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diff --git a/graphics/pgf/base/doc/pgfmanual-en-gd-usage-tikz.tex b/graphics/pgf/base/doc/pgfmanual-en-gd-usage-tikz.tex new file mode 100644 index 0000000000..e34ed4d3f0 --- /dev/null +++ b/graphics/pgf/base/doc/pgfmanual-en-gd-usage-tikz.tex @@ -0,0 +1,549 @@ +% Copyright 2019 by Till Tantau +% +% This file may be distributed and/or modified +% +% 1. under the LaTeX Project Public License and/or +% 2. under the GNU Free Documentation License. +% +% See the file doc/generic/pgf/licenses/LICENSE for more details. + + +\section{Using Graph Drawing in \tikzname} + +{\noindent {\emph{by Till Tantau}}} + +\begin{tikzlibrary}{graphdrawing} + This package provides capabilities for automatic graph drawing. It requires + that the document is typeset using Lua\TeX. This package should work with + Lua\TeX\ 0.54 or higher. +\end{tikzlibrary} + +\ifluatex +\else + This section of the manual can only be typeset using Lua\TeX. + \expandafter\endinput +\fi + + +\subsection{Choosing a Layout and a Library} + +The graph drawing engine is initialized when you load the library +|graphdrawing|. This library provides the basic framework for graph drawing, +including all options and keys described in the present section. However, this +library does \emph{not} load any actual algorithms for drawing graphs. For +this, you need to use the following command, which is defined by the +|graphdrawing| library: + +\begin{command}{\usegdlibrary\marg{list of libraries}} + This command is used to load the special graph drawing libraries (the |gd| + in the name of the command stands for ``graph drawing''). The \meta{list of + libraries} is a comma-separated list of library written in the Lua + programming language (which is why a special command is needed). + + In detail, this command does the following. For each \meta{name} in the + \meta{list of libraries} we do: + % + \begin{enumerate} + \item Check whether Lua\TeX\ can call |require| on the library file + |pgf.gd.|\meta{name}|.library|. Lua\TeX's usual file search + mechanism will search the texmf-trees in the usual manner and the + dots in the file name get converted into directory slashes. + \item If the above failed, try to |require| the string + |pgf.gd.|\meta{name}. + \item If this fails, try to |require| the string \meta{name}|.library|. + \item If this fails, try to |require| the string \meta{name}. If this + fails, print an error message. + \end{enumerate} + % + The net effect of the above is the following: Authors of graph drawing + algorithms can bundle together multiple algorithms in a library by creating + a |...xyz/library.lua| file that internally just calls |require| for all + files containing declarations. On the other hand, if a graph drawing + algorithm completely fits inside a single file, it can also be read + directly using |\usegdlibrary|. + % +\begin{codeexample}[code only] +\usetikzlibrary{graphdrawing} +\usegdlibrary{trees,force} +\end{codeexample} + + The different graph drawing libraries are documented in the following + Sections~\ref{section-first-graphdrawing-library-in-manual} to + \ref{section-last-graphdrawing-library-in-manual}. +\end{command} + +Note that in addition to the graph \emph{drawing} libraries, you may also wish +to load the normal \tikzname\ library |graphs|. It provides the powerful +|graph| path command with its easy-to-use syntax for specifying graphs, but you +can use the graph drawing engine independently of the |graphs| library, for +instance in conjunction with the |child| or the |edge| syntax. Here is a +typical setup: +% +\begin{codeexample}[code only] +\usetikzlibrary{graphs, graphdrawing} +\usegdlibrary{trees, layered} +\end{codeexample} + +Having set things up, you must then specify for which scopes the graph drawing +engine should apply a layout algorithm to the nodes in the scope. Typically, +you just add an option ending with |... layout| to the |graph| path operation +and then let the graph drawing do its magic: +% +\begin{codeexample}[preamble={\usetikzlibrary{graphs,graphdrawing} +\usegdlibrary{layered}}] +\tikz [rounded corners] + \graph [layered layout, sibling distance=8mm, level distance=8mm] + { + a -> { + b, + c -> { d, e } + } -> + f -> + a + }; +\end{codeexample} + +Whenever you use such an option, you can: +% +\begin{itemize} + \item Create nodes in the usual way. The nodes will