scaling multi column groupplot while maintaining font size and node placement

Question

This is a follow-up to two previous questions:
1: font size scaling and node placement issues using pgfplots and tikzscale
2: Scaling a multi-column TikZ/pgfplots groupplot to page width

I would like to scale a multi-column groupplot to a certain width (usually \textwidth ) while maintaining font size and node placement. From question 1 I got that, when using tikzscale, one should not define hight and/or width for the axis environment in order to maintain font sizes and node placement. The answer to question 2 is, that I should use tikzscale to scale groupplots to a desired overall width. But if one does not define hight and width, then the combination of groupplot and tikzscale will produce an error:

! Package pgfplots Error: Error: Plot height `-77.46211pt' is too small. This c annot be implemented while maintaining constant size for labels. Sorry, label s izes are only approximate. You will need to adjust your height..

The plot will not be scaled correctly.
The short version of my question would be, "How can I scale a multi-column groupplot to a certain width while still maintaining font size and node placement?''
The following MWE illustrates the issue.

\documentclass[10pt,crop,varwidth=250pt]{standalone}
\usepackage[english]{babel}
\usepackage{pgfplots}
\usepgfplotslibrary{groupplots}
\usepackage{tikzscale}
\pgfplotsset{compat=1.10}
\usepackage{filecontents}
\begin{document}
\begin{filecontents}{A.tikz}
\begin{tikzpicture}
  \begin{groupplot}[
        group style={
        group size =2 by 1,
        horizontal sep = 1cm
        },
  width=125pt,
  height=125pt,
  xmin=-1,xmax=1,ymin=-1,ymax=1,
  xlabel=xlabel,
  ]
  \nextgroupplot[
  ylabel=ylabel,
  ]
  \addplot coordinates{  (-0.9,-0.9)  (0.9,0.9)  };
  \node[anchor=west] at (axis cs:-1,0) {01};
  \coordinate (a) at (axis cs:-1,0);
  \nextgroupplot
  \addplot coordinates{  (-0.9,-0.9)  (0.9,0.9)  };  
  \end{groupplot}
  \node[anchor=west,red] at (a) {02};
\end{tikzpicture}
\end{filecontents}
\begin{filecontents}{B.tikz}
\begin{tikzpicture}[transform shape]
  \begin{groupplot}[
        group style={
        group size =2 by 1,
        horizontal sep = 1cm
        },
%   width=125pt,               %% this is now omitted
%   height=125pt,              %% this is now omitted
  xmin=-1,xmax=1,ymin=-1,ymax=1,
  xlabel=xlabel,
  ]
  \nextgroupplot[
  ylabel=ylabel,
  ]
  \addplot coordinates{  (-0.9,-0.9)  (0.9,0.9)  };
  \node[anchor=west] at (axis cs:-1,0) {01};
  \coordinate (a) at (axis cs:-1,0);
  \nextgroupplot
    \addplot coordinates{  (-0.9,-0.9)  (0.9,0.9)  };
  \end{groupplot}
  \node[anchor=west,red] at (a) {02};
\end{tikzpicture}
\end{filecontents}

\input{A.tikz}
Manually scaling height and width of the plots requires a lot of tries until an ``acceptable'' result is reached. At least the font size and node placement are correct.
\includegraphics[width=250pt]{A.tikz}
Width and height are defined and tikzscale is used. The plots scale nicely to the desired width, but font size and node placement problems occur.
\input{B.tikz}
Without defined height and width and without tikzscale, the plots are too large to fit the desired textwidth. Font size and node placement work fine.
\includegraphics[width=250pt]{B.tikz}
No definition of width and height, but using tikzscale will produce an error. The plot is not scaled correctly but font size and node placement look fine.
\end{document}

Answer 1

Disclaimer: This is not a complete answer as it only deals with plot width, label font sizes etc., but not with the node size and placement. It'd be too long as a comment unfortunately.

---

I have found that it is possible to get proper font sizes when using groupplots by compensating for the horizontal spacing between plots.

Your \includegraphics command is still invoked with the option width=\textwidth, but the width of each plot within the groupplots environment has to be set to 1/x*\textwidth-y, where x is the number of group plots placed horizontally and y is the horizontal separation specified.

