GNU bug report logs - #23749
24.3.50; can't make the cursor to the end of a buffer when that buffer is visible

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Message #5 received at submit <at> debbugs.gnu.org (full text, mbox):

From: Samuel Lê <samuel.le <at> gmail.com>
To: bug-gnu-emacs <at> gnu.org
Subject: 24.3.50; can't make the cursor to the end of a buffer when that
 buffer is visible
Date: Sun, 12 Jun 2016 04:01:28 +0200

- run "emacs -Q" from command line.
- split emacs screen (C-x 2)
- on one side open an elisp code (say test.el)
- on the other side put the *scratch* buffer
- in test.el, enter (with-current-buffer "*scratch* (insert "test\n")
(goto-char (point-max)))
- then press C-x e to evaluate that command
- it inserts "test" in *scratch* buffer but doesnt go at the end of the
- buffer.

It works fine when buffer *scratch* is not visible.

Thanks!

In GNU Emacs 24.3.50.1 (x86_64-unknown-linux-gnu, GTK+ Version 2.24.10)
 of 2013-08-17 on debianSam
Windowing system distributor `The X.Org Foundation', version 11.0.11604000
System Description:	Debian GNU/Linux 8.4 (jessie)

Configured using:
 `configure --prefix=/opt/emacs24'

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  value of $LANG: en_US.UTF-8
  locale-coding-system: utf-8-unix
  default enable-multibyte-characters: t

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  tooltip-mode: t
  mouse-wheel-mode: t
  tool-bar-mode: t
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  font-lock-mode: t
  blink-cursor-mode: t
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  line-number-mode: t
  transient-mark-mode: t

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<backspace> t e s t . e l <return> ( w i t h - c u
r r e n t - b u f f e r SPC " * s c r a t c h * " SPC
( i n s e r t SPC " t e s t \ n " ) SPC ( g o t o -
c h a t SPC ( p o i n t m <backspace> - m a x ) ) )
C-x C-e C-x k <return> <S-up> <down> C-k <S-up> C-x
o <left> <left> <left> <left> <left> <left> <left>
<left> <left> <left> <left> <left> <left> <left> <backspace>
r C-e C-x C-e <help-echo> M-x r e p o r t M-/ - e m
a c s - b u g <return>

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Message #8 received at 23749 <at> debbugs.gnu.org (full text, mbox):

From: John Mastro <john.b.mastro <at> gmail.com>
To: 23749 <at> debbugs.gnu.org
Cc: Samuel Lê <samuel.le <at> gmail.com>
Subject: Re: bug#23749: 24.3.50; can't make the cursor to the end of a buffer
 when that buffer is visible
Date: Sat, 11 Jun 2016 19:24:09 -0700

Samuel Lê <samuel.le <at> gmail.com> wrote:
> - run "emacs -Q" from command line.
> - split emacs screen (C-x 2)
> - on one side open an elisp code (say test.el)
> - on the other side put the *scratch* buffer
> - in test.el, enter (with-current-buffer "*scratch* (insert "test\n")
> (goto-char (point-max)))
> - then press C-x e to evaluate that command
> - it inserts "test" in *scratch* buffer but doesnt go at the end of the
> - buffer.
>
> It works fine when buffer *scratch* is not visible.

I confirmed that the behavior is the same in Emacs 25.0.94, but I
suspect this is not a bug because there's also a concept of "window
point" (see `window-point').

Adding `with-selected-window' will cause point to move as you expected:

(with-current-buffer "*scratch*"
  (with-selected-window (get-buffer-window (current-buffer))
    (insert "test\n")
    (goto-char (point-max))))

However, if the buffer isn't shown in a window, `get-buffer-window' will
return nil and `with-selected-window' will thus signal an error. So the
right fix really depends on the context and ultimate goal.

