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authorNorbert Preining <norbert@preining.info>2023-01-16 03:03:27 +0000
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-% 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{Key Management}
-\label{section-keys}
-
-This section describes the package |pgfkeys|. It is loaded automatically by
-both \pgfname\ and \tikzname.
-
-\begin{package}{pgfkeys}
- This package can be used independently of \pgfname. Note that no
- other package of \pgfname\ needs to be loaded (so neither the
- emulation layer nor the system layer is needed). The Con\TeX t
- abbreviation is |pgfkey| \todosp{pgfkey --> pgfkeys?} if |pgfmod| is not loaded.
-\end{package}
-
-
-\subsection{Introduction}
-
-\subsubsection{Comparison to Other Packages}
-
-The |pgfkeys| package defines a key--value management system that is in some
-sense similar to the more light-weight |keyval| system and the improved
-|xkeyval| system. However, |pgfkeys| uses a slightly different philosophy than
-these systems and it will coexist peacefully with both of them.
-
-The main differences between |pgfkeys| and |xkeyval| are the following:
-%
-\begin{itemize}
- \item |pgfkeys| organizes keys in a tree, while |keyval| and |xkeyval|
- use families. In |pgfkeys| the families correspond to the root
- entries of the key tree.
- \item |pgfkeys| has no save-stack impact (you will have to read the \TeX
- Book very carefully to appreciate this).
- \item |pgfkeys| is slightly slower than |keyval|, but not much.
- \item |pgfkeys| supports styles. This means that keys can just stand for
- other keys (which can stand for other keys in turn or which can also
- just execute some code). \tikzname\ uses this mechanism heavily.
- \item |pgfkeys| supports multi-argument key code. This can, however, be
- emulated in |keyval|.
- \item |pgfkeys| supports handlers. These are call-backs that are called
- when a key is not known. They are very flexible, in fact even
- defining keys in different ways is handled by, well, handlers.
-\end{itemize}
-
-
-\subsubsection{Quick Guide to Using the Key Mechanism}
-
-The following quick guide to \pgfname's key mechanism only treats the most
-commonly used features. For an in-depth discussion of what is going on, please
-consult the remainder of this section.
-
-Keys are organized in a large tree that is reminiscent of the Unix file tree. A
-typical key might be, say, |/tikz/coordinate system/x| or just |/x|. Again as
-in Unix, when you specify keys you can provide the complete path of the key,
-but you usually just provide the name of the key (corresponding to the file
-name without any path) and the path is added automatically.
-
-Typically (but not necessarily) some code is associated with a key. To execute
-this code, you use the |\pgfkeys| command. This command takes a list of
-so-called key--value pairs. Each pair is of the form \meta{key}|=|\meta{value}.
-For each pair the |\pgfkeys| command will execute the code stored for the
-\meta{key} with its parameter set to \meta{value}.
-
-Here is a typical example of how the |\pgfkeys| command is used:
-%
-\begin{codeexample}[code only]
-\pgfkeys{/my key=hallo,/your keys/main key=something\strange,
- key name without path=something else}
-\end{codeexample}
-
-Now, to set the code that is stored in a key you do not need to learn a new
-command. Rather, the |\pgfkeys| command can also be used to set the code of a
-key. This is done using so-called \emph{handlers}. They look like keys whose
-names look like ``hidden files in Unix'' since they start with a dot. The
-handler for setting the code of a key is appropriately called |/.code| and it
-is used as follows:
-%
-\begin{codeexample}[]
-\pgfkeys{/my key/.code=The value is '#1'.}
-\pgfkeys{/my key=hi!}
-\end{codeexample}
-%
-As you can see, in the first line we defined the code for the key |/my key|. In
-the second line we executed this code with the parameter set to |hi!|.
-
-There are numerous handlers for defining a key. For instance, we can also
-define a key whose value actually consists of more than one parameter.
-%
-\begin{codeexample}[]
-\pgfkeys{/my key/.code 2 args=The values are '#1' and '#2'.}
-\pgfkeys{/my key={a1}{a2}}
-\end{codeexample}
-
-We often want to have keys where the code is called with some default value if
-the user does not provide a value. Not surprisingly, this is also done using a
-handler, this time called |/.default|.
-%
-\begin{codeexample}[]
-\pgfkeys{/my key/.code=(#1)}
-\pgfkeys{/my key/.default=hello}
-\pgfkeys{/my key=hallo,/my key}
-\end{codeexample}
-
-The other way round, it is also possible to specify that a value \emph{must} be
-specified, using a handler called |/.value required|. Finally, you can also
-require that no value \emph{may} be specified using |/.value forbidden|.
-
-All keys for a package like, say, \tikzname\ start with the path |/tikz|. We
-obviously do not like to write this path down every time we use a key (so we do
-not have to write things like |\draw[/tikz/line width=1cm]|). What we need is
-to somehow ``change the default path to a specific location''. This is done
-using the handler |/.cd| (for ``change directory''). Once this handler has been
-used on a key, all subsequent keys {\itshape in the current call of |\pgfkeys|
-only} are automatically prefixed with this path, if necessary.
-
-Here is an example:
-%
-\begin{codeexample}[code only]
-\pgfkeys{/tikz/.cd,line width=1cm,line cap=round}
-\end{codeexample}
-%
-This makes it easy to define commands like |\tikzset|, which could be defined
-as follows (the actual definition is a bit faster, but the effect is the same):
-%
-\begin{codeexample}[code only]
-\def\tikzset#1{\pgfkeys{/tikz/.cd,#1}}
-\end{codeexample}
-
-When a key is handled, instead of executing some code, the key can also cause
-further keys to be executed. Such keys will be called \emph{styles}. A style
-is, in essence, just a key list that should be executed whenever the style is
-executed. Here is an example:
-%
-\begin{codeexample}[]
-\pgfkeys{/a/.code=(a:#1)}
-\pgfkeys{/b/.code=(b:#1)}
-\pgfkeys{/my style/.style={/a=foo,/b=bar,/a=#1}}
-\pgfkeys{/my style=wow}
-\end{codeexample}
-%
-As the above example shows, styles can also be parameterized, just like the
-normal code keys.
-
-As a typical use of styles, suppose we wish to set up the key |/tikz| so that
-it will change the default path to |/tikz|. This can be achieved as follows:
-%
-\begin{codeexample}[code only]
-\pgfkeys{/tikz/.style=/tikz/.cd}
-\pgfkeys{tikz,line width=1cm,draw=red}
-\end{codeexample}
-
-Note that when |\pgfkeys| is executed, the default path is set to~|/|. This
-means that the first |tikz| will be completed to |/tikz|. Then |/tikz| is a
-style and, thus, replaced by |/tikz/.cd|, which changes the default path to
-|/tikz|. Thus, the |line width| is correctly prefixed with |/tikz|.
-
-
-\subsection{The Key Tree}
-
-The |pgfkeys| package organizes keys in a so-called \emph{key tree}. This tree
-will be familiar to anyone who has used a Unix operating system: A key is
-addressed by a path, which consists of different parts separated by slashes. A
-typical key might be |/tikz/line width| or just |/tikz| or something more
-complicated like |/tikz/cs/x/.store in|.
-
-Let us fix some further terminology: Given a key like |/a/b/c|, we call the
-part leading up the last slash (|/a/b|) the \emph{path} of the key. We call
-everything after the last slash (|c|) the \emph{name} of the key (in a file
-system this would be the file name).
-
-We do not always wish to specify keys completely. Instead, we usually specify
-only part of a key (typically only the name) and the \emph{default path} is
-then added to the key at the front. So, when the default path is |/tikz| and
-you refer to the (partial) key |line width|, the actual key that is used is
-|/tikz/line width|. There is a simple rule for deciding whether a key is a
-partial key or a full key: If it starts with a slash, then it is a full key and
-it is not modified; if it does not start with a slash, then the default path is
-automatically prefixed.
-
-\emph{Remark:} The above rule is actually a definition, hence the corresponding
-sufficiency conditions hold. That is, if it is a full key, then it starts with
-a slash; if it is a partial key, then it does not start with a slash. Moreover,
-a path always starts with a slash.
-
-Note that the default path is not the same as a search path. In particular, the
-default path is just a single path. When a partial key is given, only this
-single default path is prefixed; |pgfkeys| does not try to look up the key in
-different parts of a search path. It is, however, possible to emulate search
-paths, but a much more complicated mechanism must be used.
-
-When you set keys (to be explained in a moment), you can freely mix partial and
-full keys and you can change the default path. This makes it possible to
-temporarily use keys from another part of the key tree (this turns out to be a
-very useful feature).
-
-Each key (may) store some \emph{tokens} and there exist commands, described
-below, for setting, getting, and changing the tokens stored in a key. However,
-you will only very seldom use these commands directly. Rather, the standard way
-of using keys is the |\pgfkeys| command or some command that uses it internally
-like, say, |\tikzset|. So, you may wish to skip the following commands and
-continue with the next subsection.
