mathabx and mathtools: \widetilde{} and \dot{} problem

Question

The problem is the odd placement of g in the second line in the align environment. Strangely, the \dot{}-character is only misplaced if it is followed by another character. I need the mathabx package for some symbols and would therefore prefer an alternative to this question. Without mathabx everything works as expected.

\documentclass[10pt,a4paper]{article}
\usepackage[ngerman]{babel}
\usepackage{mathtools}
\usepackage{mathabx} 
\begin{document}
\begin{align*}
\widetilde{g\dot{g}}\\
\widetilde{\dot{g}g}
\end{align*}
\end{document}

Answer 1

The problem is the same as exposed in Why do arguments to nested \tilde or \breve commands reappear when amsmath is used? Here it appears in a less spectacular way, the effect of mathabx is just to produce it also with widetilde. The solution is always the same:

\documentclass[10pt,a4paper]{article}
\usepackage[ngerman]{babel}
\usepackage{mathtools}
\usepackage{mathabx}

\newsavebox{\accentbox}
\newcommand{\compositeaccents}[2]{%
  \sbox\accentbox{$#2$}#1{\usebox\accentbox}}

\begin{document}
\begin{align*}
\compositeaccents{\widetilde}{g\dot{g}}\\
\compositeaccents{\widetilde}{\dot{g}g}
\end{align*}

\end{document}

Of course, you can use whatever name you want instead of \compositeaccents.

Answer 2

One fix is to put the expression in a box first (incorporating it into a redefined \widetilde):

\documentclass[10pt,a4paper]{article}
\usepackage[ngerman]{babel}
\usepackage{mathtools}
\usepackage{mathabx} 
\newsavebox\tempbox
\let\svwidetilde\widetilde
\renewcommand\widetilde[1]{\sbox\tempbox{$#1$}\svwidetilde{\usebox{\tempbox}}}
\begin{document}
\begin{align*}
\widetilde{g\dot{g}}\\
\widetilde{\dot{g}g}
\end{align*}
\end{document}

Alternately, one can, as a workaround, use scalerel package to stretch the tilde, and stackengine package to set it atop the expression.

\documentclass[10pt,a4paper]{article}
\usepackage[ngerman]{babel}
\usepackage{mathtools}
\usepackage{mathabx} 
\usepackage{stackengine}
\stackMath
\usepackage{scalerel}
\begin{document}
\begin{align*}
\widetilde{g\dot{g}}\\
\stackon[0pt]{\dot{g}g}{\hstretch{1.4}{\sim}}\\
%\widetilde{\dot{g}g}
\end{align*}
\end{document}