From 6f9e1680085e7bb4d258f6f8116369d122e196e1 Mon Sep 17 00:00:00 2001 From: Norbert Preining Date: Mon, 16 Jan 2023 03:03:27 +0000 Subject: CTAN sync 202301160303 --- .../base/doc/text-en/pgfmanual-en-base-arrows.tex | 962 --------------------- 1 file changed, 962 deletions(-) delete mode 100644 graphics/pgf/base/doc/text-en/pgfmanual-en-base-arrows.tex (limited to 'graphics/pgf/base/doc/text-en/pgfmanual-en-base-arrows.tex') diff --git a/graphics/pgf/base/doc/text-en/pgfmanual-en-base-arrows.tex b/graphics/pgf/base/doc/text-en/pgfmanual-en-base-arrows.tex deleted file mode 100644 index 5d81abf79d..0000000000 --- a/graphics/pgf/base/doc/text-en/pgfmanual-en-base-arrows.tex +++ /dev/null @@ -1,962 +0,0 @@ -% 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{Defining New Arrow Tip Kinds} -\label{section-arrows} - -\subsection{Overview} - -In present section we have a look at how you can define new arrow tips for use -in \pgfname. The low-level commands for selecting which arrow tips are to be -used have already been described in Section~\ref{section-tips}, the general -syntax rules for using arrows are detailed in -Section~\ref{section-tikz-arrows}. Although Section~\ref{section-tikz-arrows} -describes the use of arrows in \tikzname, in reality, \tikzname\ itself does -not actually do anything about arrow tips; all of the functionality is -implemented on the \pgfname\ level in the commands described in -Section~\ref{section-tikz-arrows}. Indeed, even the |/.tip| key handler -described in Section~\ref{section-tikz-arrows} is actually implemented on the -\pgfname\ layer. - -What has \emph{not} yet been covered is how you can actually define a complete -new arrow tip. In \pgfname, arrows are ``meta-arrows'' in the same way that -fonts in \TeX\ are ``meta-fonts''. When a meta-arrow is resized, it is not -simply scaled, but a possibly complicated transformation is applied to the -size. - -A meta-font is not one particular font at a specific size with a specific -stroke width (and with a large number of other parameters being fixed). Rather, -it is a ``blueprint'' (actually, more like a program) for generating such a -font at a particular size and width. This allows the designer of a meta-font to -make sure that, say, the font is somewhat thicker and wider at very small -sizes. To appreciate the difference: Compare the following texts: ``Berlin'' -and ``\tikz{\node [scale=2,inner sep=0pt,outer sep=0pt]{\tiny Berlin};}''. The -first is a ``normal'' text, the second is the tiny version scaled by a factor -of two. Obviously, the first look better. Now, compare ``\tikz{\node -[scale=.5,inner sep=0pt,outer sep=0pt]{Berlin};}'' and ``{\tiny Berlin}''. This -time, the normal text was scaled down, while the second text is a ``normal'' -tiny text. The second text is easier to read. - -\pgfname's meta-arrows work in a similar fashion: The shape of an arrow tip can -vary according to a great number of parameters, the line width of the arrow tip -being one of them. Thus, an arrow tip drawn at a line width of 5pt will -typically \emph{not} be five times as large as an arrow tip of line width 1pt. -Instead, the size of the arrow will get bigger only slowly as the line width -increases. - -To appreciate the difference, here are the |Latex| and -|Classical TikZ Rightarrow| arrows, as drawn by \pgfname\ at four different -sizes: - -\medskip -\begin{tikzpicture}[1/.tip=Latex, 2/.tip=Classical TikZ Rightarrow] - \draw[-1, line width=0.1pt] (0pt,0ex) -- +(3,0) node[thin,right] {line width is 0.1pt}; - \draw[-1, line width=0.4pt] (0pt,-2em) -- +(3,0) node[thin,right] {line width is 0.4pt}; - \draw[-1, line width=1.2pt] (0pt,-4em) -- +(3,0) node[thin,right] {line width is 1.2pt}; - \draw[-1, line width=5pt] (0pt,-6em) -- +(3,0) node[thin,right] {line width is 5pt}; - - \draw[-2, line width=0.1pt] (6cm,0ex) -- +(3,0) node[thin,right] {line width is 0.1pt}; - \draw[-2, line width=0.4pt] (6cm,-2em) -- +(3,0) node[thin,right] {line width is 0.4pt}; - \draw[-2, line width=1.2pt] (6cm,-4em) -- +(3,0) node[thin,right] {line width is 1.2pt}; - \draw[-2, line width=5pt] (6cm,-6em) -- +(3,0) node[thin,right] {line width is 5pt}; -\end{tikzpicture} - -\medskip -Here, by comparison, are the same arrows when they are simply ``resized'': - -\medskip -\begin{tikzpicture}[1/.tip=Latex, 2/.tip=Classical TikZ Rightarrow] - \draw[-{1[length=1pt]}, line width=0.1pt] (0pt,0ex) -- +(3,0) node[thin,right] {line width is 0.1pt}; - \draw[-{1[length=4pt]}, line width=0.4pt] (0pt,-2em) -- +(3,0) node[thin,right] {line width is 0.4pt}; - \draw[-{1[length=12pt]}, line width=1.2pt] (0pt,-4em) -- +(3,0) node[thin,right] {line width is 1.2pt}; - \draw[-{1[length=32pt]}, line width=5pt] (0pt,-6em) -- +(3,0) node[thin,right] {line width is 5pt}; - - \draw[-{2[length=0.455pt]}, line width=0.1pt] (6cm,0ex) -- +(3,0) node[thin,right] {line width is 0.1pt}; - \draw[-{2[length=1.82pt]}, line width=0.4pt] (6cm,-2em) -- +(3,0) node[thin,right] {line width is 0.4pt}; - \draw[-{2[length=5.46pt]}, line width=1.2pt] (6cm,-4em) -- +(3,0) node[thin,right] {line width is 1.2pt}; - \draw[-{2[length=14.56pt]}, line width=5pt] (6cm,-6em) -- +(3,0) node[thin,right] {line width is 5pt}; -\end{tikzpicture} - -\bigskip -As can be seen, simple scaling produces arrow tips that are way too large at -larger sizes and way too small at smaller sizes. - -In addition to the line width, other options may also influence the appearance -of an arrow tip. In particular, the width of the inner line (the line