Straight edge between nodes with break

Question

I would like to modify this MWE so that the edge connecting the two nodes is a straight line with a break that allows the edge connect to (b.north west) with a 135° angle. The other end of the edge connect to (a.south west) exiting to the right. The result should be like the lines connecting the nodes of this question, but I don't want to use the same package.

\documentclass[border=5mm]{standalone}
\usepackage{pgfplots}

\begin{document}
\begin{tikzpicture}
\node (a) {a};
\node (b) [right of=a, below of=a, xshift=2cm] {b};
\draw (a.south west)  to [in=135, out=0] (b.north west);
\end{tikzpicture}
\end{document}

How do I do it?

Why don't you want to use forest? It is very, very good. You can do it, probably, using one of the other tree packages or even just manually. But why make it difficult when somebody else already invented wheels and is providing them to all who want them for free? — cfr, Jan 07 '16 at 23:26
Is forest only used for creating tree graph? In that case, I can't use it since I need to picture a more complicated graph. — Nicola, Jan 08 '16 at 08:06
Well, it depends. Yes, it draws trees. However, you can also draw stuff in addition to the tree, including stuff you specify within the tree or after the tree using regular TikZ. And sometimes you can fake non-tree graphs, too, when that's more convenient. Which isn't to say that it is suitable for your case as I don't know what your requirements are. — cfr, Jan 08 '16 at 21:43

score 2 · Accepted Answer · answered Jan 07 '16 at 23:33

2

forest is much easier, but you can do everything manually if you prefer:

\documentclass[border=5pt, multi, tikz]{standalone}
\usetikzlibrary{calc}
\begin{document}
\begin{tikzpicture}
  \node (a) {a};
  \node (b) [right of=a, below of=a, xshift=2cm] {b};
  \draw (a.south west) -- (a.south west -| {$(b.north west) + (135:10mm)$}) --   (b.north west);
\end{tikzpicture}
\end{document}

answered Jan 07 '16 at 23:33

cfr

198,882

That's a better solution. However, consider that in b the node shape is a diamond, as in
\node (b) [draw, diamond, right of=a, below of=a, xshift=0.5cm] {b};

(add also \usetikzlibrary{calc,shapes.geometric} )The slope of the edge seems a bit off, it doesn't seem to touch the side of the diamond perpendicularly, isn't it? Also, it changes if I put 5mm in place of 10mm. How can I fix it?
– Nicola Jan 08 '16 at 08:31
I can fix with
\draw (a.south west) -- (a.south west -| {$(b) + (135:10mm)$}) --(b.north west);

i.e. using b and not b. north west to evaluate the coordinates in $...$
– Nicola Jan 08 '16 at 08:43
That will take the angle from the default anchor for the node b. It just depends where you want the 135 measured from. You said the north west, so that's what I used. If you want something different, obviously you can change it accordingly. – cfr Jan 08 '16 at 21:39
Now that I understand better how calc works, I see that to get a line perpendicular to the north west side of the diamond, the correct line is \draw (a.south west) -- (a.south west -| {$(b) + (180:10mm)$}) --(b.north west); – Nicola Jan 08 '16 at 22:30
There are simpler ways, but yes, that would work. But that is not what you asked how to do in this question, is it? – cfr Jan 08 '16 at 22:40

score 2 · Answer 2 · answered Jan 08 '16 at 04:44

One can also borrow the code of -| operator. I should call it -\ but then I need to hack the parser of TikZ. (\tikz@lineto, line 2699 of tikz.code.tex)

Notice that there are three changes in the definition of \tikz@@hv@lineto. The third corresponds to -| between explicit coordinates. The first two correspond to the node case.

Notice also that I did nothing about \tikz@timer. Thus pos=.5, midway, or their family is not going to work properly.

