[Tex/LaTex] Positioning and Coordinates in Tikz+Beamer

beamertikz-pgf

How exactly does positioning in beamer+tikz work?

where is the absolute origin (0,0) on a slide? Why when I specify (0,0) does it seem to move around the slide depending on the size of whats being plotted? Does it exist absolutely somewhere?
Can I draw the absolute grid (as opposed to some grid) with absolute positioning information on slides to help me when trying to position items?
Can someone help me make sense of the example below?

Im reading and rereading the tikz (especially chapter 13) and beamer documentation, but cant seem to figure out what is going on.

\documentclass[xcolor=dvipsnames]{beamer}
\usepackage{tikz,ifthen}
\usetikzlibrary{calc, intersections,through,backgrounds}
\usepackage{pgfpages}
\usetheme[progressbar=frametitle]{metropolis}
\usepackage{amsmath,amssymb,amsthm,mathrsfs,bbm,bm}
\usepackage{graphicx,subcaption,float,enumerate}
\begin{document}
\begin{frame}{Slide}
    \begin{tikzpicture} 
        \draw[help lines] (0,0) grid (0.5\textwidth,0.5\textheight);
    \end{tikzpicture}
\end{frame}
\end{document}

When I remove the 0.5, why is the grid off the slide in all dimensions?

Note: There is this related unanswered question. This question is not specifically about this MWE, just in general how to look at a slide, pick a point with my eye, and put something there exactly and absolutely in tikz.

Best Answer

If you use remember picture, overlay as options to a tikzpicture you can then use current page as a coordinate (well actually you use .north or stuff like that, just like you can use node.north as the top of a node named node).

The remember picture has the effect that the positioning of the picture is adapted to match the specified positions because the tikzpicture is not guaranteed to be at the bottom left of the current page -- you use it somewhere in the frame environment and it is there as far as LaTeX is concerned. TikZ stores that position in the .aux file and moves the picture accordingly on the second run. Therefore you need at least two runs with this approach to get correct positioning. overlay just makes sure that your picture doesn't have a size as far as LaTeX's typesetting is concerned (it still introduces white space around the spot it is used in if used at the wrong place -- make sure to not start a new paragraph accidentally and put a % after \end{tikzpicture} to not introduce unwanted spaces).

If you want to place arbitrary stuff on a specified coordinate on a frame, I'd use a \node in a tikzpicture which I know is on that slide. For a small template I created for myself I used the following approach:

Put a tikzpicture in the beamer template background. In that tikzpicture put a macro like \MyPlacedStuff and after the tikzpicture put \gdef\MyPlacedStuff{}.
In a frame you can now add stuff with \xdef\MyPlacedStuff{\unexpanded\expandafter{\MyPlacedStuff <stuff you want to place on the slide>}}

You should write a macro or two around point 2 to ease the process.

The following does that and adds the help lines if you use \HelpLinestrue outside of the frame (until you use \HelpLinesfalse).

\PlaceAt takes the coordinates in multiples of \paperwidth and \paperheight as first argument in (), optional arguments to a \node in [], and finally the contents of the node in {}. The first and last are mandatory, options to the node are optional.

\AddToPlaced takes only one argument, which should be able to contain anything you can add to a tikzpicture.

Beware the background might already contain stuff which you hereby would overwrite. You'll have to sort that out if it conflicts. It seems to not conflict in your MWE.

