Re: Edebug corrupting point in buffers.

[Eli Zaretskii]

> Date: Wed, 2 Nov 2022 16:18:24 +0000
> Cc: emacs-devel@gnu.org
> From: Alan Mackenzie <acm@muc.de>
> 
> > Yes, I see the problem, but setting edebug-save-windows to nil
> > eliminates it.  So I think we already have a solution for the rare
> > situations where this is an issue.
> 
> It remains a perplexing problem for those who stumble into it.  How about
> instead of patching the code, adding some documentation clarifying the
> problem?
> 
> I would propose the following:

Fine by me, but...

> diff --git a/doc/lispref/edebug.texi b/doc/lispref/edebug.texi
> index 6a51489d8a..b4f680fe86 100644
> --- a/doc/lispref/edebug.texi
> +++ b/doc/lispref/edebug.texi
> @@ -1019,6 +1019,7 @@ The Outside Context
>  @menu
>  * Checking Whether to Stop::    When Edebug decides what to do.
>  * Edebug Display Update::       When Edebug updates the display.
> +* Edebug Buffer Points::        When @code{point} gets corrupted.
>  * Edebug Recursive Edit::       When Edebug stops execution.
>  @end menu

...please document this in the same place where the variables we
discussed are described.  It is not a good idea from the didactic POV
to have this described separately.

> +This can be a problem when your program itself sets point in a buffer,
> +intending later to use that value of point.  For example, suppose you
> +have buffer B displayed in your selected frame, and you step through
> +the following Lisp fragment:
> +
> +@example
> +(set-buffer A)
> +(set-buffer B)
> +(goto-char (point-max))
> +(insert "foo")
> +(set-buffer A)
> +(set-buffer B)
> +(insert "bar")
> +@end example

I very much doubt that showing this example will help.  It just
muddies the water, b y forcing users to try to understand what the
example does, which is completely irrelevant to what we want to
convey.

Just say that if point gets reset in non-selected windows during
Edebug stepping, users should try customizing that variable.