\documentclass[tikz,border=9]{standalone}

\makeatletter

\def\tikz@@hv@lineto#1{%
  \edef\tikz@timer@start{\noexpand\pgfqpoint{\the\tikz@lastx}{\the\tikz@lasty}}%
  \pgf@xc=\tikz@lastx% NEW LINE
  \pgf@yc=\tikz@lasty%
  \tikz@make@last@position{#1}%
  \edef\tikz@tangent{\noexpand\pgfqpoint{\the\tikz@lastx}{\the\pgf@yc}}%
  \tikz@flush@moveto@toward{\pgfqpoint{\tikz@lastx}{\pgf@yc}}\pgf@x\pgf@yc%
  \iftikz@shapeborder%
    % ok, target is a shape. have to work now:
    {%
      %\pgf@process{\pgfpointshapeborder{\tikz@shapeborder@name}{\pgfqpoint{\tikz@lastx}{\pgf@yc}}}% Replace by the following
      \pgf@process{\pgfpointshapeborder{\tikz@shapeborder@name}{\pgfpoint{\tikz@lastx-sign(\tikz@lastx-\pgf@xc)*abs(\pgf@yc-\tikz@lasty)}{\pgf@yc}}} % NEW LINE
      \tikz@make@last@position{\pgfqpoint{\pgf@x}{\pgf@y}}%
      %\tikz@path@lineto{\pgfqpoint{\tikz@lastx}{\pgf@yc}}% Replace by the following
      \tikz@path@lineto{\pgfpoint{\tikz@lastx-sign(\tikz@lastx-\pgf@xc)*abs(\pgf@yc-\tikz@lasty)}{\pgf@yc}} % NEW LINE
      \tikz@path@lineto{\tikz@last@position}%
      \xdef\tikz@timer@end@temp{\noexpand\pgfqpoint{\the\tikz@lastx}{\the\tikz@lasty}}% move out of group
    }%
    \let\tikz@timer@end=\tikz@timer@end@temp%
    \edef\tikz@moveto@waiting{\tikz@shapeborder@name}%    
  \else%
    %\tikz@path@lineto{\pgfqpoint{\tikz@lastx}{\pgf@yc}}% Replace by the following
    \tikz@path@lineto{\pgfpoint{\tikz@lastx-sign(\tikz@lastx-\pgf@xc)*abs(\pgf@yc-\tikz@lasty)}{\pgf@yc}} % NEW LINE
    \tikz@path@lineto{\tikz@last@position}%
    \edef\tikz@timer@end{\noexpand\pgfqpoint{\the\tikz@lastx}{\the\tikz@lasty}}% move out of group
  \fi%
  \let\tikz@timer=\tikz@timer@hvline%
  \tikz@scan@next@command%
}

\begin{document}
    \begin{tikzpicture}
        \node(a){a};
        \node(b)[below right of=a, xshift=2cm]{b};
        \node(c)[below left of=a, xshift=-2cm]{c};
        \node(d)[above right of=a, xshift=2cm]{d};
        \node(e)[above left of=a, xshift=-2cm]{e};
        \draw(a.south east)-|(b.north west);
        \draw(a.south west)-|(c.north east);
        \draw(a.north east)-|(d.south west);
        \draw(a.north west)-|(e.south east);
    \end{tikzpicture}
    \begin{tikzpicture}
        \node(a){a};
        \node(b)[below right of=a, xshift=2cm]{b};
        \node(c)[below left of=a, xshift=-2cm]{c};
        \node(d)[above right of=a, xshift=2cm]{d};
        \node(e)[above left of=a, xshift=-2cm]{e};
        \draw(a)-|(b);
        \draw(a)-|(c);
        \draw(a)-|(d);
        \draw(a)-|(e);
    \end{tikzpicture}
\end{document}

Won't this work only if you want connections of this type for all -| connections? That is, you can't also use regular -| paths? — cfr, Jan 08 '16 at 21:40
@cfr I am saying that -| is a good start. One can then rename it as -/ or /-, and modify TikZ's "if-switcher". Now we can write \draw(A)--(B)-|(C)-/(D); — Symbol 1, Jan 09 '16 at 00:48
Oh, I see. OK. That makes sense. Certainly if you want a lot of these. — cfr, Jan 09 '16 at 00:55

score 1 · Answer 3 · edited Apr 13 '17 at 12:34

You can cook up your own to path. Here mypath takes an argument as to how much of the path should be drawn as a straight before breaking. If set too high obviously it will over draw but in general should be OK.

\documentclass[tikz]{standalone}
\usetikzlibrary{calc,shapes.geometric,positioning}
\begin{document}
\begin{tikzpicture}[
  mypath/.style={
    to path={let \p1=($(\tikztostart)-(\tikztotarget)$),
                 \n1={atan2(\y1,\x1)},\n2 = {(\x1<0?1:2)}
                 in 
                 -- ($(\tikztostart)!#1!180*\n2-\n1:(\tikztotarget)$)
                 -- (\tikztotarget)\tikztonodes
          }
      }]

\node (a) {a};
\foreach \x[count=\xi] in {20,130,245,330}{
  \node[diamond,draw] (b-\xi) at (\x:3cm) {b};
  \draw (a.south west) to[mypath={min(0.5,rnd)}] (b-\xi);
}
\end{tikzpicture}
\end{document}

Also please have a look at Difference between "right of=" and "right=of" in PGF/TikZ to avoid the deprecated syntax.

Straight edge between nodes with break

3 Answers3