diff options
Diffstat (limited to 'graphics/pgf/base/doc/pgfmanual-en-base-actions.tex')
| -rw-r--r-- | graphics/pgf/base/doc/pgfmanual-en-base-actions.tex | 530 |
1 files changed, 530 insertions, 0 deletions
diff --git a/graphics/pgf/base/doc/pgfmanual-en-base-actions.tex b/graphics/pgf/base/doc/pgfmanual-en-base-actions.tex new file mode 100644 index 0000000000..8a6fff31cb --- /dev/null +++ b/graphics/pgf/base/doc/pgfmanual-en-base-actions.tex @@ -0,0 +1,530 @@ +% Copyright 2019 by Till Tantau +% +% This file may be distributed and/or modified +% +% 1. under the LaTeX Project Public License and/or +% 2. under the GNU Free Documentation License. +% +% See the file doc/generic/pgf/licenses/LICENSE for more details. + + +\section{Using Paths} + +\subsection{Overview} + +Once a path has been constructed, it can be \emph{used} in different ways. For +example, you can draw the path or fill it or use it for clipping. + +Numerous graph parameters influence how a path will be rendered. For example, +when you draw a path, the line width is important as well as the dashing +pattern. The options that govern how paths are rendered can all be set with +commands starting with |\pgfset|. \emph{All options that influence how a path +is rendered always influence the complete path.} Thus, it is not possible to +draw part of a path using, say, a red color and drawing another part using a +green color. To achieve such an effect, you must use two paths. + +In detail, paths can be used in the following ways: +% +\begin{enumerate} + \item You can \emph{stroke} (also known as \emph{draw}) a path. + \item You can add \emph{arrow tips} to a path. + \item You can \emph{fill} a path with a uniform color. + \item You can \emph{clip} subsequent renderings against the path. + \item You can \emph{shade} a path. + \item You can \emph{use the path as bounding box} for the whole picture. +\end{enumerate} +% +You can also perform any combination of the above, though it makes no sense to +fill and shade a path at the same time. + +To perform (a combination of) the first four actions, you can use the following +command: +% +\begin{command}{\pgfusepath\marg{actions}} + Applies the given \meta{actions} to the current path. Afterwards, the + current path is (globally) empty. The following actions are possible: + % + \begin{itemize} + \item \declare{|fill|} fills the path. See Section~\ref{section-fill} + for further details. + % +\begin{codeexample}[] +\begin{pgfpicture} + \pgfpathmoveto{\pgfpointorigin} + \pgfpathlineto{\pgfpoint{1cm}{1cm}} + \pgfpathlineto{\pgfpoint{1cm}{0cm}} + \pgfusepath{fill} +\end{pgfpicture} +\end{codeexample} + % + \item \declare{|stroke|} strokes the path. See + Section~\ref{section-stroke} for further details. + % +\begin{codeexample}[] +\begin{pgfpicture} + \pgfpathmoveto{\pgfpointorigin} + \pgfpathlineto{\pgfpoint{1cm}{1cm}} + \pgfpathlineto{\pgfpoint{1cm}{0cm}} + \pgfusepath{stroke} +\end{pgfpicture} +\end{codeexample} + % + \item \declare{|draw|} has the same effect as |stroke|. + \item \declare{|clip|} clips all subsequent drawings against the path. + Always suppresses arrow tips. See Section~\ref{section-clip} for + further details. + % +\begin{codeexample}[] +\begin{pgfpicture} + \pgfpathmoveto{\pgfpointorigin} + \pgfpathlineto{\pgfpoint{1cm}{1cm}} + \pgfpathlineto{\pgfpoint{1cm}{0cm}} + \pgfusepath{stroke,clip} + \pgfpathcircle{\pgfpoint{1cm}{1cm}}{0.5cm} + \pgfusepath{fill} +\end{pgfpicture} +\end{codeexample} + % + \item \declare{|discard|} discards the path, that is, it is not used at + all. Giving this option (alone) has the same effect as giving an + empty options list. + \end{itemize} + % + When more than one of the first three actions are given, they are applied + in the above ordering, regardless of their ordering in \meta{actions}. + Thus, |{stroke,fill}| and |{fill,stroke}| have the same effect. +\end{command} + +To shade a