[Tex/LaTex] Beamer: Centering a tikzpicture in the background (\usebackgroundtemplate)

beamerpositioningtikz-pgf

I really thought that this can't be too hard but I struggle centering (vertically and horizontally) a tikzpicture in the \usebackgroundtemplate.

I use the code taken from one of my previous questions – in the end I want to have a progress indicator in the background of the beamer presentation.

When I use a simple \begin{center}...\end{center} (only horizontally) then I get an error saying

! LaTeX Error: Something's wrong–perhaps a
missing \item.

But \begin{center}...\end{center} works in the normal frame (see MWE).

\documentclass[]{beamer}

\usepackage{tikz}
\usetikzlibrary{decorations}

% taken from https://tex.stackexchange.com/questions/247742
% user https://tex.stackexchange.com/users/23215/mark-wibrow
\makeatletter
\tikzset{%
  get path length/.code={%
    \tikz@addoption{%
      \pgfgetpath\tikz@tmppath%
      \pgfprocessround\tikz@tmppath\tikz@tmppath%
      \pgf@decorate@parsesoftpath\tikz@tmppath\tikz@discard%
      \global\let#1=\pgf@decorate@totalpathlength%
    }%
  }
}
\makeatother

% taken from https://tex.stackexchange.com/questions/347336
% user https://tex.stackexchange.com/users/23215/mark-wibrow
\tikzset{myOwnStyle/.style={
  get path length=\pathlength,
  draw=black,
  line width=1mm,
  postaction={
    draw=red,
    line width=2mm,
    dash pattern= on \pathlength/100*#1 off \pathlength/100*(100-#1),
  }
}}

% I want to vertically and horizontally center this tikzpicture
\usebackgroundtemplate%
{
%\begin{center}
\begin{tikzpicture}
    \draw[myOwnStyle=\n,color=blue] (0,0) circle [radius = 10mm] node {\n\,\%};  
\end{tikzpicture} 
%\end{center}
}

\begin{document}

\foreach \n in {0,10,...,100}{
\begin{frame}
\frametitle{Frame Number: \n}
This is the frame with the number \n.

\begin{center}
\begin{tikzpicture}
    \draw[myOwnStyle=\n] (0,0) circle [radius = 10mm] node {\n\,\%};  
\end{tikzpicture} 
\end{center}

\end{frame}
}

\end{document}

Best Answer

Resize the tikzpicture to the paper using \useasboundingbox and position the circle in the center. There are several mechanisms, I used the coordinate (.5\paperwidth,.5\paperheight). You could also place it at half the diagonal or something else.

N.B.: Do you really want two of these circles on each frame?

\documentclass[]{beamer}

\usepackage{tikz}
\usetikzlibrary{decorations}

% taken from http://tex.stackexchange.com/questions/247742
% user http://tex.stackexchange.com/users/23215/mark-wibrow
\makeatletter
\tikzset{%
  get path length/.code={%
    \tikz@addoption{%
      \pgfgetpath\tikz@tmppath%
      \pgfprocessround\tikz@tmppath\tikz@tmppath%
      \pgf@decorate@parsesoftpath\tikz@tmppath\tikz@discard%
      \global\let#1=\pgf@decorate@totalpathlength%
    }%
  }
}
\makeatother

% taken from http://tex.stackexchange.com/questions/347336
% user http://tex.stackexchange.com/users/23215/mark-wibrow
\tikzset{myOwnStyle/.style={
  get path length=\pathlength,
  draw=black,
  line width=1mm,
  postaction={
    draw=red,
    line width=2mm,
    dash pattern= on \pathlength/100*#1 off \pathlength/100*(100-#1),
  }
}}

% I want to vertically and horizontally center this tikzpicture
\usebackgroundtemplate%
{
\begin{tikzpicture}
  \useasboundingbox (current page.north west) rectangle (current page.south east);
  \draw[myOwnStyle=\n,color=blue] (.5\paperwidth,.5\paperheight) circle [radius = 10mm] node {\n\,\%};  
\end{tikzpicture}
}

\begin{document}

\foreach \n in {0,10,...,100}{
\begin{frame}
\frametitle{Frame Number: \n}
This is the frame with the number \n.

\begin{center}
\begin{tikzpicture}
    \draw[myOwnStyle=\n] (0,0) circle [radius = 10mm] node {\n\,\%};  
\end{tikzpicture} 
\end{center}

\end{frame}
}

\end{document}

Related Solutions

[Tex/LaTex] Rotate a node but not its content: the case of the ellipse decoration

The source of the difficulty is that ellipses are constructed in a particular way in TikZ. They are paths that start from the x-axis and proceed counter-clockwise around their centre. The vast majority of the time, the exact parametrisation doesn't matter. You appear to have found the one situation where it does!

