bug#20538: 24.4; Attempt to delete a surrogate minibuffer frame

[martin rudalics <rudalics@gmx.at>]

 > I do not know how I got into this (sorry, I do not have a recipe to
 > reproduce this either).  I have a frame I want to delete by running
 > delete-frame.  Yet this only gives me the error message
 >
 >    "Attempt to delete a surrogate minibuffer frame"
 >
 > and delete-frame refuses to do its job.  What does this mean?  If
 > nothing else, Emacs could do a better job explaining to the user
 > what it believes is going on and how the user can possibly resolve
 > this.
 >
 > Possibly a relevant detail: I like to run Ediff sessions with one
 > split frame showing both buffers I need to compare.  Yet Ediff
 > sometimes comes up with its own ideas about resources it likes to
 > use, grabbing another frame to show each buffer in a separate frame.
 > If I remember correctly this happened here, too, that is, maybe
 > Emacs believes that the frame I want to delete was/is part of the
 > Ediff session.

It probably happens because ediff (by default) display the "control
panel" in a frame without minibuffer and Emacs doesn't allow to make
such a frame the last remaining one.

I use

(custom-set-variables
  '(ediff-window-setup-function (quote ediff-setup-windows-plain)))

which avoids that the control panel appears on a separate frame.

martin