used to -create the effect of a double line) influences arrow tips as well as other -options that are specific to the arrow tip. - - -\subsection{Terminology} -\label{section-arrow-terminology} - -Before we have a look at the exact commands used for defining arrow tips, we -need to fix some terminology. Consider the following drawing of an arrow tip -where the arrow tip is drawn transparently so that we can see what is -``happening behind it'': -% -\begin{tikzpicture} - \draw [red!50, ,line width=1cm] (0,0) -- (4,0); - \path [tips, opacity=.25,line width=1cm, -{Stealth[black,line width=0pt,length=4cm, width=4cm, inset=1cm]}] (0,0) -- (6,0); - - \draw [->,thick] (1,0) -- (8,0) node [right] {$x$-axis}; - \draw [->,thick] (5,-2.25) -- (5,2.25) node [above] {$y$-axis}; - - \foreach \i in {-3,-2,-1,1,2} \draw (\i+5,-1mm) -- (\i+5,1mm) node [above] {\small$\i$}; - \foreach \i in {-2,-1,1,2} \draw (49mm,\i) -- (51mm,\i) node [right] {\small$\i$};; -\end{tikzpicture} - -I have also added a coordinate system. The code for drawing an arrow tip always -draws it in the way shown above: Pointing right along the $x$-axis. - -We will use the following terminology: -% -\begin{itemize} - \item The point where tip of the arrow ends is called the \emph{tip end}. - It is at $(1,0)$ in our example and we always assume it to lie on the - $x$-axis, so we just treat it as a distance, 1 in this case. This is - the position where the original path was supposed to end (so if the - arrow tip had not been added to the red path, it would have ended - here). - \item The \emph{back end} of the arrow is where a vertical line just to the - left of the arrow intersects the $x$-axis. In our case, this is the - point $(-3,0)$ and again we treat it as a distance, $-3$ in this case. - \item The \emph{line end} is the position where the path now ends. This - should be a position inside the arrow head that gets ``covered'' by the - path. Note that a path may have a round or a rect head and should still - be covered. Clearly, necessary shortening of the path will be the - difference between the tip end and the line end. - \item The \emph{visual back end} is the position where the path and the the - arrow head ``meet last'' on the path. In our case, because of the - inset, the visual back end is not the same as the back end: The arrow - ends ``visually'' at $(-2,0)$. The difference between the back end and - the visual back end is important when the arrow tip is flexed, see - Section~\ref{section-arrow-flex} for an explanation of flexing. - \item There is also a \emph{visual tip end}, the counterpart of the visual - back end for the front. In our case, the visual tip end and the tip end - obviously coincide, but if we were to reverse the arrow tip, the visual - tip end would be different from the tip end (while the visual back end - would then coincide with the new back end). - \item There are four points that make up the \emph{convex hull} of the - arrow tip: $(1,0)$, $(-3,2)$, and $(-3,-2)$. - - Normally, \pgfname\ automatically keeps track of a bounding box of - everything you draw. However, since arrow tips are drawn so often, - \pgfname\ caches the code needing for drawing arrow tips internally and - because of this cache it cannot determine the size of the arrow tip - just based on the drawing commands used for drawing the tip. Instead, a - convex hull of the arrow tip must be explicitly provided in the - definition. -\end{itemize} - -When you design a new arrow tip, all of the above parameters must be defined. - - -\subsection{Caching and Rendering of Arrows} - -As a last preparation for the description of the commands for declaring arrows, -it is important to understand the exact process by which \pgfname\ draws -arrows. -% -\begin{enumerate} - \item First, you have to define an arrow tip kind using - |\pgfdeclarearrow{name=foo,...|. This will tell \pgfname\ that |foo| is %} - now the name of an arrow tip. In particular, the parser for arrow tip - specifications will now treat |foo| as the name of an arrow tip and - will not try to consider |f|, |o|, and |o| as the names of single-char - shorthands. - - Other than storing the definitions in the declaration internally, this - command has little other effect. In particular, no drawing or other - processing takes place. - \item Now assume that at some point the arrow tip |foo| is actually used. - In this case, certain options may have been set, for instance the user - may have requested the arrow tip |foo[length=5pt,open]|. What happens - next depends on whether it is the first time the arrow tip |foo| is - used with \emph{these exact options} or not. - \item Assume that is the first time |foo| is requested at a length of 5pt - and in an ``open'' version. \pgfname\ now retrieves the definition of - the arrow tip kind that it stored in the first step and executes the - so-called \emph{setup} code. When this code is executed, all the - options will be in force (for instance, |\pgfarrowlength| will equal - |5pt| in our case). The job of the setup code is two-fold: First, it - needs to compute all of the parameters listed in - Section~\ref{section-arrow-terminology}, that is, it has to compute - where the tip end will lie in the arrow tip's coordinate system - \emph{at the particular size of 5pt}, where the back end will be, where - the convex hull points lie, and so on. Second, the setup code should - precompute values that will be important for constructing the path of - the arrow. In our example, there is