% Copyright 2006 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[Hierarchical Structures: Package, Environments, Scopes, and Styles] {Hierarchical Structures:\\ Package, Environments, Scopes, and Styles} The present section explains how your files should be structured when you use \tikzname. On the top level, you need to include the |tikz| package. In the main text, each graphic needs to be put in a |{tikzpicture}| environment. Inside these environments, you can use |{scope}| environments to create internal groups. Inside the scopes you use |\path| commands to actually draw something. On all levels (except for the package level), graphic options can be given that apply to everything within the environment. \subsection{Loading the Package and the Libraries} \begin{package}{tikz} This package does not have any options. This will automatically load the \pgfname\ and the |pgffor| package. \pgfname\ needs to know what \TeX\ driver you are intending to use. In most cases \pgfname\ is clever enough to determine the correct driver for you; this is true in particular if you use \LaTeX. Currently, the only situation where \pgfname\ cannot know the driver ``by itself'' is when you use plain \TeX\ or Con\TeX t together with |dvipdfm|. In this case, you have to write |\def\pgfsysdriver{pgfsys-dvipdfm.def}| \emph{before} you input |tikz.tex|. \end{package} \begin{command}{\usetikzlibrary\marg{list of libraries}} Once \tikzname\ has been loaded, you can use this command to load further libraries. The list of libraries should contain the names of libraries separated by commas. Instead of curly braces, you can also use square brackets, which is something Con\TeX t users will like. If you try to load a library a second time, nothing will happen. \example |\usetikzlibrary{arrows}| The above command will load a whole bunch of extra arrow tip definitions. What this command does is to load the file |tikzlibrary|\meta{library}|.code.tex| for each \meta{library} in the \meta{list of libraries}. Thus, to write your own library file, all you need to do is to place a file of the appropriate name somewhere where \TeX\ can find it. \LaTeX, plain \TeX, and Con\TeX t users can then use your library. \end{command} \subsection{Creating a Picture} \subsubsection{Creating a Picture Using an Environment} The ``outermost'' scope of \tikzname\ is the |{tikzpicture}| environment. You may give drawing commands only inside this environment, giving them outside (as is possible in many other packages) will result in chaos. In \tikzname, the way graphics are rendered is strongly influenced by graphic options. For example, there is an option for setting the color used for drawing, another for setting the color used for filling, and also more obscure ones like the option for setting the prefix used in the filenames of temporary files written while plotting functions using an external program. The graphic options are specified in \emph{key lists}, see Section~\ref{section-graphic-options} below for details. All graphic options are local to the |{tikzpicture}| to which they apply. \begin{environment}{{tikzpicture}\opt{\oarg{options}}} All \tikzname\ commands should be given inside this environment, except for the |\tikzset| command. Unlike other packages, it is not possible to use, say, |\pgfpathmoveto| outside this environment and doing so will result in chaos. For \tikzname, commands like |\path| are only defined inside this environment, so there is little chance that you will do something wrong here. When this environment is encountered, the \meta{options} are parsed, see Section~\ref{section-graphic-options}. All options given here will apply to the whole picture. Next, the contents of the environment is processed and the graphic commands therein are put into a box. Non-graphic text is suppressed as well as possible, but non-\pgfname\ commands inside a |{tikzpicture}| environment should not produce any ``output'' since this may totally scramble the positioning system of the backend drivers. The suppressing of normal text, by the way, is done by temporarily switching the font to |\nullfont|. You can, however, ``escape back'' to normal \TeX\ typesetting. This happens, for example, when you specify a node. At the end of the environment, \pgfname\ tries to make a good guess at the size of a bounding box of the graphic and then resizes the picture box such that the box has this size. To ``make its guess,'' everytime \pgfname\ encounters a coordinate, it updates the bounding box's size such that it encompasses all these coordinates. This will usually give a good approximation of the bounding box, but will not always be accurate. First, the line thickness of diagonal lines is not taken into account correctly. Second, controls points of a curve often lie far ``outside'' the curve and make the bounding box too large. In this case, you should use the |[use as bounding box]| option. The following key influences the baseline of the resulting picture: \begin{key}{/tikz/baseline=\meta{dimension or coordinate or \texttt{default}} (default 0pt)} Normally, the lower end of the picture is put on the baseline of the surrounding text. For example, when you give the code |\tikz\draw(0,0)circle(.5ex);|, \pgfname\ will find out that the lower end of the picture is at $-.5\mathrm{ex}$ and that the upper end is at $.5\mathrm{ex}$. Then, the lower end will be put on the baseline, resulting in the following: \tikz\draw(0,0)circle(.5ex);. Using this option, you can specify that the picture should be raised or lowered such that the height \meta{dimension} is on the baseline. For example, |\tikz[baseline=0pt]\draw(0,0)circle(.5ex);| yields \tikz[baseline=0pt]\draw(0,0)circle(.5ex); since, now, the baseline is on the height of the $x$-axis. This options is often useful for ``inlined'' graphics as in \begin{codeexample}[] $A \mathbin{\tikz[baseline] \draw[->>] (0pt,.5ex) -- (3ex,.5ex);} B$ \end{codeexample} Instead of a \meta{dimension} you can also provide a coordinate in parentheses. Then the effect is to put the baseline on the $y$-coordinate that the give \meta{coordinate} has \emph{at the end of the picture}. This means that, at the end of the picture, the \meta{coordinate} is evaluated and then the baseline is set to the $y$-coordinate of the resulting point. This makes it easy to reference the $y$-coordinate of, say, the base line of nodes. \begin{codeexample}[] Hello \tikz[baseline=(X.base)] \node [cross out,draw] (X) {world.}; \end{codeexample} \begin{codeexample}[] Top align: \tikz[baseline=(current bounding box.north)] \draw (0,0) rectangle (1cm,1ex); \end{codeexample} Use |baseline=default| to reset the |baseline| option to its initial configuration. \end{key} \begin{key}{/tikz/execute at begin picture=\meta{code}} This option causes \meta{code} to be executed at the beginning of the picture. This option must be given in the argument of the |{tikzpicture}| environment itself since this option will not have an effect otherwise. After all, the picture has already ``started'' later on. The effect of multiply setting this option accumulates. This option is mainly used in styles like the |every picture| style to execute certain code at the start of a picture. \end{key} \begin{key}{/tikz/execute at end picture=\meta{code}} This option installs \meta{code} that will be executed at the end of the picture. Using this option multiple times will cause the code to accumulate. This option must also be given in the optional argument of the |{tikzpicture}| environment. \begin{codeexample}[] \begin{tikzpicture}[execute at end picture=% { \begin{pgfonlayer}{background} \path[fill=yellow,rounded corners] (current bounding box.south west) rectangle (current bounding box.north east); \end{pgfonlayer} }] \node at (0,0) {X}; \node at (2,1) {Y}; \end{tikzpicture} \end{codeexample} \end{key} All options ``end'' at the end of the picture. To set an option ``globally'' change the following style: \begin{stylekey}{/tikz/every picture (initially \normalfont empty)} This style is installed at the beginning of each picture. \begin{codeexample}[code only] \tikzset{every picture/.style=semithick} \end{codeexample} \end{stylekey} Note that you should not use |\tikzset| to set options directly. For instance, if you want to use a line width of |1pt| by default, do not try to say |\tikzset{line width=1pt}| at the beginning of your document. This will not work since the line width is changed in many places. Instead, say \begin{codeexample}[code only] \tikzset{every picture/.style={line width=1pt}} \end{codeexample} This will have the desired effect. \end{environment} In other \TeX\ format, you should use instead the following commands: \begin{plainenvironment}{{tikzpicture}\opt{\oarg{options}}} This is the plain \TeX\ version of the environment. \end{plainenvironment} \begin{contextenvironment}{{tikzpicture}\opt{\oarg{options}}} This is the Con\TeX t version of the environment. \end{contextenvironment} \subsubsection{Creating a Picture Using a Command} The following command is an alternative to |{tikzpicture}| that is particular useful for graphics consisting of a single or few commands. \begin{command}{\tikz\opt{\oarg{options}}\marg{path commands}} This command places the \meta{path commands} inside a |{tikzpicture}| environment. The \meta{path commands} may contain paragraphs and fragile material (like verbatim text). If there is only one path command, it need not be surrounded by curly braces, if there are several, you need to add them (this is similar to the |\foreach| statement and also to the rules in programming languages like Java or C concerning the placement of curly braces). \example |\tikz{\draw (0,0) rectangle (2ex,1ex);}| yields \tikz{\draw (0,0) rectangle (2ex,1ex);} \example |\tikz \draw (0,0) rectangle (2ex,1ex);| yields \tikz \draw (0,0) rectangle (2ex,1ex); \end{command} \subsubsection{Adding a Background} By default, pictures do not have any background, that is, they are ``transparent'' on all parts on which you do not draw anything. You may instead wish to have a colored background behind your