-
-\begin{command}{\pgfkeyssetvalue\marg{full key}\marg{token text}}
- Stores the \meta{token text} in the \meta{full key}. The \meta{full key}
- may not be a partial key, so no default-path-adding is done. The
- \meta{token text} can be arbitrary tokens and may even contain things like
- |#| or unbalanced \TeX-ifs.
- %
-\begin{codeexample}[]
-\pgfkeyssetvalue{/my family/my key}{Hello, world!}
-\pgfkeysvalueof{/my family/my key}
-\end{codeexample}
-
- The setting of a key is always local to the current \TeX\ group.
-\end{command}
-
-\begin{command}{\pgfkeyssetevalue\marg{full key}\marg{token text}}
- The |\edef| version of |\pgfkeyssetvalue|.
-\end{command}
-
-\begin{command}{\pgfkeyslet\marg{full key}\marg{macro}}
- Performs a |\let| statement so the \meta{full key} points to the contents
- of \meta{macro}.
- %
-\begin{codeexample}[]
-\def\helloworld{Hello, world!}
-\pgfkeyslet{/my family/my key}{\helloworld}
-\pgfkeysvalueof{/my family/my key}
-\end{codeexample}
- %
- You should never let a key be equal to |\relax|. Such a key may or may not
- be indistinguishable from an undefined key.
-\end{command}
-
-\begin{command}{\pgfkeysgetvalue\marg{full key}\marg{macro}}
- Retrieves the tokens stored in the \meta{full key} and lets \meta{macro} be
- equal to these tokens. If the key has not been set, the \meta{macro} will
- be equal to |\relax|.
- %
-\begin{codeexample}[]
-\pgfkeyssetvalue{/my family/my key}{Hello, world!}
-\pgfkeysgetvalue{/my family/my key}{\helloworld}
-\helloworld
-\end{codeexample}
- %
-\end{command}
-
-\begin{command}{\pgfkeysvalueof\marg{full key}}
- Inserts the value stored in \meta{full key} at the current position into
- the text.
- %
-\begin{codeexample}[]
-\pgfkeyssetvalue{/my family/my key}{Hello, world!}
-\pgfkeysvalueof{/my family/my key}
-\end{codeexample}
- %
-\end{command}
-
-\begin{command}{\pgfkeysifdefined\marg{full key}\marg{if}\marg{else}}
- Checks whether this key was previously set using either |\pgfkeyssetvalue|
- or |\pgfkeyslet|. If so, the code in \meta{if} is executed, otherwise the
- code in \meta{else}.
-
- This command will use e\TeX's |\ifcsname| command, if available, for
- efficiency. This means, however, that it may behave differently for \TeX\
- and for e\TeX\ when you set keys to |\relax|. For this reason you should
- not do so.
- %
-\begin{codeexample}[]
-\pgfkeyssetvalue{/my family/my key}{Hello, world!}
-\pgfkeysifdefined{/my family/my key}{yes}{no}
-\end{codeexample}
- %
-\end{command}
-
-
-\subsection{Setting Keys}
-
-Settings keys is done using a powerful command called |\pgfkeys|. This command
-takes a list of so-called \emph{key--value pairs}. These are pairs of the form
-\meta{key}|=|\meta{value}. The principal idea is the following: For each pair
-in the list, some \emph{action} is taken. This action can be one of the
-following:
-%
-\begin{enumerate}
- \item A command is executed whose argument(s) are \meta{value}. This
- command is stored in a special subkey of \meta{key}.
- \item The \meta{value} is stored in the \meta{key} itself.
- \item If the key's name (the part after the last slash) is a known
- \emph{handler}, then this handler will take care of the key.
- \item If the key is totally unknown, one of several possible \emph{unknown
- key handlers} is called.
-\end{enumerate}
-
-Additionally, if the \meta{value} is missing, a default value may or may not be
-substituted. Before we plunge into all the details, let us have a quick look at
-the command itself.
-
-\begin{command}{\pgfkeys\marg{key list}}
- The \meta{key list} should be a list of key--value pairs, separated by
- commas. A key--value pair can have the following two forms:
- \meta{key}|=|\meta{value} or just \meta{key}. Any spaces around the
- \meta{key} or around the \meta{value} are removed. It is permissible to
- surround both the \meta{key} or the \meta{value} in curly braces, which are
- also removed. Especially putting the \meta{value} in curly braces needs to
- be done quite often, namely whenever the \meta{value} contains an
- equal-sign or a comma.
-
- The key--value pairs in the list are handled in the order they appear. How
- this handling is done, exactly, is described in the rest of this section.
-
- If a \meta{key} is a partial key, the current value of the default path is
- prefixed to the \meta{key} and this ``upgraded'' key is then used. The
- default path is just the root path |/| when the first key is handled, but
- it may change later on. At the end of the command, the default path is
- reset to the value it had before this command was executed.
-
- Calls of this command may be nested. Thus, it is permissible to call
- |\pgfkeys| inside the code that is executed for a key. Since the default
- path is restored after a call of |\pgfkeys|, the default path will not
- change when you call |\pgfkeys| while executing code for a key (which is
- exactly what you want).
-\end{command}
-
-\begin{command}{\pgfqkeys\marg{default path}\marg{key list}}
- This command has the same effect as |\pgfkeys{|\meta{default
- path}|/.cd,|\meta{key list}|}|, it is only marginally quicker. This command
- should not be used in user code, but rather in commands like |\tikzset| or
- |\pgfset| that get called very often.
-\end{command}
-
-\begin{command}{\pgfkeysalso\marg{key list}}
- This command has exactly the same effect as |\pgfkeys|, only the default
- path is not modified before or after the keys are being set. This command
- is mainly intended to be called by the code that is being processed for a
- key.
-\end{command}
-
-\begin{command}{\pgfqkeysalso\marg{default path}\marg{key list}}
- This command has the same effect as |\pgfkeysalso{|\meta{default
- path}|/.cd,|\meta{key list}|}|, it is only quicker. Changing the default
- path inside a |\pgfkeyalso| is dangerous, so use with care. A rather safe
- place to call this command is at the beginning of a \TeX\ group.
-\end{command}
-
-
-\subsubsection{First Char Syntax Detection}
-\label{sec:pgf:first:char:syntax}
-
-Usually, keys are of the form \meta{key}|=|\meta{value} and how such keys are
-handled is discussed in the rest of this section. However, it is also possible
-to setup a different syntax for certain parts of the input to |\pgfkeys|. Since
-this is a rather advanced option, most readers may wish to skip the following
-discussion upon first reading; it is discussed here because this special syntax
-detection is the very first thing that is done when a key is processed, before
-any of the following operations are performed.
-
-The |\pgfkeys| command and its variants decompose their input into a list of
-\meta{string}s that are separated by commas. By default, each such
-\meta{string} must either have the form \meta{key}|=|\meta{value} or of the
-form \meta{key} with the value-part missing. However, you might wish to
-interpret some of these strings differently. For instance, when a \meta{string}
-has the form |"|\meta{text}|"|, you might wish the \meta{string} to be
-interpreted as if one had written |label text={|\meta{text}|}|. Then, people
-could write
-%
-\begin{codeexample}[code only]
-\myset{red, "main valve", thick}
-\end{codeexample}
-%
-instead of the more cumbersome
-%
-\begin{codeexample}[code only]
-\myset{red, label text=main valve, thick}
-\end{codeexample}
-%
-An example where such a syntax reinterpretation is done is the |quotes|
-library, which allows you to write things like
-%
-\begin{codeexample}[preamble={\usetikzlibrary{graphs,quotes}}]
-\tikz \graph { a ->["1" red] b ->["0"] c };
-\end{codeexample}
-%
-\noindent instead of the somewhat longer
-%
-\begin{codeexample}[preamble={\usetikzlibrary{graphs}}]
-\tikz \graph { a ->[edge node={node[red,auto]{1}}] b ->[edge label=0] c };
-\end{codeexample}
-
-In order to detect whether a \meta{string} has a special syntax, you can
-request that the \emph{first character} of \meta{string} is analysed by the key
-parser. If this first character matches a character that has been flagged as a
-special character, the \meta{string} is not interpreted as a usual key--value
-pair. Instead, \meta{string} is passed as a parameter to a special macro that
-should take care of the \meta{string}. After this macro has finished, the
-parsing continues with the \meta{next string} in the list.
-
-In order to setup a special syntax handling for \meta{strings} that begin with
-a certain character, two things need to be done:
-%
-\begin{enumerate}
- \item First, the whole |first char syntax| detection must be ``switched on'',
- since, by default, it is turned off for efficiency reasons (the
- overhead is rather small, however). This is done by setting the
- following key:
- %
- \begin{key}{/handlers/first char syntax=\opt{\meta{true or false}} (default true, initially false)}
- \end{key}
- \item Second, in order to handle strings starting with a certain
- \meta{character} in a special way, you need to store a macro in the
- following key:
- %
- \begin{key}{/handlers/first char syntax/\meta{meaning of character}}
- The \meta{meaning of character} should be the text that \TeX's
- command |\meaning| returns for a macro that has been |\let| to the
- \meta{character}. For instance, when strings starting with |"|
- should be treated in a special way, the \meta{meaning of character}
- would be the string |the character "| since this is what \TeX\
- writes when you say
- %
-\begin{codeexample}[]
-\let\mycharacter="
-\meaning\mycharacter
-\end{codeexample}
- %
- Now, the key |/handlers/first char syntax/|\meta{meaning of
- character} should be setup (using |\pgfkeyssetvalue| or using the
- |.initial| handler) to store a \meta{macro name}.