little to do in this regard, but - for more complicated arrows, all time-consuming preparations are done - now. - - It is \emph{not} the job of the setup to actually draw the arrow tip, - only to ``prepare'' this as much as possible. - - The setup code will always be executed only once for each arrow tip - kind for a given set of options. Thus, when a user uses - |foo[length=5pt,open]| once more later anywhere in the document, the - setup code will not be executed again. - \item The next thing that happens is that we have a look at the - \emph{drawing code} stored in the |code| field of the arrow. In our - example, the drawing code would consist of creating a filled path with - four straight segments. - - In most cases, what happens now is that the drawing code is executed in - a special sandbox in which the low-level driver commands that do the - actual drawing are intercepted and stored away in a so-called - \emph{cache}. Once such a cache has been created, its contents will be - reused whenever |foo[length=5pt,open]| is requested by a user and just - like the setup code, the drawing code will not be executed again. - - There are, however, two cases in which the drawing code gets executed - each time the arrow is used: First, an arrow tip kind can specify that - this should always happen by saying |cachable=false| in its definition. - This is necessary if the drawing code contains low-level drawing - commands that cannot be intercepted such as a use of |\pgftext| for - arrow tips that ``contain text''. Second, when the |bend| option is - used, the same arrow tip will look different each time it is used, - namely in dependence on the exact curvature of the path to which it is - added. - - Because the drawing code may be executed several times, while the setup - code may not, we must find a way to ``communicate'' the values computed - by the setup code to the drawing code. This is done by explicitly - calling |\pgfarrowssave| inside the setup code. Whatever is ``saved'' - in this way is restored each time before the drawing code is executed. -\end{enumerate} - -As can be seen, the process is a bit involved, but it leads to a reasonably -fast arrow tip management. - - -\subsection{Declaring an Arrow Tip Kind} - -\begin{command}{\pgfdeclarearrow\marg{config}} - This command is both used to define a new arrow tip kind and to to declare - a so-called shorthand. We have a look at the case that a complete new arrow - tip kind is created and then have a look how the command can be used to - create shorthands. - - - \medskip - \noindent\textbf{Defining a Complete New Arrow Tip Kind.} - The \meta{config} is a key--value list in which different keys are used to - setup the to-be defined arrow. The following keys can be given: - % - \begin{itemize} - \item \declare{|name|}|=|\meta{name} or |name=|\meta{start - name}|-|\meta{end name} - - This defines the name of the arrow tip. It is legal to define an - arrow tip a second time, in this case the previous definition will - be overwritten in the current \TeX\ scope. It is customary to use a - name with an uppercase first letter for a ``complete'' arrow tip - kind. Short names and lower case names should be used for - shorthands that change their meaning inside a document, while arrow - tips with uppercase first letters should not be redefined. - - If the name contains a hyphen, the second syntax is assumed and - everything before the hyphen will be the name used in start arrow - specifications, while the text after the hyphen is the name used in - end specifications. - \item \declare{|parameters|}|=|\marg{list of macros} - - As explained earlier, an arrow tip typically needs to be redrawn - each time an option like |length| or |inset| is changed. However, - for some arrow tips, the |inset| has no influence, while for other - it is important whether the arrow is reversed or not. (How keys - like |length| actually set \TeX\ dimensions like |\pgfarrowlength| - is explained in Section~\ref{section-arrow-options}.) - - The job of the |parameters| key is to specify which dependencies - the arrow tip has. Everything that will influence any of the - parameters computed in the setup code or used in the drawing code - should be listed here. - - The \meta{list of macros} will be used inside a - |\csname|-|\endcsname| pair and should expand to the current values - of the relevant parameters have. For example, if the arrow tip - depends on the current value of |\pgfarrowlength| and - |\pgfarrowwidth| only, then \meta{list of macros} should be set to - |\the\pgfarrowlength,\the\pgfarrowwidth|. (Actually, the comma is - optional, the \meta{list of macros} does not really have to be a - list, just something that can be expanded unambiguously.) - - Note that the line width (|\pgflinewidth|) and the inner line width - (|\pgfinnerlinewidth|) are always parameters and need not be - specified in the |parameters|. - - It is important to get this parameter right. Otherwise, arrow tips - may look wrong because \pgfname\ thinks that it can reuse some code - when, in reality, this code actually depends on a parameter not - listed here. - \item \declare{|setup code|}|=|\marg{code} - - When an arrow tip is used, the value stored in |parameters| is - expanded and it is tested whether the result was encountered - before. If not, the \meta{code} gets executed (only this once). The - code can now do arbitrarily complicated computations the prepare - the later drawing of the arrow tip. Also the \meta{code} must - specify the different tip and back ends and the convex hull points. - This is done by calling the following macros inside the - \meta{code}: - % - \begin{command}{\pgfarrowssettipend\marg{dimension}} - When this command is called inside the setup code of an arrow - tip, it specifies that the tip of the drawn arrow will end - exactly at \meta{dimension}. For example, for our earlier - example of the large arrow tip, where the tip end was at 1cm, - we would call - % -\begin{codeexample}[code only] -\pgfarrowssettipend{1cm} -\end{codeexample} - % - Note that for efficiency reasons, the \meta{dimension} is not - passed through |\pgfmathsetlength|; rather what happens is that - |\pgf@x=|\meta{dimension} gets executed. In particular, you can - pack further computations into the \meta{dimension} by simply - starting it with a number and then appending some code that - modifies |\pgf@x|. Here is an example where instead of 1cm we - use $1\mathrm{cm} - \frac12\mathrm{linewidth}$ as the tip end: - % -\begin{codeexample}[code only] -\pgfarrowssettipend{1cm\advance\pgf@x by-.5\pgflinewidth} -\end{codeexample} - % - If the command is not called at all inside the setup code, the - tip end is set to |0pt|. - \end{command} - - \begin{command}{\pgfarrowssetbackend\marg{dimension}} - Works like the command for the tip end, only it sets the back - end. In our example we would call - % -\begin{codeexample}[code only] -\pgfarrowssettipend{-3cm} -\end{codeexample} - % - Defaults to |0pt|. - \end{command} - - \begin{command}{\pgfarrowssetlineend\marg{dimension}} - Sets the line end, so in the example we have - |\pgfarrowssettipend{-1cm}|. Default to |0pt|. - \end{command} - - \begin{command}{\pgfarrowssetvisualbackend\marg{dimension}} - Sets the visual back end, |\pgfarrowssetvisualbackend{-2cm}| in - our example. Default to the value of the normal back end. - \end{command} - - \begin{command}{\pgfarrowssetvisualtipend\marg{dimension}} - Sets the visual tip end. Default to the value of the normal tip - end and, thus, we need not set it in our example. - \end{command} - - \begin{command}{\pgfarrowshullpoint\marg{x dimension}\marg{y dimension}} - Adds a point to the convex hull of the arrow tip. As for the - previous commands, no math parsing is done; instead \pgfname\ - says |\pgf@x=|\meta{x dimension} and then |\pgf@y=|\meta{y - dimension}. Thus, both ``dimensions'' can contain code for - advancing and thus modifying |\pgf@x| and |\pgf@y|. - - In our example we would write - % -\begin{codeexample}[code only] -\pgfarrowshullpoint{1cm}{0pt} -\pgfarrowshullpoint{-3cm}{2cm} -\pgfarrowshullpoint{-3cm}{-2cm} -\end{codeexample} - \end{command} - - \begin{command}{\pgfarrowsupperhullpoint\marg{x dimension}\marg{y dimension}} - This command works like the previous command, only it normally - adds \emph{two} points to the convex hull: First, the point - $(\meta{x dimension},\meta{y dimension})$ and, secondly, the - point $(\meta{x dimension},-\meta{y dimension})$. However, the - second point is only added if the arrow is not a harpoon. - - Thus, in our example we could simplify the convex hull to - % -\begin{codeexample}[code only] -\pgfarrowshullpoint{1cm}{0pt} -\pgfarrowsupperhullpoint{-3cm}{2cm} -\end{codeexample} - % - If the \meta{y dimension} is zero or less, only one point, - namely $(\meta{x dimension},\meta{y dimension})$, is added to - the hull. Thus, we could also have used the upper convex hull - command in the first of the two of the above commands. - \end{command} - - \begin{command}{\pgfarrowssave\marg{macro}} - As explained earlier, the setup code needs to ``communicate'' - with the drawing code via ``saved values''. This command get - the name of a macro and will store the value this macro had - internally. Then, each time drawing code is executed, the value - of this macro will be restored. - \end{command} - - \begin{command}{\pgfarrowssavethe\marg{register}} - Works like |\pgfarrowssave|, only the parameter must be a - register and |\the|\meta{register} will be saved. Typically, - you will write something like - % -\begin{codeexample}[code only] -\pgfarrowssavethe{\pgfarrowlength} -\pgfarrowssavethe{\pgfarrowwidth} -\end{codeexample} - % - To ensure that inside the drawing code the the dimension - registers |\pgfarrowlength| and |\pgfarrowwidth| are setup with - the values they had during the setup. - \end{command} - \item \declare{|drawing code|}|=|\marg{code} - - This code will be executed at least once for each setting of the - parameters when the time arrow tip is actually drawn. Usually, this - one execution will be all and the low-level commands generated - inside the \meta{code} will we stored in a special cache; but in - some cases the \meta{code} gets executed each time the arrow tip is - used, so do not assume anything about it. Inside the \meta{code}, - you have access to all values that were saved in the setup code as - well as to the line width. - - The \meta{code} should draw the arrow tip ``going right along the - $x$-axis''. \pgfname\ will take care of setting up a canvas - transformation beforehand to a rotation such that when the drawing - is rendered, the arrow tip that is actually drawn points in the - direction of the line. Alternatively, when bending is switched on, - even more complicated low-level transformations will be done - automatically. - - The are some special considerations concerning the \meta{code}: - % - \begin{itemize} - \item In the \meta{code} you may \emph{not} use |\pgfusepath| - since this would