In the actual question, you only want to be able to mirror the ellipse, and so draw it starting from the negative x-axis (the title of the question suggests a more flexible approach). That's actually not too hard since we can exploit the symmetry of the ellipse. The key is to provide it with a negative x-radius, since then it will start from the negative x-axis (and proceed clockwise, but we could correct for that by negating the y-radius as well). To do this, we interrupt the call from the node shape to the drawing command and flip the sign of the x-radius. The simplest way to do this is to redefine the \pgfpathellipse macro to do the negation and then call the original macro. The following code does this.

\documentclass{article}
\usepackage{tikz}
\usetikzlibrary{decorations,shapes,decorations.markings}
\makeatletter
\let\origpgfpathellipse=\pgfpathellipse
\def\revpgfpathellipse#1#2#3{%
  #2%
  \pgf@xa=-\pgf@x
  \origpgfpathellipse{#1}{\pgfqpoint{\pgf@xa}{0pt}}{#3}}
\makeatother

\tikzset{
  reversed ellipse/.style={
    ellipse,
    reverse the ellipse%
  },
  reverse the ellipse/.code={
    \let\pgfpathellipse=\revpgfpathellipse
  }
}
\begin{document}
\begin{tikzpicture}
\node[ellipse,
  draw,
  postaction={
    decorate,
    decoration={
      markings,
      mark=at position 1 with {
        \arrow[line width=5pt,blue]{>}
      }
    }
  }
] at (0,0) {hello world};

\node[reversed ellipse,
  draw,
  postaction={
    decorate,
    decoration={
      markings,
      mark=at position 1 with {
        \arrow[line width=5pt,blue]{>}
      }
    }
  }
] at (0,-2) {hello world};
\end{tikzpicture}

\end{document}

Here's the result:

rotated ellipse

(the arrow got clipped, but you can see where it lies)

[Tex/LaTex] Numerical conditional within tikz keys

I am definitely unfamiliar with both beamer and tikz (do not quite get what the \only are supposed to do) but perhaps this could go in the direction you want:

\documentclass{beamer}
\usepackage{tikz}
\usetikzlibrary{chains}
\newcounter{count}

% helper macro:
\long\def\GobToSemiColon #1;{}

\newcommand\myPicture{
\begin{tikzpicture}
  \begin{scope}[start chain = going below]
  \ifnum\value{count}<1 \expandafter\GobToSemiColon\fi
  \ifnum\value{count}>3 \expandafter\GobToSemiColon\fi
  \node[draw, rectangle, on chain] {display only when counter is between
    1 and 3};

  \ifnum\value{count}>-1 \expandafter\GobToSemiColon\fi
  \node[draw, rectangle, on chain] {display only when counter is
    negative}; 

  \ifnum\value{count}<100 \expandafter\GobToSemiColon\fi
  \ifnum\value{count}>200 \expandafter\GobToSemiColon\fi  
  \node[draw, rectangle, on chain] {display only if counter is between
    100 and 200};

  \ifnum\value{count}<3 \expandafter\GobToSemiColon\fi
  \ifnum\value{count}>20 \expandafter\GobToSemiColon\fi
  \node[draw, circle, on chain] {only when counter is in the range 3 to 20};
  \end{scope}
\end{tikzpicture}
}

\begin{document}
\begin{frame}
\only{\setcounter{count}{-3}\myPicture}
\only{\setcounter{count}{105}\myPicture}
\only{\setcounter{count}{39}\myPicture}
\only{\setcounter{count}{2}\myPicture}
\only{\setcounter{count}{5}\myPicture}
\end{frame}
\end{document}

beamer

Best Answer

Related Solutions

[Tex/LaTex] Rotate a node but not its content: the case of the ellipse decoration

[Tex/LaTex] Numerical conditional within tikz keys

Related Question