# [Xy-pic] Background colour

Ross Moore ross.moore at mq.edu.au
Thu Feb 24 00:22:37 CET 2011

Hello Damjan,

On 23/02/2011, at 4:42 PM, Damjan Perenic wrote:

> On Tue, Feb 22, 2011 at 1:46 AM, Daniel Müllner
>> Hi Damjan,
>>
>> currently, the xypdf driver cannot vary the line thickness. In fact, support
>> for Xy-pic's "line" extension is the last piece that is missing for
>> completeness. I simply haven't had the time to implement it, but I am
>> definitely planning to add this.
>>
>> For now, I am afraid that I must recommend the PostScript driver if you need
>> lines of different widths in your diagrams.
>
> Is it possible to "frame" an arrow? Then I could make an invisible
> line with coloured frame. For lines (not arrows) this would work.
>
> I experimented with \ar@{-}@[F-][r] but could not get the results I wanted.

An \ar does not produce an <object> but a <connection>, which is
a way of drawing a line/curve/arrow/... that in some sense represents
a connection between two <objects>.

A frame, on the other hand, is a <decoration> that can be applied to
an <object>.

Read the Xy-pic Reference Manual, (in a file  xyrefer.pdf ,
that should have been distributed with your TeX installation)
to understand the principles on which Xy-pic is constructed.
This will help you understand better what can, and cannot, be done.

Now maybe the following coding is relevant to what you want to do.

>>> \documentclass[11pt]{article}
>>> \usepackage[ps,dvips,all,line,color]{xy}
>>> \begin{document}
>>>
>>> \xymatrix{
>>>  A & B \\
>>>  C\ar@{-}@[yellow]@[thicker]@[butt]@[thicker]@[thicker]@[thicker]@[thicker][ur]
>>>    \ar@[red][ur] & D
>>> }
>>>
>>> \xymatrix{
>>>  A & B \\
>>>  C\ar@{-}@[yellow]@[thicker]@[roundcap]@[thicker]@[thicker]@[thicker]@[thicker][ur]
>>>    \ar@[red][ur] & D
>>> }
>>>
>>> \xymatrix{
>>>  A & B \\
>>>  C\ar@{-}@[yellow]@[thicker]@[projcap]@[thicker]@[thicker]@[thicker]@[thicker][ur]
>>>    \ar@[red][ur] & D
>>> }
>>>
>>> \end{document}

The result is shown in the attached image.

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Make sure that you process this using TeX+DVI mode, rather
than using pdf-(La)TeX as the processing engine.

This draws first a wide coloured line as an arrow with no tips,
over which you then draw the (coloured) arrow that you want framed.
Thus the first arrow drawn serves as a background for the second one.

Note that you may want to choose the line-cap for the wide line,
else you can get an overlap with the objects being connected.

>
> Damjan

Hope this helps,

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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