GNU bug report logs - #25169
26.0.50; display-buffer doesn't set window width correctly

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

From: Liu Hui <liuhui1610 <at> gmail.com>
To: bug-gnu-emacs <at> gnu.org
Subject: 26.0.50; display-buffer doesn't set window width correctly
Date: Sun, 11 Dec 2016 20:18:33 +0800

Recipe 1:

1. Emacs -Q
2. evaluate the following code in *scratch*:

   (display-buffer (get-buffer-create "aaa")
                  '(display-buffer-pop-up-window
                    (window-width . 20)))
   ;; => correct window width for buffer "aaa"

   (display-buffer (get-buffer-create "bbb")
                  '(display-buffer-pop-up-window
                    (window-width . 20)))
   ;; => changed and larger window width for buffer "bbb"


Recipe 2:

1. Emacs -Q
2. evaluate the following code in *scratch*:

   (display-buffer (get-buffer-create "aaa")
		  '(display-buffer-in-side-window
		    (window-width . 20)
		    (side . right)))
   ;; => correct window width for buffer "aaa"

   (display-buffer (get-buffer-create "bbb")
		  '(display-buffer-in-side-window
		    (window-width . 20)
		    (side . left)))
   ;; => correct width for buffer "bbb", but the window width of
   ;; buffer "aaa" is changed and becomes larger


In GNU Emacs 26.0.50.2 (x86_64-pc-linux-gnu, GTK+ Version 3.18.9)
 of 2016-12-10 built on lgw01-57
Windowing system distributor 'The X.Org Foundation', version 11.0.11804000
System Description:	Ubuntu 16.04.1 LTS

Message #8 received at 25169 <at> debbugs.gnu.org (full text, mbox):

From: martin rudalics <rudalics <at> gmx.at>
To: Liu Hui <liuhui1610 <at> gmail.com>, 25169 <at> debbugs.gnu.org
Subject: Re: bug#25169: 26.0.50;
 display-buffer doesn't set window width correctly
Date: Sun, 11 Dec 2016 17:19:47 +0100

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

Thanks for the report.

> Recipe 1:
>
> 1. Emacs -Q
> 2. evaluate the following code in *scratch*:
>
>     (display-buffer (get-buffer-create "aaa")
>                    '(display-buffer-pop-up-window
>                      (window-width . 20)))
>     ;; => correct window width for buffer "aaa"
>
>     (display-buffer (get-buffer-create "bbb")
>                    '(display-buffer-pop-up-window
>                      (window-width . 20)))
>     ;; => changed and larger window width for buffer "bbb"

Recipe 1 is difficult to reproduce here.  I made my initial frame 169
columns wide to get a side-by-side split when displaying aaa and to
_not_ get another side-by-side split when displaying bbb.  What happens
is that ‘display-buffer-pop-up-window’ refuses to make a new window for
bbb (you can reduce the value of ‘split-width-threshold’ to get a split)
so ‘display-buffer’ rather uses aaa's window to display bbb via
‘display-buffer-use-some-window’.  The latter ignores the ‘window-width’
entry but applies ‘window--even-window-sizes’ instead.

So this is not a bug but admittedly a very confusing sequence of events.

> Recipe 2:
>
> 1. Emacs -Q
> 2. evaluate the following code in *scratch*:
>
>     (display-buffer (get-buffer-create "aaa")
>            '(display-buffer-in-side-window
>              (window-width . 20)
>              (side . right)))
>     ;; => correct window width for buffer "aaa"
>
>     (display-buffer (get-buffer-create "bbb")
>            '(display-buffer-in-side-window
>              (window-width . 20)
>              (side . left)))
>     ;; => correct width for buffer "bbb", but the window width of
>     ;; buffer "aaa" is changed and becomes larger

This is a bug and I attached a fix for it.  Please try it.

Note, however, that in general you can rely on Emacs to preserve the
size of a window like that of aaa in recipe 2 if and only if you run
‘window-preserve-size’ on that window - either explicitly or via a
`preserve-size' argument.

martin

(BTW: Does the ibuffer scenario from bug#25115 work orderly now?)

[window.el.diff (text/plain, attachment)]

Message #11 received at 25169 <at> debbugs.gnu.org (full text, mbox):

From: Liu Hui <liuhui1610 <at> gmail.com>
To: martin rudalics <rudalics <at> gmx.at>
Cc: 25169 <at> debbugs.gnu.org
Subject: Re: bug#25169: 26.0.50; display-buffer doesn't set window width
 correctly
Date: Mon, 12 Dec 2016 12:53:08 +0800

> Recipe 1 is difficult to reproduce here.  I made my initial frame 169
> columns wide to get a side-by-side split when displaying aaa and to
> _not_ get another side-by-side split when displaying bbb.  What happens
> is that ‘display-buffer-pop-up-window’ refuses to make a new window for
> bbb (you can reduce the value of ‘split-width-threshold’ to get a split)
> so ‘display-buffer’ rather uses aaa's window to display bbb via
> ‘display-buffer-use-some-window’.  The latter ignores the ‘window-width’
> entry but applies ‘window--even-window-sizes’ instead.
>
> So this is not a bug but admittedly a very confusing sequence of events.

I see. Thanks for the explanation.


> This is a bug and I attached a fix for it.  Please try it.
>
> Note, however, that in general you can rely on Emacs to preserve the
> size of a window like that of aaa in recipe 2 if and only if you run
> ‘window-preserve-size’ on that window - either explicitly or via a
> `preserve-size' argument.

The problem is fixed. Thanks again!


> (BTW: Does the ibuffer scenario from bug#25115 work orderly now?)

Yes, and I'll add some information in that thread.

Message #16 received at 25169-done <at> debbugs.gnu.org (full text, mbox):

From: martin rudalics <rudalics <at> gmx.at>
To: Liu Hui <liuhui1610 <at> gmail.com>
Cc: 25169-done <at> debbugs.gnu.org
Subject: Re: bug#25169: 26.0.50;
 display-buffer doesn't set window width correctly
Date: Mon, 12 Dec 2016 11:00:06 +0100

> The problem is fixed. Thanks again!

Installed on master.  Closing this bug.

Thanks, martin

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