try to add arrow tips to the arrow tip and - lead to a recursion. Use the ``quick'' versions - |\pgfusepathqstroke| and so on instead, which never try to - add arrow tips. - \item If you stroke the path that you construct, you should - first set the dashing to solid and set up fixed joins and - caps, as needed. This will ensure that the arrow tip will - always look the same. - \item When the arrow tip code is executed, it is automatically - put inside a low-level scope, so nothing will ``leak out'' - from the scope. - \item The high-level coordinate transformation matrix will be - set to the identity matrix when the code is executed for - the first time. - \end{itemize} - \item \declare{|cache|}|=|\meta{true or false} - - When set to |true|, which is the default, the \meta{code} will be - executed only once for a particular value of parameters and the - low-level commands created by the drawing code (using the system - layer protocol subsystem, see Section~\ref{section-protocols}) will - be cached and reused later on. However, when the drawing code - contains ``uncachable'' code like a call to |\pgftext|, caching - must be switched off by saying |cache=false|. - \item \declare{|bending mode|}|=|\meta{mode} - - This key is important only when the |bend| option is used with an - arrow, see Section~\ref{section-arrow-flex} for an introduction to - this option. The |bend| option asks us to, well, bend the arrow - head. For some arrow head this is not possible or leads to very - strange drawings (for instance, when the |\pgftext| command is - used) and then it is better to switch bending off for the arrow - head (|flex| will then be used instead). To achieve this, set - \meta{mode} to |none|. - - For most arrow tips it does, however, make sense to bend them. - There are (at least) two different mathematical ways of doing so, - see Section~\ref{section-library-curvilinear} for details. Which of - these ways is use can be configured by setting \meta{mode} to - either |orthogonal| or to |polar|. It is best to try simply try out - both when designing an arrow tip to see which works better. Since - |orthogonal| is quicker and often gives good oder even better - results, it is the default. Some arrow tips, however, profit from - saying |bending mode=polar|. - \item \declare{|defaults|}|=|\meta{arrow keys} - - The \meta{arrow keys} allow you to configure the default values for - the parameters on which an arrow tip depends. The \meta{arrow keys} - will be executed first before any other arrow tip options are - executed, see Section~\ref{section-arrow-scopes} for the exact - sequence. Also see Section~\ref{section-arrow-options} below for - more details on arrow options. - \end{itemize} - - This concludes the description of the keys you provide for the declaration - of an arrow. Let us now have a look at a simple example that uses these - features: We want to define an arrow tip kind |foo| that produces the arrow - tip we used as our running example. However, to make things a bit more - interesting, let us make it ``configurable'' insofar as the length of the - arrow tip can be configured using the |length| option, which sets the - |\pgfarrowlength|. By default, this length should be the gigantic 4cm we - say in the example, but uses should be able to set it to anything they - like. We will not worry about the arrow width or insets, of arrow line - width, or harpoons, or anything else in this example to keep it simple. - - Here is the code: - % -\begin{codeexample}[code only] -\pgfdeclarearrow{ - name = foo, - parameters = { \the\pgfarrowlength }, - setup code = { - % The different end values: - \pgfarrowssettipend{.25\pgfarrowlength} - \pgfarrowssetlineend{-.25\pgfarrowlength} - \pgfarrowssetvisualbackend{-.5\pgfarrowlength} - \pgfarrowssetbackend{-.75\pgfarrowlength} - % The hull - \pgfarrowshullpoint{.25\pgfarrowlength}{0pt} - \pgfarrowshullpoint{-.75\pgfarrowlength}{.5\pgfarrowlength} - \pgfarrowshullpoint{-.75\pgfarrowlength}{-.5\pgfarrowlength} - % Saves: Only the length: - \pgfarrowssavethe\pgfarrowlength - }, - drawing code = { - \pgfpathmoveto{\pgfqpoint{.25\pgfarrowlength}{0pt}} - \pgfpathlineto{\pgfqpoint{-.75\pgfarrowlength}{.5\pgfarrowlength}} - \pgfpathlineto{\pgfqpoint{-.5\pgfarrowlength}{0pt}} - \pgfpathlineto{\pgfqpoint{-.75\pgfarrowlength}{-.5\pgfarrowlength}} - \pgfpathclose - \pgfusepathqfill - }, - defaults = { length = 4cm } -} -\end{codeexample} - % - We can now use it: - % -\pgfdeclarearrow{ - name = foo, - parameters = { \the\pgfarrowlength }, - setup code = { - % The different end values: - \pgfarrowssettipend{.25\pgfarrowlength} - \pgfarrowssetlineend{-.25\pgfarrowlength} - \pgfarrowssetvisualbackend{-.5\pgfarrowlength} - \pgfarrowssetbackend{-.75\pgfarrowlength} - % The hull - \pgfarrowshullpoint{.25\pgfarrowlength}{0pt} - \pgfarrowshullpoint{-.75\pgfarrowlength}{.5\pgfarrowlength} - \pgfarrowshullpoint{-.75\pgfarrowlength}{-.5\pgfarrowlength} - % Saves: Only the length: - \pgfarrowssavethe\pgfarrowlength - }, - drawing code = { - \pgfpathmoveto{\pgfqpoint{.25\pgfarrowlength}{0pt}} - \pgfpathlineto{\pgfqpoint{-.75\pgfarrowlength}{.5\pgfarrowlength}} - \pgfpathlineto{\pgfqpoint{-.5\pgfarrowlength}{0pt}} - \pgfpathlineto{\pgfqpoint{-.75\pgfarrowlength}{-.5\pgfarrowlength}} - \pgfpathclose - \pgfusepathqfill - }, - defaults = { length = 4cm } -} -\begin{codeexample}[ - preamble={\usetikzlibrary{arrows.meta}}, - pre={\pgfdeclarearrow{ - name = foo, - parameters = { \the\pgfarrowlength }, - setup code = { - % The different end values: - \pgfarrowssettipend{.25\pgfarrowlength} - \pgfarrowssetlineend{-.25\pgfarrowlength} - \pgfarrowssetvisualbackend{-.5\pgfarrowlength} - \pgfarrowssetbackend{-.75\pgfarrowlength} - % The hull - \pgfarrowshullpoint{.25\pgfarrowlength}{0pt} - \pgfarrowshullpoint{-.75\pgfarrowlength}{.5\pgfarrowlength} - \pgfarrowshullpoint{-.75\pgfarrowlength}{-.5\pgfarrowlength} - % Saves: Only the length: - \pgfarrowssavethe\pgfarrowlength - }, - drawing code = { - \pgfpathmoveto{\pgfqpoint{.25\pgfarrowlength}{0pt}} - \pgfpathlineto{\pgfqpoint{-.75\pgfarrowlength}{.5\pgfarrowlength}} - \pgfpathlineto{\pgfqpoint{-.5\pgfarrowlength}{0pt}} - \pgfpathlineto{\pgfqpoint{-.75\pgfarrowlength}{-.5\pgfarrowlength}} - \pgfpathclose - \pgfusepathqfill - }, - defaults = { length = 4cm } -}}, -] -\tikz \draw [-foo] (0,0) -- (8,0); -\end{codeexample} -\begin{codeexample}[ - preamble={\usetikzlibrary{arrows.meta,bending}}, - pre={\pgfdeclarearrow{ - name = foo, - parameters = { \the\pgfarrowlength }, - setup code = { - % The different end values: - \pgfarrowssettipend{.25\pgfarrowlength} - \pgfarrowssetlineend{-.25\pgfarrowlength} - \pgfarrowssetvisualbackend{-.5\pgfarrowlength} - \pgfarrowssetbackend{-.75\pgfarrowlength} - % The hull - \pgfarrowshullpoint{.25\pgfarrowlength}{0pt} - \pgfarrowshullpoint{-.75\pgfarrowlength}{.5\pgfarrowlength} - \pgfarrowshullpoint{-.75\pgfarrowlength}{-.5\pgfarrowlength} - % Saves: Only the length: - \pgfarrowssavethe\pgfarrowlength - }, - drawing code = { - \pgfpathmoveto{\pgfqpoint{.25\pgfarrowlength}{0pt}} - \pgfpathlineto{\pgfqpoint{-.75\pgfarrowlength}{.5\pgfarrowlength}} - \pgfpathlineto{\pgfqpoint{-.5\pgfarrowlength}{0pt}} - \pgfpathlineto{\pgfqpoint{-.75\pgfarrowlength}{-.5\pgfarrowlength}} - \pgfpathclose - \pgfusepathqfill - }, - defaults = { length = 4cm } -}}, -] -\tikz \draw [-{foo[length=2cm,bend]}] (0,0) to [bend left] (3,0); -\end{codeexample} - - - \medskip - \noindent\textbf{Defining a Shorthand.} - The |\pgfdeclarearrow| command can also used to define - \emph{shorthands}. This works as follows: - \begin{itemize} - \item First, you must provide a |name| just in the same way as when you - define a full-flung new arrow tip kind. - \item Second, instead of all of the other options listed above, you - just use one more option: - - \smallskip - \declare{|means|}|=|\meta{end arrow specification} - - This sets up things so that whenever \meta{name} is now used in an - arrow specification, it will be replaced by the \meta{end arrow - specification} (the problems resulting form the \meta{name} begin - used in a start arrow specification are taken care of - automatically). See also Section~\ref{section-arrow-tip-macro} for - details on the order in which options get executed in such cases. - - Note that the \meta{end arrow specification} will be executed - immediately to build the so-called arrow option caches, a concept - explored in more detail in - Section~\ref{section-arrow-option-cache}. In practice, this has - mainly two effects: First, all arrow tips referred to in the - specification must already exist (at least as ``dummy'' versions). - Second, all dimensions mentioned in options of the \meta{end arrow - specification} will be evaluated immediately. For instance, when - you write - % -\begin{codeexample}[code only] -\pgfdeclarearrow{ name=foo, means = bar[length=2cm+\mydimen] } -\end{codeexample} - % - The value |2cm+\mydimen| is evaluated immediately. When |foo| is - used later on and |\mydimen| has changed, this has no effect. - \end{itemize} -\end{command} - - -\subsection{Handling Arrow Options} -\label{section-arrow-options} - -When you declare an arrow tip, your drawing code should take into account the -different arrow keys set for it (like the arrow tip length, width, or -harpooning). The different arrow keys that are available have been described in -detail in Section~\ref{section-arrow-config}; but how do we access the values -set by an option like |length| or |harpoon| or |bend| in the drawing code? In -the present section we have a look at how this works. - - -\subsubsection{Dimension Options} - -Most arrow keys, like |length| or |width'|, simple set a \TeX\ dimension -register to a certain value. For example, |length| sets the value of the \TeX\ -dimension register |\pgfarrowlength|. Note that |length| takes several values -as input with a complicated semantics as explained for the |length| key on -page~\pageref{length-arrow-key}. All of these settings are not important for -the setup code: When it gets executed, the code behind the |length| key will -have computed a simple number that is stored in |\pgfarrowlength|. Indeed, -inside the setup code you do not have access to the exact value given to the -|length| key; just to the final computed value. - -The following \TeX\ dimensions are available to the setup code: -% -\begin{itemize} - \item |\pgfarrowslength|. It gets set by the arrow keys |length| and - |angle|. - \item |\pgfarrowswidth|. It gets set by |width|, |width'|, and |angle|. - \item |\pgfarrowsinset|. It gets set by |inset| and |inset'|. - \item |\pgfarrowslinewidth|. It gets set by |line width| and |line width'|. -\end{itemize} - -If your setup code depends on any of them, add them to the |parameters| key of -the arrow tip. - - -\subsubsection{True--False Options} - -A number of arrow keys just do a yes/no switch, like |reversed|. All of them -setup a \TeX-if that you can access in the setup code: -% -\begin{itemize} - \item |\ifpgfarrowreversed| is