Why does my text along the line intersect nodes?

Question

everyone!

I am plotting some diagrams and encountered a problem. Here is my code

\documentclass{article}
\usepackage{tikz}
\usetikzlibrary{positioning}
\usetikzlibrary{arrows.meta, positioning, quotes, shadows}
\usepackage{tikz}
\usetikzlibrary{fadings}
\usetikzlibrary{patterns}
\usetikzlibrary{shadows.blur}
\usetikzlibrary{shapes}
\usetikzlibrary{decorations.pathreplacing}
\usetikzlibrary{calc,intersections}
\usepackage{tikz}
\usetikzlibrary{shapes,arrows,chains}
\usetikzlibrary[calc]
\begin{document}
\begin{tikzpicture}[auto,>=stealth,
node distance = 25mm and 10mm, 
   box/.style = {draw, rounded corners, fill=blue!6, 
                 minimum width=22mm, minimum height=5mm, align=center},
   squarednode/.style={rectangle, draw=black!0, fill=blue!1, very thick, minimum size=1mm},
            > = {Straight Barb[angle=60:2pt 3]},
   bend angle = 15,
         auto = right,
                        ]
\node (node1)  [box,draw,name path=node1]                     {\large{Heat} \ \large{market}};
\node (node2)  [box,draw,name path=node2, above right=of node1]    {\large{Combined Heat and Power Plants, }\\large{Power-to-Heat units}};
\node (node3)  [box, draw, name path=node3, below right=of node2]    {\large{Electricity} \ \large{market}};
\node (node4)  [box, left =of node2]  {};
\path       [name path=node12]                      let \p1 = ($(node2)-(node1)$) 
             in       (node1)       ($(node1)!5pt!($(node1)+(-\y1,\x1)$)$)       to       +(\p1);
\path       [name path=node21]                      let \p1 = ($(node2)-(node1)$) 
             in       (node1)       ($(node1)!-5pt!($(node1)+(-\y1,\x1)$)$)      to       +(\p1);
\path       [name path=node23]                      let \p1 = ($(node3)-(node2)$) 
             in       (node2)       ($(node2)!5pt!($(node2)+(-\y1,\x1)$)$)       to       +(\p1);
\path       [name path=node32]                      let \p1 = ($(node3)-(node2)$) 
             in       (node2)       ($(node2)!-5pt!($(node2)+(-\y1,\x1)$)$)      to       +(\p1);
\node       [name intersections={of=node1 and node12}]     (start) at (intersection-1){};
\draw       [<-,very thick,name intersections={of=node2 and node12}] 
            (start.center) -- node[text width=3.5cm,sloped,swap,midway,above, align=center] {1. Heat offer}  (intersection-1);
\node       [name intersections={of=node2 and node21}]     (start) at (intersection-1){};
\draw       [<-,very thick,name intersections={of=node1 and node21}] 
            (start.center) -- node[text width=3cm,sloped, align=center] {2. Heat dispatch and price} (intersection-1);
\node       [name intersections={of=node2 and node23}]     (start) at (intersection-1){};
\draw       [<-,very thick,name intersections={of=node3 and node23}] 
            (start.center) -- node[text width=3cm,sloped,swap,midway,above, align=center] {4. Electricity dispatch and price}  (intersection-1);
\node       [name intersections={of=node3 and node32}]     (start) at (intersection-1){};
\draw       [<-,very thick,name intersections={of=node2 and node32}] 
            (start.center) -- node[sloped] {3. Electricity offer} (intersection-1);
\draw       [->]  (node4) --node[text width=3cm, above, midway] {Electricity price forecast}  (node2);
\end{tikzpicture}
\end{document}

First I plot some nodes, then I calculate distances to plot parallel lines as in https://tex.stackexchange.com/a/232828/262804. Then, I am plotting the text above the line as in https://tex.stackexchange.com/a/249540/262804 with the following line

\draw [->] (node4) --node[text width=3cm, above, midway] {Electricity price forecast} (node2);

And then I am getting this result

How can I make "Electricity price forecast" text node be always between node4 and node2 and never cross them?

Answer 1

Huh, your MWE is very (to my opinion unnecessary) complex (consequently in it can be easily lost)

• My suggestion is mostly off-topic -- possible solution is already mentioned in @SebGlav comment -- but seems to be better to increase common node distances, for example to node distance = 19mm and 17mm and at same time use smaller font size for edge quotes.
• In your MWE preamble you load packages and libraries up to three times! Why? Sufficient is just once.
• Please, in MWE preamble provide only to it relevant stuff, as is done in my answer.
• Complexity of your MWE can reduced and make shorter by using transform canvas for inner edges in picture and quotes library for edge labels:

%\documentclass{article}
\documentclass[border=3.141592]{standalone}
\usepackage{tikz}
\usetikzlibrary{positioning}
\usetikzlibrary{arrows.meta,
                positioning, 
                quotes}
\begin{document}
\begin{tikzpicture}[
node distance = 19mm and 17mm,
   box/.style = {draw, rounded corners, fill=blue!6,
                 minimum width=22mm, minimum height=11mm, align=center},
every edge/.style = {draw, -{Straight Barb[angle=60:2pt 3]}, semithick},
every edge quotes/.style = {auto, align=center,
                            font=\footnotesize\linespread{0.84}\selectfont,
                            sloped},
                    ]
\node (n1)  [box] {Combined Heat\ 
                    and Power Plants,\
                    Power-to-Heat units};
\node (n2)  [box, left=of n1]   {};
\node (n3)  [box, below  left=of n1]    {Heat\ market};
\node (n4)  [box, below right=of n1]    {Electricity\ market};
%
\path   (n2) edge["Electricity\price\forecast"]   (n1)
        (n1) edge["1. Heat offer"]                  (n3.north)
        (n1) edge["3. Electricity\offer"]          (n4.north)
        ;
\path[transform canvas={xshift=+9pt}]

        (n3.north) edge["2. Heat dispatch\ 
                        and price" ']               (n1);

\path[transform canvas={xshift=-9pt}]
        (n4.north) edge["4. Electricity\ dispatch and\ 
                        price" ']                   (n1);
\end{tikzpicture}
\end{document}