pgfplots: fill between and soft clip don't work as expected

Question

This question is related to this other question. Fill between fails to fill the correct region in this MWE.

\documentclass{article}

\usepackage{pgfplots}
\usepgfplotslibrary{fillbetween} 
\usetikzlibrary{patterns}

\pgfplotsset{
    every tick/.append style={thin},
    axis x line=center,
    axis y line=center,
    xtick={-100,-99,...,100},
    ytick={-100,-99,...,100},
    xlabel=$x$,
    ylabel=$y$,
    xticklabel=\empty,
    yticklabel=\empty,
    xlabel style={at=(current axis.right of origin), anchor=west}, 
    ylabel style={at=(current axis.above origin), anchor=south}, 
    every tick label/.append style={font=\scriptsize},
    axis equal image,
    axis line style={black!66!white},
    every axis plot/.append style={smooth,thick,mark=none,font=\small},
    every node/.style={label font=\small},
    every axis legend/.append style={at={(1,1)},anchor=south east,empty legend},
    }

\pgfplotsset{rellenoa/.style={pattern=north west lines,pattern color=green,}}
\pgfplotsset{rellenob/.style={pattern=north east lines,pattern color=green,}}
\pgfplotsset{rellenoc/.style={pattern=horizontal lines,pattern color=green,}}

\begin{document}

\begin{center}
\begin{tikzpicture}
    \def\xmi{-4.5} \def\xma{6.5} \def\ymi{-4.9} \def\yma{12.5} 
    \def\coa{-2} \def\cob{0.5} \def\coc{4} 
\begin{axis}[
        %scale=0.7, % this works
width=0.6\textwidth,xmin=\xmi,xmax=\xma,ymin=\ymi,ymax=\yma,y=1.5cm,
declare function={curvaa(\t)=-2*\t+4;},
declare function={curvab(\t)=2*\t+2;},
declare function={caminoa(\t)=-2*\t+1;},
declare function={caminob(\t)=2*\t-1;},]
%Lines
\addplot[domain=\xmi-1:\cob,samples=2,blue,name path=crva]{curvaa(x)};
\addplot[domain=\cob:\xma+1,samples=2,blue,name path=crvb]{curvab(x)};
\addplot[domain=\xmi-1:\cob,samples=2,purple]{caminoa(x)};
\addplot[domain=\cob:\xma+1,samples=2,purple]{caminob(x)};
%Points
\node[blue](X1t) at (axis cs:{\coa,caminoa(\coa)}) {};
\node[blue](X2t) at (axis cs:{\coa,curvaa(\coa)}) {};
    \node[](X2m) at (axis cs:{\coa,curvaa(\cob)}) {};
    \node[](X2b) at (axis cs:\coa,0) {};
\node[blue](X3t) at (axis cs:{\cob,curvaa(\cob)}) {};
    \node[](X3b) at (axis cs:\cob,0) {};
\node[blue](X4t) at (axis cs:{\coc,curvab(\coc)}) {};
    \node[](X4m) at (axis cs:{\coc,curvab(\cob)}) {};
    \node[](X4b) at (axis cs:\coc,0) {};
\node[blue](X5t) at (axis cs:{\coc,caminob(\coc)}) {};
%Barriers
\draw[/pgfplots,red,dashed,] (X1t.center) -- (X2b.center);
\draw[/pgfplots,red,dashed,] (X5t.center) -- (X4b.center);
\draw[/pgfplots,red,dashed,] (X2t.center) -- (X2b.center);
\draw[/pgfplots,red,dashed,] (X4t.center) -- (X4b.center);
    \path[name path=bed] (X2b.center)-- (X4b.center);
\draw[/pgfplots,red,dashed,name path=mid] (X2m.center) -- (X4m.center);
%Fills
\addplot[rellenoa] fill between [of=mid and crva,soft clip={domain=\coa:\cob},];
\addplot[rellenob] fill between [of=crvb and mid,soft clip={domain=\cob:\coc},];
\addplot[rellenoc] fill between [of=bed and mid,soft clip={domain=\coa:\coc},];
%Legends
%\legend{\empty,\empty,\empty,\empty,$A_1$,$A_2$,$A_3$}
\end{axis}
\end{tikzpicture}
\end{center}

\end{document}

I've encountered this bug (maybe?) before, and I've dealt with it by playing around with the value of y, but nothing seems to work with this one.

Answer 1

IMHO, there is no bug, and the fills are precisely as one would expect them to be from the manual. I am referring to the statement starting in the third line of p. 104

The soft clip key restricts the filled segments to the bounding rectangle defined by some path ⟨lower corner⟩ rectangle ⟨upper corner⟩ where the two arguments are the lower and upper corner of an invisible rectangular bounding box.

