Path: utzoo!utgpu!water!watmath!clyde!cbosgd!mandrill!hal!ncoast!axcess!allbery
From: allbery@axcess.UUCP (Brandon S. Allbery)
Newsgroups: comp.emacs
Subject: Is there a cleaner way to check for a narrowed buffer?
Keywords: GNU Emacs narrow-to-region
Message-ID: <138@axcess.UUCP>
Date: 16 Jan 88 02:19:36 GMT
Organization: aXcess Company, Mentor, Ohio
Lines: 29

I have a function which wants to narrow the current buffer to a region only if
it is not already narrowed.  (The narrowing separates parts of a buffer which
are edited with different major modes.)  If the buffer is already narrowed, I
want the function to signal an error.

The only way I have figured out so far to do this is the following piece of
ugliness:

	(let ((old-min (point-min))
	      (old-max (point-max)))
	  (unwind-protect
	      (progn
		(widen)
		(if (not (and (= old-min (point-min))
			      (= old-max (point-max))))
		    (error "You already have a C section in this file.")))
		  (narrow-to-region old-min old-max)))

I personally consider stuff like "unwind-protect" to be for use in special
situations -- and checking for narrowing isn't one of them, or shouldn't be.
I guess it's done in the C code rather than Lisp (since the format %n is used
in the modeline rather than checking for a variable's value), but why isn't
some special function provided ( (narrowp) or something ) to do this?
-- 
 ___  ________________,	Brandon S. Allbery	       cbosgd \
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