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From: jr@LF-SERVER-2.BBN.COM (John Robinson)
Newsgroups: comp.emacs
Subject: Re: How many windows?
Message-ID: <8711091632.AA27117@ucbvax.Berkeley.EDU>
Date: Mon, 9-Nov-87 11:32:23 EST
Article-I.D.: ucbvax.8711091632.AA27117
Posted: Mon Nov  9 11:32:23 1987
Date-Received: Wed, 11-Nov-87 06:15:41 EST
References: <231@usl-pc.UUCP>
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Reply-To: jr@ALEXANDER.BBN.COM
Organization: The ARPA Internet
Lines: 45

>> Is there any way to find out how many windows are on the screen in a
>> Elisp program (GNU Emacs version 18.??).

Yes. There is a lisp structure that tracks what buffers are visible.

>> I have a program that I want
>> to automatically split the screen into two windows, ONLY two windows,
>> that is, if we already have two windows on the screen, we DON'T want
>> to split into THREE windows.

Emacs' functions that pop up windows generally won't go from two to
three windows.  For example:

 odisplay-buffer:
 Make BUFFER appear in some window but don't select it.
 BUFFER can be a buffer or a buffer name.
 If BUFFER is shown already in some window, just uses that one,
 unless the window is the selected window and NOTTHISWINDOW is non-nil.
 Returns the window displaying BUFFER.

and

 pop-to-buffer:
 Select buffer BUFFER in some window, preferably a different one.
 If  pop-up-windows  is non-nil, windows can be split to do this.
 If second arg  OTHER-WINDOW is non-nil, insist on finding another
 window even if BUFFER is already visible in the selected window.

The mh-e package (lisp/mh-e.el) has a fairly crufty example of how to
arrange the screen to have a particular appearance:

    ;; These contortions are to force the summary line to be the top window.
    (switch-to-buffer-other-window folder)
    (delete-other-windows)
    (switch-to-buffer-other-window mh-show-buffer)
    (switch-to-buffer-other-window folder)
    (shrink-window (- (window-height) mh-summary-height))
    (recenter 1)

which makes the top window be mh-summary-height on buffer "folder",
and the rest of the screen (except the minibuffer) be on the buffer
"mh-show-buffer".

/jr
jr@bbn.com or jr@bbn.nLro