How to automatically trim a URL up to a certain length measured from the right?

Question

Current condition

A long URL makes a bad look as follows.

\documentclass{article}
\usepackage{xcolor,listings}
\lstset
{
    language={[LaTeX]TeX},
    backgroundcolor=\color{yellow!50},
    breaklines=true,
}
\usepackage[colorlinks]{hyperref}

\def\InputCode#1#2{%
\lstinputlisting[caption=\href{#2}{#2}]{#1}}

\begin{document}

\minipage{0.5\linewidth}
\InputCode{\jobname.tex}{http://www.oakfurniturehouse.co.uk/userfiles/image/3B4K1820.jpg}
\endminipage

\end{document}

Expected Result

I want to trim the left part up to a certain length measured from the right as follows. The trimmed part will be replaced by ....

How to do this automatically because the minipage width can vary throughout my document.

Answer 1

Let me start with some side notes:

• do not use \def -- In the frontend it's more comfortable to use xparse.
• Combinations like \minipage --- \endminipage should be avoided. Use \begin{minipage} --- \end{minipage}.

---

Here a suggestion using the benefits of expl3. The following mechanism is used:

1. Save the url in a hbox and compare the with of the box with the required width.
2. If the width of the url is too long the url will be saved as a token list. Now the first token of the list will be removed and the result will be saved inside a hbox. And now see 1.

Here The code:

\listfiles
\documentclass{article}
\usepackage{xcolor,listings}
\lstset
{
    language={[LaTeX]TeX},
    backgroundcolor=\color{yellow!50},
    breaklines=true,
}
\usepackage[colorlinks]{hyperref}

\newlength\sideoffset
\setlength\sideoffset{2cm}

\usepackage{xparse}
\ExplSyntaxOn
\NewDocumentCommand \InputCode { m m }
 {
    \lstinputlisting
      [caption=\href{#2}{
        \hbox_set:Nn \l_tmpa_box { #2 }
        \dim_compare:nNnTF
            { \linewidth - 2\sideoffset} > { \box_wd:N  \l_tmpa_box  }
            {%TRUE
                 #2        
            }
            {%FALSE
             \tl_set:Nx \l_tmpa_tl { \tl_tail:n { #2 } }
             \hbox_set:Nn \l_tmpa_box {  \tl_use:N \l_tmpa_tl }
             \dim_while_do:nNnn { \box_wd:N  \l_tmpa_box } >  { \linewidth - 2\sideoffset}
               {
                 \tl_set:Nx \l_tmpa_tl { \tl_tail:N  \l_tmpa_tl  } 
                \hbox_set:Nn \l_tmpa_box { \tl_use:N  \l_tmpa_tl  }
               }
            \ldots   \tl_use:N \l_tmpa_tl 
          }
      }
      ] 
      {#1}
 }
\ExplSyntaxOff

\begin{document}

\begin{minipage}{0.5\linewidth}
\InputCode{\jobname.tex}{http://www.oakfurniturehouse.co.uk/userfiles/image/3B4K1820.jpg}
\end{minipage}

\end{document}