size is apparently ignored
> entirely, as I don't get errors, and don't see any change in the
> output.
>
> Is there any way I can, say, double the size of the arrows?

See above.
The "thickness" parameter is independent of the scaling.
It alters the appearance of the arrows, making them
"rounder" as well as thicker in the stem.

By combining thickness and scale-factor you can get
a significant range of effects.
The Xy-pic reference manual has a few examples,
and describes the complete syntax.

>
> Thanks, -- Peter
>

Hope this helps,

	Ross Moore

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