picture or a black frame around it or lines above and below it or some other kind of decoration. Since backgrounds are often not needed at all, the definition of styles for adding backgrounds has been put in the library package |backgrounds|. This package is documented in Section~\ref{section-tikz-backgrounds}. \subsection{Using Scopes to Structure a Picture} Inside a |{tikzpicture}| environment you can create scopes using the |{scope}| environment. This environment is available only inside the |{tikzpicture}| environment, so once more, there is little chance of doing anything wrong. \subsubsection{The Scope Environment} \begin{environment}{{scope}\opt{\oarg{options}}} All \meta{options} are local to the \meta{environment contents}. Furthermore, the clipping path is also local to the environment, that is, any clipping done inside the environment ``ends'' at its end. \begin{codeexample}[] \begin{tikzpicture}[ultra thick] \begin{scope}[red] \draw (0mm,10mm) -- (10mm,10mm); \draw (0mm,8mm) -- (10mm,8mm); \end{scope} \draw (0mm,6mm) -- (10mm,6mm); \begin{scope}[green] \draw (0mm,4mm) -- (10mm,4mm); \draw (0mm,2mm) -- (10mm,2mm); \draw[blue] (0mm,0mm) -- (10mm,0mm); \end{scope} \end{tikzpicture} \end{codeexample} The following style influences scopes: \begin{stylekey}{/tikz/every scope (initially \normalfont empty)} This style is installed at the beginning of every scope. \end{stylekey} The following options are useful for scopes: \begin{key}{/tikz/execute at begin scope=\meta{code}} This option install some code that will be executed at the beginning of the scope. This option must be given in the argument of the |{scope}| environment. The effect applies only to the current scope, not to subscopes. \end{key} \begin{key}{/tikz/execute at end scope=\meta{code}} This option installs some code that will be executed at the end of the current scope. Using this option multiple times will cause the code to accumulate. This option must also be given in the optional argument of the |{scope}| environment. Again, the effect applies only to the current scope, not to subscopes. \end{key} \end{environment} \begin{plainenvironment}{{scope}\opt{\oarg{options}}} Plain \TeX\ version of the environment. \end{plainenvironment} \begin{contextenvironment}{{scope}\opt{\oarg{options}}} Con\TeX t version of the environment. \end{contextenvironment} \subsubsection{Shorthand for Scope Environments} There is a small library that makes using scopes a bit easier: \begin{tikzlibrary}{scopes} This library defines a shorthand for starting and ending |{scope}| environments. \end{tikzlibrary} When this library is loaded, the following happens: At certain places inside a \tikzname\ picture, it is allowed to start a scope just using a single brace, provided the single brace is followed by options in square brackets: \begin{codeexample}[] \begin{tikzpicture} { [ultra thick] { [red] \draw (0mm,10mm) -- (10mm,10mm); \draw (0mm,8mm) -- (10mm,8mm); } \draw (0mm,6mm) -- (10mm,6mm); } { [green] \draw (0mm,4mm) -- (10mm,4mm); \draw (0mm,2mm) -- (10mm,2mm); \draw[blue] (0mm,0mm) -- (10mm,0mm); } \end{tikzpicture} \end{codeexample} In the above example, |{ [thick]| actually causes a |\begin{scope}[thick]| to be inserted, and the corresponding closing |}| causes an |\end{scope}| to be inserted. The ``certain places'' where an opening brace has this special meaning are the following: First, right after the semicolon that ends a path. Second, right after the end of a scope. Third, right at the beginning of a scope, which includes the beginning of a picture. Also note that some square bracket must follow, otherwise the brace is treated as a normal \TeX\ scope. \subsubsection{Using Scopes Inside Paths} The |\path| command, which is described in much more detail in later sections, also takes graphic options. These options are local to the path. Furthermore, it is possible to create local scopes within a path simply by using curly braces as in \begin{codeexample}[] \tikz \draw (0,0) -- (1,1) {[rounded corners] -- (2,0) -- (3,1)} -- (3,0) -- (2,1); \end{codeexample} Note that many options apply only to the path as a whole and cannot be scoped in this way. For example, it is not possible to scope the |color| of the path. See the explanations in the section on paths for more details. Finally, certain elements that you specify in the argument to the |\path| command also take local options. For example, a node specification takes options. In this case, the options apply only to the node, not to the surrounding path. \subsection{Using Graphic Options} \label{section-graphic-options} \subsubsection{How Graphic Options Are Processed} Many commands and environments of \tikzname\ accept \emph{options}. These options are so-called \emph{key lists}. To process the options, the following command is used, which you can also call yourself. Note that it is usually better not to call this command directly, since this will ensure that the effect of options are local to a well-defined scope. \begin{command}{\tikzset\marg{options}} This