(line-move): Add fourth optional arg try-vscroll which

must be set to perform auto-window-vscroll.
When moving backwards and doing auto-window-vscroll, automatically
vscroll to the last part of lines which are taller than the window.
(next-line, previous-line): Set try-vscroll arg on line-move.

1 files changed, 15 insertions, 8 deletions

diff --git a/lisp/simple.el b/lisp/simple.el
index 3f3c41422a1..3d3178888bc 100644
--- a/lisp/simple.el
+++ b/lisp/simple.el
@@ -3158,12 +3158,12 @@ and more reliable (no dependence on goal column, etc.)."
           (let ((abbrev-mode nil))
             (end-of-line)
             (insert "\n"))
-        (line-move arg))
+        (line-move arg nil nil t))
     (if (interactive-p)
         (condition-case nil
-            (line-move arg)
+            (line-move arg nil nil t)
           ((beginning-of-buffer end-of-buffer) (ding)))
-      (line-move arg)))
+      (line-move arg nil nil t)))
   nil)
 
 (defun previous-line (&optional arg)
@@ -3186,9 +3186,9 @@ to use and more reliable (no dependence on goal column, etc.)."
   (or arg (setq arg 1))
   (if (interactive-p)
       (condition-case nil
-          (line-move (- arg))
+          (line-move (- arg) nil nil t)
         ((beginning-of-buffer end-of-buffer) (ding)))
-    (line-move (- arg)))
+    (line-move (- arg) nil nil t))
   nil)
 
 (defcustom track-eol nil
@@ -3227,8 +3227,8 @@ Outline mode sets this."
           (assq prop buffer-invisibility-spec)))))
 
 ;; Perform vertical scrolling of tall images if necessary.
-(defun line-move (arg &optional noerror to-end)
-  (if auto-window-vscroll
+(defun line-move (arg &optional noerror to-end try-vscroll)
+  (if (and auto-window-vscroll try-vscroll)
       (let ((forward (> arg 0))
             (part (nth 2 (pos-visible-in-window-p (point) nil t))))
         (if (and (consp part)
@@ -3244,7 +3244,14 @@ Outline mode sets this."
                                                (* (frame-char-height) (- arg))))))
                                 t)
           (set-window-vscroll nil 0)
-          (line-move-1 arg noerror to-end)))
+          (when (line-move-1 arg noerror to-end)
+            (sit-for 0)
+            (if (and (not forward)
+                     (setq part (nth 2 (pos-visible-in-window-p
+                                        (line-beginning-position) nil t)))
+                     (> (cdr part) 0))
+                (set-window-vscroll nil (cdr part) t))
+            t)))
     (line-move-1 arg noerror to-end)))
 
 ;; This is the guts of next-line and previous-line.