path, use the |\pgfshadepath| command, which is explained in +Section~\ref{section-shadings}. + + +\subsection{Stroking a Path} +\label{section-stroke} + +When you use |\pgfusepath{stroke}| to stroke a path, several graphic parameters +influence how the path is drawn. The commands for setting these parameters are +explained in the following. + +Note that all graphic parameters apply to the path as a whole, never only to a +part of it. + +All graphic parameters are local to the current |{pgfscope}|, but they persists +past \TeX\ groups, \emph{except} for the interior rule (even-odd or nonzero) +and the arrow tip kinds. The latter graphic parameters only persist till the +end of the current \TeX\ group, but this may change in the future, so do not +count on this. + + +\subsubsection{Graphic Parameter: Line Width} + +\begin{command}{\pgfsetlinewidth\marg{line width}} + This command sets the line width for subsequent strokes (in the current + |pgfscope|). The line width is given as a normal \TeX\ dimension like + |0.4pt| or |1mm|. + % +\begin{codeexample}[] +\begin{pgfpicture} + \pgfsetlinewidth{1mm} + \pgfpathmoveto{\pgfpoint{0mm}{0mm}} + \pgfpathlineto{\pgfpoint{2cm}{0mm}} + \pgfusepath{stroke} + \pgfsetlinewidth{2\pgflinewidth} % double in size + \pgfpathmoveto{\pgfpoint{0mm}{5mm}} + \pgfpathlineto{\pgfpoint{2cm}{5mm}} + \pgfusepath{stroke} +\end{pgfpicture} +\end{codeexample} + % +\end{command} + +\begin{textoken}{\pgflinewidth} + You can access the current line width via the \TeX\ dimension + |\pgflinewidth|. It will be set to the correct line width, that is, even + when a \TeX\ group closed, the value will be correct since it is set + globally, but when a |{pgfscope}| closes, the value is set to the correct + value it had before the scope. +\end{textoken} + + +\subsubsection{Graphic Parameter: Caps and Joins} + +\begin{command}{\pgfsetbuttcap} + Sets the line cap to a butt cap. See Section~\ref{section-cap-joins} for an + explanation of what this is. +\end{command} +% +\begin{command}{\pgfsetroundcap} + Sets the line cap to a round cap. See again Section~\ref{section-cap-joins}. +\end{command} +\begin{command}{\pgfsetrectcap} + Sets the line cap to a square cap. See again Section~\ref{section-cap-joins}. +\end{command} +% +\begin{command}{\pgfsetroundjoin} + Sets the line join to a round join. See again Section~\ref{section-cap-joins}. +\end{command} +% +\begin{command}{\pgfsetbeveljoin} + Sets the line join to a bevel join. See again Section~\ref{section-cap-joins}. +\end{command} +% +\begin{command}{\pgfsetmiterjoin} + Sets the line join to a miter join. See again Section~\ref{section-cap-joins}. +\end{command} +% +\begin{command}{\pgfsetmiterlimit\marg{miter limit factor}} + Sets the miter limit to \meta{miter limit factor}. See again + Section~\ref{section-cap-joins}. +\end{command} + + +\subsubsection{Graphic Parameter: Dashing} + +\begin{command}{\pgfsetdash\marg{list of even length of dimensions}\marg{phase}} + Sets the dashing of a line. The first entry in the list specifies the + length of the first solid part of the list. The second entry specifies the + length of the following gap. Then comes the length of the second solid + part, following by the length of the second gap, and so on. The + \meta{phase} specifies where the first solid part starts relative to the + beginning of the line. + % +\begin{codeexample}[] +\begin{pgfpicture} + \pgfsetdash{{0.5cm}{0.5cm}{0.1cm}{0.2cm}}{0cm} + \pgfpathmoveto{\pgfpoint{0mm}{0mm}} + \pgfpathlineto{\pgfpoint{2cm}{0mm}} + \pgfusepath{stroke} + \pgfsetdash{{0.5cm}{0.5cm}{0.1cm}{0.2cm}}{0.1cm} + \pgfpathmoveto{\pgfpoint{0mm}{1mm}} + \pgfpathlineto{\pgfpoint{2cm}{1mm}} + \pgfusepath{stroke} + \pgfsetdash{{0.5cm}{0.5cm}{0.1cm}{0.2cm}}{0.2cm} + \pgfpathmoveto{\pgfpoint{0mm}{2mm}} + \pgfpathlineto{\pgfpoint{2cm}{2mm}} + \pgfusepath{stroke} +\end{pgfpicture} +\end{codeexample} + + Use |\pgfsetdash{}{0pt}| to