GNU bug report logs - #73446
29.1; Curious behaviour with with-current-buffer and read-string

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From: help-debbugs <at> gnu.org (GNU bug Tracking System)
To: Eli Zaretskii <eliz <at> gnu.org>
Cc: tracker <at> debbugs.gnu.org
Subject: bug#73446: closed (29.1; Curious behaviour with with-current-buffer
 and read-string )
Date: Tue, 24 Sep 2024 16:05:02 +0000

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Your message dated Tue, 24 Sep 2024 18:50:19 +0300
with message-id <86setpcapw.fsf <at> gnu.org>
and subject line Re: bug#73446: 29.1; Curious behaviour with with-current-buffer and read-string
has caused the debbugs.gnu.org bug report #73446,
regarding 29.1; Curious behaviour with with-current-buffer and read-string 
to be marked as done.

(If you believe you have received this mail in error, please contact
help-debbugs <at> gnu.org.)


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73446: https://debbugs.gnu.org/cgi/bugreport.cgi?bug=73446
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From: Al Haji-Ali <abdo.haji.ali <at> gmail.com>
To: bug-gnu-emacs <at> gnu.org
Subject: 29.1; Curious behaviour with with-current-buffer and read-string 
Date: Tue, 24 Sep 2024 09:19:56 +0100

Consider this code snippet:

,----
| (with-current-buffer (get-buffer "*scratch*")
|   (message "START point %S %S" (current-buffer) (point))
|   (goto-char 10)
|   (message "BEFORE point %S %S" (current-buffer) (point))
|   (with-current-buffer (get-buffer "*Messages*") ;; some random buffer
|     (read-string "Test: "))
|   (message "AFTER point %S %S" (current-buffer) (point)))
`----

Assuming that *scratch* has a point at something other than 10 and *is visible in a window*, I get this output in Messages

,----
| START point #<buffer *scratch*> 2952
| BEFORE point #<buffer *scratch*> 10
| AFTER point #<buffer *scratch*> 2952
`----

I was expecting (point) AFTER to be 100, as it was BEFORE.

This only happens when `read-string` is called and when `with-current-buffer` is nested, and only when *scratch* is visible in a window.

I can easily solve this issue with `save-excursion`, but I thought this might be an unintended behaviour worth reporting.

Best regards,
-- Al

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From: Eli Zaretskii <eliz <at> gnu.org>
To: Al Haji-Ali <abdo.haji.ali <at> gmail.com>
Cc: 73446-done <at> debbugs.gnu.org
Subject: Re: bug#73446: 29.1; Curious behaviour with with-current-buffer and
 read-string
Date: Tue, 24 Sep 2024 18:50:19 +0300

> From: Al Haji-Ali <abdo.haji.ali <at> gmail.com>
> Cc: 73446 <at> debbugs.gnu.org
> Date: Tue, 24 Sep 2024 16:07:42 +0100
> 
> 
> On 24/09/2024, Eli Zaretskii wrote:
> > If this is what you do, then it's the expected behavior: test1 is
> > displayed in another window, and so its window-point overrides what
> > you do.  See the node "Window Point" in the ELisp manual.
> >
> > This is not a bug.
> 
> Ah I see. It is interesting that even if the window displaying the
> buffer is shown but seemingly not selected (since the focus is on the
> minibuffer during `read-string`), the point gets reset to the
> window-point when Emacs waits for user input.
> 
> I vote to close this issue and apologies for the noise.

Thanks, I'm closing it.  But there's no need to apologize: Emacs is a
very complex beast, and no one knows all of its subtleties by heart.

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