TikZ/PGF - switching off shading

Question

Is there a way to switch off shading for one node, in a scope where the nodes are shaded? In other words, I want something like shading=none, but did not find it. Motivation:

\documentclass{article}
\usepackage{tikz}
\tikzset{default/.style={}}
\tikzstyle{st1}=[circle, shading=ball, ball color=red, inner sep=1.5pt]
\tikzstyle{st2}=[default, rectangle, inner xsep=0pt, inner ysep=2pt, draw] 
\begin{document}
    \begin{tikzpicture}[grow=right, level distance=10pt, every node/.style={st1}]
        \path node{} child {node{} child {node{} child {node[st2]{}}}};
    \end{tikzpicture}
\end{document}

This gives the following result: . The problem is that the shading is inherited in the last node, which I want without shading. I thought the default option in definition of st2 might help, but it does not have any effect.

The only way to achieve what I want is to add [every node/.style={default}] to the last child in the command; this resets/clears the style for all children. While writing this question, I realized that I can define \tikzstyle{st3}=[every node/.style={default, st2}] and use it on the last child. This makes it easy to use - but I would still like to know why I have to put the 'style reset' on the child, instead of on the node?

And one more thing: the reason I have inner ysep=0.0pt on the last node is that I actually want a single line, i.e. a box with zero width. Is there a way to achieve this in my setup, i.e. in a sequence of nodes?

Thanks.

Answer 1

At the moment, the shade key is only a one way switch: It only switches shadings on, but it can't switch them off. It's easy to redefine, however:

\makeatletter
\def\tikz@falsetext{false}
\tikzset{
    shade/.code={
        \edef\tikz@temp{#1}%
        \ifx\tikz@temp\tikz@falsetext%
            \tikz@addmode{\tikz@mode@shadefalse}%
        \else%  
            \tikz@addmode{\tikz@mode@shadetrue}%
        \fi
    }
}
\makeatother

Now you can say shade=false to deactivate the shading:

\documentclass[a4paper]{article}
\usepackage{tikz}

\makeatletter
\def\tikz@falsetext{false}
\tikzset{
    shade/.code={
        \edef\tikz@temp{#1}%
        \ifx\tikz@temp\tikz@falsetext%
            \tikz@addmode{\tikz@mode@shadefalse}%
        \else%  
            \tikz@addmode{\tikz@mode@shadetrue}%
        \fi
    }
}
\makeatother

\begin{document}
\tikzset{
    st1/.style={circle, shading=ball, ball color=red, inner sep=1.5pt},
    st2/.style={rectangle, shade=false, inner xsep=1.5pt, inner ysep=0.0pt, draw}
}

\begin{tikzpicture}[grow=right, level distance=10pt, every node/.style={st1}]
    \path node{} child {
        node{} child {
            node{} child {
                node[st2]{}
            }
        }
    };
\end{tikzpicture}
\end{document}

Answer 2

Here is a ... ehm ... wonderful, fantastic, new shading called none. It basically fills the node and does nothing else. One can use it in the same way of a ball shading, so by means of shading=none; to specify the color I was in doubt if let this operation to fill or not, then I preferred keeping the same behaviour of the other shadings, so there's a none shade color key defined.

An example:

\documentclass[a4paper]{article}
\usepackage{tikz}

\makeatletter
\def\tikz@shading{none}
\def\tikz@shading{none}\def\tikz@shade@angle{0}\tikz@addmode{\tikz@mode@shadetrue}
\tikzoption{none shade color}{\pgfutil@colorlet{tikz@none@color}{#1}\def\tikz@shading{none}\tikz@addmode{\tikz@mode@shadetrue}}

\pgfdeclareverticalshading[tikz@none@color]{none}{100bp}{%
  color(0bp)=(tikz@none@color);
  color(25bp)=(tikz@none@color);
  color(50bp)=(tikz@none@color);
  color(75bp)=(tikz@none@color);
  color(100bp)=(tikz@none@color)}

\pgfutil@colorlet{tikz@none@color}{white}
\makeatother

\begin{document}
\tikzset{st1/.style={circle, shading=ball, ball color=red, inner sep=1.5pt}}
\tikzset{st2/.style={rectangle, inner xsep=1.5pt, inner ysep=1.0pt, draw,shading=none, none shade color=red}}
\tikzset{st3/.style={circle,shading=ball, ball color=blue, inner sep=1.5pt}}
% one could also avoid saying shading=none and just specifying the color, as for the ball shading
\tikzset{st4/.style={circle,  inner sep=1.5pt, none shade color=blue!50}}
\begin{tikzpicture}[grow=right, level distance=10pt, every node/.style={st1}]
    \path node{} child {node[st2]{} child {node{} child {node[st2]{} child{node[st3]{} child{node[st4]{}}}}}};
\end{tikzpicture}
\end{document}

The result:

BTW: in the original code I replaced \tikzstyle with \tikzset as per Should \tikzset or \tikzstyle be used to define TikZ styles?.