tikz-pgf
I need to draw the lower part of a split circle node differently: I want it to have a double-style border, whereas the upper nodepart stays the same.
I've read this but cannot tell how to modify it to draw an extra border.
Also it doesn't appear to be the most generic solution for styling the lower semicircle of a circle node separately.
The multipart nodes have anchors called <node name>.one, <node name>.two east, etc., that allow you to reference the individual parts. The anchors for the rectangle split node are shown in the section Shapes with Multiple Text Parts of the pgfmanual. As percusse points out in the comment on the question, the node parts can also be referenced using .second, .third, etc., although this is not documented in the manual.
As a side note, for positioning your nodes in this case, I would not use a tree but rather the positioning library, which introduces the syntax right = of <node name> to place new nodes.
\documentclass{article}
\usepackage{tikz}
\usetikzlibrary{shapes,positioning}
\begin{document}
\begin{tikzpicture}
\node[name=block, rectangle split, rectangle split parts=4, draw]
{ \textbf{Block 1}
\nodepart{second} connect to a
\nodepart{third} connect to b
\nodepart{fourth} connect to c
};
\node[name=block2, rectangle split, rectangle split parts=4, draw, right= of block]
{ \textbf{Block 2}
\nodepart{second} \Huge{a}
\nodepart{third} \Huge{b}
\nodepart{fourth} \Huge{c}
};
\draw [-latex] (block.two east) -- (block2.two west);
\draw [-latex] (block.three east) -- (block2.three west);
\draw [-latex] (block.four east) -- (block2.four west);
\end{tikzpicture}
\end{document}
The real trick here is how to put the outer boxes around the inner nodes.
As you may have already discovered, it's not possible to embed a \node inside another \node. It is also a really bad idea to embed one tikzpicture inside another (which might appear to be another solution to this problem. Here's a solution that is based on Mark Everitt's answer to this question tikz: a big box with fixed width containing smaller boxes.
It uses the shapes.multipart library to split the tree nodes, and the fit library to put outer boxes around the tree nodes. The positioning and calc libraries are used to calculate the placement of the outer node text, and the edge from parent path, so that although the tree is built on the inner nodes, the branches actually connect at a point that appears to be the edge of the outer nodes.
Update: Based on this question: How to make tikz multipart node parts have uniform size? I've added some code to make all the inner nodes (both split and single) uniform size.
\documentclass{article}
\usepackage{tikz-qtree}
\usetikzlibrary{fit,backgrounds,shapes.multipart,calc,positioning}
\begin{document}
\tikzset{
sibling distance=2cm,
level distance=2.5cm,
split/.style={draw,
rectangle split, rectangle split parts=2,draw,inner
sep=0pt,rectangle split horizontal,minimum size=3ex,text width=3ex,align=center,rectangle split part align=base},
boxed/.style={draw,minimum size=3ex,inner sep=0pt,align=center},
edge from parent/.style={draw,
edge from parent path={[->,thick]
(\tikzparentnode) -- ($(\tikzchildnode.north) + 25*(0pt,1pt)$) }}
}
\begin{tikzpicture}
\Tree [.\node[split] (M1) {g\nodepart{two}t};
[.\node[split] (M2) {h\nodepart{two}r};
[.\node[boxed] (M3) {o};
[.\node[boxed] (M4) {s};
[.\node[boxed] (M5) {t};
[.\node[boxed] (E1) {};]
]
]
]
[.\node[boxed] (M6) {e};
[.\node[boxed] (M7) {e};
[.\node[boxed] (M8) {n};
[.\node[boxed] (E2) {};]
]
]
]
]
[.\node[split] (M9) {a\nodepart{two}r};
[.\node[boxed] (M10) {n};
[.\node[boxed] (E3) {};]
]
[.\node[split] (M11) {e\nodepart{two}i};
[.\node[boxed] (M12) {e};
[.\node[boxed] (E4) {};]
]
[.\node[boxed] (M13) {e};
[.\node[boxed] (E5) {};]
]
]
]
]
\begin{pgfonlayer}{background}
\foreach \x in {1,...,13}{
\node (A\x) [above =5pt of M\x] {Middle};
\node[draw,red,] [fit=(M\x) (A\x) ] {};}
\foreach \x in {1,...,5}{
\node (B\x) [above =5pt of E\x] {End};
\node[draw,red,] [fit=(E\x) (B\x) ] {};}
\end{pgfonlayer}
\end{tikzpicture}
\end{document}
Best Answer
Update
Now the code is more efficient with Jake's idea.