-
- If this is the case and if \meta{string} starts with the
- \meta{character} (blanks at the beginning of \meta{string} are
- deleted prior to this test), then \meta{macro name} is called with
- \meta{string} as its argument.
- \end{key}
-\end{enumerate}
-
-Let us now have a look at an example. We install two handlers, one for strings
-starting with |"| and one for strings starting with |<|.
-%
-\begin{codeexample}[]
-\pgfkeys{
- /handlers/first char syntax=true,
- /handlers/first char syntax/the character "/.initial=\myquotemacro,
- /handlers/first char syntax/the character </.initial=\mypointedmacro,
-}
-
-\def\myquotemacro#1{Quoted: #1. }
-\def\mypointedmacro#1{Pointed: #1. }
-
-\ttfamily \pgfkeys{"foo", <bar>}
-\end{codeexample}
-
-Naturally, in the above examples, the two handling macros did not do something
-particularly exciting. In the next example, we setup a more elaborate macro
-that mimics a small part the behavior of the |quotes| library, only for single
-quotes:
-%
-\begin{codeexample}[]
-\pgfkeys{
- /handlers/first char syntax=true,
- /handlers/first char syntax/the character '/.initial=\mysinglequotemacro
-}
-
-\def\mysinglequotemacro#1{\pgfkeysalso{label={#1}}}
-
-\tikz \node [circle, 'foo', draw] {bar};
-\end{codeexample}
-
-Note that in the above example, the macro |\mysinglequotemacro| gets passed the
-complete string, including the single quotes. It is the job of the macro to get
-rid of them, if this is necessary.
-
-The first char syntax detection allows you to perform rather powerful
-transformations on the syntax of keys -- provided you can ``pin down'' the
-syntax on the first character. In the following example, you can write
-expressions in parentheses in front of a key--value pair and the pair will only
-be executed when the expression evaluates to true:
-%
-\begin{codeexample}[]
-\pgfkeys{
- /handlers/first char syntax=true,
- /handlers/first char syntax/the character (/.initial=\myparamacro
-}
-
-\def\myparamacro#1{\myparaparser#1\someendtext}
-\def\myparaparser(#1)#2\someendtext{
- \pgfmathparse{#1}
- \ifx\pgfmathresult\onetext
- \pgfkeysalso{#2}
- \fi
-}
-\def\onetext{1}
-
-\foreach \i in {1,...,4}
- \tikz \node [draw, thick, rectangle, (pi>\i) circle, (pi>\i*2) draw=red] {x};
-\end{codeexample}
-
-
-\subsubsection{Default Arguments}
-
-The arguments of the |\pgfkeys| command can either be of the form
-\meta{key}|=|\meta{value} or of the form \meta{key} with the value-part
-missing. In the second case, the |\pgfkeys| will try to provide a \emph{default
-value} for the \meta{value}. If such a default value is defined, it will be
-used as if you had written \meta{key}|=|\meta{default value}.
-
-In the following, the details of how default values are determined is
-described; however, you should normally use the handlers |/.default| and
-|/.value required| as described in Section~\ref{section-default-handlers} and
-you may wish to skip the following details.
-
-When |\pgfkeys| encounters a \meta{key} without an equal-sign, the following
-happens:
-%
-\begin{enumerate}
- \item The input is replaced by \meta{key}|=\pgfkeysnovalue|. In particular,
- the commands |\pgfkeys{my key}| and
- % FIXME: there is a bug in the pretty printer ... fix it and get rid of '||' here:
- |\pgfkeys{my key=||\pgfkeysnovalue}| have exactly the same effect and
- you can ``simulate'' a missing value by providing the value
- |\pgfkeysnovalue|, which is sometimes useful.
- \item If the \meta{value} is |\pgfkeysnovalue|, then it is checked whether
- the subkey \meta{key}|/.@def| exists. For instance, if you write
- |\pgfkeys{/my key}|, then it is checked whether the key |/my key/.@def|
- exists.
- \item If the key \meta{key}|/.@def| exists, then the tokens stored in this
- key are used as \meta{value}.
- \item If the key does not exist, then |\pgfkeysnovalue| is used as the
- \meta{value}.
- \item At the end, if the \meta{value} is now equal to
- |\pgfkeysvaluerequired|, then the code (or something fairly equivalent)
- |\pgfkeys{/errors/value required=|\meta{key}|{}}| is executed. Thus, by
- changing this key you can change the error message that is printed or
- you can handle the missing value in some other way.
-\end{enumerate}
-
-
-\subsubsection{Keys That Execute Commands}
-\label{section-key-code}
-
-After the transformation process described in the previous subsection, we
-arrive at a key of the form \meta{key}=\meta{value}, where \meta{key} is a full
-key. Different things can now happen, but always the macro |\pgfkeyscurrentkey|
-will have been set up to expand to the text of the \meta{key} that is currently
-being processed.
-
-The first things that is tested is whether the key \meta{key}|/.@cmd| exists.
-If this is the case, then it is assumed that this key stores the code of a
-macro and this macro is executed. The argument of this macro is \meta{value}
-directly followed by |\pgfeov|, which stands for ``end of value''. The
-\meta{value} is not surrounded by braces. After this code has been executed,
-|\pgfkeys| continues with the next key in the \meta{key list}.
-
-It may seem quite peculiar that the macro stored in the key \meta{key}|/.@cmd|
-is not simply executed with the argument |{|\meta{value}|}|. However, the
-approach taken in the |pgfkeys| packages allows for more flexibility. For
-instance, assume that you have a key that expects a \meta{value} of the form
-``\meta{text}|+|\meta{more text}'' and wishes to store \meta{text} and
-\meta{more text} in two different macros. This can be achieved as follows:
-%
-\begin{codeexample}[]
-\def\mystore#1+#2\pgfeov{\def\a{#1}\def\b{#2}}
-\pgfkeyslet{/my key/.@cmd}{\mystore}
-\pgfkeys{/my key=hello+world}
-
-|\a| is \a, |\b| is \b.
-\end{codeexample}
-
-Naturally, defining the code to be stored in a key in the above manner is too
-awkward. The following commands simplify things a bit, but the usual manner of
-setting up code for a key is to use one of the handlers described in
-Section~\ref{section-code-handlers}.
-
-\begin{command}{\pgfkeysdef\marg{key}\marg{code}}
- This command temporarily defines a \TeX-macro with the argument list
- |#1\pgfeov| and then lets \meta{key}|/.@cmd| be equal to this macro. The
- net effect of all this is that you have then set up code for the key
- \meta{key} so that when you write |\pgfkeys{|\meta{key}|=|\meta{value}|}|,
- then the \meta{code} is executed with all occurrences of |#1| in
- \meta{code} being replaced by \meta{value}. (This behavior is quite
- similar to the |\define@key| command of |keyval| and |xkeyval|).
- %
-\begin{codeexample}[]
-\pgfkeysdef{/my key}{#1, #1.}
-\pgfkeys{/my key=hello}
-\end{codeexample}
-\end{command}
-
-\begin{command}{\pgfkeysedef\marg{key}\marg{code}}
- This command works like |\pgfkeysdef|, but it uses |\edef| rather than
- |\def| when defining the key macro. If you do not know the difference
- between the two, then you will not need this command; and if you know the
- difference, then you will know when you need this command.
-\end{command}
-
-\begin{command}{\pgfkeysdefnargs\marg{key}\marg{argument count}\marg{code}}
- This command works like |\pgfkeysdef|, but it allows you to provide an
- arbitrary \meta{argument count} between $0$ and $9$ (inclusive).
- %
-\begin{codeexample}[]
-\pgfkeysdefnargs{/my key}{2}{\def\a{#1}\def\b{#2}}
-\pgfkeys{/my key=
- {hello}
- {world}}
-
-|\a| is `\a', |\b| is `\b'.
-\end{codeexample}
- %
- The resulting key will expect exactly \marg{argument count} arguments.
-\end{command}
-%
-\begin{command}{\pgfkeysedefnargs\marg{key}\marg{argument count}\marg{code}}
- The |\edef| version of |\pgfkeysdefnargs|.
-\end{command}
-
-\begin{command}{\pgfkeysdefargs\marg{key}\marg{argument pattern}\marg{code}}
- This command works like |\pgfkeysdefnargs|, but it allows you to provide an
- arbitrary \meta{argument pattern} rather than just a number of arguments.
