# Starting a path on a decoration of another path

In the following code, I would like to connect the plus sign to the focusing rectangle containing 2 * 3 + 11 = 17. I have a connection but it is not the wanted one.

I do not want the small red line crossed off in green, and I would like a line starting from the PLUS sign.

What am I missing ?

\documentclass[12pt]{article}

\usepackage{tikz}
\usetikzlibrary{arrows, matrix}

\tikzset{ope/.style={circle,draw,fill=white,inner sep=1pt, outer sep=1pt},
block/.style={
rectangle,
draw=blue,
thick,
fill=blue!20,
text width=5em,
align=center,
rounded corners,
minimum height=2em},
blur/.style={opacity=0.3},
focus/.style={rectangle,
thick,
rounded corners,
minimum height=2em,
align=center,
draw=red,
text=magenta}}

\begin{document}

% Source for decorated paths
%    * https://tex.stackexchange.com/a/507419/6880

\begin{tikzpicture}
\matrix[matrix of nodes,
row sep  = 1em,
column sep = 1.5em
](mat){
&  9665              &              && |[focus]| {$2 \times 3 + 11 = 17$}  \\
|[block]| 2 &  |[blur]|488888887 & |[block]| 3                                         \\
&  777               & |[block]| 11                                        \\
&                    &  99                                                 \\
};

\draw[red] (mat-2-1) -- (mat-2-3) node[midway,draw,ope]{$\times$};

\draw[red] (mat-2-3.east) -- ++ (1,0) -| ++ (0,-.5) coordinate[pos=0.5] (aux) |- (mat-3-3.east);

\draw[red] (mat-3-3.east) -| (aux) node[pos=0.75,draw,ope]{$+$}  -| (mat-1-5.south);

\draw[red,-triangle 60] (mat-1-5.west) -- ++ (-1,0);
\end{tikzpicture}

\end{document}


How about using positioning to position the new node (instead of putting it into the matrix)?

\documentclass[12pt]{article}

\usepackage{tikz}
\usetikzlibrary{arrows, matrix,positioning}

\tikzset{ope/.style={circle,draw,fill=white,inner sep=1pt, outer sep=1pt},
block/.style={
rectangle,
draw=blue,
thick,
fill=blue!20,
text width=5em,
align=center,
rounded corners,
minimum height=2em},
blur/.style={opacity=0.3},
focus/.style={rectangle,
thick,
rounded corners,
minimum height=2em,
align=center,
draw=red,
text=magenta}}

\begin{document}

% Source for decorated paths
%    * https://tex.stackexchange.com/a/507419/6880

\begin{tikzpicture}
\matrix[matrix of nodes,
row sep  = 1em,
column sep = 1.5em
](mat){
&  9665              &              \\
|[block]| 2 &  |[blur]|488888887 & |[block]| 3                                         \\
&  777               & |[block]| 11                                        \\
&                    &  99                                                 \\
};

\draw[red] (mat-2-1) -- (mat-2-3) node[midway,draw,ope]{$\times$};

\draw[red] (mat-2-3.east) -- ++ (1,0) |- (mat-3-3.east)
node[pos=0.25,draw,ope](plus){$+$}
node[above right=1cm and 1cm of plus,focus] (f){$2 \times 3 + 11 = 17$} ;
\draw[red,-triangle 60] (plus) -| (f) (f.west) --  ++(-1,0);
\end{tikzpicture}

\end{document}


• Thanks but I would like the + to stay between and connect to 3 and 11. Then I would like a path from + to 2*3+11=37. (I'm very new to TikZ) – projetmbc Sep 8 '19 at 22:02
• @projetmbc Yes, sorry, there was a typo |- (mat-2-3.east) needed to become |- (mat-3-3.east). – Schrödinger's cat Sep 8 '19 at 22:05
• Thanks. I really need to practice TiKz. So cute and no so hard to read. – projetmbc Sep 8 '19 at 22:14
• @projetmbc You're welcome! TikZ has become a really large package so it takes time to get used to it but I think on the long run it pays off. – Schrödinger's cat Sep 8 '19 at 22:17