From 36b397480763811bfbd3e70ae21fbbab2468b3df Mon Sep 17 00:00:00 2001
From: Chris Hanson <org/chris-hanson/cph>
Date: Thu, 16 Feb 1995 22:45:37 +0000
Subject: [PATCH] Fix bug in redisplay: when variables that affect display
 (e.g. truncate-lines) are changed, the window start marks must be erased.
 Otherwise, the old start marks are used, and with the new display variables
 in effect, these marks could cause point to be left offscreen, or even force
 all of the buffer's text to be offscreen!

---
 v7/src/edwin/bufwin.scm | 24 ++++++++++++++----------
 1 file changed, 14 insertions(+), 10 deletions(-)

diff --git a/v7/src/edwin/bufwin.scm b/v7/src/edwin/bufwin.scm
index 12da7cc35..ec1d18f09 100644
--- a/v7/src/edwin/bufwin.scm
+++ b/v7/src/edwin/bufwin.scm
@@ -1,8 +1,8 @@
 ;;; -*-Scheme-*-
 ;;;
-;;;	$Id: bufwin.scm,v 1.303 1994/09/08 20:34:04 adams Exp $
+;;;	$Id: bufwin.scm,v 1.304 1995/02/16 22:45:37 cph Exp $
 ;;;
-;;;	Copyright (c) 1986, 1989-93 Massachusetts Institute of Technology
+;;;	Copyright (c) 1986, 1989-95 Massachusetts Institute of Technology
 ;;;
 ;;;	This material was developed by the Scheme project at the
 ;;;	Massachusetts Institute of Technology, Department of
@@ -807,8 +807,7 @@
 (define (%clear-window-buffer-state! window)
   (%set-window-buffer! window false)
   (%set-window-point! window false)
-  (if (%window-start-line-mark window)
-      (clear-window-start! window))
+  (clear-window-start! window)
   (%clear-window-incremental-redisplay-state! window))
 
 (define (%clear-window-incremental-redisplay-state! window)
@@ -837,7 +836,7 @@
 	(mark-temporary! (%window-end-clip-mark window))
 	(%set-window-end-clip-mark! window false)))
   (%set-window-point-moved?! window false))
-
+
 (define-integrable (update-modified-tick! window)
   (%set-window-modified-tick! window
 			      (group-modified-tick (%window-group window))))
@@ -849,6 +848,7 @@
 	     (if (not (eqv? new-value old-value))
 		 (begin
 		   (%set-window-force-redraw?! window #t)
+		   (clear-window-start! window)
 		   (write window new-value))))))
 	(buffer (%window-buffer window)))
     (maybe-recache
@@ -1044,11 +1044,15 @@ This number is a percentage, where 0 is the window's top and 100 the bottom."
       (%set-window-point-moved?! window true))
   (window-needs-redisplay! window))
 
-(define-integrable (clear-window-start! window)
-  (mark-temporary! (%window-start-line-mark window))
-  (%set-window-start-line-mark! window false)
-  (mark-temporary! (%window-start-mark window))
-  (%set-window-start-mark! window false)
+(define (clear-window-start! window)
+  (if (%window-start-line-mark window)
+      (begin
+	(mark-temporary! (%window-start-line-mark window))
+	(%set-window-start-line-mark! window #f)))
+  (if (%window-start-mark window)
+      (begin
+	(mark-temporary! (%window-start-mark window))
+	(%set-window-start-mark! window #f)))
   (%set-window-start-line-y! window 0)
   (%set-window-start-column! window 0)
   (%set-window-start-partial! window 0))
-- 
2.25.1