- %
-\begin{codeexample}[]
-\pgfkeysdefargs{/my key}{#1+#2}{\def\a{#1}\def\b{#2}}
-\pgfkeys{/my key=hello+world}
-
-|\a| is \a, |\b| is \b.
-\end{codeexample}
- %
- Note that |\pgfkeysdefnargs| is \emph{better} when it comes to simple
- argument \emph{counts}\footnote{When the resulting keys are used, the
- \texttt{defnargs} variant allows spaces between arguments whereas the
- \texttt{defargs} variant does not; it considers the spaces as part of the
- argument.}.
-\end{command}
-
-\begin{command}{\pgfkeysedefargs\marg{key}\marg{argument pattern}\marg{code}}
- The |\edef| version of |\pgfkeysdefargs|.
-\end{command}
-
-
-\subsubsection{Keys That Store Values}
-
-Let us continue with what happens when |\pgfkeys| processes the current key and
-the subkey \meta{key}|/.@cmd| is not defined. Then it is checked whether the
-\meta{key} itself exists (has been previously assigned a value using, for
-instance, |\pgfkeyssetvalue|). In this case, the tokens stored in \meta{key}
-are replaced by \meta{value} and |\pgfkeys| proceeds with the next key in the
-\meta{key list}.
-
-
-\subsubsection{Keys That Are Handled}
-\label{section-key-handlers}
-
-If neither the \meta{key} itself nor the subkey \meta{key}|/.@cmd| are defined,
-then the \meta{key} cannot be processed ``all by itself''. Rather, a
-\meta{handler} is needed for this key. Most of the power of |pgfkeys| comes
-from the proper use of such handlers.
-
-Recall that the \meta{key} is always a full key (if it was not originally, it
-has already been upgraded at this point to a full key). It decomposed into two
-parts:
-
-\begin{enumerate}
- \item The \meta{path} of \meta{key} (everything before the last slash) is
- stored in the macro |\pgfkeyscurrentpath|.
- \item The \meta{name} of \meta{key} (everything after the last slash) is
- stored in the macro |\pgfkeyscurrentname|.
-
- It is recommended (but not necessary) that the name of a handler starts
- with a dot (but not with |.@|), so that they are easy to detect for the
- reader.
-\end{enumerate}
-
-(For efficiency reasons, these two macros are only set up at this point; so
-when code is executed for a key in the ``usual'' manner then these macros are
-not set up.)
-
-The |\pgfkeys| command now checks whether the key
-|/handlers/|\meta{name}|/.@cmd| exists. If so, it should store a command and
-this command is executed exactly in the same manner as described in
-Section~\ref{section-key-code}. Thus, this code gets the \meta{value} that was
-originally intended for \meta{key} as its argument, followed by |\pgfeov|. It
-is the job of the handlers to do something useful with the \meta{value}.
-
-For an example, let us write a handler that will output the value stored in a
-key to the log file. We call this handler |/.print to log|. The idea is that
-when someone tries to use the key |/my key/.print to log|, then this key will
-not be defined and the handler gets executed. The handler will then have access
-to the path-part of the key, which is |/my key|, via the macro
-|\pgfkeyscurrentpath|. It can then lookup which value is stored in this key and
-print it.
-%
-\begin{codeexample}[code only]
-\pgfkeysdef{/handlers/.print to log}
-{%
- \pgfkeysgetvalue{\pgfkeyscurrentpath}{\temp}
- \writetolog{\temp}
-}
-\pgfkeyssetvalue{/my key}{Hi!}
-...
-\pgfkeys{/my key/.print to log}
-\end{codeexample}
-%
-The above code will print |Hi!| in the log, provided the macro |\writetolog| is
-set up appropriately.
-
-For a more interesting handler, let us program a handler that will set up a key
-so that when the key is used, some code is executed. This code is given as
-\meta{value}. All the handler must do is to call |\pgfkeysdef| for the path of
-the key (which misses the handler's name) and assign the parameter value to it.
-%
-\begin{codeexample}[]
-\pgfkeysdef{/handlers/.my code}{\pgfkeysdef{\pgfkeyscurrentpath}{#1}}
-\pgfkeys{/my key/.my code=(#1)}
-\pgfkeys{/my key=hallo}
-\end{codeexample}
-
-There are some parameters for handled keys which prove to be useful in some
-(possibly rare) special cases:
-%
-\begin{key}{/handler config=\mchoice{all,only existing,full or existing} (initially all)}
- Changes the initial configuration how key handlers will be used.
-
- This configuration is for advanced users and rarely necessary.
- %
- \begin{description}
- \item[\texttt{all}] The preconfigured setting |all| works as described
- above and imposes no restriction on the key setting process.
- \item[\texttt{only existing}] The value |only existing| modifies the
- algorithm for handled keys as follows: a handler \meta{key
- name}|/.|\meta{handler} will be executed only if \meta{key name} is
- either a key which stores its value directly or a command key for
- which |/.@cmd| exists. If \meta{key name} does \emph{not} exist
- already, the complete string \meta{key name}|/.|\meta{handler} is
- considered to be an unknown key and the procedure described in the
- next section applies (for the path of \meta{key name}).
- %
-\begin{codeexample}[]
-% Define a test key and error handlers:
-\pgfkeys{/the/key/.code={Initial definition. }}
-\pgfkeys{/handlers/.unknown/.code={Unknown key `\pgfkeyscurrentkey'. }}
-
-% calling the test key yields 'Initial definition. ':
-\pgfkeys{/the/key}
-
-% Change configuration:
-\pgfkeys{/handler config=only existing}
-
-% allowed: key *re*-definition:
-\pgfkeys{/the/key/.code={Re-Definition. }}
-% calling the key yields 'Re-Definition. ':
-\pgfkeys{/the/key}
-
-% not allowed: definition of new keys:
-% this checks for '/the/other key/.unknown'
-% and '/handlers/.unknown'
-% and yields finally
-% 'Unknown key `/the/other key/.code`'
-\pgfkeys{/the/other key/.code={New definition. }}
-\end{codeexample}
- %
- It is necessary to exclude some key handlers from this procedure.
- Altogether, the detailed procedure is as follows:
- %
- \begin{enumerate}
- \item If a handled key like |/a path/a key/.a handler=value| is
- encountered, it is checked whether the handler should be
- invoked. This is the case if
- %
- \begin{itemize}
- \item An exception from |only existing| for this key
- exists (see below),
- \item The key |/a path/a key| exists already -- either
- directly as storage key or with the |.@cmd| suffix.
- \end{itemize}
- %
- \item If the check passes, everything works as before.
- \item If the check fails, the complete key will be considered
- to be unknown. In that case, the handling of unknown keys
- as described in the next section applies. There, the
- current key path will be set to |/a path| and the current
- key's name to |key/.a handler|.
- \end{enumerate}
-
- A consequence of this configuration is to provide more meaningful
- processing of handled keys if a search path for keys is in effect,
- see section~\ref{sec:pgf:unknown:keys} for an example.
- \item[\texttt{full or existing}] Finally, the choice |full or existing|
- is a variant of |only existing|: it works in the same way for keys
- which do not have a full key path. For example, the style
-
- |\pgfkeys{/my path/.cd,key/.style={|$\dotsc$|}}|
-
- can only be redefined: it doesn't have a full path, so the
- |only existing| mechanism applies. But the style
-
- |\pgfkeys{/my path/key/.style={|$\dotsc$|}}|
-
- will still work. This allows users to override the |only existing|
- feature if they know what they're doing (and provide full key
- paths).
- \end{description}
-\end{key}
-
-\begin{key}{/handler config/only existing/add exception=\marg{key handler name}}
- Allows to add exceptions to the |/handler config=only existing| feature.
- Initially exceptions for the key handlers |/.cd|, |/.try|, |/.retry|,
- |/.lastretry| and |/.unknown| are defined. The value \marg{key handler
- name} should be the name of a key handler.
-\end{key}
-
-
-\subsubsection{Keys That Are Unknown}
-\label{sec:pgf:unknown:keys}
-
-For some keys, neither the key, nor its |.@cmd| subkey nor a handler is
-defined. In this case, it is checked whether the key \meta{current
-path}|/.unknown/.@cmd| exists. Thus, when you try to use the key
-|/tikz/strange|, then it is checked whether |/tikz/.unknown/.@cmd| exists. If
-this key exists (which it does), it is executed. This code can then try to make
-sense of the key. For instance, the handler for \tikzname\ will try to
-interpret the key's name as a color or as an arrow specification or as a
-\pgfname\ option.
-
-You can set up unknown key handlers for your own keys by simply setting the
-code of the key \meta{my path prefix}|/.unknown|. This also allows you to set
-up ``search paths''. The idea is that you would like keys to be searched not
-only in a single default path, but in several. Suppose, for instance, that you
-would like keys to be searched for in |/a|, |/b|, and |/b/c|. We set up a key
-|/my search path| for this:
-%
-\begin{codeexample}[code only]
-\pgfkeys{/my search path/.unknown/.code=
- {%
- \let\searchname=\pgfkeyscurrentname%
- \pgfkeysalso{%
- /a/\searchname/.try=#1,
- /b/\searchname/.retry=#1,
- /b/c/\searchname/.retry=#1%
- }%
- }%
-}
-\pgfkeys{/my search path/.cd,foo,bar}
-\end{codeexample}
-%
-In the above code, |foo| and |bar| will be searched for in the three
-directories |/a|, |/b|, and |/b/c|. Before you start implementing search paths
-using this pattern, consider the |/.search also| handler discussed below.
