Figure/Table Captions in the Margin?

KOMA script environment captionbeside provides a lot of the functionality that is needed to achive this. You just have to set its width to \linewidth+marginparsep+marginparwidth and occupy \linewidth with your figure or table. The rest \marginparsep+\marginparwidth is then used for a small horizontal skip and caption. The captionbeside environment is aligned horizontally using the starred version of its last optional parameter.

There are several draw backs in the code below:

1. As horizontal skip inserted between figure content and caption and \marginparsep seem to be equally large here (1em?) I ignored both in the code.

2. As I don't know how to provide multiple optional parameters I
didn't provide one to adjust figure alignment. Content is hardcoded to be centered, but can be aligned differently using a \parbox manually.

3. Caption alignment is hardcoded to be \raggedright on both even and odd pages. There is no option to control this behaviour currently. If you want to use \RaggedRight from the ragged2e package (to allow for hyphenation) or want a \raggedleft alignment on even pages you have to change the code.

Markus, as I think this environment is quite usefull, could the piece of code below be a starting point for a new KOMA script feature?

Regards,
Stephan Hennig

\documentclass{scrbook}
\usepackage[english]{babel}
\usepackage{blindtext}
\usepackage{ifthen}

%provide \margincap command
\makeatletter
\newsavebox{\mcap@figbox}
\newlength{\mcap@capbesidewidth}
\newcommand{\margincap}[3][]{%
%save content in a box
\sbox{\mcap@figbox}{#3}%
%calculate total width used by figure and caption
\setlength{\mcap@capbesidewidth}{\linewidth}%
\addtolength{\mcap@capbesidewidth}{\marginparsep}%
\addtolength{\mcap@capbesidewidth}{\marginparwidth}%
%call captionbeside environment
%with or without optional argument
\ifthenelse{\equal{#1}{}}{%
\begin{captionbeside}[#2]{%
\raggedright #2}[o][\mcap@capbesidewidth][0pt]*%
}{%
\begin{captionbeside}[#1]{%
\raggedright #2}[o][\mcap@capbesidewidth][0pt]*%
}%
%write figure horizontally centered
\makebox[\linewidth][c]{\usebox{\mcap@figbox}}%
%end environment
\end{captionbeside}%
}
\makeatother

%set small captions without indentation,
%starting on second line
\setcapindent*{0em}
\addtokomafont{caption}{\small}
\begin{document}
\listoffigures
\chapter{blubb}
\blindtext[3]
\marginpar{this is text in the margin}\par
\begin{figure}
\margincap{A first long figure caption
in the left or right margin.}{\rule{3cm}{4cm}}
\end{figure}

\blindtext[2]
\marginpar{this is text in the margin}\par
\begin{figure}
\margincap[short caption]{A second long figure caption
in the leftor right margin.}{\rule{2cm}{1cm}}
\end{figure}

\blindtext[4]
\end{document}