\documentclass[xcolor=dvipsnames]{beamer}
\usepackage{tikz,ifthen}
\usepackage{xparse}
\usetikzlibrary{calc, intersections,through,backgrounds}
\usepackage{pgfpages}
\usetheme[progressbar=frametitle]{metropolis}

\newif\ifHelpLines
\newcommand*\MyPlacedStuff{}
\setbeamertemplate{background}{%>>>
  \begin{tikzpicture}
    \useasboundingbox (0,0) rectangle(\paperwidth,\paperheight);
    \ifHelpLines
      \draw[help lines] (0,0) grid (\paperwidth,\paperheight);
    \fi
    \MyPlacedStuff
  \end{tikzpicture}\gdef\MyPlacedStuff{}}

\NewDocumentCommand{\PlaceAt}{ >{\SplitArgument{1}{,}}r() O{} +m }
  {%
    \PlaceAtB#1{#2}{#3}%
  }
\NewDocumentCommand{\PlaceAtB}{ m m m +m }
  {%
    \xdef\MyPlacedStuff%
      {%
        \unexpanded\expandafter{\MyPlacedStuff
          \node[#3] at (#1\paperwidth,#2\paperheight) {#4};%
        }%
      }%
  }
\newcommand{\AddToPlaced}[1]
  {%
    \xdef\MyPlacedStuff%
      {%
        \unexpanded\expandafter{\MyPlacedStuff#1}%
      }%
  }

\begin{document}
\HelpLinestrue
\begin{frame}{Slide}
  \PlaceAt(.8,.6){This text}
  \AddToPlaced{\draw (.1,1) -- (.9\textwidth,.9\textheight);}
\end{frame}
\end{document}

Related Solutions

[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

[Tex/LaTex] Line up nested tikz enviroments or how to get rid of them

As is explained in How do I draw shapes inside a tikz node? pics can be used for defining new objects. My main problem using pics is how to place where you want because they aren't nodes and positioning them is not so easy.

Following code shows how to define EDFA block.

    EDFA/.pic={
        \begin{scope}[scale=.5]
        \draw (-1,0) coordinate (in) --  (-1,1) -- (1,0) coordinate (out) --  (-1,-1) -- cycle;
        \node[anchor=north,inner sep=2pt] at (0,-1) {$1$};
        \end{scope}

In this case, coordinate (-1,0) will act as west anchor and 1,0 as east. Both point will have an special name for further reference. Every pic is placed according its own origin (0,0). You can use Claudio's answer to Anchoring TiKZ pics for better positioning.

As your example was simple, I'd prefer to star with EDFA and place Source and Sink after it.

\documentclass[]{article}

% tikz
\usepackage{tikz}
\usetikzlibrary{positioning} %relative positioning

\begin{document}

\tikzset{%
    EDFA/.pic={
        \begin{scope}[scale=.5]
        \draw (-1,0) coordinate (in) --  (-1,1) -- (1,0) coordinate (out) --  (-1,-1) -- cycle;
        \node[anchor=north,inner sep=2pt] at (0,-1) {$1$};
        \end{scope}
    }
}

\begin{tikzpicture}[
block/.style={draw},
]

\draw pic (edfa) {EDFA};

\node[block, left=of edfain] (source) {Source};

\node[block, right= of edfaout] (sink) {Sink};

\draw[->] (source) -- (edfain);
\draw[->] (edfaout) -- (sink);

\end{tikzpicture}

\end{document}

I understand that your components are more complex than EDFA because for this particular case an isosceles triangle node with a label will do the work and it can be used as a node and not as a pic:

\documentclass[]{article}

% tikz
\usepackage{tikz}
\usetikzlibrary{positioning} %relative positioning
\usetikzlibrary{shapes.geometric}

\begin{document}

\begin{tikzpicture}[
    block/.style={draw},
    edfa/.style={isosceles triangle, minimum width=1cm, 
         draw, anchor=west, isosceles triangle stretches, 
         minimum height=1cm, label=-80:#1}
]

\node[block] (source) {Source};

\node[edfa=1, right=of source] (edfa) {};

\node[block, right= of edfa] (sink) {Sink};

\draw[->] (source) -- (edfa);
\draw[->] (edfa) -- (sink);

\end{tikzpicture}

\end{document}

Best Answer

Related Solutions

[Tex/LaTex] Numerical conditional within tikz keys

[Tex/LaTex] Line up nested tikz enviroments or how to get rid of them

Related Question