GNU bug report logs - #18712
24.3; IELM fails to move point in a working buffer that is also displayed

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

From: Trevor Murphy <trevor.m.murphy <at> gmail.com>
To: bug-gnu-emacs <at> gnu.org
Subject: 24.3;
 IELM fails to move point in a working buffer that is also displayed
Date: Mon, 13 Oct 2014 18:16:05 -0400

Hi, list.  I just noticed the following.  If I start from `emacs 
-Q', then go:
1. M-x ielm RET
2. C-c C-b *scratch* RET
3. Type `(goto-char 1)' at the ELISP prompt and hit RET
4. C-x 4 C-o *scratch* RET

Then I see the *scratch* buffer in the other window with its point 
on the first character in the buffer (the first `;' on the first 
line).

However, if I reverse the order of steps (3) and (4) above, again 
starting from `emacs -Q':
1. M-x ielm RET
2. C-c C-b *scratch* RET
3. C-x 4 C-o *scratch* RET
4. Type `(goto-char 1)' at the ELISP prompt and hit RET

Then I see the *scratch* buffer in the other window with its point 
unmoved (still at the start of the second line after the initial 
scratch message).

Is this a bug?  And, if so, is it reproducible given the info 
below?

Thanks in advance.

In GNU Emacs 24.3.1 (i686-pc-linux-gnu, GTK+ Version 3.12.2)
of 2014-06-11 on var-lib-archbuild-staging-i686-jgc
Windowing system distributor `The X.Org Foundation', version 
11.0.11601000
System Description:	Arch Linux

Configured using:
`configure '--prefix=/usr' '--sysconfdir=/etc' 
'--libexecdir=/usr/lib'
'--localstatedir=/var' '--with-x-toolkit=gtk3' '--with-xft'
'CFLAGS=-march=i686 -mtune=generic -O2 -pipe 
-fstack-protector-strong
--param=ssp-buffer-size=4'
'LDFLAGS=-Wl,-O1,--sort-common,--as-needed,-z,relro'
'CPPFLAGS=-D_FORTIFY_SOURCE=2''
Important settings:
 value of $LANG: en_US.UTF-8
 locale-coding-system: utf-8-unix
 default enable-multibyte-characters: t

--
Trevor Murphy
GnuPG Key: 0x83881C0A

Message #8 received at 18712 <at> debbugs.gnu.org (full text, mbox):

From: Glenn Morris <rgm <at> gnu.org>
To: Trevor Murphy <trevor.m.murphy <at> gmail.com>
Cc: 18712 <at> debbugs.gnu.org
Subject: Re: bug#18712: 24.3;
 IELM fails to move point in a working buffer that is also displayed
Date: Tue, 14 Oct 2014 11:41:06 -0400

Trevor Murphy wrote:

> 1. M-x ielm RET
> 2. C-c C-b *scratch* RET
> 3. Type `(goto-char 1)' at the ELISP prompt and hit RET
> 4. C-x 4 C-o *scratch* RET
>
> Then I see the *scratch* buffer in the other window with its point on
> the first character in the buffer (the first `;' on the first line).
>
> However, if I reverse the order of steps (3) and (4) above, again
> starting from `emacs -Q':
> 1. M-x ielm RET
> 2. C-c C-b *scratch* RET
> 3. C-x 4 C-o *scratch* RET
> 4. Type `(goto-char 1)' at the ELISP prompt and hit RET
>
> Then I see the *scratch* buffer in the other window with its point
> unmoved (still at the start of the second line after the initial
> scratch message).

I think this is not a bug; you are seeing the difference between "window
point" and "point". See section "Windows and Point" in the elisp manual.

Message #13 received at 18712 <at> debbugs.gnu.org (full text, mbox):

From: Stefan Monnier <monnier <at> IRO.UMontreal.CA>
To: Trevor Murphy <trevor.m.murphy <at> gmail.com>
Cc: 18712 <at> debbugs.gnu.org
Subject: Re: bug#18712: 24.3;
 IELM fails to move point in a working buffer that is also displayed
Date: Tue, 14 Oct 2014 14:53:53 -0400

> Is this a bug?

No, but it's a common trap.  Every buffer has as many "points" as it has
windows displaying it (plus one for the buffer itself).
So if you want to move point in a specific window, you need to either
select the window before moving, or use `set-window-point'.


        Stefan

Message #16 received at 18712 <at> debbugs.gnu.org (full text, mbox):

From: Josh <josh <at> foxtail.org>
To: Stefan Monnier <monnier <at> iro.umontreal.ca>
Cc: Trevor Murphy <trevor.m.murphy <at> gmail.com>, 18712 <at> debbugs.gnu.org
Subject: Re: bug#18712: 24.3; IELM fails to move point in a working buffer
 that is also displayed
Date: Tue, 14 Oct 2014 12:57:53 -0700

[Message part 1 (text/plain, inline)]

On Tue, Oct 14, 2014 at 11:53 AM, Stefan Monnier <monnier <at> iro.umontreal.ca>
wrote:

> > Is this a bug?
>
> No, but it's a common trap.  Every buffer has as many "points" as it has
> windows displaying it (plus one for the buffer itself).
> So if you want to move point in a specific window, you need to either
> select the window before moving, or use `set-window-point'.
>

What would be involved in implementing something like a
`ielm-change-working-window-buffer' that behaved as the OP
expected?

[Message part 2 (text/html, inline)]

Message #19 received at 18712 <at> debbugs.gnu.org (full text, mbox):

From: Stefan Monnier <monnier <at> iro.umontreal.ca>
To: Josh <josh <at> foxtail.org>
Cc: Trevor Murphy <trevor.m.murphy <at> gmail.com>, 18712 <at> debbugs.gnu.org
Subject: Re: bug#18712: 24.3;
 IELM fails to move point in a working buffer that is also displayed
Date: Tue, 14 Oct 2014 19:49:12 -0400

> What would be involved in implementing something like a
> `ielm-change-working-window-buffer' that behaved as the OP
> expected?

The same kind of code as used in ielm-change-working-buffer.


        Stefan

Message #22 received at 18712 <at> debbugs.gnu.org (full text, mbox):

From: Trevor Murphy <trevor.m.murphy <at> gmail.com>
To: Glenn Morris <rgm <at> gnu.org>, Stefan Monnier <monnier <at> iro.umontreal.ca>,
 Josh <josh <at> foxtail.org>
Cc: 18712 <at> debbugs.gnu.org
Subject: Re: bug#18712: 24.3;
 IELM fails to move point in a working buffer that is also displayed
Date: Fri, 17 Oct 2014 15:05:18 -0400

Glenn Morris <rgm <at> gnu.org> writes:

> I think this is not a bug; you are seeing the difference between 
> "window point" and "point". See section "Windows and Point" in 
> the elisp manual.

Thank you for the manual reference, Glenn.

Stefan Monnier <monnier <at> IRO.UMontreal.CA> writes:

> 
> No, but it's a common trap.  Every buffer has as many "points" 
> as it has windows displaying it (plus one for the buffer 
> itself).  So if you want to move point in a specific window, you 
> need to either select the window before moving, or use 
> `set-window-point'.

Window points!  That makes so much sense now.

Rather than rewrite the `ielm-change-working-buffer' code, I've 
just after-advised `ielm-send-input' to set the window point in 
the working buffer.

Thanks, all!

--
Trevor Murphy
GnuPG Key: 0x83881C0A

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