-
-If the key \meta{current path}|/.unknown/.@cmd| does not exist, the handler
-|/handlers/.unknown| is invoked instead, which is always defined and which
-prints an error message by default.
-
-
-\subsubsection{Search Paths And Handled Keys}
-
-There is one special case which occurs in the search path example above. What
-happens if we want to change a style? For example,
-%
-\begin{codeexample}[code only]
-\pgfkeys{/my search path/.cd,custom/.style={variables}}
-\end{codeexample}
-%
-\noindent could mean a style in |/my search path/|, |/a/|, |/b/| or even
-|/b/c/|!
-
-Due to the rules for handled keys, the answer is
-|/my search path/custom/.style={variables}|. It may be useful to modify this
-default behavior. One useful thing would be to search for \emph{existing}
-styles named |custom| and redefine them. For example, if a style |/b/custom|
-exists, the assignment |custom/.style={variables}| should probably redefine
-|/b/custom| instead of |/my search path/custom|. This can be done using
-|handler config|:
-%
-\begin{codeexample}[]
-\pgfkeys{/my search path/.unknown/.code=
- {%
- \let\searchname=\pgfkeyscurrentname%
- \pgfkeysalso{%
- /a/\searchname/.try=#1,
- /b/\searchname/.retry=#1,
- /b/c/\searchname/.retry=#1%
- }%
- }%
-}
-
-% Let's define /b/custom here:
-\pgfkeys{/b/custom/.code={This is `\pgfkeyscurrentkey'. }}
-
-% Reconfigure treatment of key handlers:
-\pgfkeys{/handler config=only existing}
-
-% The search path procedure will find /b/custom
-% -> leads to This is `/b/custom'
-\pgfkeys{/my search path/.cd,custom}
-
-% Due to the reconfiguration, this will find /b/custom instead of
-% defining /my search path/custom:
-\pgfkeys{/my search path/.cd,custom/.append code={Modified. }}
-
-% So using the search path, we again find /b/custom which
-% leads to This is `/b/custom' Modified
-\pgfkeys{/my search path/.cd,custom}
-\end{codeexample}
-
-A slightly different approach to search paths can be realized using the
-|/.search also| key handler, see below.
-
-
-\subsection{Key Handlers}
-
-We now describe which key handlers are defined by default. You can also define
-new ones as described in Section~\ref{section-key-handlers}.
-
-
-\subsubsection{Handlers for Path Management}
-
-\begin{handler}{{.cd}}
- This handler causes the default path to be set to \meta{key}. Note that the
- default path is reset at the beginning of each call to |\pgfkeys| to be
- equal to~|/|.
-
- \example |\pgfkeys{/tikz/.cd,...}|
-\end{handler}
-
-\begin{handler}{{.is family}}
-\label{section-is family-handler}
- This handler sets up things such that when \meta{key} is executed, then the
- current path is set to \meta{key}. A typical use is the following:
- %
-\begin{codeexample}[code only]
-\pgfkeys{/tikz/.is family}
-\pgfkeys{tikz,line width=1cm}
-\end{codeexample}
- %
- The effect of this handler is the same as if you had written
- \meta{key}|/.style=|\meta{key}|/.cd|, only the code produced by the
- |/.is family| handler is quicker.
-\end{handler}
-
-
-\subsubsection{Setting Defaults}
-\label{section-default-handlers}
-
-\begin{handler}{{.default}|=|\meta{value}}
- Sets the default value of \meta{key} to \meta{value}. This means that
- whenever no value is provided in a call to |\pgfkeys|, then this
- \meta{value} will be used instead.
-
- \example |\pgfkeys{/width/.default=1cm}|
-\end{handler}
-
-\begin{handler}{{.value required}}
- This handler causes the error message key |/erros/value required| to be
- issued whenever the \meta{key} is used without a value.
-
- \example |\pgfkeys{/width/.value required}|
-\end{handler}
-
-\begin{handler}{{.value forbidden}}
- This handler causes the error message key |/erros/value forbidden| to be
- issued whenever the \meta{key} is used with a value.
-
- This handler works be adding code to the code of the key. This means that
- you have to define the key first before you can use this handler.
- %
-\begin{codeexample}[code only]
-\pgfkeys{/my key/.code=I do not want an argument!}
-\pgfkeys{/my key/.value forbidden}
-
-\pgfkeys{/my key} % Ok
-\pgfkeys{/my key=foo} % Error
-\end{codeexample}
- %
-\end{handler}
-
-
-\subsubsection{Defining Key Codes}
-\label{section-code-handlers}
-
-A number of handlers exist for defining the code of keys.
-
-\begin{handler}{{.code}|=|\meta{code}}
- This handler executes |\pgfkeysdef| with the parameters \meta{key} and
- \meta{code}. This means that, afterwards, whenever the \meta{key} is used,
- the \meta{code} gets executed. More precisely, when
- \meta{key}|=|\meta{value} is encountered in a key list, \meta{code} is
- executed with any occurrence of |#1| replaced by \meta{value}. As always,
- if no \meta{value} is given, the default value is used, if defined, or the
- special value |\pgfkeysnovalue|.
-
- It is permissible that \meta{code} calls the command |\pgfkeys|. It is also
- permissible the \meta{code} calls the command |\pgfkeysalso|, which is
- useful for styles, see below.
- %
-\begin{codeexample}[code only]
-\pgfkeys{/par indent/.code={\parindent=#1},/par indent/.default=2em}
-\pgfkeys{/par indent=1cm}
-...
-\pgfkeys{/par indent}
-\end{codeexample}
- %
-\end{handler}
-
-\begin{handler}{{.ecode}|=|\meta{code}}
- This handler works like |/.code|, only the command |\pgfkeysedef| is used.
-\end{handler}
-
-\begin{handler}{{.code 2 args}|=|\meta{code}}
- This handler works like |/.code|, only two arguments rather than one are
- expected when the \meta{code} is executed. This means that when
- \meta{key}|=|\meta{value} is encountered in a key list, the \meta{value}
- should consist of two arguments. For instance, \meta{value} could be
- |{first}{second}|. Then \meta{code} is executed with any occurrence of |#1|
- replaced |first| and any occurrence of |#2| replaced by |second|.
- %
-\begin{codeexample}[code only]
-\pgfkeys{/page size/.code 2 args={\paperheight=#2\paperwidth=#1}}
-\pgfkeys{/page size={30cm}{20cm}}
-\end{codeexample}
- %
- Because of the special way the \meta{value} is parsed, if you set
- \meta{value} to, for instance, |first| (without any braces), then |#1| will
- be set to |f| and |#2| will be set to |irst|.
-\end{handler}
-
-\begin{handler}{{.ecode 2 args}|=|\meta{code}}
- This handler works like |/.code 2 args|, only an |\edef| is used rather
- than a |\def| to define the macro.
-\end{handler}
-
-\begin{handler}{{.code n args}|=|\marg{argument count}\marg{code}}
- This handler also works like |/.code|, but you can now specify a number of
- arguments between $0$ and $9$ (inclusive).
- %
-\begin{codeexample}[]
-\pgfkeys{/a key/.code n args={2}{First=`#1', Second=`#2'}}
-\pgfkeys{/a key={A}{B}}
-\end{codeexample}
- %
- In contrast to |/.code 2 args|, there must be exactly \meta{argument count}
- arguments, not more and not less and these arguments should be properly
- delimited.
-\end{handler}
-
-\begin{handler}{{.ecode n args}|=|\marg{argument count}\marg{code}}
- This handler works like |/.code n args|, only an |\edef| is used rather
- than a |\def| to define the macro.
-\end{handler}
-
-\begin{handler}{{.code args}|=|\marg{argument pattern}\marg{code}}
- This handler is the most flexible way to define a |/.code| key: you can now
- specify an arbitrary \meta{argument pattern}. Such a pattern is a usual
- \TeX\ macro pattern. For instance, suppose \meta{argument pattern} is
- |(#1/#2)| and \meta{key}|=|\meta{value} is encountered in a key list with
- \meta{value} being |(first/second)|. Then \meta{code} is executed with any
- occurrence of |#1| replaced |first| and any occurrence of |#2| replaced by
- |second|. So, the actual \meta{value} is matched against the \meta{argument
- pattern} in the standard \TeX\ way.
- %
-\begin{codeexample}[code only]
-\pgfkeys{/page size/.code args={#1 and #2}{\paperheight=#2\paperwidth=#1}}
-\pgfkeys{/page size=30cm and 20cm}
-\end{codeexample}
-
- Note that |/.code n args| should be preferred in case you need just a
- number of arguments (when the resulting keys are used, |/.code n args|
- gobbles spaces between the arguments whereas |/.code args| considers spaces
- to be part of the argument).
