What is the unit of the coordinate system in PSTricks?

Question

If I use the following code, there two different kinds of units. One for the coordinate system used to declare \begin{pspicture} with (0,0) to (20,10), and the centimeter used in 4.2cm.

\begin{pspicture}(0,0)(20,10)
\rput[lt](0.5,9){\psframebox[linewidth=1pt,framearc=0]{\parbox[c]{4.2cm}{\raggedright Text Goes Here...}}}
\end{pspicture}

Can I use a unified dimension for both PSTricks objects and \parbox?

Answer 1

The pstricks manual says on page 6:

The values of the runit, xunit and yunit parameters are stored in the dimension registers \psunit (also \psrunit), \psxunit and \psyunit.

So you should be able to use:

\parbox[c]{4.2\psxunit}{...}

to get the width of 4.2 in the pstricks coordinate system. However, if you using complex transformations this might not work correctly, I guess. You can set the units using \psset{xunit=1cm} etc.

Answer 2

The parbox is a TeX macro and arguments follow the TeX rules for units. Values without a unit are not possible without rewriting the macro. In PSTricks you can mix all kinds of units; \psline(3,4in)(5cm,2) The current default unit is set by \psset{unit=...}, preset to 1cm. And you can you \psTextFrame instead of \rput:

\documentclass{minimal}
\usepackage{pstricks}
\begin{document}

\begin{pspicture}(0,0)(20,10)
\psTextFrame[linewidth=1pt](0.5,8.5)(4.7,9){\parbox[c]{4\psunit}{Text Goes Here...}}
\end{pspicture}

\end{document}