Qfyilyi

The following code uses a decorator to add an arrow tip to an edge. Logically, the tip is part of the edge, and so I want it to be colored with the line-color. However, because the tip is rendered using fill, it takes its color from the fill parameter. How can I make the color to respond to draw=red, and also not respond to fill=blue?

documentclass[tikz, crop,border=1]{standalone}

usetikzlibrary{decorations.markings, decorations.pathreplacing}



newcommand{drawArrow}[2]{

    draw[

        decoration={

            markings,

            mark=at position 0.8 with {%

                fill (0, 0.5pt) -- ++ (-0.25, 0.075) -- ++ (0, -0.075) -- cycle;

            }

        },

        postaction=decorate

    ] #1 -- #2;

}



begin{document}

begin{tikzpicture}[scale=2]

tikzset{

    pe/.style={

        line width = 1pt,

        decoration={

            show path construction, 

            lineto code={%

                drawArrow{(tikzinputsegmentfirst)}{(tikzinputsegmentlast)}

            },

            closepath code={%

                drawArrow{(tikzinputsegmentfirst)}{(tikzinputsegmentlast)}

            }

        },

        postaction=decorate

    }

}



% Not what I want

draw[pe, draw = red] (0, 0) -- (1, 0);



% Not what I want

draw[pe, draw = red, fill=blue] (0, 0.25) -- (1, 0.25) -- (1, 0.5) -- (0, 0.5) -- cycle;



% What I want

draw[pe, red] (0, 0.6) -- (1, 0.6);



% Not what I want

draw[pe, red, fill=blue] (0, 0.75) -- (1, 0.75) -- (1, 1) -- (0, 1) -- cycle;



% What I want, simulated

fill[pe, fill=blue] (0, 1.1) -- (1, 1.1) -- (1, 1.35) -- (0, 1.35) -- cycle;

draw[pe, red] (0, 1.1) -- (1, 1.1) -- (1, 1.35) -- (0, 1.35) -- cycle;



end{tikzpicture}

end{document}

Update 2

You can make the color of the decoration a parameter of the style.

decoration={

    markings, mark=at position 0.8 with {%

        fill[#1] (0, 0.5pt) -- ++ (-0.25, 0.075) -- ++ (0, -0.075) -- cycle;

    }

Just call this style pe=yellow, by default these style is red.

documentclass[tikz, crop,border=1]{standalone}

usetikzlibrary{decorations.markings}



begin{document}

begin{tikzpicture}

tikzset{

    pe/.style={

        %line width = 1pt,

        decoration={

            markings, mark=at position 0.8 with {%

                fill[#1] (0, 0.5pt) -- ++ (-0.25, 0.075) -- ++ (0, -0.075) -- cycle;

            }

        },

        postaction=decorate

    },

    pe/.default=red

}

% Incorrect

draw[pe=yellow, draw = red] (0, 0) -- (1, 0);



% Incorrect

draw[pe=black, draw = red, fill=blue] (0, 0.25) -- (1, 0.25) -- (1, 0.5) -- (0, 0.5) -- cycle;



% Correct

draw[pe, red] (0, 0.6) -- (1, 0.6);



% Incorrect

draw[pe, red, fill=blue] (0, 0.75) -- (1, 0.75) -- (1, 1) -- (0, 1) -- cycle;



% Correct, simulated

fill[pe, fill=blue] (0, 1.1) -- (1, 1.1) -- (1, 1.35) -- (0, 1.35) -- cycle;

end{tikzpicture}

end{document}

Update

If I understood correctly, you must specify the color in the decoration.

decoration={

            markings, mark=at position 0.8 with {%

                fill[red] (0, 0.5pt) -- ++ (-0.25, 0.075) -- ++ (0, -0.075) -- cycle;

            }

        },

documentclass[tikz, crop,border=1]{standalone}

usetikzlibrary{decorations.markings}



begin{document}

begin{tikzpicture}

tikzset{

    pe/.style={

        %line width = 1pt,

        decoration={

            markings, mark=at position 0.8 with {%

                fill[red] (0, 0.5pt) -- ++ (-0.25, 0.075) -- ++ (0, -0.075) -- cycle;

            }

        },

        postaction=decorate

    },

}



% Incorrect

draw[pe, draw = red] (0, 0) -- (1, 0);



% Incorrect

draw[pe, draw = red, fill=blue] (0, 0.25) -- (1, 0.25) -- (1, 0.5) -- (0, 0.5) -- cycle;



% Correct

draw[pe, red] (0, 0.6) -- (1, 0.6);



% Incorrect

draw[pe, red, fill=blue] (0, 0.75) -- (1, 0.75) -- (1, 1) -- (0, 1) -- cycle;