-\end{handler}
-
-\begin{handler}{{.ecode args}|=|\marg{argument pattern}\marg{code}}
- This handler works like |/.code args|, only an |\edef| is used rather than
- a |\def| to define the macro.
-\end{handler}
-
-There are also handlers for modifying existing keys.
-
-\begin{handler}{{.add code}|=|\marg{prefix code}\marg{append code}}
- This handler adds code to an existing key. The \meta{prefix code} is added
- to the code stored in \meta{key}|/.@cmd| at the beginning, the \meta{append
- code} is added to this code at the end. Either can be empty. The argument
- list of \meta{code} cannot be changed using this handler. Note that both
- \meta{prefix code} and \meta{append code} may contain parameters like |#2|.
- %
-\begin{codeexample}[code only]
-\pgfkeys{/par indent/.code={\parindent=#1}}
-\newdimen\myparindent
-\pgfkeys{/par indent/.add code={}{\myparindent=#1}}
-...
-\pgfkeys{/par indent=1cm} % This will set both \parindent and
- % \myparindent to 1cm
-\end{codeexample}
- %
-\end{handler}
-
-\begin{handler}{{.prefix code}|=|\meta{prefix code}}
- This handler is a shortcut for \meta{key}|/.add code={|\meta{prefix
- code}|}{}|. That is, this handler adds the \meta{prefix code} at the
- beginning of the code stored in \meta{key}|/.@cmd|.
-\end{handler}
-
-\begin{handler}{{.append code}|=|\meta{append code}}
- This handler is a shortcut for \meta{key}|/.add code={}{|\meta{append
- code}|}{}|.
-\end{handler}
-
-
-\subsubsection{Defining Styles}
-
-The following handlers allow you to define \emph{styles}. A style is a key list
-that is processed whenever the style is given as a key in a key list. Thus, a
-style ``stands for'' a certain key value list. Styles can be parameterized just
-like normal code.
-
-\begin{handler}{{.style}|=|\meta{key list}}
- This handler sets things up so that whenever \meta{key}|=|\meta{value} is
- encountered in a key list, then the \meta{key list}, with every occurrence
- of |#1| replaced by \meta{value}, is processed instead. As always, if no
- \meta{value} is given, the default value is used, if defined, or the
- special value |\pgfkeysnovalue|.
-
- You can achieve the same effect by writing
- \meta{key}|/.code=\pgfkeysalso{|\meta{key list}|}|. This means, in
- particular, that the code of a key could also first execute some normal
- code and only then process some further keys.
- %
-\begin{codeexample}[code only]
-\pgfkeys{/par indent/.code={\parindent=#1}}
-\pgfkeys{/no indent/.style={/par indent=0pt}}
-\pgfkeys{/normal indent/.style={/par indent=2em}}
-\pgfkeys{/no indent}
-...
-\pgfkeys{/normal indent}
-\end{codeexample}
- %
- The following example shows a parameterized style ``in action''.
- %
-\begin{codeexample}[]
-\begin{tikzpicture}[outline/.style={draw=#1,fill=#1!20}]
- \node [outline=red] {red box};
- \node [outline=blue] at (0,-1) {blue box};
-\end{tikzpicture}
-\end{codeexample}
- %
-\end{handler}
-
-\begin{handler}{{.estyle}|=|\meta{key list}}
- This handler works like |/.style|, only the \meta{code} is set using
- |\edef| rather than |\def|. Thus, all macros in the \meta{code} are
- expanded prior to saving the style.
-\end{handler}
-
-For styles the corresponding handlers as for normal code exist:
-
-\begin{handler}{{.style 2 args}|=|\meta{key list}}
- This handler works like |/.code 2 args|, only for styles. Thus, the
- \meta{key list} may contain occurrences of both |#1| and |#2| and when the
- style is used, two parameters must be given as \meta{value}.
- %
-\begin{codeexample}[code only]
-\pgfkeys{/paper height/.code={\paperheight=#1},/paper width/.code={\paperwidth=#1}}
-\pgfkeys{/page size/.style 2 args={/paper height=#1,/paper width=#2}}
-\pgfkeys{/page size={30cm}{20cm}}
-\end{codeexample}
- %
-\end{handler}
-
-\begin{handler}{{.estyle 2 args}|=|\meta{key list}}
- This handler works like |/.style 2 args|, only an |\edef| is used rather
- than a |\def| to define the macro.
-\end{handler}
-
-\begin{handler}{{.style n args}|=|\marg{argument count}\meta{key list}}
- This handler works like |/.code n args|, only for styles. Here, \meta{key
- list} may depend on all \meta{argument count} parameters.
-\end{handler}
-
-\begin{handler}{{.add style}|=|\marg{prefix key list}\marg{append key list}}
- This handler works like |/.add code|, only for styles. However, it is
- permissible to add styles to keys that have previously been set using
- |/.code|. (It is also permissible to add normal \meta{code} to a key that
- has previously been set using |/.style|). When you add a style to a key
- that was previously set using |/.code|, the following happens: When
- \meta{key} is processed, the \meta{prefix key list} will be processed
- first, then the \meta{code} that was previously stored in
- \meta{key}|/.@cmd|, and then the keys in \meta{append key list} are
- processed.
- %
-\begin{codeexample}[code only]
-\pgfkeys{/par indent/.code={\parindent=#1}}
-\pgfkeys{/par indent/.add style={}{/my key=#1}}
-...
-\pgfkeys{/par indent=1cm} % This will set \parindent and
- % then execute /my key=#1
-\end{codeexample}
- %
-\end{handler}
-
-\begin{handler}{{.style args}|=|\marg{argument pattern}\marg{key list}}
- This handler works like |/.code args|, only for styles.
-\end{handler}
-
-\begin{handler}{{.estyle args}|=|\marg{argument pattern}\marg{code}}
- This handler works like |/.ecode args|, only for styles.
-\end{handler}
-
-\begin{handler}{{.prefix style}|=|\meta{prefix key list}}
- Works like |/.add style|, but only for the prefix key list.
-\end{handler}
-
-\begin{handler}{{.append style}|=|\meta{append key list}}
- Works like |/.add style|, but only for the append key list.
-\end{handler}
-
-
-\subsubsection{Defining Value-, Macro-, If- and Choice-Keys}
-
-For some keys, the code that should be executed for them is rather
-``specialized''. For instance, it happens often that the code for a key just
-sets a certain \TeX-if to true or false. For these cases, predefined handlers
-make it easier to install the necessary code.
-
-However, we start with some handlers that are used to manage the value that is
-directly stored in a key.
-
-\begin{handler}{{.initial}|=|\meta{value}}
- This handler sets the value of \meta{key} to \meta{value}. Note that no
- subkeys are involved. After this handler has been used, by the rules
- governing keys, you can subsequently change the value of the \meta{key} by
- just writing \meta{key}|=|\meta{value}. Thus, this handler is used to set
- the initial value of key.
- %
-\begin{codeexample}[code only]
-\pgfkeys{/my key/.initial=red}
-% "/my key" now stores the value "red"
-\pgfkeys{/my key=blue}
-% "/my key" now stores the value "blue"
-\end{codeexample}
-
- Note that with this configuration, writing |\pgfkeys{/my key}| will not
- have the effect you might expect (namely that |blue| is inserted into the
- main text). Rather, |/my key| will be promoted to |/my key=\pgfkeysnovalue|
- and, thus, |\pgfkeysnovalue| will be stored in |/my key|.
-
- To retrieve the value stored in a key, the handler |/.get| is used.
-
- \medskip
- \emph{Remark:} A key can both store a value and execute commands%
- \footnote{This behavior was partially changed in \pgfname{} 3.1.6 and then
- restored in 3.1.7. For compatibility reasons, this behavior will not be
- changed in future releases anymore.}.
- If so, using \meta{key} will \emph{always} execute commands with the passed
- value, or the default value |\pgfkeysnovalue| if no value is provided.
- Note that the stored value is never used. To update the stored value, the
- handler |/.initial| or command |\pgfkeyssetvalue| is used.
- %
-\begin{codeexample}[]
-\pgfkeys{/my key/.initial=red}
-\pgfkeys{/my key/.code=#1}
-% "/my key" now both stores the value "red" and executes commands
-\pgfkeys{/my key=blue}
-% "/my key" now still stores the value "red"
-\end{codeexample}
- %
-\end{handler}
-
-\begin{handler}{{.get}|=|\meta{macro}}
- Executes a |\let| command so that \meta{macro} contains the contents stored
- in \meta{key}.
- %
-\begin{codeexample}[]
-\pgfkeys{/my key/.initial=red}
-\pgfkeys{/my key=blue}
-\pgfkeys{/my key/.get=\mymacro}
-\mymacro
-\end{codeexample}
- %
-\end{handler}
-
-\begin{handler}{{.add}|=|\marg{prefix value}\marg{append value}}
- Adds the \meta{prefix value} at the beginning and the \meta{append value}
- at the end of the value stored in \meta{key}.
