[texhax] Odd behavior of \check at mathfonts

[Michael Barr]

If you compile the following file

\documentclass{article}
\makeatletter
\check at mathfonts
\newdimen\axis \axis=\fontdimen22\textfont2%
\makeatother
\begin{document}

$$e=mc^2$$
xxx xxx xxx xxx xxx xxx xxx xxx xxx xxx
xxx xxx xxx xxx xxx xxx xxx xxx xxx xxx
xxx xxx xxx xxx xxx xxx xxx xxx xxx xxx
xxx xxx xxx xxx xxx xxx
$$e=mc^2$$
xxx xxx xxx xxx xxx xxx xxx xxx xxx xxx
xxx xxx xxx xxx xxx xxx xxx xxx xxx xxx
xxx xxx xxx xxx xxx xxx xxx xxx xxx xxx
xxx xxx xxx xxx xxx xxx

\end{document}

you will see that there is a spurious indentation in the line following 
the first display, but not the second.  If you comment out the setting of 
\axis, the behavior persists.  If you comment out the line 
\check at mathfonts, you get an error message from the setting of \axis.  If 
you comment out both of those lines, the indentation disappears.  I 
haven't checked it thoroughly, but it looks as though I can work around it 
by simply setting \setbox0=\hbox{$x$}, so it isn't crucial.  Still, it 
seems rather odd behavior.  Is there a better way of getting the mathfont 
recognized?

Michael Barr