# Unlike PGF/Tikz uses the middle part of stroke as the reference, what is the reason for choosing dimen=outer as the default in PSTricks?

The question has been written in the title above.

Why not dimen=middle ?

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only historical reason to allow a line, which didn't know anything about inner and outer to touch a circle/rectangle by default

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

\begin{pspicture}[showgrid,linewidth=5pt,
linecolor=red!60,strokeopacity=0.4](10,5)
\psframe[dimen=outer](0,1)(3,4)
\psframe[dimen=middle](4,1)(6,4)
\psframe[dimen=inner](7,1)(9,4)
\psline[linewidth=1pt,linecolor=black](0,4)(10,4)
\end{pspicture}

\begin{pspicture}[showgrid,linewidth=5pt,
linecolor=red!60,strokeopacity=0.4](10,5)
\pscircle[dimen=outer](2,1.5){1.5}
\pscircle[dimen=middle](5,1.5){1.5}
\pscircle[dimen=inner](8,1.5){1.5}
\psline[linewidth=1pt,linecolor=black](0,3)(10,3)
\end{pspicture}

\end{document}

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If I use \usepackage[showframe]{geometry}, which distance is equal to \textwidth: the horizontal distance between the frame rule's inner edges or the horizontal distance between the frame rule's outer edges? –  xport Dec 24 '10 at 16:07
@xport: Isn't that the question you asked elsewhere? What does it have to do with this question or answer? –  TH. Dec 25 '10 at 4:14
I get that your answer is that the reasons are historical, but what does "which didn't anything about inner and outer to touch a circle/rectangle by default" mean? –  TH. Dec 25 '10 at 4:15
@TH, I want to know which edge is used to measure \textwidth, \linewidth, etc. –  xport Dec 25 '10 at 4:45
\textwidth, \linewidth, etc. are absolute values and not in relation to inner/outer. This changes if you want to draw a square of width \textwidth, then you have to say how the frame of a given width should be drawn, inside, ouside or in the middle. but this is only a question of the used package, not a question of TeX. –  Herbert Dec 25 '10 at 6:14