-\end{handler}
-
-\begin{handler}{{.prefix}|=|\marg{prefix value}}
- Adds the \meta{prefix value} and the beginning of the value stored in
- \meta{key}.
-\end{handler}
-
-\begin{handler}{{.append}|=|\marg{append value}}
- Adds the \meta{append value} at the end of the value stored in \meta{key}.
-\end{handler}
-
-\begin{handler}{{.link}|=|\meta{another key}}
- Stores the value |\pgfkeysvalueof{|\meta{another key}|}| in the \meta{key}.
- The idea is that when you expand the \meta{key}, the value of \meta{another
- key} is expanded instead. This corresponds loosely to the notion of soft
- links in Unix, hence the name.
-\end{handler}
-
-The next handler is useful for the common situation where
-\meta{key}|=|\meta{value} should cause the \meta{value} to be stored in some
-macro. Note that, typically, you could just as well store the value in the key
-itself.
-
-\begin{handler}{{.store in}|=|\meta{macro}}
- This handler has the following effect: When you write
- \meta{key}|=|\meta{value}, the code |\def|\meta{macro}|{|\meta{value}|}| is
- executed. Thus, the given value is ``stored'' in the \meta{macro}.
- %
-\begin{codeexample}[]
-\pgfkeys{/text/.store in=\mytext}
-\def\a{world}
-\pgfkeys{/text=Hello \a!}
-\def\a{Gruffalo}
-\mytext
-\end{codeexample}
- %
-\end{handler}
-
-\begin{handler}{{.estore in}|=|\meta{macro}}
- This handler is similar to |/.store in|, only the code
- |\edef|\meta{macro}|{|\meta{value}|}| is used. Thus, the macro-expanded
- version of \meta{value} is stored in the \meta{macro}.
- %
-\begin{codeexample}[]
-\pgfkeys{/text/.estore in=\mytext}
-\def\a{world}
-\pgfkeys{/text=Hello \a!}
-\def\a{Gruffalo}
-\mytext
-\end{codeexample}
- %
-\end{handler}
-
-In another common situation a key is used to set a \TeX-if to true or false.
-
-\begin{handler}{{.is if}|=|\meta{\TeX-if name}}
- This handler has the following effect: When you write
- \meta{key}|=|\meta{value}, it is first checked that \meta{value} is |true|
- or |false| (the default is |true| if no \meta{value} is given). If this is
- not the case, the error key |/errors/boolean expected| is executed.
- Otherwise, the code |\|\meta{\TeX-if name}\meta{value} is executed, which
- sets the \TeX-if accordingly.
- %
-\begin{codeexample}[]
-\newif\iftheworldisflat
-\pgfkeys{/flat world/.is if=theworldisflat}
-\pgfkeys{/flat world=false}
-\iftheworldisflat
- Flat
-\else
- Round?
-\fi
-\end{codeexample}
- %
-\end{handler}
-
-The next handler deals with the problem when a \meta{key}|=|\meta{value} makes
-sense only for a small set of possible \meta{value}s. For instance, the line
-cap can only be |rounded| or |rect| or |butt|, but nothing else. For this
-situation the following handler is useful.
-
-\begin{handler}{{.is choice}}
- This handler sets things up so that writing \meta{key}|=|\meta{value} will
- cause the subkey \meta{key}|/|\meta{value} to be executed. So, each of the
- different possible choices should be given by a subkey of \meta{key}.
- %
-\begin{codeexample}[code only]
-\pgfkeys{/line cap/.is choice}
-\pgfkeys{/line cap/round/.code={\pgfsetbuttcap}}
-\pgfkeys{/line cap/butt/.code={\pgfsetroundcap}}
-\pgfkeys{/line cap/rect/.code={\pgfsetrectcap}}
-\pgfkeys{/line cap/rectangle/.style={/line cap=rect}}
-...
-\draw [/line cap=butt] ...
-\end{codeexample}
- %
- If the subkey \meta{key}|/|\meta{value} does not exist, the error key
- |/errors/unknown choice value| is executed.
-\end{handler}
-
-
-\subsubsection{Expanded and Multiple Values}
-
-When you write \meta{key}|=|\meta{value}, you usually wish to use the
-\meta{value} ``as is''. Indeed, great care is taken to ensure that you can even
-use things like |#1| or unbalanced \TeX-ifs inside \meta{value}. However,
-sometimes you want the \meta{value} to be expanded before it is used. For
-instance, \meta{value} might be a macro name like |\mymacro| and you do not
-want |\mymacro| to be used as the macro, but rather the \emph{contents} of
-|\mymacro|. Thus, instead of using \meta{value}, you wish to use whatever
-\meta{value} expands to. Instead of using some fancy |\expandafter| hackery,
-you can use the following handlers:
-
-\begin{handler}{{.expand once}|=|\meta{value}}
- This handler expands \meta{value} once (more precisely, it executes an
- |\expandafter| command on the first token of \meta{value}) and then process
- the resulting \meta{result} as if you had written
- \meta{key}|=|\meta{result}. Note that if \meta{key} contains a handler
- itself, this handler will be called normally.
- %
-\begin{codeexample}[]
-\def\a{bottom}
-\def\b{\a}
-\def\c{\b}
-
-\pgfkeys{/key1/.initial=\c}
-\pgfkeys{/key2/.initial/.expand once=\c}
-\pgfkeys{/key3/.initial/.expand twice=\c}
-\pgfkeys{/key4/.initial/.expanded=\c}
-
-\def\a{{\ttfamily\string\a}}
-\def\b{{\ttfamily\string\b}}
-\def\c{{\ttfamily\string\c}}
-
-\begin{tabular}{ll}
-Key 1:& \pgfkeys{/key1} \\
-Key 2:& \pgfkeys{/key2} \\
-Key 3:& \pgfkeys{/key3} \\
-Key 4:& \pgfkeys{/key4}
-\end{tabular}
-\end{codeexample}
- %
-\end{handler}
-
-\begin{handler}{{.expand twice}|=|\meta{value}}
- This handler works like saying
- \meta{key}|/.expand once/.expand once=|\meta{value}.
-\end{handler}
-
-\begin{handler}{{.expanded}|=|\meta{value}}
- This handler will completely expand \meta{value} (using |\edef|) before
- processing \meta{key}|=|\meta{result}.
-\end{handler}
-
-\begin{handler}{{.evaluated}|=|\meta{value}}
- This handler will evaluate \meta{value} as a mathematical
- expression with |\pgfmathparse| and assign \meta{key}|=\pgfmathresult|.
- %
-\begin{codeexample}[]
-\pgfkeys{
- /golden ratio/.initial/.evaluated={(1 + sqrt(5))/2},
-}
-\pgfkeys{/golden ratio}
-\end{codeexample}
- %
-\end{handler}
-
-\begin{handler}{{.list}|=|\meta{comma-separated list of values}}
- This handler causes the key to be used repeatedly, namely once for every
- element of the list of values. Note that the list of values should
- typically be surrounded by braces since, otherwise, \TeX\ will not be able
- to tell whether a comma starts a new key or a new value.
-
- The \meta{list of values} is processed using the |\foreach| statement, so
- you can use the |...| notation.
- %
-\begin{codeexample}[]
-\pgfkeys{/foo/.code=(#1)}
-\pgfkeys{/foo/.list={a,b,0,1,...,5}}
-\end{codeexample}
- %
-\end{handler}
-
-
-\subsubsection{Handlers for Forwarding}
-
-\begin{handler}{{.forward to}|=|\meta{another key}}
- This handler causes the \meta{key} to ``forward'' its argument to
- \meta{another key}. When the \meta{key} is used, its normal code will be
- executed first. Then, the value is (additionally) passed to \meta{another
- key}. If the \meta{key} has not yet been defined prior to the use of
- |.forward to|, it will be defined then (and do nothing by itself, expect
- for forwarding it to \meta{key name}). The \meta{another key} must be a
- fully qualified key name.
- %
-\begin{codeexample}[]
-\pgfkeys{
- /a/.code=(a:#1),
- /b/.code=(b:#1),
- /b/.forward to=/a,
- /c/.forward to=/a
-}
-\pgfkeys{/b=1} \pgfkeys{/c=2}
-\end{codeexample}
- %
-\end{handler}
-
-\begin{handler}{{.search also}=\marg{path list}}
- A style which installs a |/.unknown| handler into \meta{key}. This
- |/.unknown| handler will then search for unknown keys in every path
- provided in \marg{path list}.
- %
-\begin{codeexample}[]
-% define a key:
-\pgfkeys{/secondary path/option/.code={Invoking /secondary path/option with `#1'}}
-
-% set up a search path:
-\pgfkeys{/main path/.search also={/secondary path}}
-
-% try searching for `option=value' in '/main path':
-% -> this finds `/secondary path/option'!
