Re: displaying margins leads to Emacs hanging

[Eli Zaretskii <eliz@gnu.org>]

> From: dalanicolai <dalanicolai@gmail.com>
> Date: Fri, 24 Feb 2023 20:29:02 +0100
> 
> I am encountering the problem as described in the subject of this email.
> 
> I hope you could enlighten me again about this issue.
> 
> Some brief context:
> I am trying to build a kind of swiper/swoop for searching documents.
> I have tried to use Ivy/Vertico (see https://github.com/minad/consult/issues/625),
> but I think they are not well suited/too heavy for this. So, I concluded that,
> unfortunately, I have to 'reinvent the wheel'.
> 
> Anyway, to reproduce the issue starting from emacs -q,
> please load the attached file and do `M-x baleen` (the file is large because
> it includes the text of `An Introduction to Programming in Emacs Lisp`).

That's a huge file.

> Then type 'ho' and optionally continue typing to narrow down the results.
> Press RET to finish (I am just starting development, so never mind further
> 'testing' the current functionality. Although of course, suggestions for
> improvements are welcome).
> As you will find, hopefully, things seem to work fine.
> Page numbers are nicely displayed in the margins.
> 
> Now, do `M-x baleen2`. This time, the data consists of the contents of the
> the book `An Introduction to Programming in Emacs Lisp.' Now type e.g.
> 'emacs' to narrow down the results. The page numbers are not displayed
> in the margins, to show that things still work fine.
> 
> NOTE the next step should (well, should not of course) make Emacs hang:
> 
> Now just uncomment the line
>   ;; (set-window-margins nil 4)
> in the function `baleen2` and repeat the last step (`M-x baleen2`).
> Again, try to type 'emacs'. Unfortunately, Emacs more or less hangs.
> 
> I have no idea why suddenly Emacs hangs. I was wondering if any of
> you could explain this behavior, and hopefully suggest how to
> prevent it.
> (Of course, if there is no other solution, then I could just display the
> page numbers in the buffer text).
> 
> I also have a second question, but I will send it in another mail (with its
> own subject).

Did you try yourself to establish where Emacs loops and why?  The file
etc/DEBUG includes instructions for how to debug what looks like an
infloop; search for "If the symptom of the bug is that Emacs fails to
respond".

I notice that you say "more or less hangs".  What does this mean,
exactly?  Does C-g interrupt the "hang"?