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From: ram-ashwin@YALE.ARPA (Ashwin Ram)
Newsgroups: comp.emacs
Subject: walk-windows
Message-ID: <8711161522.AA06021@ELI.CS.YALE.EDU>
Date: Mon, 16-Nov-87 10:22:24 EST
Article-I.D.: ELI.8711161522.AA06021
Posted: Mon Nov 16 10:22:24 1987
Date-Received: Wed, 18-Nov-87 02:49:51 EST
Sender: daemon@eddie.MIT.EDU
Lines: 54

Here's a nice abstraction that lets you do things like count-windows and
balance-windows pretty easily.  The function walk-windows applies its
argument, a procedure of one argument, to every visible window.

Now it's trivial to define count-windows (pass down a lambda that increments
a count), Mike's balance-windows (pass down a lambda that does an
enlarge-window on each window).  Etc. etc...

-- Ashwin Ram --

ARPA:    Ram-Ashwin@cs.yale.edu
UUCP:    {decvax,linus,seismo}!yale!Ram-Ashwin
BITNET:  Ram@yalecs

----------------------------------- cut -----------------------------------
;; walk-windows and friends.
;; Ashwin Ram, 11/12/87.

(defun walk-windows (proc &optional no-mini)
   "Applies PROC to each visible window.
Optional arg NO-MINI non-nil means don't apply PROC to the minibuffer
even if it is active."
   (let ((start (selected-window))
         (current (next-window (selected-window) no-mini)))
      (while (not (eq current start))
         (funcall proc current)
         (setq current (next-window current no-mini)))))

(defun count-windows (&optional no-mini)
   "Returns the number of visible windows.
Optional arg NO-MINI non-nil means don't count the minibuffer
even if it is active."
   (let ((count 1))
      (walk-windows (function (lambda (w) (ignore w)
                                 (setq count (+ count 1))))
                    no-mini)
      count))

(defun balance-windows ()
   "Makes all visible windows the same size."
   (interactive)
   (let ((start (selected-window))
         (size (/ (screen-height) (count-windows))))
      (walk-windows (function (lambda (w)
                                 (select-window w)
                                 (enlarge-window (- size (window-height)))))
                    'no-mini)
      (select-window start)))

----------------------------------- cut -----------------------------------

P.S. enlarge-window really should take a window as its argument, rather than
making you have to select the window first.  When called interactively, that
argument should default to the current window.