كيف أرسم شكل على LaTeX باستعمال pgf/tikz ؟

الفكرة المستعملة لإنشاء هذا النوع من الأشكال، هي إنشاء شكل مستطيلي مع تغيير في مكان بعض النقط الموجودة على الإطار الخارجي له.

تُعرّف هذه الأشكال بـ macro \myshapepath، حيث تستعمل مكتبة خاصة بتقاطع النقط the intersection library، وهذا الكود مخصص لإنشاء شكل بهذه الطريقة:

\documentclass{standalone}
\usepackage{tikz}
\usetikzlibrary{intersections}

\makeatletter
\def\myslant{0.2} % defines the skew of the right and left side
\def\myxsep{0.5}  % extra distance in x direction; relative to node height
\def\myvhandlelen{.85} % length of the vertical bezier handles; relative to node height
\def\myhhandlelen{.65} % length of the horizontal bezier handles; relative to node width
\def\mypoint#1#2#3{
    % #1 = x coordinate, in multiples of the width
    % #2 = y coordinate, in multiples of the height, slanted
    % #3 = x coordinate, relative to height and slant factor
    \pgfpointdiff{\southwest}{\northeast}
    \pgf@xc=\pgf@x          % xc = width of the node
    \pgf@yc=\pgf@y          % yc = height of the node
    \pgf@xb=\myslant\pgf@yc % xb = width of the node scaled by \myslant
    \southwest
    \advance\pgf@x by .5\pgf@xc
    \advance\pgf@y by .5\pgf@yc
    \advance\pgf@x by  #1\pgf@xc
    \advance\pgf@y by  #2\pgf@yc
    \advance\pgf@x by  #2\pgf@xb
    \advance\pgf@x by  #3\pgf@xb
}
% this defines the shape of the node; the macro is used for drawing the shape as well as for calculating intersection points
\def\myshapepath{
    \pgfpathmoveto{\mypoint{-.5}{0}{-\myxsep}}
    \pgfpathcurveto{\mypoint{-.5}{\myvhandlelen}{-\myxsep}}{\mypoint{-\myhhandlelen}{.5}{0}}{\mypoint{0}{.5}{0}}
    \pgfpathcurveto{\mypoint{\myhhandlelen}{.5}{0}}{\mypoint{.5}{\myvhandlelen}{\myxsep}}{\mypoint{.5}{0}{\myxsep}}
    \pgfpathcurveto{\mypoint{.5}{-\myvhandlelen}{\myxsep}}{\mypoint{\myhhandlelen}{-.5}{0}}{\mypoint{0}{-.5}{0}}
    \pgfpathcurveto{\mypoint{-\myhhandlelen}{-.5}{0}}{\mypoint{-.5}{-\myvhandlelen}{-\myxsep}}{\mypoint{-.5}{0}{-\myxsep}}
    \pgfpathclose
}
% compute an intersection point between a line and \myshapepath
\def\myshapeanchorborder#1#2{
    % #1 = point inside the shape
    % #2 = direction
    \pgftransformreset % without this, the intersection commands yield strange results
    \pgf@relevantforpicturesizefalse % don't include drawings in bounding box
    \pgfintersectionofpaths{
        \myshapepath
        %\pgfgetpath\temppath\pgfusepath{stroke}\pgfsetpath\temppath % draw path for debugging
    }{
        \pgfpathmoveto{
            \pgfpointadd{
                \pgfpointdiff{\southwest}{\northeast}\pgf@xc=\pgf@x \advance\pgf@xc by \pgf@y % calculate a distance that is guaranteed to be outside the shape
                \pgfpointscale{
                    \pgf@xc
                }{
                    \pgfpointnormalised{
                        #2
                    }
                }
            } {
                #1
            }
        }
        \pgfpathlineto{#1}
        %\pgfgetpath\temppath\pgfusepath{stroke}\pgfsetpath\temppath % draw path for debugging
    }
    \pgfpointintersectionsolution{1}
}
\def\myshapeanchorcenter{
    \pgfpointscale{.5}{\pgfpointadd{\southwest}{\northeast}}
}
% we could probably re-use some existing \dimen, but better be careful
\newdimen\myshapedimenx
\newdimen\myshapedimeny

\pgfdeclareshape{myshape}{
    % some stuff, we can inherit from the rectangle shape
    \inheritsavedanchors[from=rectangle]
    \inheritanchor[from=rectangle]{center}
    \inheritanchor[from=rectangle]{mid}
    \inheritanchor[from=rectangle]{base}

    % calculate these anchors so they lie on a coorinate line with .center
    \anchor{west}{\myshapeanchorborder{\myshapeanchorcenter}{\pgfpoint{-1cm}{0cm}}}
    \anchor{east}{\myshapeanchorborder{\myshapeanchorcenter}{\pgfpoint{1cm}{0cm}}}
    \anchor{north}{\myshapeanchorborder{\myshapeanchorcenter}{\pgfpoint{0cm}{1cm}}}
    \anchor{south}{\myshapeanchorborder{\myshapeanchorcenter}{\pgfpoint{0cm}{-1cm}}}

