ediff behavior with ediff-setup-windows-plain

[Klaus Zeitler]

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In GNU Emacs 21.2.2 (sparc-sun-solaris2.7, Motif Version 2.1.0)
 of 2002-04-25 on sfsw54
configured using `configure  --with-gcc 
--prefix=/vol/freeware/SunOS-5.7/emacs/21.2 
--sharedstatedir=/vol/freeware/SunOS-5.7/emacs/21.2/share 
--with-x-toolkit=motif --x-includes=/usr/openwin/include:/usr/local/gnu/include 
--x-libraries=/usr/openwin/lib:/usr/local/gnu/lib --with-pop'
Important settings:
  value of $LC_ALL: nil
  value of $LC_COLLATE: nil
  value of $LC_CTYPE: nil
  value of $LC_MESSAGES: nil
  value of $LC_MONETARY: nil
  value of $LC_NUMERIC: nil
  value of $LC_TIME: nil
  value of $LANG: C
  locale-coding-system: nil
  default-enable-multibyte-characters: t

Please describe exactly what actions triggered the bug
and the precise symptoms of the bug:

in emacs 20.7 I've used the following sequence to start ediff in a new frame
but with all diff buffers in one frame (maybe one should do that differently
but at least it worked):


(add-hook 'ediff-mode-hook (lambda () (select-frame (make-frame))))
(setq ediff-window-setup-function 'ediff-setup-windows-plain)
(add-hook 'ediff-startup-hook 'ediff-toggle-wide-display)


this doesn't work properly anymore in emacs 21.2.
emacs now displays the diffs in both frames and jumps back and forth between
those 2 frames.
I debugged a bit and I think it's caused by the function
ediff-skip-unsuitable-frames that seems to be rewritten in version 21.
When I change this function back to the old one from 20.7 emacs
behaves normally (the way I expect it), i.e. opens a new frame with 3 windows
and the other frame doesn't change.

Here's the call stack for ediff-files upto what I think is the culprit:

* ediff-skip-unsuitable-frames()
  ediff-destroy-control-frame(#<buffer *Ediff Control Panel*>)
  ediff-setup-windows-plain-compare(#<buffer c1> #<buffer c2> nil #<buffer 
*Ediff Control Panel*>)
  ediff-setup-windows-plain(#<buffer c1> #<buffer c2> nil #<buffer *Ediff 
Control Panel*>)
  ediff-setup-windows(#<buffer c1> #<buffer c2> nil #<buffer *Ediff Control 
Panel*>)
  ediff-setup(#<buffer c1> "/home/kzeitler/tst/c1" #<buffer c2> 
"/home/kzeitler/tst/c2" nil nil nil ((ediff-job-name . ediff-files)) nil)
  ediff-files-internal("/home/kzeitler/tst/c1" "/home/kzeitler/tst/c2" nil nil 
ediff-files)
  ediff-files("/home/kzeitler/tst/c1" "/home/kzeitler/tst/c2")



Recent input:
<down-mouse-1> <mouse-1> <down-mouse-2> <mouse-2> <up> 
<up> <left> C-j <down> <down> <left> C-j <down> <down> 
<left> C-j <escape> x e d i f f - f i l e s <return> 
C-a C-k ~ / t s t / c 1 <return> <up> <backspace> 2 
<return> <switch-frame> <help-echo> <down-mouse-1> 
<mouse-1> n <switch-frame> <switch-frame> <switch-frame> 
<switch-frame> <down-mouse-1> <mouse-1> q y <help-echo> 
<help-echo> <help-echo> <help-echo> <switch-frame> 
<down-mouse-1> <mouse-movement> <mouse-1> C-x 5 0 C-a 
C-x k <return> C-x k <return> <help-echo> <help-echo> 
<menu-bar> <help-menu> <report-emacs-bug>

Recent messages:
Reading file /home/kzeitler/tst/c1 ... 
Reading file /home/kzeitler/tst/c2 ... 
Computing differences between c1 and c2 ...

Buffer A: Processing difference region 0 of 1
Buffer B: Processing difference region 0 of 1
Processing difference regions ... done
Refining difference region 1 ...
 [4 times]
Loading emacsbug...done