get a solid dashing. +\end{command} + + +\subsubsection{Graphic Parameter: Stroke Color} + +\begin{command}{\pgfsetstrokecolor\marg{color}} + Sets the color used for stroking lines to \meta{color}, where \meta{color} + is a \LaTeX\ color like |red| or |black!20!red|. Unlike the |\color| + command, the effect of this command lasts till the end of the current + |{pgfscope}| and not till the end of the current \TeX\ group. + + The color used for stroking may be different from the color used for + filling. However, a |\color| command will always ``immediately override'' + any special settings for the stroke and fill colors. + + In plain \TeX, this command will also work, but the problem of + \emph{defining} a color arises. After all, plain \TeX\ does not provide + \LaTeX\ colors. For this reason, \pgfname\ implements a minimalistic + ``emulation'' of the |\definecolor|, |\colorlet|, and |\color| commands. + Only gray-scale and rgb colors are supported. For most cases this turns out + to be enough. + % +\begin{codeexample}[] +\begin{pgfpicture} + \pgfsetlinewidth{1pt} + \color{red} + \pgfpathcircle{\pgfpoint{0cm}{0cm}}{3mm} \pgfusepath{fill,stroke} + \pgfsetstrokecolor{black} + \pgfpathcircle{\pgfpoint{1cm}{0cm}}{3mm} \pgfusepath{fill,stroke} + \color{red} + \pgfpathcircle{\pgfpoint{2cm}{0cm}}{3mm} \pgfusepath{fill,stroke} +\end{pgfpicture} +\end{codeexample} + % +\end{command} + +\begin{command}{\pgfsetcolor\marg{color}} + Sets both the stroke and fill color. The difference to the normal |\color| + command is that the effect lasts till the end of the current |{pgfscope}|, + not only till the end of the current \TeX\ group. +\end{command} + + +\subsubsection{Graphic Parameter: Stroke Opacity} + +You can set the stroke opacity using |\pgfsetstrokeopacity|. This command is +described in Section~\ref{section-transparency}. + + +\subsubsection{Inner Lines} + +When a path is stroked, it is possible to request that it is stroked twice, the +second time with a different line width and a different color. This is a useful +effect for creating ``double'' lines, for instance by setting the line width to +2pt and stroking a black line and then setting the inner line width to 1pt and +stroking a white line on the same path as the original path. This results in +what looks like two lines, each of thickness 0.5pt, spaced 1pt apart. + +You may wonder why there is direct support for this ``double stroking'' in the +basic layer. After all, this effect is easy to achieve ``by hand''. The main +reason is that arrow tips must be treated in a special manner when such +``double lines'' are present. First, the order of actions is important: First, +the (thick) main line should be stroked, then the (thin) inner line, and only +then should the arrow tip be drawn. Second, the way an arrow tip looks +typically depends strongly on the width of the inner line, so the arrow tip +code, which is part of the basic layer, needs access to the inner line +thickness. + +Two commands are used to set the inner line width and color. + +\begin{command}{\pgfsetinnerlinewidth\marg{dimension}} + This command sets the width of the inner line. Whenever a path is stroked + (and only then), it will be stroked normally and, afterward, it is stroked + once more with the color set to the inner line color and the line width set + to \meta{dimension}. + + In case arrow tips are added to a path, the path is first stroked normally, + then the inner line is stroked, and then the arrow tip is added. In case + the main path is shortened because of the added arrow tip, this shortened + path is double stroked, not the original path (which is exactly what you + want). + + When the inner line width is set to 0pt, which is the default, no inner + line is stroked at all (not even a line of width 0pt). So, in order to + ``switch off'' double stroking, set \meta{dimension} to~|0pt|. + + The