be created completely, + but then tucked away in an internal table. This means that all of + \tikzname's options for nodes can be applied. You can also name a node + and reference it later. + \item Create edges using either the syntax of the |graph| command (using + |--|, |<-|, |->|, or |<->|), or using the |edge| command, or using the + |child| command. These edges will, however, not be created immediately. + Instead, the basic layer's command |\pgfgdedge| will be called, which + stores ``all the information concerning the edge''. The actual drawing + of the edge will only happen after all nodes have been positioned. + \item Most of the keys that can be passed to an edge will work as expected. + In particular, you can add labels to edges using the usual |node| + syntax for edges. + \item The |label| and |pin| options can be used in the usual manner with + nodes inside a graph drawing scope. Only, the labels and nodes will + play no role in the positioning of the nodes and they are added when + the nodes are finally positioned. + \item Similarly, nodes that are placed ``on an edge'' using the implicit + positioning syntax can be used in the usual manner. +\end{itemize} +% +Here are some things that will \emph{not} work: +% +\begin{itemize} + \item Only edges created using the graph syntax, the |edge| command, or the + |child| command will correctly pass their connection information to the + basic layer. When you write |\draw (a)--(b);| inside a graph drawing + scope, where |a| and |b| are nodes that have been created inside the + scope, you will get an error message / things will look wrong. The + reason is that the usual |--| is not ``caught'' by the graph drawing + engine and, thus, tries to immediately connect two nodes that do not + yet exist (except inside some internal table). + \item The options of edges are executed twice: Once when the edge is + ``examined'' by the |\pgfgdedge| command (using some magic to shield + against the side effects) and then once more when the edge is actually + created. Fortunately, in almost all cases, this will not be a problem; + but if you do very evil magic inside your edge options, you must roll a + D100 to see what strange things will happen. (Do no evil, by the way.) +\end{itemize} + +If you are really interested in the ``fine print'' of what happens, please see +Section~\ref{section-gd-pgf}. + + +\subsection{Graph Drawing Parameters} + +Graph drawing algorithms can typically be configured in some way. For instance, +for a graph drawing algorithm that visualizes its nodes as a tree, it will +typically be useful when the user can change the so-called \emph{level +distance} and the \emph{sibling distance}. For other algorithms, like +force-based algorithms, a large number of parameters influence the way the +algorithms work. Options that influence graph drawing algorithms will be called +\emph{(graph drawing) parameters} in the following. From the user's point of +view, these parameters look like normal \tikzname\ keys and you set them in the +usual way. Internally, they are treated a bit differently from normal keys +since their ``effect'' becomes apparent only later on, namely during the run of +the graph drawing algorithm. + +A graph drawing algorithm may or may not take different graph parameters into +account. After all, these options may even outright contradict each other, so +an algorithm can only try to ``do its best''. While many graph parameters are +very specific to a single algorithm, a number of graph parameters will be +important for many algorithms and they are documented in the course of the +present section. Here is an example of an option the ``always works'': +% +\begin{codeexample}[preamble={\usetikzlibrary{graphs,graphdrawing} +\usegdlibrary{force}}] +\tikz \graph [spring layout, vertical=1 to 2] { 1--2--3--1 }; +\end{codeexample} + +\includeluadocumentationof{pgf.gd.control.Distances} +\includeluadocumentationof{pgf.gd.control.Anchoring} +\includeluadocumentationof{pgf.gd.control.Orientation} + +\includeluadocumentationof{pgf.gd.control.FineTune} + +\includeluadocumentationof{pgf.gd.control.Components} +\includeluadocumentationof{pgf.gd.control.ComponentOrder} +\includeluadocumentationof{pgf.gd.control.ComponentDirection} +\includeluadocumentationof{pgf.gd.control.ComponentAlign} +\includeluadocumentationof{pgf.gd.control.ComponentDistance} + +\includeluadocumentationof{pgf.gd.control.NodeAnchors} + +\includeluadocumentationof{pgf.gd.model.Hyperedge} + + +\subsection{Using