GNU bug report logs - #12854
24.2.50; `display-buffer-alist': conditions are not handled as documented

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From: help-debbugs <at> gnu.org (GNU bug Tracking System)
To: martin rudalics <rudalics <at> gmx.at>
Cc: tracker <at> debbugs.gnu.org
Subject: bug#12854: closed (24.2.50; `display-buffer-alist': conditions
 are not handled as documented)
Date: Fri, 16 Nov 2012 15:34:03 +0000

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Your message dated Fri, 16 Nov 2012 16:32:51 +0100
with message-id <50A65CA3.5070701 <at> gmx.at>
and subject line Re: bug#12854: 24.2.50;	`display-buffer-alist': conditions are not handled as documented
has caused the debbugs.gnu.org bug report #12854,
regarding 24.2.50; `display-buffer-alist': conditions are not handled as documented
to be marked as done.

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From: Michael Heerdegen <michael_heerdegen <at> web.de>
To: bug-gnu-emacs <at> gnu.org
Subject: 24.2.50;
	`display-buffer-alist': conditions are not handled as documented
Date: Sat, 10 Nov 2012 20:18:36 +0100

Hi,

The doc says:

> display-buffer-alist is a variable defined in `window.el'.
> [...]
> 
> Alist of conditional actions for `display-buffer'.
> This is a list of elements (CONDITION . ACTION), where:
> 
>  CONDITION is either a regexp matching buffer names, or a function
>   that takes a buffer and returns a boolean.

But the CONDITION is handled very differently by
`display-buffer-assq-regexp':

(defun display-buffer-assq-regexp (buffer-name alist)
  "Retrieve ALIST entry corresponding to BUFFER-NAME."
  (catch 'match
    (dolist (entry alist)
      (let ((key (car entry)))
	(when (or (and (stringp key)
		       (string-match-p key buffer-name))
		  (and (symbolp key) (functionp key)
		       (funcall key buffer-name alist)))
	  (throw 'match (cdr entry)))))))


Obviously, two things are wrong here:

(1) If CONDITION is a function, it currently must be a symbol.  I don't
see why lambda expressions should be forbidden.  The user should not
need to use defun only to be able specify an argument.

(2) If CONDITION is a function, it takes _two_ arguments: a buffer
_name_ (not a buffer) _and_ an alist.  That should be clarified in the
docstring.


Regards,

Michael.
    





In GNU Emacs 24.2.50.1 (x86_64-pc-linux-gnu, GTK+ Version 3.4.2)
 of 2012-11-01 on dex, modified by Debian
 (emacs-snapshot package, version 2:20121101-1)
Windowing system distributor `The X.Org Foundation', version 11.0.10707000
System Description:	Debian GNU/Linux testing (wheezy)

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From: martin rudalics <rudalics <at> gmx.at>
To: 12854-done <at> debbugs.gnu.org
Cc: michael_heerdegen <at> web.de
Subject: Re: bug#12854: 24.2.50;	`display-buffer-alist': conditions are not
	handled as documented
Date: Fri, 16 Nov 2012 16:32:51 +0100

> Obviously, two things are wrong here:
>
> (1) If CONDITION is a function, it currently must be a symbol.  I don't
> see why lambda expressions should be forbidden.  The user should not
> need to use defun only to be able specify an argument.

I lifted this restriction in revision 110885 on the Emacs-24 release
branch.

> (2) If CONDITION is a function, it takes _two_ arguments: a buffer
> _name_ (not a buffer) _and_ an alist.  That should be clarified in the
> docstring.

As a matter of fact, the code called that function with the variable
`display-buffer-alist' as second argument which doesn't make any sense.
I now pass it the ACTION argument of `display-buffer' instead and tried
to document this in the same revision as above.

Thanks, martin

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