setting of the inner line width is local to the current \TeX\ group and + \emph{not} to the current \pgfname\ scope. + + Note that inner lines will \emph{not} be drawn for paths that are also used + for clipping. However, this may change in the future, so you should not + depend on this. + % +\begin{codeexample}[] +\begin{pgfpicture} + \pgfpathmoveto{\pgfpointorigin} + \pgfpathlineto{\pgfpoint{1cm}{1cm}} + \pgfpathlineto{\pgfpoint{1cm}{0cm}} + \pgfsetlinewidth{2pt} + \pgfsetinnerlinewidth{1pt} + \pgfusepath{stroke} +\end{pgfpicture} +\end{codeexample} + % +\end{command} + +\begin{command}{\pgfsetinnerstrokecolor\marg{color}} + This command sets the \meta{color} that is to be used when the inner line + is stroked. The effect of this command is also local to the current \TeX\ + group. + % +\begin{codeexample}[] +\begin{pgfpicture} + \pgfpathmoveto{\pgfpointorigin} + \pgfpathlineto{\pgfpoint{1cm}{1cm}} + \pgfpathlineto{\pgfpoint{1cm}{0cm}} + \pgfsetlinewidth{2pt} + \pgfsetinnerlinewidth{1pt} + \pgfsetinnerstrokecolor{red!50} + \pgfusepath{stroke} +\end{pgfpicture} +\end{codeexample} + % +\end{command} + + +\subsection{Arrow Tips on a Path} +\label{section-tips} + +After a path has been drawn, \pgfname\ can add arrow tips at the ends, +depending on how the |tips| key is set, on whether |stroke| or |clip| are used +and on whether the path contains closed subpaths. The exact rules when arrow +tips are added are explained in Section~\ref{section-arrow-tips-where}. + +\begin{command}{\pgfsetarrowsstart\marg{start arrow tip specification}} + Sets the arrow tip kind used at the start of a (possibly curved) path. The + syntax of the \meta{start arrow specification} is detailed in + Section~\ref{section-arrow-spec}. + + To ``clear'' the start arrow, say |\pgfsetarrowsstart{}|. + % +\begin{codeexample}[preamble={\usepgflibrary{arrows.meta}}] +\begin{pgfpicture} + \pgfsetarrowsstart{Latex[length=10pt]} + \pgfpathmoveto{\pgfpointorigin} + \pgfpathlineto{\pgfpoint{1cm}{0cm}} + \pgfusepath{stroke} + \pgfsetarrowsstart{Computer Modern Rightarrow} + \pgfpathmoveto{\pgfpoint{0cm}{2mm}} + \pgfpathlineto{\pgfpoint{1cm}{2mm}} + \pgfusepath{stroke} +\end{pgfpicture} +\end{codeexample} + + The effect of this command persists only till the end of the current \TeX\ + scope. +\end{command} + +\begin{command}{\pgfsetarrowsend\marg{end arrow tip specification}} + Sets the arrow tip kind used at the end of a path. + % +\begin{codeexample}[preamble={\usepgflibrary{arrows.meta}}] +\begin{pgfpicture} + \pgfsetarrowsstart{Latex[length=10pt]} + \pgfsetarrowsend{Computer Modern Rightarrow} + \pgfpathmoveto{\pgfpointorigin} + \pgfpathlineto{\pgfpoint{1cm}{0cm}} + \pgfusepath{stroke} +\end{pgfpicture} +\end{codeexample} + % +\end{command} + +\begin{command}{\pgfsetarrows\marg{argument}} + The \meta{argument} can be of the form \meta{start arrow tip + specification}|-|\meta{end arrow tip specification}. In this case, both the + start and the end arrow specification are set: + % +\begin{codeexample}[preamble={\usepgflibrary{arrows.meta}}] +\begin{pgfpicture} + \pgfsetarrows{Latex[length=10pt]->>} + \pgfpathmoveto{\pgfpointorigin} + \pgfpathlineto{\pgfpoint{1cm}{0cm}} + \pgfusepath{stroke} +\end{pgfpicture} +\end{codeexample} + % + Alternatively, \meta{argument} can be of the form |[|\meta{arrow keys}|]|. + In this case, the \meta{arrow keys} will be set for all arrow tips in the + current scope, see Section~\ref{section-arrow-scopes}. +\end{command} + +\begin{command}{\pgfsetshortenstart\marg{dimension}} + This command will shortened the start of every stroked path by the given + dimension. This shortening is done in addition to automatic shortening done + by a start arrow, but it can be used even if no start arrow is given. + + It is usually better to use the |sep| key with arrow tips. + + This command is useful if you wish arrows or lines to ``stop shortly + before'' a given