Output:

As far as I can tell, the width of the tikzscale-d figures is close to perfection and the fonts are not distorted.

But unfortunately this does not also solve the node placement issue. I hope this is a good starting point and someone else can help you with that. I use tikzscale very often as well and it'd be great to have a robust solution for scaling groupplots.

Solution:

\documentclass{article}
\usepackage[showframe]{geometry}
\usepackage{pgfplots}
\usepgfplotslibrary{groupplots}
\pgfplotsset{compat=1.10}
\usepackage{tikzscale}
\usepackage{filecontents}
\begin{filecontents}{notikzscale.tikz}
\begin{tikzpicture}
  \begin{groupplot}[
    group style={
      group size=2 by 1,
      horizontal sep=2cm,
    },
    scale only axis,
    width=0.38*\textwidth,
    height=3cm,
    xlabel=$x$,
  ]
\nextgroupplot[ylabel={This}]
  \addplot coordinates { (-0.9,-0.9) (0.9,0.9) };
  \node[anchor=west] (a) at (axis cs:-1,0) {01};

\nextgroupplot[ylabel={That}]
  \addplot coordinates { (-0.9,-0.9) (0.9,0.9) };


\end{groupplot}
\node[anchor=west,red] at (a) {0.2};
\end{tikzpicture}
\end{filecontents}
\begin{filecontents}{2by1.tikz}
\begin{tikzpicture}
  \begin{groupplot}[
    group style={
      group size=2 by 1,
      horizontal sep=2cm,
    },
    width=1/2*\textwidth-2cm,
    height=3cm,
    xlabel=$x$,
  ]
\nextgroupplot[ylabel={This}]
  \addplot coordinates { (-0.9,-0.9) (0.9,0.9) };
  \node[anchor=west] (a) at (axis cs:-1,0) {01};

\nextgroupplot[ylabel={That}]
  \addplot coordinates { (-0.9,-0.9) (0.9,0.9) };


\end{groupplot}
\node[anchor=west,red] at (a) {0.2};
\end{tikzpicture}
\end{filecontents}
\begin{filecontents}{3by1.tikz}
\begin{tikzpicture}
  \begin{groupplot}[
    group style={
      group size=3 by 1,
      horizontal sep=1cm,
    },
    scale only axis,
    width=1/3*\textwidth-1cm,
    height=3cm,
    xlabel=$x$,
  ]
\nextgroupplot[ylabel={This}]
  \addplot coordinates { (-0.9,-0.9) (0.9,0.9) };
  \node[anchor=west] (a) at (axis cs:-1,0) {01};

\nextgroupplot
  \addplot coordinates { (-0.9,-0.9) (0.9,0.9) };

\nextgroupplot
  \addplot coordinates { (-0.9,-0.9) (0.9,0.9) };


\end{groupplot}
\node[anchor=west,red] at (a) {0.2};
\end{tikzpicture}
\end{filecontents}
\begin{filecontents}{4by1.tikz}
\begin{tikzpicture}
  \begin{groupplot}[
    group style={
      group size=4 by 1,
      horizontal sep=1cm,
    },
    width=1/4*\textwidth-1cm,
    height=3cm,
    xlabel=$x$,
  ]
\nextgroupplot[ylabel={This}]
  \addplot coordinates { (-0.9,-0.9) (0.9,0.9) };
  \node[anchor=west] (a) at (axis cs:-1,0) {01};

\nextgroupplot
  \addplot coordinates { (-0.9,-0.9) (0.9,0.9) };

\nextgroupplot
  \addplot coordinates { (-0.9,-0.9) (0.9,0.9) };

\nextgroupplot
  \addplot coordinates { (-0.9,-0.9) (0.9,0.9) };


\end{groupplot}
\node[anchor=west,red] at (a) {0.2};
\end{tikzpicture}
\end{filecontents}
\begin{document}
This does not use \texttt{tikzscale}. Manually-sized.
\begin{center}
\input{notikzscale.tikz}
\end{center}
\vspace{0.5cm}
The below use \texttt{tikzscale}.
\centering
\includegraphics[width=\textwidth]{2by1.tikz}
\vspace{0.5cm}
\includegraphics[width=\textwidth]{3by1.tikz}
\vspace{0.5cm}
\includegraphics[width=\textwidth]{4by1.tikz}
\end{document}