Several Different Layouts to Draw a Single Graph} +\label{section-gd-sublayouts} + +Inside each graph drawing scope, a main algorithm is used to perform the graph +drawing. However, parts of the graph may be drawn using different algorithms: +For instance, a graph might consist of several, say, cliques that are arranged +in a tree-like fashion. In this case, it might be useful to layout each clique +using a circular layout, but then lay out all laid out cliques using a tree +drawing algorithm. + +In order to lay out a graph using multiple algorithms, we need two things: +First, we must be able to \emph{specify} which algorithms should be used where +and, second, we must be able to \emph{resolve} conflicts that may result from +different algorithms ``having different ideas'' concerning where nodes should +be placed. + + +\subsubsection{Sublayouts} + +Specifying different layouts for a graph is easy: Inside a graph drawing scope, +simply open scopes, in which you use an option like |tree layout| for the nodes +mentioned in this scope. Inside these scopes, you can open even subscopes for +sublayouts, and so on. Furthermore, the |graphs| library has special support +for sublayouts. + +Let us start with the ``plain'' syntax for opening sublayouts: You pass a key +for creating layouts to a |scope|: +% +\begin{codeexample}[preamble={\usetikzlibrary{graphdrawing} +\usegdlibrary{force,trees}}] +\tikz [spring layout] { + \begin{scope}[tree layout] + \node (a) {a}; + \node (b) {b}; + \node (c) {c}; + \draw (a) edge (b) edge (c); + \end{scope} + + \begin{scope}[tree layout] + \node (1) {1}; + \node (2) {2}; + \draw (1) edge (2); + \end{scope} + + \draw (a) edge (1); +} +\end{codeexample} + +Let us see, what is going on here. The main layout (|spring layout|) contains +two sublayouts (the two |tree layouts|). Both of them are laid out +independently (more on the details in a moment). Then, from the main layout's +point of view, the sublayouts behave like ``large nodes'' and, thus, the edge +between |a| and |1| is actually the only edge that is used by the +|spring layout| -- resulting in a simple layout consisting of one big node at +the top and a big node at the bottom. + +The |graphs| library has a special support for sublayouts: The syntax is as +follows: wherever a normal node would go, you can write +% +\begin{quote} + |//| \opt{\oarg{layout options}} |{|\meta{sublayout}|}| +\end{quote} + +Following the double slash, you may provide \meta{layout options} in square +brackets. However, you \emph{must} provide a sublayout in braces. The contents +of \meta{sublayout} will be parsed using the usual |graph| syntax, but will +form a sublayout. +% +\begin{codeexample}[preamble={\usetikzlibrary{graphs,graphdrawing} +\usegdlibrary{force,trees}}] +\tikz \graph [spring layout] { + // [tree layout] { a -- {b, c} }; + // [tree layout] { 1 -- 2 }; + a -- 1; +}; +\end{codeexample} + +In the above example, there is no node before the double slash, which means +that the two sublayouts will be part of the main graph, but will not be +indicated otherwise. +% +\begin{codeexample}[preamble={\usetikzlibrary{graphs,graphdrawing} +\usegdlibrary{circular,trees}}] +\tikz \graph [simple necklace layout] { + // [simple necklace layout] { a -> b -> c -> d -> e -> f -> a }; + + // [tree layout] { % first tentacle + a -> {1, 2}; + }; + + // [tree layout] {% second tentacle + d -> {3, 4 -> {5, 6}} + }; +}; +\end{codeexample} + +In the above example, the first sublayout is the one for the nodes with letter +names. These nodes are arranged using a simple necklace layout as the sublayout +inherits this option from the main layout. The two small trees (|a -> {1, 2}| +and the tree starting at the |d| node) are also sublayouts, triggered by the +|tree layout| option. They are also arranged. Then, all of the layouts are +merged (as described later). The result is actually a single node, so the main +layout does nothing here. + +Compare the above to the following code: +% +\begin{codeexample}[preamble={\usetikzlibrary{graphs,graphdrawing} +\usegdlibrary{circular,trees}}] +\tikz \graph [simple necklace layout] { + // [tree layout] { % first ``giant node'' + a -> {1, 2}; + }; + + a -> b -> c -> d; + + // [tree layout] {% second ``giant node'' + d -> {3, 4 -> {5, 