[Tex/LaTex] Problems with filling a path that includes decorations in TikZ

decorationstikz-pgf

I want to construct a rectangle with two sides having a slight curvature and the other two sides being zigzag lines. In the end, I want to fill it. While the construction of the path worked the way I expected, the filling did not. How can I tell TikZ to fill the area inside this rectangle?

enter image description here

\documentclass{article}
\usepackage{tikz}
\usetikzlibrary{intersections, decorations}
\usepackage{pgfplots}
\pgfplotsset{compat=newest}
\begin{document}
\begin{tikzpicture}[scale=2]

\coordinate (A) at (0,0);
\coordinate (B) at (8,0);
\coordinate (C) at (8,2);
\coordinate (D) at (0,2);

\begin{scope}[decoration=zigzag]
\def\mypath{ (A)  to[out=10,in=170] (B)
decorate[decoration=zigzag] {(B)-- (C)}  (C) to[out=170,in=10] (D)
decorate[decoration=zigzag]{(D)--(A)}
  };
  \draw [fill=red] \mypath;
\end{scope}
\end{tikzpicture}
\end{document}

Best Answer

You are breaking the path into pieces by repeating the coordinate names (B) and (D) hence each piece is filled individually. Removing them inside the braces (and the extra (C)) fixes the problem.

\documentclass{article}
\usepackage{tikz}
\usetikzlibrary{decorations.pathmorphing}
\begin{document}
\begin{tikzpicture}
\coordinate (A) at (0,0);
\coordinate (B) at (2,0);
\coordinate (C) at (2,2);
\coordinate (D) at (0,2);
\begin{scope}[decoration=zigzag]
  \draw[fill=red] (A) to[out=10,in=170] (B) 
                decorate {-- (C)}  
                to[out=170,in=10] (D) 
                decorate {--(A)};
\end{scope}
\end{tikzpicture}
\end{document}

enter image description here

Related Solutions

[Tex/LaTex] TikZ: multiple decorations on a path.

The problem is not caused by wrong syntax or a recursion. If you for instance change the position to 1:

postaction={decoration={markings,mark=at position 1 with {\arrow{>}}},decorate}

your file compiles without errors and you get:

alt text

Similar for position 0. This doesn't place the arrow where it's desired but it shows that that way of nesting decorations is ok, though the calculation for TikZ seems to be too hard.

[Tex/LaTex] Rotate a node but not its content: the case of the ellipse decoration

The source of the difficulty is that ellipses are constructed in a particular way in TikZ. They are paths that start from the x-axis and proceed counter-clockwise around their centre. The vast majority of the time, the exact parametrisation doesn't matter. You appear to have found the one situation where it does!

In the actual question, you only want to be able to mirror the ellipse, and so draw it starting from the negative x-axis (the title of the question suggests a more flexible approach). That's actually not too hard since we can exploit the symmetry of the ellipse. The key is to provide it with a negative x-radius, since then it will start from the negative x-axis (and proceed clockwise, but we could correct for that by negating the y-radius as well). To do this, we interrupt the call from the node shape to the drawing command and flip the sign of the x-radius. The simplest way to do this is to redefine the \pgfpathellipse macro to do the negation and then call the original macro. The following code does this.

\documentclass{article}
\usepackage{tikz}
\usetikzlibrary{decorations,shapes,decorations.markings}
\makeatletter
\let\origpgfpathellipse=\pgfpathellipse
\def\revpgfpathellipse#1#2#3{%
  #2%
  \pgf@xa=-\pgf@x
  \origpgfpathellipse{#1}{\pgfqpoint{\pgf@xa}{0pt}}{#3}}
\makeatother

\tikzset{
  reversed ellipse/.style={
    ellipse,
    reverse the ellipse%
  },
  reverse the ellipse/.code={
    \let\pgfpathellipse=\revpgfpathellipse
  }
}
\begin{document}
\begin{tikzpicture}
\node[ellipse,
  draw,
  postaction={
    decorate,
    decoration={
      markings,
      mark=at position 1 with {
        \arrow[line width=5pt,blue]{>}
      }
    }
  }
] at (0,0) {hello world};

\node[reversed ellipse,
  draw,
  postaction={
    decorate,
    decoration={
      markings,
      mark=at position 1 with {
        \arrow[line width=5pt,blue]{>}
      }
    }
  }
] at (0,-2) {hello world};
\end{tikzpicture}

\end{document}

Here's the result:

rotated ellipse

(the arrow got clipped, but you can see where it lies)

Best Answer

Related Solutions

[Tex/LaTex] TikZ: multiple decorations on a path.

[Tex/LaTex] Rotate a node but not its content: the case of the ellipse decoration

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