Calculating a common height for nodes with different amounts of text in Tikz

Question

When using labelled nodes (e.g. for a flow chart), their sizes are automatically chosen. One can enforce the same size, which must be known a priori, for multiple nodes by using "large enough" values for minimum height and minimum width.

In the following example the node width is restricted for spacial reasons. This leads to the boxes containing different numbers of lines and therefore different box sizes.

    \documentclass{beamer}
    \usepackage{tikz}
    \usetikzlibrary{positioning}

    \begin{document}
    \begin{frame}
    \begin{tikzpicture}[node distance=2cm]
        \node[rectangle,text width=5em,draw=black] (leftnode) {Short text};
        \node[rectangle,text width=5em,draw=black,right=of leftnode] (rightnode) {A text longer than the other one};
    \end{tikzpicture}
    \end{frame}
    \end{document}

Given two strings, that shall be written in two separate nodes of equal size: Is it possible to let LaTeX calculate the minimal node height that is large enough for both cases and use it as a parameter for the nodes?

Answer 1

Identical Heights:

When you specify the text width, the text is placed in a \parbox of the width provided by text width. So, a simple fix is to use a \vphantom{} in the shorter node to ensure that it is of the same height:

Code:

\documentclass{article}
\usepackage{tikz}
\usetikzlibrary{positioning}

\newcommand*{\TextWidth}{5em}%
\newcommand*{\StringA}{Short}%
\newcommand*{\StringB}{A text longer than the other one}%

\newcommand{\VPhantom}{\vphantom{\parbox{\TextWidth}{\StringB}}}%

\begin{document}
\begin{tikzpicture}[node distance=0.1cm]
    \node[rectangle,text width=\TextWidth,draw=black, red] (leftnode) {\VPhantom\StringA};
    \node[rectangle,text width=\TextWidth,draw=black, blue, right=of leftnode] (rightnode) {\StringB};
\end{tikzpicture}
\end{document}

---

Identical Widths

You can use the \widthof{} to compute the length and then chose the maximum width as the minimum length:

Note

• The 2*\InnerSep adjusts for the value of inner sep that is on both sides of the node, so if that value is changed this formula will need to be adjusted as well.

Code:

\documentclass{article}
\usepackage{tikz}

\newcommand*{\InnerSep}{0.333em}%
\newcommand*{\StringA}{short}%
\newcommand*{\StringB}{a longer string}%

\begin{document}

\pgfmathsetmacro{\MinimumWidth}{%
    max(\widthof{\StringA},\widthof{\StringB})+2*\InnerSep%
}%

\begin{tikzpicture}[minimum width=\MinimumWidth]
    \node [rectangle, draw=red]  at (0,0) {\StringA};
    \node [rectangle, draw=blue] at (0,1) {\StringB};
\end{tikzpicture}
\end{document}

Answer 2

The answer above works well if the smaller string only uses one line. For multiple lines in both nodes I came to the following solution (combining both approaches given above and using the calc package).

    \documentclass{beamer}
    \usepackage{calc}
    \usepackage{tikz}
    \usetikzlibrary{positioning}

    \newcommand*{\TextWidth}{5em}
    \newcommand*{\Innersep}{0.33em}
    \newcommand{\StringA}{Short multiline text}
    \newcommand{\StringB}{A text longer than the other one}
    \newlength\myheight
    \setlength{\myheight}{\totalheightof{\parbox{\TextWidth}{\StringB}}+Innersep*2}

    \begin{document}
    \begin{frame}
    \begin{tikzpicture}[node distance=2cm]
        \node[rectangle,text width=\TextWidth,inner sep=\Innersep,minimum height=\myheight,draw=black] (leftnode) {\StringA};
        \node[rectangle,text width=\TextWidth,inner sep=\Innersep,minimum height=\myheight,draw=black,right=of leftnode] (rightnode) {\StringB};
    \end{tikzpicture}     
    \end{frame}     
    \end{document}