6}} + }, + + d -> e -> f -> a; +}; +\end{codeexample} + +Here, only the two trees are laid out first. They are then contracted into +``giant nodes'' and these are then part of the set of nodes that are arranged +by the |simple necklace layout|. For details of how this contracting works, see +below. + + +\subsubsection{Subgraph Nodes} + +A \emph{subgraph node} is a special kind of node that ``surrounds'' the +vertices of a subgraph. The special property of a subgraph node opposed to a +normal node is that it is created only after the subgraph has been laid out. +However, the difference to a collection like |hyper| is that the node is +available immediately as a normal node in the sense that you can connect edges +to it. + +The syntax used to declare a subgraph node in a |graph| specification is as +follows: +% +\begin{quote} + \opt{|"|}\meta{node name}\opt{|"|}\opt{|/|\opt{|"|}\meta{text}\opt{|"|}} + \opt{\oarg{node options}} |//| \opt{\oarg{layout options}} |{|\meta{subgraph}|}| +\end{quote} + +The idea ist that a subgraph node is declared like a normal node specification, +but is followed by a double slash and a subgraph: +% +\begin{codeexample}[ + width=5cm, + preamble={\usetikzlibrary{graphs,graphdrawing} +\usegdlibrary{circular,trees}}, +] +\tikz \graph [simple necklace layout] { + tree 1[draw, circle] // [tree layout] { a -> {1, 2}; } + -> b + -> c + -> tree 2[draw] // [tree layout] { d -> {3, 4 -> {5, 6} } } + -> e + -> f + -> tree 1; +}; +\end{codeexample} + +Note how the two subgraph nodes |tree 1| and |tree 2| surround the two smaller +trees. In the example, both had trees as contents and these trees were rendered +using a sublayout. However, a subgraph layout does not need to have its own +layout: If you do \emph{not} provide a layout name after the double slash, the +subgraph node will simply surround all nodes that were placed by the main +layout wherever they were placed: +% +\begin{codeexample}[preamble={\usetikzlibrary{graphs,graphdrawing} +\usegdlibrary{trees}}] +\tikz [subgraph text bottom=text centered, + subgraph nodes={font=\itshape}] + \graph [tree layout] { + a -> { b -> {c, d}, e -> {f, g -> h} }; + + left [draw] // { b, c, d }; + right [draw] // { e, f, g, h}; + + left <-> right; + }; +\end{codeexample} + +Every time a subgraph node is created, the following style is execute: + +\begin{key}{/tikz/every subgraph node} + Set a subgraph node style. +\end{key} + +\begin{key}{/tikz/subgraph nodes=\meta{style}} + Sets the |every subgraph node| style to \meta{style}. + % +\begin{codeexample}[preamble={\usetikzlibrary{graphs,graphdrawing} +\usegdlibrary{trees}}] +\tikz [subgraph text bottom=text centered, + subgraph nodes=red] + \graph [tree layout] { + a -> { b -> {c, d}, e -> {f, g -> h} }; + + left [draw] // { b, c, d }; + right [draw] // { e, f, g, h}; + + left <-> right; + }; +\end{codeexample} + % +\end{key} + +\begin{key}{/tikz/subgraph text none} + When this option is used, the text of a subgraph node is not shown. Adding + a slash after the node name achieves roughly the same effect, but this + option is useful in situations when subgraph nodes generally should not + have any text inside them. + % +\begin{codeexample}[preamble={\usetikzlibrary{graphs,graphdrawing} +\usegdlibrary{trees}}] +\tikz [subgraph text none] + \graph [tree layout] { + a -> { b -> {c, d}, e -> {f, g -> h} }; + + left [draw] // { b, c, d }; + right [draw] // { e, f, g, h}; + + left <-> right; + }; +\end{codeexample} + % +\end{key} + +\begin{key}{/tikz/subgraph text top=\meta{text alignment options} (default text ragged right)} + Specifies that the text of a subgraph node should be placed at the top of + the subgraph node: Still inside the node, but above all nodes inside the + subgraph node. + % +\begin{codeexample}[preamble={\usetikzlibrary{graphs,graphdrawing} +\usegdlibrary{trees}}] +\tikz [subgraph text top=text ragged left] + \graph [tree layout] { + a -> { b -> {c, d}, e -> {f, g -> h} }; + + left [draw] // { b, c, d }; + right [draw] // { e, f, g, h}; + + left <-> right; + }; +\end{codeexample} + % + You can pass any of the \meta{text alignment options} understood by + \tikzname, such as |text centered|: + % +\begin{codeexample}[ + width=5cm, + preamble={\usetikzlibrary{graphs,graphdrawing} +\usegdlibrary{trees}}, +] +\tikz [subgraph text top=text centered] + \graph [tree layout] { + a -> { b -> {c, d}, e -> {f, g -> h} }; + + left [draw, circle] // { b, c, d }; + }; +\end{codeexample} + % + To place a label \emph{outside} the subgraph node, use a label, typically + defined using the |quotes| library: + % +\begin{codeexample}[preamble={\usetikzlibrary{graphs,graphdrawing,quotes} +\usegdlibrary{trees}}] +\tikz \graph [tree layout] { + a -> { b -> {c, d}, e -> {f, g -> h} }; + + / ["left", draw] // { b, c, d } <-> + / ["right", draw] // { e, f, g, h}; + }; +\end{codeexample} + % +\end{key} + +\begin{key}{/tikz/subgraph text bottom=\meta{text alignment options} (default ragged right)} + Works like |subgraph text top|, only the text placed at the bottom. +\end{key} + +Note that there are no keys |subgraph text left| or |... right|, for somewhat +technical reasons. + +\begin{key}{/tikz/subgraph text sep=\meta{dimension} (initially .1em)} + Some space added between the inner nodes of a subgraph node and the text + labels. +\end{key} + + +\subsubsection{Overlapping Sublayouts} +\label{section-gd-layout-resolve} + +Nodes and edges can be part of several layouts. This will inevitably lead to +conflicts because algorithm will disagree on where a node should be placed on +the canvas. For this reason, there are some rules governing how such conflicts +are resolved: Given a layout, starting with the main layout, the graph drawing +system does the following: +% +\begin{enumerate} + \item We start by first processing the (direct) sublayouts of the current + layout (recursively). Sublayouts may overlap (they may share one or + more nodes), but we run the specified layout algorithm for each + sublayout independently on a ``fresh copy'' of all the nodes making up + the sublayout. In particular, different, conflicting positions may be + computed for nodes when they are present in several sublayouts. + \item Once all nodes in the sublayouts have been laid out in this way, we + \emph{join} overlapping elements. The idea is that if two layouts share + exactly one vertex, we can shift them around so that his vertex is at + the same position in both layouts. In more detail, the following + happens: + + We build a (conceptual) graph whose nodes are the sublayouts and in + which there is an edge between two nodes if the sublayouts represented + by these elements have a node in common. Inside the resulting graph, we + treat each connected component separately. Each component has the + property that the sublayouts represented by the nodes in the component + overlap by at least one node. We now \emph{join} them as follows: We + start with the first sublayout in the component (``first'' with respect + to the order in which they appear in the input graph) and ``mark'' this + sublayout. We loop the following instructions as long as possible: + Search for the first sublayout (again, with respect to the order in + which they appear in the input) that is connect by an edge to a marked + sublayout. The sublayout will now have at least one node in common with + the marked sublayouts (possibly, even more). We consider the first such + node (again, first respect to the input ordering) and shift the whole + sublayout is such a way that this particular node is at the position is + has in the marked sublayouts. Note that after the shift, other nodes + that are also present in the marked sublayouts may lie at a different + position in the current sublayout. In this case, the position in the + marked sublayouts ``wins''. We then mark the sublayout. + \item When the above algorithm has run, we will have computed positions for + all nodes in all sublayouts of each of the components. For each + component, we contract all nodes of the component to a single node. + This new node will be ``large'' in the sense that its convex hull is + the convex hull of all the nodes in the component. All nodes that used + to be part of the component are removed and the new large node is added + (with arcs adjusted appropriately). + \item We now run the layout's algorithm on the resulting nodes (the + remaining original nodes and the contracted nodes). + \item In a last step, once the graph has been laid out, we expand the nodes + that were previously contracted. For this, the nodes that were deleted + earlier get reinserted, but shifted by whatever amount the contraction + node got shifted. +\end{enumerate} + + +\subsection{Miscellaneous Options} + +\includeluadocumentationof{pgf.gd.control.library} |