point. + % +\begin{codeexample}[preamble={\usepgflibrary{arrows.meta}}] +\begin{pgfpicture} + \pgfpathcircle{\pgfpointorigin}{5mm} + \pgfusepath{stroke} + \pgfsetarrows{Latex-} + \pgfsetshortenstart{4pt} + \pgfpathmoveto{\pgfpoint{5mm}{0cm}} % would be on the circle + \pgfpathlineto{\pgfpoint{2cm}{0cm}} + \pgfusepath{stroke} +\end{pgfpicture} +\end{codeexample} + % +\end{command} + +\begin{command}{\pgfsetshortenend\marg{dimension}} + Works like |\pgfsetshortenstart|. +\end{command} + + +\subsection{Filling a Path} +\label{section-fill} + +Filling a path means coloring every interior point of the path with the current +fill color. It is not always obvious whether a point is ``inside'' a path when +the path is self-intersecting and/or consists or multiple parts. In this case +either the nonzero winding number rule or the even-odd crossing number rule is +used to decide which points lie ``inside''. These rules are explained in +Section~\ref{section-rules}. + + +\subsubsection{Graphic Parameter: Interior Rule} + +You can set which rule is used using the following commands: + +\begin{command}{\pgfseteorule} + Dictates that the even-odd rule is used in subsequent fillings in the + current \emph{\TeX\ scope}. Thus, for once, the effect of this command does + not persist past the current \TeX\ scope. + % +\begin{codeexample}[] +\begin{pgfpicture} + \pgfseteorule + \pgfpathcircle{\pgfpoint{0mm}{0cm}}{7mm} + \pgfpathcircle{\pgfpoint{5mm}{0cm}}{7mm} + \pgfusepath{fill} +\end{pgfpicture} +\end{codeexample} + % +\end{command} + +\begin{command}{\pgfsetnonzerorule} + Dictates that the nonzero winding number rule is used in subsequent + fillings in the current \TeX\ scope. This is the default. + % +\begin{codeexample}[] +\begin{pgfpicture} + \pgfsetnonzerorule + \pgfpathcircle{\pgfpoint{0mm}{0cm}}{7mm} + \pgfpathcircle{\pgfpoint{5mm}{0cm}}{7mm} + \pgfusepath{fill} +\end{pgfpicture} +\end{codeexample} + % +\end{command} + + +\subsubsection{Graphic Parameter: Filling Color} + +\begin{command}{\pgfsetfillcolor\marg{color}} + Sets the color used for filling paths to \meta{color}. Like the stroke + color, the effect lasts only till the next use of |\color|. +\end{command} + + +\subsubsection{Graphic Parameter: Fill Opacity} + +You can set the fill opacity using |\pgfsetfillopacity|. This command is +described in Section~\ref{section-transparency}. + + +\subsection{Clipping a Path} +\label{section-clip} + +When you add the |clip| option, the current path is used for clipping +subsequent drawings. The same rule as for filling is used to decide whether a +point is inside or outside the path, that is, either the even-odd rule or the +nonzero rule. + +Clipping never enlarges the clipping area. Thus, when you clip against a +certain path and then clip again against another path, you clip against the +intersection of both. + +The only way to enlarge the clipping path is to end the |{pgfscope}| in which +the clipping was done. At the end of a |{pgfscope}| the clipping path that was +in force at the beginning of the scope is reinstalled. + + +\subsection{Using a Path as a Bounding Box} +\label{section-using-bb} + +When you add the |use as bounding box| option, the bounding box of the picture +will be enlarged such that the path in encompassed, but any \emph{subsequent} +paths of the current \TeX\ scope will not have any effect on the size of the +bounding box. Typically, you use this command at the very beginning of a +|{pgfpicture}| environment. Alternatively, you can use |\pgfresetboundingbox|, +followed by |\pgfusepath{use as bounding box}| to overrule the picture's +bounding box completely. +% +\begin{codeexample}[] +Left +\begin{pgfpicture} + \pgfpathrectangle{\pgfpointorigin}{\pgfpoint{2ex}{1ex}} + \pgfusepath{use as bounding box} % draws nothing + + \pgfpathcircle{\pgfpointorigin}{2ex} + \pgfusepath{stroke} +\end{pgfpicture} +right. +\end{codeexample} |