Correct fallback from display-buffer-function

[Tomohiro Matsuyama]

Hi all,

I have some problem about display-buffer-function. My poor extension,
popwin.el, uses display-buffer-function for handling all operations to
windows in order to pop up particular windows in popwin's way.

If one of pop up rules matches against the buffer being to be displayed,
popwin will be responsible about the window of the buffer, and there is
no problem in this case. However, if no rules match, popwin can't
fallback the operations to windows correctly.

Currently, popwin has the following ugly code for fallback in the entity
of display-buffer-function.

;; Assume display-buffer-function to be nil here
(if (and (>= emacs-major-version 24)
(boundp 'action)
(boundp 'frame))
;; Use variables ACTION and FRAME which are formal parameters
;; of DISPLAY-BUFFER.
(display-buffer buffer action frame)
;; handle it
)

You may notice that there is no proper way to get `action' and `frame'
variables for correct fallback.
So, could you tell me a good solution for this problem?

Regards,
Tomohiro