bug#23131: switch-to-buffer-other-frame problem

[martin rudalics]

> e.g Start emacs, then drag a file (say sample.txt) onto it. File opens fine.
>
> Type C-x 5 b
>
> - minibuffer shows
> "Switch to buffer in other frame (default *GNU Emacs*):"
>
> I type "sam" [tab key for completion]
>
> - minibuffer says
> "Switch to buffer in other frame (default *GNU Emacs*): sam[No Match]"
>
> odd. If I remove the "sam" I just typed then type '?' to show the
> buffer list, it opens a 2nd buffer at the bottom and shows
>
> Possible completions are:
> *GNU Emacs*
> *Messages*
> *scratch*
>
> which does not show sample.txt, which is definitly there as I can see
> it open in the buffer at the top.

If, in this situation, you type C-x b, Emacs won't offer you sample.txt
as completion either.  Ditto for ‘switch-to-buffer-other-window’.  It's
difficult to say what the correct behavior should be.  I never use the
buffer switching commands, so I have no preference.  But I suppose that
some people would complain if C-x b offered them the buffer already
shown in the selected window as possible completion.  So where would you
draw the line?

Basically, to switch to a buffer already shown in a window W, I wouldn't
type C-x b but use C-x o to get there.  To show the buffer shown in W in
another window on the same frame, I'd type C-x 2 in W.  To show the
buffer shown in W in a window on another frame, I'd type C-x 5 2 in W.

> Also, the behaviour is apparently broken if the current buffer/window is 
split:
>
> a. open sample.txt
> b. C-x 2   -- split window in 2, top and bottom
> c. C-x 5 b  -- try to get 2nd frame
> d. sample.txt   -- type in full filename in minibuffer
> e. 2nd frame does *not* appear, cursor jumps to top of split window,
> even if was originally in bottom.
>
> can reproduce?

Why don't you just use C-x 5 2 here?  Anyway, this happens because of
the last two forms in

(defvar display-buffer--other-frame-action
  '((display-buffer-reuse-window
     display-buffer-pop-up-frame)
    (reusable-frames . 0)
    (inhibit-same-window . t))

which OT1H inhibit using the selected window and OTOH, since we have no
value for ‘reusable-frames’ to exclude the selected frame from the list
of reusable frames, allows reusing the window on the bottom.

If people think that it's worth fixing this, we would probably have to
invent a new alist entry like ‘inhibit-same-frame’.  That change might
be obtrusive though, so I would not ardently recommend it for emacs-25.

martin