Re: Info: Console Vs GUI difference?

[Eli Zaretskii <eliz@gnu.org>]

> Date: Thu, 31 Oct 2013 16:23:17 -0400
> From: Richard Stallman <rms@gnu.org>
> Cc: emacs-devel@gnu.org
> 
>     But why do you call it a problem or an error? Since the signals are 
>     caught, everything is alright. That's what I think and said so in bug 
>     report 15670 [1]. And that's the reason why the bug was closed as "not a 
>     bug".
> 
> It may not cause incorrect functioning, but it sounds like a cause
> of slowdown.  Unless there is a reason why redisplay is supposed
> to raise a signal, this is making Emacs slower than it needs to be,
> and investigating the cause might be useful.

The cause is clear.  Redisplay does not raise a signal, it just
evaluates conditions of a menu bar item, to be able to display the
"Next" item as disabled when there's no "next" node.  The Lisp code
that is invoked by redisplay to do that throws an error that is
supposed to be caught by that Lisp code.  However, Emacsspeak advises
the Lisp function Info-extract-pointer, which is involved in this
evaluation, with the result that the thrown error becomes visible.
See the Lisp backtrace here:

  http://debbugs.gnu.org/cgi/bugreport.cgi?bug=15670#5

and the Lisp code involved here:

  http://debbugs.gnu.org/cgi/bugreport.cgi?bug=15670#14

So the bottom line here is that the reason for the problem was a
bad/suboptimal advice used by Emacsspeak to advise the Info functions
in question.