% Correct, simulated

fill[pe, fill=blue] (0, 1.1) -- (1, 1.1) -- (1, 1.35) -- (0, 1.35) -- cycle;

draw[pe, red] (0, 1.1) -- (1, 1.1) -- (1, 1.35) -- (0, 1.35) -- cycle;



end{tikzpicture}

end{document}



Simply by not specifying `draw=red`, but just `red`



    draw[pe, red] (0, 0) -- (1, 0);



[![red][2]][2]



    documentclass[tikz, crop,border=5mm]{standalone}

    usetikzlibrary{decorations.markings}



    begin{document}

    begin{tikzpicture}

    tikzset{

        pe/.style={

            decoration={

                markings, mark=at position 0.8 with {%

                    fill (0, 0.5pt) -- ++ (-0.25, 0.075) -- ++ (0, -0.075) -- cycle;

                }

            },

            postaction=decorate

        }

    }

    draw[pe, red] (0, 0) -- (1, 0);

    end{tikzpicture}

    end{document}

Just define a style for the arrow and set it accordingly.

documentclass[tikz, crop,border=1]{standalone}

usetikzlibrary{decorations.markings, decorations.pathreplacing}

tikzset{pearrow/.style={fill},

peset/.code={tikzset{pearrow/.style={#1}}}}

newcommand{drawArrow}[2]{

    draw[

        decoration={

            markings,

            mark=at position 0.8 with {%

                path[pearrow] (0, 0.5pt) -- ++ (-0.25, 0.075) -- ++ (0, -0.075) -- cycle;

            }

        },

        postaction=decorate

    ] #1 -- #2;

}



begin{document}

begin{tikzpicture}[scale=2]

tikzset{

    pe/.style={

        line width = 1pt,

        decoration={

            show path construction, 

            lineto code={%

                drawArrow{(tikzinputsegmentfirst)}{(tikzinputsegmentlast)}

            },

            closepath code={%

                drawArrow{(tikzinputsegmentfirst)}{(tikzinputsegmentlast)}

            }

        },

        postaction=decorate

    }

}





% with peset

draw[pe, red, fill=blue,peset={fill=red}] (0, 0.75) -- (1, 0.75) -- (1, 1) -- (0, 1) -- cycle;



% What I want, simulated

fill[pe, fill=blue] (0, 1.1) -- (1, 1.1) -- (1, 1.35) -- (0, 1.35) -- cycle;

draw[pe, red] (0, 1.1) -- (1, 1.1) -- (1, 1.35) -- (0, 1.35) -- cycle;



end{tikzpicture}

end{document}

The following findArrowColor style, based on this Georg Sievelson's answer, picks the current stroke color if such is available, then the current text color if such is available, and black color as the last resort.

documentclass[tikz, crop,border=1]{standalone}

usetikzlibrary{decorations.markings, decorations.pathreplacing}



usepackage{ifthen}



makeatletter

tikzset{

  /tikz/findArrowColor/.style={/utils/exec={%

    ifthenelse{equal{tikz@strokecolor}{}}%

    {%

        ifthenelse{equal{tikz@textcolor}{}}%

        {%

            colorlet{#1}{black}%

        }%

        {colorlet{#1}{tikz@textcolor}}%

    }%

    {%

        colorlet{#1}{tikz@strokecolor}%

    }%

  }}

}

makeatother



newcommand{drawArrow}[2]{

    draw[

        decoration={

            markings,

            mark=at position 0.8 with {%

                begin{scope}

                    tikzset{findArrowColor=arrowColor}

                    fill[fill=arrowColor] (0, 0.5pt) -- ++ (-0.25, 0.075) -- ++ (0, -0.075) -- cycle;

                end{scope}

            }

        },

        postaction=decorate

    ] #1 -- #2;

}



begin{document}

begin{tikzpicture}[scale=2]



tikzset{

    pe/.style={

        line width = 1pt,

        decoration={

            show path construction, 

            lineto code={%

                begin{scope}[#1]

                drawArrow{(tikzinputsegmentfirst)}{(tikzinputsegmentlast)}

                end{scope}

            },

            closepath code={%

                begin{scope}[#1]

                drawArrow{(tikzinputsegmentfirst)}{(tikzinputsegmentlast)}

                end{scope}

            }

        },

        postaction=decorate

    }

}



draw[pe, fill = blue] (0, -0.2) -- (1, -0.2);

draw[pe, draw = red] (0, 0) -- (1, 0);

draw[pe, draw = red, fill=blue] (0, 0.25) -- (1, 0.25) -- (1, 0.5) -- (0, 0.5) -- cycle;

draw[pe, red, fill=blue] (0, 0.75) -- (1, 0.75) -- (1, 1) -- (0, 1) -- cycle;



fill[fill=blue] (0, 1.1) -- (1, 1.1) -- (1, 1.35) -- (0, 1.35) -- cycle;

draw[pe, red] (0, 1.1) -- (1, 1.1) -- (1, 1.35) -- (0, 1.35) -- cycle;



end{tikzpicture}

end{document}