    % calculate these anchors so they lie on a line through .center and the corresponding anchor of the underlying rectangle
    \anchor{south west}{\myshapeanchorborder{\myshapeanchorcenter}{\pgfpointdiff{\myshapeanchorcenter}{\southwest}}}
    \anchor{north east}{\myshapeanchorborder{\myshapeanchorcenter}{\pgfpointdiff{\myshapeanchorcenter}{\northeast}}}
    \anchor{south east}{\myshapeanchorborder{\myshapeanchorcenter}{\pgfpointdiff{\myshapeanchorcenter}{\northeast\pgf@xa=\pgf@x\southwest\pgf@x=\pgf@xa}}}
    \anchor{north west}{\myshapeanchorborder{\myshapeanchorcenter}{\pgfpointdiff{\myshapeanchorcenter}{\southwest\pgf@xa=\pgf@x\northeast\pgf@x=\pgf@xa}}}

    % somewhat more special anchors. The coordinate calculations were taken from the rectangle node
    \anchor{mid west}{\myshapeanchorborder{\myshapeanchorcenter\pgfmathsetlength\pgf@y{.5ex}}{\pgfpoint{-1cm}{0cm}}}
    \anchor{mid east}{\myshapeanchorborder{\myshapeanchorcenter\pgfmathsetlength\pgf@y{.5ex}}{\pgfpoint{1cm}{0cm}}}
    \anchor{base west}{\myshapeanchorborder{\myshapeanchorcenter\pgf@y=0pt}{\pgfpoint{-1cm}{0cm}}}
    \anchor{base east}{\myshapeanchorborder{\myshapeanchorcenter\pgf@y=0pt}{\pgfpoint{1cm}{0cm}}}

    \backgroundpath{
        % uncomment to draw underlying rectangle node
        %\southwest\pgf@xa=\pgf@x \pgf@ya=\pgf@y
        %\northeast\pgf@xb=\pgf@x \pgf@yb=\pgf@y
        %\pgfpointdiff{\southwest}{\northeast}\pgf@xc=\pgf@x \pgf@yc=\pgf@y
        %\pgfpathmoveto{\pgfpoint{\pgf@xa}{\pgf@ya}}
        %\pgfpathlineto{\pgfpoint{\pgf@xa}{\pgf@yb}}
        %\pgfpathlineto{\pgfpoint{\pgf@xb}{\pgf@yb}}
        %\pgfpathlineto{\pgfpoint{\pgf@xb}{\pgf@ya}}
        %\pgfpathclose

        \myshapepath
    }
    \anchorborder{
        \myshapedimenx=\pgf@x
        \myshapedimeny=\pgf@y
        \myshapeanchorborder{\myshapeanchorcenter}{\pgfpoint{\myshapedimenx}{\myshapedimeny}}
    }
}

\makeatother

\tikzset{shape example/.style={color=black!30,draw,fill=yellow!30,line width=.5cm,inner xsep=2.5cm,inner ysep=0.5cm}}

\begin{document}
    {\Huge\begin{tikzpicture}
        \node[name=s,shape=myshape,shape example] {myshape\vrule width 1pt height 2cm};

        \foreach \anchor/\placement in {
            north west/above left,
            north/above,
            north east/above right,
            west/left,
            center/above,
            east/right,
            mid west/right,
            mid/above,
            mid east/left,
            base west/left,
            base/below,
            base east/right,
            south west/below left,
            south/below,
            south east/below right,
            text/left,
            10/right,
            130/above%
        } {
            \draw[shift=(s.\anchor)] plot[mark=x] coordinates{(0,0)}
            node[\placement] {\scriptsize\texttt{(s.\anchor)}};
        }
    \end{tikzpicture}}

    \begin{tikzpicture}
        \draw (-2.0, 0.0) node[draw,myshape] (a) {normal};
        \draw (-0.5, 2.0) node[draw,myshape] (b) {very long node indeed};
        \draw ( 2.0, 0.0) node[draw,myshape,align=left] (c) {h\\i\\g\\h\\\\n\\o\\d\\e};
        \draw ( 0.0,-1.5) node[draw,myshape,align=left] (d) {almost\\square\\node};

        \draw[->] (a) -> (b);
        \draw[->] (b) -> (c);
        \draw[->] (c) -> (d);
        \draw[->] (d) -> (a);
    \end{tikzpicture}
\end{document}

وهذا شكل توضيحي لكيفية الرسم:

الميزة المُميزة هنا هي إمكانية التحكم في الشكل ككل رغم أن الأمر قد يبدو صعبا نوعاً ما.