Fix scrolling back with scroll-down-aggressively.

 src/xdisp.c (try_scrolling): Clean up the case of PT below the
 margin at bottom of window: scroll_max can no longer be INT_MAX.
 (redisplay_window): Find character position of margin and use
 that, rather than adding margin to PT.

diff --git a/src/ChangeLog b/src/ChangeLog
index d4301c482e998200c507c5a49ba4a2e122ed042e..e7a93ab7819168f2eea37adedd5bbbeb97df9115 100644 (file)
--- a/src/ChangeLog
+++ b/src/ChangeLog
@@ -1,3 +1,10 @@
+2011-03-27  Eli Zaretskii  <eliz@gnu.org>
+
+       * xdisp.c (try_scrolling): Clean up the case of PT below the
+       margin at bottom of window: scroll_max can no longer be INT_MAX.
+       (redisplay_window): Find character position of margin and use
+       that, rather than adding margin to PT.
+
 2011-03-26  Eli Zaretskii  <eliz@gnu.org>
 
        * xdisp.c (redisplay_window): Don't check buffer's clip_changed

diff --git a/src/xdisp.c b/src/xdisp.c
index 230e2fa18640f22c892c5cf0f3789cbfb380dc94..1b72f2e308120bed9cd4e29cdc6de21bc596d89a 100644 (file)
--- a/src/xdisp.c
+++ b/src/xdisp.c
@@ -13083,10 +13083,7 @@ try_scrolling (Lisp_Object window, int just_this_one_p,
             always finds PT if scroll_conservatively is set to a large
             number, such as most-positive-fixnum.  */
          int slack = max (scroll_max, 10 * FRAME_LINE_HEIGHT (f));
-         int y_to_move =
-           slack >= INT_MAX - it.last_visible_y
-           ? INT_MAX
-           : it.last_visible_y + slack;
+         int y_to_move = it.last_visible_y + slack;
 
          /* Compute the distance from the scroll margin to PT or to
             the scroll limit, whichever comes first.  This should
@@ -13198,8 +13195,8 @@ try_scrolling (Lisp_Object window, int just_this_one_p,
          start_display (&it, w, startp);
 
          if (arg_scroll_conservatively)
-           amount_to_scroll
-             = max (dy, FRAME_LINE_HEIGHT (f) * max (scroll_step, temp_scroll_step));
+           amount_to_scroll = max (dy, FRAME_LINE_HEIGHT (f) *
+                                   max (scroll_step, temp_scroll_step));
          else if (scroll_step || temp_scroll_step)
            amount_to_scroll = scroll_max;
          else
@@ -14238,8 +14235,22 @@ redisplay_window (Lisp_Object window, int just_this_one_p)
        scroll_margin > 0
        ? min (scroll_margin, WINDOW_TOTAL_LINES (w) / 4)
        : 0;
-      int scrolling_up = PT > CHARPOS (startp) + margin;
-      Lisp_Object aggressive =
+      EMACS_INT margin_pos = CHARPOS (startp);
+      int scrolling_up;
+      Lisp_Object aggressive;
+
+      /* If there is a scroll margin at the top of the window, find
+        its character position.  */
+      if (margin)
+       {
+         struct it it1;
+
+         start_display (&it1, w, startp);
+         move_it_vertically (&it1, margin);
+         margin_pos = IT_CHARPOS (it1);
+       }
+      scrolling_up = PT > margin_pos;
+      aggressive =
        scrolling_up
        ? BVAR (current_buffer, scroll_up_aggressively)
        : BVAR (current_buffer, scroll_down_aggressively);
@@ -14280,7 +14291,8 @@ redisplay_window (Lisp_Object window, int just_this_one_p)
            centering_position = margin * FRAME_LINE_HEIGHT (f) + pt_offset;
        }
       else
-       /* Move backward from point half the height of the window.  */
+       /* Set the window start half the height of the window backward
+          from point.  */
        centering_position = window_box_height (w) / 2;
     }
   move_it_vertically_backward (&it, centering_position);