        John

Message #11 received at 23749 <at> debbugs.gnu.org (full text, mbox):

From: Noam Postavsky <npostavs <at> users.sourceforge.net>
To: Samuel Lê <samuel.le <at> gmail.com>
Cc: 23749 <at> debbugs.gnu.org
Subject: Re: bug#23749: 24.3.50; can't make the cursor to the end of a buffer
 when that buffer is visible
Date: Sat, 11 Jun 2016 22:25:17 -0400

tag 23749 + notabug
quit

On Sat, Jun 11, 2016 at 10:01 PM, Samuel Lê <samuel.le <at> gmail.com> wrote:
> - run "emacs -Q" from command line.
> - split emacs screen (C-x 2)
> - on one side open an elisp code (say test.el)
> - on the other side put the *scratch* buffer
> - in test.el, enter (with-current-buffer "*scratch* (insert "test\n")
> (goto-char (point-max)))
> - then press C-x e to evaluate that command
> - it inserts "test" in *scratch* buffer but doesnt go at the end of the
> - buffer.
>
> It works fine when buffer *scratch* is not visible.
>
> Thanks!
>
> In GNU Emacs 24.3.50.1 (x86_64-unknown-linux-gnu, GTK+ Version 2.24.10)

I see the same with 25.0.95. I think it's not a bug, it's simply that
the window point is stored separately. You can use

(with-current-buffer "*scratch*"
  (insert "test\n")
  (set-window-point (get-buffer-window) (point-max)))

to set it. Or if there are multiple windows and you want to set the
point in all of them:

(with-current-buffer "*scratch*"
  (insert "test\n")
  (dolist (w (get-buffer-window-list))
    (set-window-point w (point-max))))

Message #16 received at 23749 <at> debbugs.gnu.org (full text, mbox):

From: Samuel Lê <samuel.le <at> gmail.com>
To: Noam Postavsky <npostavs <at> users.sourceforge.net>
Cc: 23749 <at> debbugs.gnu.org
Subject: Re: bug#23749: 24.3.50; can't make the cursor to the end of a buffer
 when that buffer is visible
Date: Sun, 12 Jun 2016 17:44:26 +0200

I managed to do what I wanted with:

(defun insert-into-buffer (buffer text)
  (let ((buffer-window (get-buffer-window buffer)))
    (if (not buffer-window)
        (with-current-buffer buffer
          (beginning-of-line)
          (insert text)
          (goto-char (point-max)))
      (with-current-buffer buffer
        (beginning-of-line)
        (insert text)
        (set-window-point (get-buffer-window) (point-max))))))

Thanks!

On 6/12/16, Noam Postavsky <npostavs <at> users.sourceforge.net> wrote:
> tag 23749 + notabug
> quit
>
> On Sat, Jun 11, 2016 at 10:01 PM, Samuel Lê <samuel.le <at> gmail.com> wrote:
>> - run "emacs -Q" from command line.
>> - split emacs screen (C-x 2)
>> - on one side open an elisp code (say test.el)
>> - on the other side put the *scratch* buffer
>> - in test.el, enter (with-current-buffer "*scratch* (insert "test\n")
>> (goto-char (point-max)))
>> - then press C-x e to evaluate that command
>> - it inserts "test" in *scratch* buffer but doesnt go at the end of the
>> - buffer.
>>
>> It works fine when buffer *scratch* is not visible.
>>
>> Thanks!
>>
>> In GNU Emacs 24.3.50.1 (x86_64-unknown-linux-gnu, GTK+ Version 2.24.10)
>
> I see the same with 25.0.95. I think it's not a bug, it's simply that
> the window point is stored separately. You can use
>
> (with-current-buffer "*scratch*"
>   (insert "test\n")
>   (set-window-point (get-buffer-window) (point-max)))
>
> to set it. Or if there are multiple windows and you want to set the
> point in all of them:
>
> (with-current-buffer "*scratch*"
>   (insert "test\n")
>   (dolist (w (get-buffer-window-list))
>     (set-window-point w (point-max))))
>

Message #21 received at 23749-done <at> debbugs.gnu.org (full text, mbox):

From: Noam Postavsky <npostavs <at> users.sourceforge.net>
To: Samuel Lê <samuel.le <at> gmail.com>
Cc: 23749-done <at> debbugs.gnu.org
Subject: Re: bug#23749: 24.3.50; can't make the cursor to the end of a buffer
 when that buffer is visible
Date: Sun, 12 Jun 2016 11:51:31 -0400

Cool, could be compacted a little:

(defun insert-into-buffer (buffer text)
  (with-current-buffer buffer
    (beginning-of-line)
    (insert text)
    (let ((buffer-window (get-buffer-window)))
      (if buffer-window
          (set-window-point buffer-window (point-max))
        (goto-char (point-max))))))

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