(window_scroll): Handle scroll_margin

by putting point at a place that won't force recentering.

1 files changed, 28 insertions, 3 deletions

diff --git a/src/window.c b/src/window.c
index 6f8cd8188f3..f9905e38c16 100644
--- a/src/window.c
+++ b/src/window.c
@@ -2684,18 +2684,43 @@ window_scroll (window, n, noerror)
 
   if (pos < ZV)
     {
+      extern int scroll_margin;
+
+      int this_scroll_margin = scroll_margin;
+
+      /* Don't use a scroll margin that is negative or too large.  */
+      if (this_scroll_margin < 0)
+        this_scroll_margin = 0;
+
+      if (XINT (w->height) < 4 * scroll_margin)
+        this_scroll_margin = XINT (w->height) / 4;
+
       set_marker_restricted (w->start, make_number (pos), w->buffer);
       w->start_at_line_beg = bolp;
       w->update_mode_line = Qt;
       XSETFASTINT (w->last_modified, 0);
       XSETFASTINT (w->last_overlay_modified, 0);
+
+      /* If we scrolled forward, put point enough lines down
+         that it is outside the scroll margin.  */
+      if (n > 0 && this_scroll_margin > 0)
+        {
+          SET_PT (pos);
+          Fvertical_motion (make_number (this_scroll_margin), window);
+          pos = PT;
+        }
+
       if (pos > opoint)
-        SET_PT (pos);
+        {
+          SET_PT (pos);
+        }
       if (n < 0)
         {
+          /* If we scrolled backward, put point near the end of the window
+             but not within the scroll margin.  */
           SET_PT (pos);
-          tem = Fvertical_motion (make_number (ht), window);
-          if (PT > opoint || XFASTINT (tem) < ht)
+          tem = Fvertical_motion (make_number (ht - this_scroll_margin), window);
+          if (PT > opoint || XFASTINT (tem) < ht - this_scroll_margin)
             SET_PT (opoint);
           else
             Fvertical_motion (make_number (-1), window);