Continuing to read on p. 104 suggests the code

\documentclass{article}
\usepackage{pgfplots}
\usepgfplotslibrary{fillbetween} 
\usetikzlibrary{patterns}

\pgfplotsset{compat=1.16,
    every tick/.append style={thin},
    axis x line=center,
    axis y line=center,
    xtick={-100,-99,...,100},
    ytick={-100,-99,...,100},
    xlabel=$x$,
    ylabel=$y$,
    xticklabel=\empty,
    yticklabel=\empty,
    xlabel style={at=(current axis.right of origin), anchor=west}, 
    ylabel style={at=(current axis.above origin), anchor=south}, 
    every tick label/.append style={font=\scriptsize},
    axis equal image,
    axis line style={black!66!white},
    every axis plot/.append style={smooth,thick,mark=none,font=\small},
    every node/.style={label font=\small},
    every axis legend/.append style={at={(1,1)},anchor=south east,empty legend},
    }

\pgfplotsset{rellenoa/.style={pattern=north west lines,pattern color=green,}}
\pgfplotsset{rellenob/.style={pattern=north east lines,pattern color=green,}}
\pgfplotsset{rellenoc/.style={pattern=horizontal lines,pattern color=green,}}

\begin{document}

\begin{center}
\begin{tikzpicture}
    \def\xmi{-4.5} \def\xma{6.5} \def\ymi{-4.9} \def\yma{12.5} 
    \def\coa{-2} \def\cob{0.5} \def\coc{4} 
\begin{axis}[
        %scale=0.7, % this works
width=0.6\textwidth,xmin=\xmi,xmax=\xma,ymin=\ymi,ymax=\yma,y=1.5cm,
declare function={curvaa(\t)=-2*\t+4;},
declare function={curvab(\t)=2*\t+2;},
declare function={caminoa(\t)=-2*\t+1;},
declare function={caminob(\t)=2*\t-1;},]
%Lines
\addplot[domain=\xmi-1:\cob,samples=2,blue,name path=crva]{curvaa(x)};
\addplot[domain=\cob:\xma+1,samples=2,blue,name path=crvb]{curvab(x)};
\addplot[domain=\xmi-1:\cob,samples=2,purple]{caminoa(x)};
\addplot[domain=\cob:\xma+1,samples=2,purple]{caminob(x)};
%Points
\coordinate(X1t) at (axis cs:{\coa,caminoa(\coa)});
\coordinate(X2t) at (axis cs:{\coa,curvaa(\coa)});
\coordinate(X2m) at (axis cs:{\coa,curvaa(\cob)});
\coordinate(X2b) at (axis cs:\coa,0);
\coordinate(X3t) at (axis cs:{\cob,curvaa(\cob)});
\coordinate(X3b) at (axis cs:\cob,0);
\coordinate(X4t) at (axis cs:{\coc,curvab(\coc)});
\coordinate(X4m) at (axis cs:{\coc,curvab(\cob)});
\coordinate(X4b) at (axis cs:\coc,0);
\coordinate(X5t) at (axis cs:{\coc,caminob(\coc)});
%Barriers
% \draw[red,dashed] (X1t.center) -- (X2b.center);
% \draw[red,dashed] (X5t.center) -- (X4b.center);
\draw[red,dashed] (X2t) -- (X2b);
\draw[red,dashed] (X4t) -- (X4b);
\path[name path=bed] (X2b)-- (X4b);
\draw[red,dashed,name path=mid] (X2m) -- (X4m);
%Fills
\addplot[rellenoa] fill between [of=mid and crva,soft clip={domain=\coa:\cob}];
\def\clippath{
        (X3t) rectangle (X4t)
    }
\addplot[rellenob] fill between [of=mid and crvb,soft clip={\clippath}];
\addplot[rellenoc] fill between [of=bed and mid,soft clip={domain=\coa:\coc}];
%Legends
%\legend{\empty,\empty,\empty,\empty,$A_1$,$A_2$,$A_3$}
\end{axis}
\end{tikzpicture}
\end{center}
\end{document}

I have a couple of remarks:

1. I cleaned up your code. Many of your nodes can be more conveniently defined as coordinates, in which case you can drop many {} and .center.
2. If you were to set compat to something recent (1.11 or higher), you could get rid of the axis cs:.
3. Some of your paths were redundant, I commented them out.
4. In \draw[/pgfplots,red,dashed,]... /pgfplots has AFAIK no effect.