command will process the \meta{options} using the |\pgfkeys| command, documented in detail in Section~\ref{section-keys}, with the default path set to |/tikz|. Under normal circumstances, the \meta{options} will be lists of comma-separated pairs of the form \meta{key}|=|\meta{value}, but more fancy things can happen when you use the power of the |pgfkeys| mechanism, see Section~\ref{section-keys} once more. When a pair \meta{key}|=|\meta{value} is processed, the following happens: \begin{enumerate} \item If the \meta{key} is a full key (starts with a slash) it is handled directly as described in Section~\ref{section-keys}. \item Otherwise (which is usually the case), it is checked whether |/tikz/|\meta{key} is a key and, if so, it is executed. \item Otherwise, it is checked whether |/pgf/|\meta{key} is a key and, if so, it is executed. \item Otherwise, it is checked whether \meta{key} is a color and, if so, |color=|\meta{key} is executed. \item Otherwise, it is checked whether \meta{key} contains a dash and, if so, |arrows=|\meta{key} is executed. \item Otherwise, it is checked whether \meta{key} is the name of a shape and, if so, |shape=|\meta{key} is executed. \item Otherwise, an error message is printed. \end{enumerate} Note that by the above description, all keys starting with |/tikz| and also all keys starting with |/pgf| can be used as \meta{key}s in an \meta{options} list. \end{command} \subsubsection{Using Styles to Manage How Pictures Look} There is a way of organizing sets of graphic options ``orthogonally'' to the normal scoping mechanism. For example, you might wish all your ``help lines'' to be drawn in a certain way like, say, gray and thin (do \emph{not} dash them, that distracts). For this, you can use \emph{styles}. A style is a key that, when used, causes a set of graphic options to be processed. Once a style has been defined, it can be used like any other key. For example, the predefined |help lines| style, which you should use for lines in the background like grid lines or construction lines. \begin{codeexample}[] \begin{tikzpicture} \draw (0,0) grid +(2,2); \draw[help lines] (2,0) grid +(2,2); \end{tikzpicture} \end{codeexample} Defining styles is also done using options. Suppose we wish to define a style called |my style| and when this style is used, we want the draw color to be set to |red| and the fill color be set to |red!20|. To achieve this, we use the following option: \begin{codeexample}[code only] my style/.style={draw=red,fill=red!20} \end{codeexample} The meaning of the curious |/.style| is the following: ``The key |my style| should not be used here but, rather, be defined. So, setup things such that using the key |my style| will, in the following, have the same effect as if we had written |draw=red,fill=red!20| instead.'' Returning to the help lines example, suppose we prefer blue help lines. This could be achieved as follows: \begin{codeexample}[] \begin{tikzpicture}[help lines/.style={blue!50,very thin}] \draw (0,0) grid +(2,2); \draw[help lines] (2,0) grid +(2,2); \end{tikzpicture} \end{codeexample} Naturally, one of the main ideas behind styles is that they can be used in different pictures. In this case, we have to use the |\tikzset| command somewhere at the beginning. \begin{codeexample}[] \tikzset{help lines/.style={blue!50,very thin}} % ... \begin{tikzpicture} \draw (0,0) grid +(2,2); \draw[help lines] (2,0) grid +(2,2); \end{tikzpicture} \end{codeexample} Since styles are just special cases of |pgfkeys|'s general style facility, you can actually do quite a bit more. Let us start with adding options to an already existing style. This is done using |/.append style| instead of |/.style|: \begin{codeexample}[] \begin{tikzpicture}[help lines/.append style=blue!50] \draw (0,0) grid +(2,2); \draw[help lines] (2,0) grid +(2,2); \end{tikzpicture} \end{codeexample} In the above example, the option |blue!50| is appended to the style |help lines|, which now has the same effect as |black!50,very thin,blue!50|. Note that two colors are set, so the last one will ``win.'' There also exists a handler called |/.prefix style| that adds something at the beginning of the style. Just as normal keys, styles can be parameterized. This means that you write \meta{style}|=|\meta{value} when you use the style instead of just \meta{style}. In this case, all occurrences of |#1| in \meta{style} are replaced by \meta{value}. Here is an example that shows how this can be used. \begin{codeexample}[] \begin{tikzpicture}[outline/.style={draw=#1,thick,fill=#1!50}] \node [outline=red] at (0,1) {red}; \node [outline=blue] at (0,0) {blue}; \end{tikzpicture} \end{codeexample} For parameterized styles you can also set a \emph{default} value using the |/.default| handler: \begin{codeexample}[] \begin{tikzpicture}[outline/.style={draw=#1,thick,fill=#1!50}, outline/.default=black] \node [outline] at (0,1) {default}; \node [outline=blue] at (0,0) {blue}; \end{tikzpicture} \end{codeexample} For more details on using and setting styles, see also Section~\ref{section-keys}.