Implement GNU Emacs's NEXT-LINE behaviour, which only conditionally

inserts a newline if the point is at the end of the buffer, controlled
by the new variable NEXT-LINE-ADD-NEWLINES, which is by default set to
#T so as to preserve the old behaviour.

diff --git a/v7/src/edwin/motcom.scm b/v7/src/edwin/motcom.scm
index 380a7dd53e09af78414135d619a9d796c8ee0754..7a6fc20a265e13fb05487e161fc67a7544bb4ff1 100644 (file)
--- a/v7/src/edwin/motcom.scm
+++ b/v7/src/edwin/motcom.scm
@@ -1,8 +1,9 @@
 #| -*-Scheme-*-
 
-$Id: motcom.scm,v 1.51 2003/02/25 20:53:12 cph Exp $
+$Id: motcom.scm,v 1.52 2005/11/24 00:00:59 riastradh Exp $
 
 Copyright 1987,1989,1991,1993,2003 Massachusetts Institute of Technology
+Copyright 2005 Massachusetts Institute of Technology
 
 This file is part of MIT/GNU Scheme.
 
@@ -122,10 +123,20 @@ Only \\[previous-line] and \\[next-line] are affected."
        identity-procedure
        current-column)))
 
+(define-variable next-line-add-newlines
+  "Controls whether `next-line' may add newlines at buffer end.
+If true, when `next-line' is run at the end of a buffer, it will
+  insert a new line to travel onto.
+If false, when `next-line' is run at the end of a buffer, it will
+  beep and do nothing."
+  #t
+  boolean?)
+
 (define-command next-line
   "Move down vertically to next real line.
-Continuation lines are skipped.  If given after the
-last newline in the buffer, makes a new one at the end."
+Continuation lines are skipped.
+If `next-line-add-newlines' is true and this command is given after
+  the last newline in the buffer, make a new one at the end."
   "P"
   (lambda (argument)
     (let ((argument (command-argument-value argument))
@@ -136,7 +147,9 @@ last newline in the buffer, makes a new one at the end."
                   (set-current-point! (move-to-column mark column))
                   (begin
                     (set-current-point! (group-end (current-point)))
-                    (insert-newlines 1)))))
+                    (if (ref-variable next-line-add-newlines)
+                         (insert-newline)
+                         (editor-failure))))))
            ((not (zero? argument))
             (set-current-point!
              (move-to-column (line-start (current-point) argument 'FAILURE)