TikZ - How to draw an interrupted line?

Question

Please tell me of an (as simple as possible) solution to draw an interrupted line. I don't know how this is technically called; interrupted line, interleaved line, broken line, discontinuous line?

Here is an image of what I want. It doesn't have to be wavy (but it would be nice).

Answer 1

Here's a decoration that will place a wavy discontinuity symbol at the midpoint of the first segment of a path. You can control the distance between the two waves using the segment length key, the width of the waves using amplitude and the degree of waviness using meta-segment length:

\documentclass{article}
\usepackage{tikz}
\usetikzlibrary{decorations}

\begin{document}

\pgfdeclaredecoration{discontinuity}{start}{
  \state{start}[width=0.5\pgfdecoratedinputsegmentremainingdistance-0.5\pgfdecorationsegmentlength,next state=first wave]
  {}
  \state{first wave}[width=\pgfdecorationsegmentlength, next state=second wave]
  {
    \pgfpathlineto{\pgfpointorigin}
    \pgfpathmoveto{\pgfqpoint{0pt}{\pgfdecorationsegmentamplitude}}
    \pgfpathcurveto
        {\pgfpoint{-0.25*\pgfmetadecorationsegmentlength}{0.75\pgfdecorationsegmentamplitude}}
        {\pgfpoint{-0.25*\pgfmetadecorationsegmentlength}{0.25\pgfdecorationsegmentamplitude}}
        {\pgfpoint{0pt}{0pt}}
    \pgfpathcurveto
        {\pgfpoint{0.25*\pgfmetadecorationsegmentlength}{-0.25\pgfdecorationsegmentamplitude}}
        {\pgfpoint{0.25*\pgfmetadecorationsegmentlength}{-0.75\pgfdecorationsegmentamplitude}}
        {\pgfpoint{0pt}{-\pgfdecorationsegmentamplitude}}
}
\state{second wave}[width=0pt, next state=do nothing]
  {
    \pgfpathmoveto{\pgfqpoint{0pt}{\pgfdecorationsegmentamplitude}}
    \pgfpathcurveto
        {\pgfpoint{-0.25*\pgfmetadecorationsegmentlength}{0.75\pgfdecorationsegmentamplitude}}
        {\pgfpoint{-0.25*\pgfmetadecorationsegmentlength}{0.25\pgfdecorationsegmentamplitude}}
        {\pgfpoint{0pt}{0pt}}
    \pgfpathcurveto
        {\pgfpoint{0.25*\pgfmetadecorationsegmentlength}{-0.25\pgfdecorationsegmentamplitude}}
        {\pgfpoint{0.25*\pgfmetadecorationsegmentlength}{-0.75\pgfdecorationsegmentamplitude}}
        {\pgfpoint{0pt}{-\pgfdecorationsegmentamplitude}}
    \pgfpathmoveto{\pgfpointorigin}
}
  \state{do nothing}[width=\pgfdecorationsegmentlength,next state=do nothing]{
    \pgfpathlineto{\pgfpointdecoratedinputsegmentlast}
  }
  \state{final}
  {
    \pgfpathlineto{\pgfpointdecoratedpathlast}
  }
}

\begin{tikzpicture}
\draw [decoration={%
        discontinuity,
        amplitude=0.75cm},
    decorate](0,0) -- (3,2);
\draw [decoration={%
        discontinuity,
        amplitude=0.5cm,
        segment length=0.25cm,
        meta-segment length=0.5cm},
    decorate](1,-1) -- (3,-2);
\end{tikzpicture}
\end{document}

Answer 2

Here is a way to include an interruption. I used straight lines, but now that you see how it is done, you could arrange it to your liking.

\documentclass{minimal}

\usepackage{tikz}
\usetikzlibrary{decorations.markings}

\tikzstyle{interrupt}=[
    postaction={
        decorate,
        decoration={markings,
                    mark= at position 0.5 
                          with
                          {
                            \fill[white] (-0.1,-0.3) rectangle (0.1,0.3);
                            \draw (-0.1,0.3) -- (-0.1,-0.3)
                                  (0.1,0.3) -- (0.1,-0.3);
                          }
                    }
                }
]

\begin{document}

\begin{tikzpicture}

\draw[interrupt] (0,0) -- (5,5);

\end{tikzpicture}

\end{document}

The result is