setup by |reversed|. - \item |\ifpgfarrowswap| is setup by |swap| and also |right|. - \item |\ifpgfarrowharpoon| is setup by |harpoon| and also |left| and - |right|. - \item |\ifpgfarrowroundcap| is set to true by |line cap=round| and set to - false by |line cap=butt|. It also gets (re)set by |round| and |sharp|. - \item |\ifpgfarrowroundjoin| is set to true by |line join=round| and set to - false by |line join=miter|. It also gets (re)set by |round| and - |sharp|. - \item |\ifpgfarrowopen| is set to true by |fill=none| and by |open| (which - is a shorthand for |fill=none|) and set to false by |color| and all - other |fill=|\meta{color}. -\end{itemize} - -If you code depends on any of these, you must add them to the |parameters| in -such a way that the parameters are different when the \TeX-if is set from when -it is not set. An easy way to achieve this is to write something like -% -\begin{codeexample}[code only] - parameters = { \the\pgfarrowlength,..., - \ifpgfarrowharpoon h\fi\ - \ifpgfarrowroundjoin j\fi} -\end{codeexample} -% -In other words, for each set parameter on which the arrow tip depends, a -specific letter is added to the parameters, making them unique. - -The first two of the above keys are a bit special: Reversing and swapping an -arrow tip can be done just by fiddling with the transformation matrix: a -reverse is a ``flip'' along the $y$-axis and a swap is a flip along the -$x$-axis. This is done automatically by \pgfname. - -Nevertheless, you may wish to modify you code in dependence especially of the -|reverse| key: When |\ifpgfarrowreverse| is true, \pgfname\ will flip the -coordinate system along the $y$-axis, will negate all end values (like line -end, tip end, and so on) and will exchange the meaning of back end and tip end -as well as of visual back end and visual back end. Usually, this is exactly -what one need; \emph{except} that the line end may no longer be appropriate. -After all, the line end should be chosen so that it is completely covered by -the arrow. Now, when the arrow tip is open, a reversed arrow should no longer -have the line end near the old visual back end, but near to the old visual tip -end. - -For these reasons, you may need to make the computation of the line end -dependent on whether the arrow is reversed or not. Note that when you specify a -different line end for a reversed arrow tip, the transformation and inverting -of the coordinate system will still be done, meaning that if |reverse| is true, -you need to specify a line end in the ``old'' coordinate system that is at the -position where, after everything is inverted, it will be at the correct -position. Usually that means that if the |reverse| option is set, you need to -\emph{increase} the line end. - - -\subsubsection{Inaccessible Options} - -There are some options that influence the way an arrow tip looks, but that you -cannot access inside the setup code. Handling these options lies entirely with -\pgfname. If you wish your setup code to handle these options, you have to -setup your own ``parallel'' options. -% -\begin{itemize} - \item |quick|, |flex|, |flex'|, and |bend| are all handled automatically. - You can, however, set the |bending mode| to avoid bending of your arrow - tip. - \item The colors set by |color| and |fill|. You can, however, access them - indirectly, namely through the current stroke and fill colors. - \item |sep| -\end{itemize} - - -\subsubsection{Defining New Arrow Keys} -\label{section-arrow-option-cache} - -The set of predefined options is already quite long and most arrow tips will -not need more than the predefined options. However, sometimes an arrow tip may -need to introduce a new special-purpose option. For instance, suppose we wish -to introduce a new fictive arrow key |depth|. In such cases, you must do two -things: -% -\begin{enumerate} - \item Introduce a new dimension register or macro that will hold the - configuration value and which will be accessed by the setup code. The - could be achieved by saying - % -\begin{codeexample}[code only] -\newdimen\pgfarrowdepth -\end{codeexample} - % - \item Introduce a new arrow key option |/pgf/arrow keys/depth| that allows - users to configure the new macro or register. -\end{enumerate} - -When an arrow is selected via for instance |foo[depth=5pt]|, the key--value -pairs between the square brackets are executed with the path prefix -|/pgf/arrow keys|. Thus, in the example, our depth key would get executed. -Thus, it is tempting to write something like -% -\begin{codeexample}[code only] -\pgfkeys{/pgf/arrow keys/depth/.code = \pgfmathsetlength{\pgfarrowdepth}{#1}} -\end{codeexample} - -Sadly, this will not work. The reason is that there is yet another level of -caching involved when \pgfname\ processes arrow tips: The option cache! The -problem is each time an arrow tip is used, even when the drawing code of the -arrow tip is nicely cached, we still need to process the options in -|foo[length=5pt]| to find out which version in the cache we would like to -access. To make matters worse, |foo| might be a shorthand that calls other -arrow tips, which add more options, and so on. Unfortunately, executing keys is -quite an expensive operation (\pgfname's key--value parser is powerful, but -that power comes at a price). So, whenever possible, we do \emph{not} want the -key--value parser to be started. - -For these reasons, when something like |foo[|\meta{options}|]| is encountered -inside a shorthand, the \meta{options} are executed only