GNU bug report logs - #16793
window-state-put needs a live window

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From: help-debbugs <at> gnu.org (GNU bug Tracking System)
To: Juanma Barranquero <lekktu <at> gmail.com>
Subject: bug#16793: closed (Re: bug#16793: window-state-put needs a live
 window)
Date: Wed, 19 Feb 2014 11:11:03 +0000

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Your bug report

#16793: window-state-put needs a live window

which was filed against the emacs package, has been closed.

The explanation is attached below, along with your original report.
If you require more details, please reply to 16793 <at> debbugs.gnu.org.

-- 
16793: http://debbugs.gnu.org/cgi/bugreport.cgi?bug=16793
GNU Bug Tracking System
Contact help-debbugs <at> gnu.org with problems

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From: Juanma Barranquero <lekktu <at> gmail.com>
To: martin rudalics <rudalics <at> gmx.at>
Cc: 16793-done <at> debbugs.gnu.org, Stefan Monnier <monnier <at> iro.umontreal.ca>
Subject: Re: bug#16793: window-state-put needs a live window
Date: Wed, 19 Feb 2014 12:09:24 +0100

> Installed (with the throw) in revision 116477.  You should be able to
> remove your workaround now.

Done. Thanks.

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From: Juanma Barranquero <lekktu <at> gmail.com>
To: Bug-Gnu-Emacs <bug-gnu-emacs <at> gnu.org>
Subject: window-state-put needs a live window
Date: Tue, 18 Feb 2014 17:20:04 +0100

Package: emacs
Version: 24.3.50
X-Debbugs-Cc: rudalics <at> gmx.at

There's a problem when restoring a frameset where "put"ing a window
state into the root window of a frame fails for some windows if the
frame is split (which is common enough).

It's easy to see the problem with

  emacs -Q
  C-x 2
  C-x r f a
  C-x r j a
  => "Error (frameset): #<window 6> is not a live window"

or

  emacs -Q
  ;; eval this in *scratch*
  (let (ws frw)
    (split-window)
    (setq frw (frame-root-window))
    (setq ws (window-state-get frw))
    (window-state-put ws frw))
  => "Lisp error: (error "#<window 6> is not a live window")"

Strictly speaking It's not a bug, because the docstring of
`window-state-put' says "Optional argument WINDOW must specify a live
window". But as the examples above show, it is less than useful to be
able to get the state of a window and not being able to put it again
into the same window.

In framesets, the problem arises because it's often the case that the
preferred frame to restore a window-state is the very same one the
window-state was saved from, particularly for saving/restoring in the
same session (as it happens with frameset-to-register /
jump-to-register). That minimizes flicker and simplifies dealing with
non-reused frames.

Martin suggests that frameset--restore should check that the root
window of the matching frame found is alive, and if not, discard that
frame and create a new one. That's doable, but it seems less than
optimal, from both a coding and UI perspective.

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