Tikz: purely vertical arrow from nodeA.south to nodeB.north

Question

I have the following tikz code

% compilation command: pdflatex --jobname=Diag-f1 Diag.tex
\documentclass{book}
\usepackage{tikz}
\pgfrealjobname{Diag}
\begin{document}
\beginpgfgraphicnamed{Diag-f1}
\begin{tikzpicture}[node distance=3em]
\node(G)[rectangle,fill=red!5,draw=red,text width=5cm]{};
\node(H)[below of=G]{H};
\node(H1)[left of=H]{H1};
\node(H2)[right of=H]{H2};
\draw[->](G.south)-|(H1.north);
\draw[->](G.south)--(H.north);
\draw[->](G.south)-|(H2.north);
\end{tikzpicture}
\endpgfgraphicnamed
\end{document}

but I am not happy with the two arrows going from G.south to H1.north and H2.north. Because of the -| command, there is a spurious horizontal line. How can I achieve the same result without this annoying horizontal line? \draw[->](G.south)--(H1.north); is not a solution. There are available tricks but I may have missed an obvious solution here.

Answer 1

The line is normal: -| means: draw an horizontal line, then a vertical.

You could use this:

\draw[->] (G.south -| H1.north) -- (H1.north)

That will compute the intersection between a vertical line through H1.north and a horizontal one through G.south, and then draw a line from it to H1.north

Answer 2

I like the use of to paths.

Advantage: The target coordinate/node has only to be given once.

Code

\documentclass[tikz]{standalone}
\tikzset{
    *|/.style={
        to path={
            (perpendicular cs: horizontal line through={(\tikztostart)},
                                 vertical line through={(\tikztotarget)})
            % is the same as (\tikztostart -| \tikztotarget)
            % but just to be safe: http://tex.stackexchange.com/a/29781/16595
            -- (\tikztotarget) \tikztonodes
        }
    }
}
\begin{document}
\begin{tikzpicture}[node distance=3em]
\node(G)  [rectangle,fill=red!5,draw=red,text width=5cm] {};
\node(H)  [below of=G] {H};
\node(H1) [left of=H]  {H1};
\node(H2) [right of=H] {H2};
\draw[->,*|] (G.south) to     (H1.north);
\draw[->]    (G.south) --     (H.north);
\draw[->]    (G.south) to[*|] (H2.north);
\end{tikzpicture}
\end{document}

Output

---

For various different possibilities of this (and without the need to declare the anchors), you can define more styles like this. This is also part of my paths.ortho library (see my user info).

Note that this (as well as the original answer, see above) does currently not take the current transformation in account and just uses the anchors .north, .south, .east and .west.

