pgfplots: trim axis in tikzpicture messes up legend position

Question

So I will begin this question by linking to an existing unanswered question on the same matter: Link. I am unsure if I should revive the old question or post a new one, so I just ended up making a new post.

So the problem is that when you use the option \begin{tikzpicture}[trim axis left, trim axis right] along with a reference to a legend through the use of legend to name and \ref{} or \pgfplotslegendfromname{}, the legend position will be messed up.

I have provided an MWE below illustrating the issue.

Has anyone been able to find a good solution to this problem?

\documentclass{article}
\usepackage{pgfplots}
\pgfplotsset{compat=1.6}
\usepgfplotslibrary{groupplots}
\begin{document}
\begin{figure}
    \centering
    \begin{tikzpicture}[trim axis left, trim axis right]%used for centering only axis and not ylabels etc
    \begin{groupplot}[group style={group size=1 by 2, vertical sep=2.5cm},small]
\nextgroupplot[title=Plot 1, xlabel=$x$, ylabel=$y_1$,
legend entries={Entry 1,Entry 2,Entry 3}, legend to name=myLegends1, legend columns=3]
\addplot+[domain=0:360] {sin(x)};
\addplot+[domain=0:360] {sin(x)+1};
\addplot+[domain=0:360] {sin(x)+2};

\nextgroupplot[title=Plot 2, xlabel=$x$, ylabel=$y_2$]
\addplot+[domain=0:360] {cos(x)};
\end{groupplot}

\node[anchor=north] at (group c1r1.below south) {\pgfplotslegendfromname{myLegends1}};

\end{tikzpicture}%

\end{figure}
\begin{figure}
    \centering
    \begin{tikzpicture}%[trim axis left, trim axis right]%used for centering only axis and not ylabels etc
    \begin{groupplot}[group style={group size=1 by 2, vertical sep=2.5cm}, small]
\nextgroupplot[title=Plot 1, xlabel=$x$, ylabel=$y_1$,
legend entries={Entry 1,Entry 2,Entry 3}, legend to name=myLegends2, legend columns=3]

\addplot+[domain=0:360] {sin(x)};
\addplot+[domain=0:360] {sin(x)+1};
\addplot+[domain=0:360] {sin(x)+2};

\nextgroupplot[title=Plot 2, xlabel=$x$, ylabel=$y_2$]
\addplot+[domain=0:360] {cos(x)};
\end{groupplot}

\node[anchor=north] at (group c1r1.below south) {\pgfplotslegendfromname{myLegends2}};

\end{tikzpicture}%

\end{figure}
\end{document}

The first figure shows the plot when the ´trim axis´ is active (here the legend is placed wrong). The second figure shows the plot without the trim axis and here the legend is placed correctly.

Answer 1

It seems that [trim axis] affects all nodes, including the one with the legend in it.

An additional fix was added to center the bounding box by adding additional space to the right side.

\documentclass{article}
\usepackage{pgfplots}
\pgfplotsset{compat=1.6}
\usepgfplotslibrary{groupplots}
\begin{document}
\begin{figure}
    \centering
    \begin{tikzpicture}
    \begin{groupplot}[group style={group size=1 by 2, vertical sep=2.5cm},small,
      trim axis left, trim axis right]
\nextgroupplot[title=Plot 1, xlabel=$x$, ylabel=$y_1$,
legend entries={Entry 1,Entry 2,Entry 3}, legend to name=myLegends1, legend columns=3]
\addplot+[domain=0:360] {sin(x)};
\addplot+[domain=0:360] {sin(x)+1};
\addplot+[domain=0:360] {sin(x)+2};

\nextgroupplot[title=Plot 2, xlabel=$x$, ylabel=$y_2$]
\addplot+[domain=0:360] {cos(x)};
\end{groupplot}

\path (current bounding box.west);% orgin at axis left
\pgfgetlastxy{\xaxis}{\yaxis}%
\path (current bounding box.east) ++(-\xaxis,0);% add left margin to right

\node[anchor=north] (test) at (group c1r1.below south) {\pgfplotslegendfromname{myLegends1}};
\draw[red] (test.south west) rectangle (test.north east);
\draw[red] (current bounding box.south west) rectangle (current bounding box.north east);
\end{tikzpicture}%

\end{figure}
\end{document}

---

This version uses \pgfextractx instead of \pgfgetlastxy (better , but ugly).

\documentclass{article}
\usepackage{pgfplots}
\pgfplotsset{compat=1.6}
\usepgfplotslibrary{groupplots}
\newlength{\xleft}
\newlength{\xright}
\begin{document}
\begin{figure}
    \centering
    \begin{tikzpicture}
    \begin{groupplot}[group style={group size=1 by 2, vertical sep=2.5cm},small,
      trim axis left, trim axis right]
\nextgroupplot[title=Plot 1, xlabel=$x$, ylabel=$y_1$,
legend entries={Entry 1,Entry 2,Entry 3}, legend to name=myLegends1, legend columns=3]
\addplot+[domain=0:360] {sin(x)};
\addplot+[domain=0:360] {sin(x)+1};
\addplot+[domain=0:360] {sin(x)+2};

\nextgroupplot[title=Plot 2, xlabel=$x$, ylabel=$y_2$]
\addplot+[domain=0:360] {cos(x)};
\end{groupplot}

\pgfextractx{\xleft}{\pgfpointdiff{\pgfpointanchor{current bounding box}{west}}
  {\pgfpointanchor{group c1r1}{west}}}% current left margin
\pgfextractx{\xright}{\pgfpointdiff{\pgfpointanchor{group c1r1}{east}}
  {\pgfpointanchor{current bounding box}{east}}}% current right margin
\ifdim \xleft>\xright
  \path (current bounding box.east) ++(\xleft-\xright,0);% add left margin to right
\else
  \path (current bounding box.west) ++(\xleft-\xright,0);% add right margin to left
\fi

\node[anchor=north] (test) at (group c1r1.below south) {\pgfplotslegendfromname{myLegends1}};
\draw[red] (test.south west) rectangle (test.north east);
\draw[red] (current bounding box.south west) rectangle (current bounding box.north east);
\end{tikzpicture}%

\end{figure}
\end{document}