once. They should now -setup the \emph{arrow option cache}, which is some code that, when executed, -should setup the values that the \meta{options} configure. In our example, the -|depth| key should add something to the arrow option cache that sets -|\pgfarrowdepth| to the given value. - -Adding something to the arrow option cache is done using the following command: - -\begin{command}{\pgfarrowsaddtooptions\marg{code}} - This command should be called by keys with the prefix |/pgf/arrow keys| to - add code to the arrow option cache. For our |depth| key example, we could - use this key as follows: - % -\begin{codeexample}[code only] -\pgfkeys{/pgf/arrow keys/depth/.code= - \pgfarrowsaddtooptions{\pgfmathsetlength{\pgfarrowdepth}{#1}} -\end{codeexample} - % - Actually, this is still not optimal since the expensive |\pgfmathsetlength| - command is now called each time an arrow tip is used with the |depth| - option set. The trick is to do the expensive operation only once and then - store only very quick code in the arrow option cache: - % -\begin{codeexample}[code only] -\pgfkeys{/pgf/arrow keys/depth/.code= - \pgfmathsetlength{\somedimen}{#1} - \pgfarrowsaddtooptions{\pgfarrowdepth=\somedimen} % buggy -\end{codeexample} - % - The above code will not (yet) work since |\somedimen| will surely have a - different value when the cache is executed. The trick is to use some - |\expandafter|s: - % -\begin{codeexample}[code only] -\pgfkeys{/pgf/arrow keys/depth/.code= - \pgfmathsetlength{\somedimen}{#1} - \expandafter\pgfarrowsaddtooptions\expandafter{\expandafter\pgfarrowdepth\expandafter=\the\somedimen} -\end{codeexample} - % -\end{command} - -\begin{command}{\pgfarrowsaddtolateoptions\marg{code}} - This command works like |\pgfarrowsaddtooptions|, only the \meta{code} will - be executed ``later'' than the code added by the normal version of the - command. This is useful for keys that depend on the length of an arrow: - Keys like |width'| want to define the arrow width as a multiple of the - arrow length, but when the |width'| key is given, the length may not yet - have been specified. By making the computation of the width a ``late'' - option, we ensure that |\pgfarrowlength| will have been setup correctly. -\end{command} - -If you define a new option that sets a dimensions and if that dimension should -change in accordance to the setting of either |scale length| or |scale width|, -you need to make \pgfname\ ``aware'' of this using the following key: - -\begin{command}{\pgfarrowsaddtolengthscalelist\marg{dimension register}} - Each time an arrow tip is used, the given \meta{dimension register} will be - multiplied by the |scale length| factor prior to the actual drawing. You - call this command only once in the preamble somewhere. -\end{command} - -\begin{command}{\pgfarrowsaddtowidthscalelist\marg{dimension register}} - Works like |\pgfarrowsaddtolengthscalelist|, only for width parameters. -\end{command} - - -\begin{command}{\pgfarrowsthreeparameters\marg{line-width dependent size specification}} - This command is useful for parsing the values given to keys like |length| - or |width| the expect a dimension followed optionally for some numbers. - This command converts the \meta{line-width dependent size specification}, - which may consist of one, two, or three numbers, into a triple of three - numbers in curly braces, which gets stored in the macro - |\pgfarrowstheparameters|. Here is an example, where |\showvalueofmacro| is - used in this example to show the value stored in a macro: - % -\begin{codeexample}[setup code,hidden] - \makeatletter - \def\showvalueofmacro#1{% - \texttt{\expandafter\expandafter\expandafter\expandafter\expandafter\expandafter\expandafter\pgfutil@gobble\expandafter\expandafter\expandafter\string\expandafter\csname#1\endcsname} - }% -\end{codeexample} -% -\begin{codeexample}[] -\pgfarrowsthreeparameters{2pt 1} -\showvalueofmacro\pgfarrowstheparameters -\end{codeexample} - % -\end{command} - -\begin{command}{\pgfarrowslinewidthdependent\marg{dimension}\marg{line width factor}\marg{outer factor}} - This command takes three parameters and does the ``line width dependent - computation'' described on page~\pageref{length-arrow-key} for the |length| - key. The result is returned in |\pgf@x|. - - The idea is that you can setup line-width dependent keys like |length| or - |width| using code like the following: - % -\begin{codeexample}[code only] -\pgfkeys{/pgf/arrow keys/depth/.code={% - \pgfarrowsthreeparameters{#1}% - \expandafter\pgfarrowsaddtolateoptions\expandafter{% - \expandafter\pgfarrowslinewidthdependent\pgfarrowstheparameters% compute... - \pgfarrowdepth\pgf@x% ... and store. - }% -} -\end{codeexample} - % -\end{command} - -\begin{command}{\pgfarrowslengthdependent\marg{dimension}\marg{length factor}\marg{dummy}} - This command takes three parameters, of which the last one is ignored, and - does the ``length dependent computation'' described for the |width'| and - |inset'| keys. The result is returned in |\pgf@x|. - - You can setup length dependent keys using code like the following: - % -\begin{codeexample}[code only] -\pgfkeys{/pgf/arrow keys/depth'/.code={% - \pgfarrowsthreeparameters{#1}% - \expandafter\pgfarrowsaddtolateoptions\expandafter{% - \expandafter\pgfarrowslengthdependent\pgfarrowstheparameters% compute... - \pgfarrowdepth\pgf@x% ... and store. - }% -} -\end{codeexample} - % -\end{command} - - -%%% Local Variables: -%%% mode: latex -%%% TeX-master: "pgfmanual" -%%% End: -- cgit v1.2.3