Code

\documentclass[tikz]{standalone}
\makeatletter
\newif\iftikz@ortho@preflush
\tikz@ortho@preflushtrue
\let\tikz@origtotarget\pgfutil@empty
\tikzset{
  |-/.style={to path={|- (\tikztotarget) \tikztonodes}},
  -|/.style={to path={-| (\tikztotarget) \tikztonodes}},
  *|/.style={to path={%
    \pgfextra
      \iftikz@shapeborder
        \tikz@scan@one@point\pgfutil@firstofone(\tikztotarget)\relax
        \ifdim\pgf@y>\tikz@lasty\relax
          \edef\tikztostart{\tikztostart.north}%
        \else
          \edef\tikztostart{\tikztostart.south}%
        \fi
      \fi
    \endpgfextra
    (perpendicular cs: horizontal line through={(\tikztostart)},
                 vertical line through={(\tikztotarget)}) -- (\tikztotarget) \tikztonodes
  }},
  *-/.style={to path={%
    \pgfextra
      \iftikz@shapeborder
        \tikz@scan@one@point\pgfutil@firstofone(\tikztotarget)\relax
        \ifdim\pgf@x>\tikz@lastx\relax
          \edef\tikztostart{\tikztostart.east}%
        \else
          \edef\tikztostart{\tikztostart.west}%
        \fi
      \fi
    \endpgfextra
    (perpendicular cs: vertical line through={(\tikztostart)},
                     horizontal line through={(\tikztotarget)}) -- (\tikztotarget) \tikztonodes
  }},
  |*/.style={to path={%
    \pgfextra
      \tikz@scan@one@point\pgfutil@firstofone(\tikztotarget)\relax
      \iftikz@shapeborder
        \let\tikz@origtotarget\tikztotarget
        \ifdim\pgf@y>\tikz@lasty\relax
          \edef\tikztotarget{\tikztotarget.south}%
        \else
          \edef\tikztotarget{\tikztotarget.north}%
        \fi
      \fi
    \endpgfextra
    (\tikztostart) -- (perpendicular cs: vertical line through={(\tikztostart)},
                                         horizontal line through={(\tikztotarget)})
    \tikztonodes \ifx\tikz@origtotarget\pgfutil@empty\else\iftikz@ortho@preflush(\tikz@origtotarget)\fi\fi
  }},
  -*/.style={to path={%
    \pgfextra
      \tikz@scan@one@point\pgfutil@firstofone(\tikztotarget)\relax
      \iftikz@shapeborder
        \let\tikz@origtotarget\tikztotarget
        \ifdim\pgf@x>\tikz@lastx\relax
          \edef\tikztotarget{\tikztotarget.west}%
        \else
          \edef\tikztotarget{\tikztotarget.east}%
        \fi
      \fi
    \endpgfextra
    (\tikztostart) -- (perpendicular cs: horizontal line through={(\tikztostart)},
                                         vertical line through={(\tikztotarget)})
    \tikztonodes \ifx\tikz@origtotarget\pgfutil@empty\else\iftikz@ortho@preflush(\tikz@origtotarget)\fi\fi
  }},
  node as new start/.is if=tikz@ortho@preflush
}
\makeatother
\begin{document}
\begin{tikzpicture}
\begin{scope}[nodes={shape=rectangle, draw, minimum width=+1.5cm, minimum height=+1cm}]
  \node (a)                {A};
  \node (b) at (  .5, 2  ) {B};
  \node (c) at ( 2.5,- .2) {C};
  \node (d) at (- .5,-2  ) {D};
  \node (e) at (-2.5,  .2) {E};
\end{scope}
\tikzset{nodes={auto,font=\small\ttfamily}}
\path[->] (a) edge[*|]                 (b)
          (b) edge[*|] node {*|}       (a)
          (a) edge[*-]                 (c)
          (c) edge[*-] node[swap] {*-} (a)
          (a) edge[|*]                 (d)
          (d) edge[|*] node[swap] {|*} (a)
          (a) edge[-*]                 (e)
          (e) edge[-*] node       {-*} (a)
          %
          {[every edge/.append style=blue]
            {[|-]
              (e) edge (b)
                  edge (d)}
            {[-|]
              (b) edge (c)
              (d) edge (c)}}
;
\end{tikzpicture}
\begin{tikzpicture}[nodes={shape=rectangle, draw, minimum width=+1cm, minimum height=+1cm}]
  \node (a)              {A};
  \node (b) at ( .25, 2) {B};
  \node (c) at (1.25,-0) {C};
  \draw (a) to [|*] (b) to (c);

  \begin{scope}[xshift=3cm, node as new start=false]
    \node (a)              {A};
    \node (b) at ( .25, 2) {B};
    \node (c) at (1.25,-0) {C};
    \draw (a) to [|*] (b) to (c);
  \end{scope}
\end{tikzpicture}
\begin{tikzpicture}[nodes={rectangle,draw,anchor=west,minimum height=+1cm}]
\node (rechteck1)[minimum width=+3cm] at (1,5){};
\node (rechteck2)[minimum width=+2cm] at (1,3){};

\draw [->] (rechteck1) to[*|] (rechteck2);
\end{tikzpicture}
\end{document}

Output