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% Copyright 2006 by Till Tantau
%
% This file may be distributed and/or modified
%
% 1. under the LaTeX Project Public License and/or
% 2. under the GNU Free Documentation License.
%
% See the file doc/generic/pgf/licenses/LICENSE for more details.
\section{Angle Library}
\label{section-angle}
\begin{tikzlibrary}{angles}
This library defines pic types for drawing angles.
\end{tikzlibrary}
\begin{pictype}{angle}{\opt{|=|\meta{A}|--|\meta{B}|--|\meta{C}}}
This pic adds a drawing of an angle to the current path. This
``drawing of an angle'' consist of a ``sector'' or ``wedge'' or
``slice'' whose pointed end is at point \meta{B} and whose straight
sides lie on the lines form \meta{B} to \meta{A} and from \meta{B}
to \meta{C}. The length of these lines is governed by the following
key:
\begin{key}{/tikz/angle radius=\meta{dimension} (initially 5mm)}
The length of the sides of the angle's wedge:
\begin{codeexample}[]
\tikz \draw (2,0) coordinate (A) -- (0,0) coordinate (B)
-- (-1,-1) coordinate (C)
pic [fill=black!50] {angle = A--B--C}
pic [draw,->,red,thick,angle radius=1cm] {angle = C--B--A};
\end{codeexample}
\end{key}
The three points \meta{A}, \meta{B}, and \meta{C} \emph{must} be the
names of nodes or coordinates; you cannot use direct coordinates like
``|(1,1)|'' here.
You can leave out the three points, in this case the text |A--B--C|
is used; so in the above examples we could just have written
|{angle}| in the first pic.
Concerning the sector that makes up the drawing of the angle, the
angular part of this sector is drawn in front of the path if the
|draw| option is given to the |pic|, while filled sector is drawn
behind the |pic|, provided an option like |fill| or |shade| is
passed to the pic. The following example shows the difference:
\begin{codeexample}[]
\tikz \draw [line width=2mm]
(2,0) coordinate (A) -- (0,0) coordinate (B)
-- (1,1) coordinate (C)
pic [draw=blue, fill=blue!50, angle radius=1cm] {angle};
\end{codeexample}
When |pic text| is set (which you typically do by using the quotes
syntax), a node will be created whose name is empty
(and, thus, inherits the pic's name) and which will be at the
half-way angle between the lines to \meta{A} and \meta{C} and whose
distance from \meta{B} is |angle radius| times the following factor:
\begin{key}{/tikz/angle eccentricity=\meta{factor} (initially 0.6)}
\begin{codeexample}[]
\tikz \draw (2,0) coordinate (A) -- (0,0) coordinate (B)
-- (1,1) coordinate (C)
pic ["$\alpha$", draw, ->] {angle};
\end{codeexample}
\begin{codeexample}[]
\tikz \draw (2,0) coordinate (A) -- (0,0) coordinate (B)
-- (1,1) coordinate (C)
pic ["$\alpha$", draw, angle eccentricity=1] {angle};
\end{codeexample}
\begin{codeexample}[]
\tikz {
\draw (2,0) coordinate (A) -- (0,0) coordinate (B)
-- (1,1) coordinate (C)
pic (alpha) ["$\alpha$", draw] {angle};
\draw (alpha) circle [radius=5pt];
}
\end{codeexample}
\end{key}
\end{pictype}
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