Re: doubling of input events on focus (X, 21.1 and later)

[Richard Stallman]

    Thanks for following up on this.  Any ideas on how to debug the
    switch-frame event handling?

It is not easy to debug unreproducible problems like this.  The only I
have is to add debugging code to record histories of various actions,
so you can examine them after you see the problem.  That way you can
learn about what happened inside Emacs at various points where the
history was recorded.