Path: utzoo!utgpu!water!watmath!clyde!ima!bbn!rochester!quiroz
From: quiroz@cs.rochester.edu (Cesar Quiroz)
Newsgroups: comp.emacs
Subject: Re: Is there a cleaner way to check for a narrowed buffer?
Summary: Not enough to check (point-min)
Message-ID: <5959@sol.ARPA>
Date: 18 Jan 88 04:38:50 GMT
References: <138@axcess.UUCP> <2336@bloom-beacon.MIT.EDU>
Reply-To: quiroz@cs.rochester.edu (Cesar Quiroz)
Organization: U of Rochester, CS Dept, Rochester, NY 14627
Lines: 31
Expires:
Sender:
Followup-To:

Brandon Allbery wants a function defined to check if the current
buffer is under narrowing.  I take he was thinking of a C primitive
or such, to complement the other narrowing functions.  Wolfgang
Rupprecht suggests this function:
:(defun narowp () 
:"Return t if buffer is narrowed."
:  (/= 1 (point-min)))

This doesn't work, as a little reflection shows.  The narrowing
might permit (= 1 (point-min))!  Think of narrowing to the first
page, for instance.  The original idea (to check if either point-min
or point-max changed) is better.  A possible implementation,
although I suspect Brandon doesn't need this code:

      (defun narrowp ()
        "True if the current buffer is narrowed.
      The value actually returned is a list of the end points of the
      restriction."
        (let ((min (point-min))
              (max (point-max)))
          (if (and (= min 1) (= max (1+ (buffer-size))))
              nil
            (list min max))))

This still fails if the restriction coincides with the whole
buffer... 
-- 
Cesar Augusto  Quiroz Gonzalez
Department of Computer Science     ...allegra!rochester!quiroz
University of Rochester            or
Rochester,  NY 14627               quiroz@cs.rochester.edu