-\pgfkeys{/main path/.cd,option=value}
-\end{codeexample}
-
- The |/.search also| handler follows the strategy
- %
- \begin{enumerate}
- \item If a user provides a fully qualified key which could not be
- found, for example the full string |/main path/option|, it assumes
- that the user knew what she is doing -- and does \emph{not}
- continue searching for |option| in \marg{path list}.
- \item If a user provides only the key's name, for example |option| and
- |option| cannot be found in the current default path (which is
- |/main path| in our example above), the current default path is set
- to the next element in \marg{path list} (which is |/secondary path|
- here) and |\pgfkeys| will be restarted.
-
- This will be iterated until either a match has been found or all
- elements in \marg{path list} have been tested.
- \item If all
- elements in \marg{path list} have been checked and the key is still
- unknown, the fall-back handler |/handlers/.unknown| will be
- invoked.
- \end{enumerate}
- %
-\begin{codeexample}[]
-% define a key:
-\pgfkeys{/secondary path/option/.code={Invoking /secondary path/option with `#1'}}
-
-% set up a search path:
-\pgfkeys{/main path/.search also={/secondary path}}
-
-% try searching for `option=value' in '/main path':
-% -> this finds `/secondary path/option'!
-\pgfkeys{/main path/.cd,option=value}
-
-% negative example:
-% try searching for fully qualified key /main path/option.
-% This won't be handled by .search also.
-\pgfkeys{/handlers/.unknown/.code={Found unknown option \pgfkeyscurrentkeyRAW={#1}!}}%
-\pgfkeys{/main path/.cd,/main path/option=value}
-\end{codeexample}
-
- Please note that the strategy of |/.search also| is different from the
- first example provided in section~\ref{sec:pgf:unknown:keys} ``Unknown
- Keys'' because |/.search also| only applies to keys that are not fully
- qualified.
-
- For those who are familiar with |\pgfkeys|, the actual implementation of
- |/.search also| might be interesting:
- %
- \begin{enumerate}
- \item |\pgfkeys{/path/.search also={/tikz}}| is equivalent to
- %
-\begin{codeexample}[code only]
-\pgfkeys{/path/.unknown/.code={%
- \def\pgfkeys@searchalso@temp@value{#1}%
- \ifpgfkeysaddeddefaultpath
- \expandafter\pgfkeys@firstoftwo
- \else
- \expandafter\pgfkeys@secondoftwo
- \fi{%
- % only process keys for which no full path has been
- % provided:
- \pgfkeyssuccessfalse
- \let\pgfkeys@searchalso@name=\pgfkeyscurrentkeyRAW
- \ifpgfkeyssuccess
- \else
- % search with /tikz as default path:
- \pgfqkeys{/tikz}{\pgfkeys@searchalso@name/.expand once=%
- \pgfkeys@searchalso@temp@value}%
- \fi
- }{%
- \pgfkeysgetvalue{/handlers/.unknown/.@cmd}{\pgfkeys@code}%
- \expandafter\pgfkeys@code\pgfkeys@searchalso@temp@value\pgfeov
- }%
- }
-}
-\end{codeexample}
- %
- \item |\pgfkeys{/path/.search also={/tikz,/pgf}}| is equivalent to
- %
-\begin{codeexample}[code only]
-\pgfkeys{/path/.unknown/.code={%
- \def\pgfkeys@searchalso@temp@value{#1}%
- \ifpgfkeysaddeddefaultpath
- \expandafter\pgfkeys@firstoftwo
- \else
- \expandafter\pgfkeys@secondoftwo
- \fi{%
- \pgfkeyssuccessfalse
- \let\pgfkeys@searchalso@name=\pgfkeyscurrentkeyRAW
- \ifpgfkeyssuccess
- \else
- % step 1: search in /tikz with .try:
- \pgfqkeys{/tikz}{\pgfkeys@searchalso@name/.try/.expand once=%
- \pgfkeys@searchalso@temp@value}%
- \fi
- \ifpgfkeyssuccess
- \else
- % step 2: search in /pgf (without .try!):
- \pgfqkeys{/pgf}{\pgfkeys@searchalso@name/.expand once=\pgfkeys@searchalso@}%
- \fi
- }{%
- \pgfkeysgetvalue{/handlers/.unknown/.@cmd}{\pgfkeys@code}%
- \expandafter\pgfkeys@code\pgfkeys@searchalso@temp@value\pgfeov
- }%
- }
-}
-\end{codeexample}
- \end{enumerate}
-
- To also enable searching for styles (or other handled keys), consider
- changing the configuration for handled keys to
- |/handler config=full or existing| when you use |/.search also|, that is,
- use
- %
-\begin{codeexample}[code only]
-\pgfkeys{
- /main path/.search also={/secondary path},
- /handler config=full or existing}
-\end{codeexample}
- %
-\end{handler}
-
-
-\subsubsection{Handlers for Testing Keys}
-
-\begin{handler}{{.try}|=|\meta{value}}
- This handler causes the same things to be done as if
- \meta{key}|=|\meta{value} had been written instead. However, if neither
- \meta{key}|/.@cmd| nor the key itself is defined, no handlers will be
- called. Instead, the execution of the key just stops. Thus, this handler
- will ``try'' to use the key, but no further action is taken when the key is
- not defined.
-
- The \TeX-if |\ifpgfkeyssuccess| will be set according to whether the
- \meta{key} was successfully executed or not.
- %
-\begin{codeexample}[]
-\pgfkeys{/a/.code=(a:#1)}
-\pgfkeys{/b/.code=(b:#1)}
-\pgfkeys{/x/.try=hmm,/a/.try=hallo,/b/.try=welt}
-\end{codeexample}
- %
-\end{handler}
-
-\begin{handler}{{.retry}|=|\meta{value}}
- This handler works just like |/.try|, only it will not do anything if
- |\ifpgfkeyssuccess| is false. Thus, this handler will only retry to set a
- key if ``the last attempt failed''.
- %
-\begin{codeexample}[]
-\pgfkeys{/a/.code=(a:#1)}
-\pgfkeys{/b/.code=(b:#1)}
-\pgfkeys{/x/.try=hmm,/a/.retry=hallo,/b/.retry=welt}
-\end{codeexample}
- %
-\end{handler}
-
-\begin{handler}{{.lastretry}|=|\meta{value}}
- This handler works like |/.retry|, only it will invoke the usual handlers
- for unknowns keys if |\ifpgfkeyssuccess| is false. Thus, this handler
- will only try to set a key if ``the last attempt failed''. Furthermore,
- this here is the last such attempt.
-\end{handler}
-
-
-\subsubsection{Handlers for Key Inspection}
-
-\begin{handler}{{.show value}}
- This handler executes a |\show| command on the value stored in \meta{key}.
- This is useful mostly for debugging.
-
- \example |\pgfkeys{/my/obscure key/.show value}|
-\end{handler}
-
-\begin{handler}{{.show code}}
- This handler executes a |\show| command on the code stored in
- \meta{key}|/.@cmd|. This is useful mostly for debugging.
-
- \example |\pgfkeys{/my/obscure key/.show code}|
-\end{handler}
-
-The following key is not a handler, but it also commonly used for inspecting
-things:
-%
-\begin{key}{/utils/exec=\meta{code}}
- This key will simply execute the given \meta{code}.
-
- % FIXME: there is a bug in the pretty printer ... fix it!
- \example \verb|\pgfkeys{some key=some value,/utils/exec=\show\hallo,obscure key=obscure}|
-\end{key}
-
-
-\subsection{Error Keys}
-
-In certain situations errors can occur, like using an undefined key. In these
-situations error keys are executed. They should store a macro that gets two
-arguments: The first is the offending key (possibly only after macro
-expansion), the second is the value that was passed as a parameter (also
-possibly only after macro expansion).
-
-Currently, error keys are simply executed. In the future it might be a good
-idea to have different subkeys that are executed depending on the language
-currently set so that users get a localized error message.
-
-\begin{key}{/errors/value required=\marg{offending key}\marg{value}}
- This key is executed whenever an \meta{offending key} is used without a
- value when a value is actually required.
-\end{key}
-
-\begin{key}{/errors/value forbidden=\marg{offending key}\marg{value}}
- This key is executed whenever a key is used with a value when a value is
- actually forbidden.
-\end{key}
-
-\begin{key}{/errors/boolean expected=\marg{offending key}\marg{value}}
- This key is executed whenever a key set up using |/.is if| gets called with
- a \meta{value} other than |true| or |false|.
-\end{key}
-
-\begin{key}{/errors/unknown choice value=\marg{offending key}\marg{value}}
- This key is executed whenever a choice is used as a \meta{value} for a key
- set up using the |/.is choice| handler that is not defined.
-\end{key}
-
-\begin{key}{/errors/unknown key=\marg{offending key}\marg{value}}
- This key is executed whenever a key is unknown and no specific |/.unknown|
- handler is found.
-\end{key}
-
-
-\input{pgfmanual-en-pgfkeysfiltered.tex}