[Tex/LaTex] How to define a different style for edges and nodes

tikz-pgf

Given this image (a simple edge between two nodes):

\begin{tikzpicture}[>=latex,line join=bevel,]
  \node (a1) at (44bp,8bp) [draw,trapezium] {$A$};
  \node (d1) at (44bp,82bp) [draw,trapezium, shape border rotate=180] {$B$};
  \draw [->] (d1) ..controls (44bp,62.836bp) and (44bp,41.478bp)  .. node {$edge$} (a1);
\end{tikzpicture}

I defined:

\tikzstyle{every node}=[drop shadow, fill=white, draw]

What happends is that also the node on the edge gets rendered in a box and with shadow. I want the edge label to be just the text without loosing the every node rule.

Thus my question is: Is there a way I can specify specific rendering for nodes in edges while keeping all other nodes with shadow?

I must note that my tikz picture is generated, thus I only have control over the every styles.

Best Answer

You're not using an edge in the TikZ sense in your drawing, it's just a normal path with a node ( TikZ edge is created by using \path (A) edge (B)). As such, no every ... style that's specific to the "edge" node is installed, and you can't hook into it.

Since you say your image is generated (how?), you might have to approach this a bit differently. Instead of making every node have a drop shadow, you can apply the shadow just to every trapezium node in this example.

\documentclass{article}
\usepackage{tikz}
\usetikzlibrary{shapes.geometric,shadows}
\begin{document}
\tikzset{every trapezium node/.style={
        drop shadow, fill=white, draw
    }
}
\begin{tikzpicture}[>=latex,line join=bevel,]
  \node (a1) at (44bp,8bp) [draw,trapezium] {$A$};
  \node (d1) at (44bp,82bp) [draw,trapezium, shape border rotate=180] {$B$};
  \draw [->] (d1) ..controls (44bp,62.836bp) and (44bp,41.478bp)  .. node {$edge$} (a1);
\end{tikzpicture}
\end{document}

Related Solutions

[Tex/LaTex] Rotate a node but not its content: the case of the ellipse decoration

The source of the difficulty is that ellipses are constructed in a particular way in TikZ. They are paths that start from the x-axis and proceed counter-clockwise around their centre. The vast majority of the time, the exact parametrisation doesn't matter. You appear to have found the one situation where it does!

In the actual question, you only want to be able to mirror the ellipse, and so draw it starting from the negative x-axis (the title of the question suggests a more flexible approach). That's actually not too hard since we can exploit the symmetry of the ellipse. The key is to provide it with a negative x-radius, since then it will start from the negative x-axis (and proceed clockwise, but we could correct for that by negating the y-radius as well). To do this, we interrupt the call from the node shape to the drawing command and flip the sign of the x-radius. The simplest way to do this is to redefine the \pgfpathellipse macro to do the negation and then call the original macro. The following code does this.

\documentclass{article}
\usepackage{tikz}
\usetikzlibrary{decorations,shapes,decorations.markings}
\makeatletter
\let\origpgfpathellipse=\pgfpathellipse
\def\revpgfpathellipse#1#2#3{%
  #2%
  \pgf@xa=-\pgf@x
  \origpgfpathellipse{#1}{\pgfqpoint{\pgf@xa}{0pt}}{#3}}
\makeatother

\tikzset{
  reversed ellipse/.style={
    ellipse,
    reverse the ellipse%
  },
  reverse the ellipse/.code={
    \let\pgfpathellipse=\revpgfpathellipse
  }
}
\begin{document}
\begin{tikzpicture}
\node[ellipse,
  draw,
  postaction={
    decorate,
    decoration={
      markings,
      mark=at position 1 with {
        \arrow[line width=5pt,blue]{>}
      }
    }
  }
] at (0,0) {hello world};

\node[reversed ellipse,
  draw,
  postaction={
    decorate,
    decoration={
      markings,
      mark=at position 1 with {
        \arrow[line width=5pt,blue]{>}
      }
    }
  }
] at (0,-2) {hello world};
\end{tikzpicture}

\end{document}

Here's the result:

rotated ellipse

(the arrow got clipped, but you can see where it lies)

[Tex/LaTex] Drawing a proper shadow for overlapping objects

The follow-up question Pass options to the scope that is internally created by preaction was, to my amazement, solvable with my code from "Z-level" in TikZ. I'm going to have to resort to astonishment (and plagarism) now because it turns out that this works with drop shadow with no modification (my solutions tend to be the epitome of hackishness so the fact that one works for something it was not tested with is Definitely Unusual).

Here's the code. I've taken the liberty of removing the nested tikzpictures (see What are most important variables set at the beginning of a tikzpicture? of a scope? and links therein).

\documentclass{article}
%\url{https://tex.stackexchange.com/q/43618/86}
\usepackage{tikz}
\usetikzlibrary{shapes.geometric}
\usetikzlibrary{shadows}

\pgfdeclarelayer{back}
\pgfsetlayers{back,main}

\makeatletter
\pgfkeys{%
  /tikz/on layer/.code={
    \pgfonlayer{#1}\begingroup
    \aftergroup\endpgfonlayer
    \aftergroup\endgroup
  },
  /tikz/node on layer/.code={
    \pgfonlayer{#1}\begingroup
    \expandafter\def\expandafter\tikz@node@finish\expandafter{\expandafter\endgroup\expandafter\endpgfonlayer\tikz@node@finish}%
  },
}
\makeatother

\newcommand{\dbpart}[1]{
    \node[drop shadow={opacity=1.0,on layer=back},draw, cylinder, shape aspect=1.5, inner sep=0.3333em, fill=white,
    rotate=90, minimum width=1cm, minimum height=0.45cm] (cyl) at (0,#1) {};
}
\newcommand{\dbicon}[1][]{
  \begin{scope}[#1]
      \dbpart{0cm}%
      \dbpart{0.4cm}%
  \end{scope}
}

\begin{document}
\begin{tikzpicture}
      \dbicon
\end{tikzpicture}
\end{document}

Here's what happens (oh, and I put fill=white as I agree with Frédéric that it looks nicer).

Drop shadow on background layer

Let's have it without the fill just to see.

Drop shadow on background layer, main shape not filled

Best Answer

Related Solutions

[Tex/LaTex] Rotate a node but not its content: the case of the ellipse decoration

[Tex/LaTex] Drawing a proper shadow for overlapping objects

Related Question