(try_window_reusing_current_matrix)

<new start <= old start>:  Disable rows in the current matrix
which are below the window after scrolling.

2 files changed, 17 insertions, 2 deletions

diff --git a/src/ChangeLog b/src/ChangeLog
index 8c8fb7d43d8..7d54241ad0a 100644
--- a/src/ChangeLog
+++ b/src/ChangeLog
@@ -1,5 +1,15 @@
 2000-12-29  Gerd Moellmann  <gerd@gnu.org>
 
+        * dispnew.c (check_current_matrix_flags) [GLYPH_DEBUG]: New
+        function.
+        (update_window) [GLYPH_DEBUG]: Call it.
+        (scrolling_window): Prevent including current rows which are below
+        what's displayed in the window.
+
+        * xdisp.c (try_window_reusing_current_matrix)
+        <new start <= old start>:  Disable rows in the current matrix
+        which are below the window after scrolling.
+        
         * xdisp.c (move_it_by_lines): Don't do optimizations if NEED_Y_P
         is zero.  It's not worth the complexity.
         (invisible_text_between_p): Put in #if 0 because unused.
diff --git a/src/xdisp.c b/src/xdisp.c
index ae35c982e97..ed98ced48a2 100644
--- a/src/xdisp.c
+++ b/src/xdisp.c
@@ -10185,10 +10185,10 @@ try_window_reusing_current_matrix (w)
                          MATRIX_ROW_VPOS (bottom_row, w->current_matrix),
                          nrows_scrolled);
           
-          /* Disable lines not reused.  */
+          /* Disable lines that must be updated.  */
           for (i = 0; i < it.vpos; ++i)
             (start_row + i)->enabled_p = 0;
-          
+
           /* Re-compute Y positions.  */
           min_y = WINDOW_DISPLAY_HEADER_LINE_HEIGHT (w);
           max_y = it.last_visible_y;
@@ -10213,6 +10213,11 @@ try_window_reusing_current_matrix (w)
               if (MATRIX_ROW_BOTTOM_Y (row) >= it.last_visible_y)
                 break;
             }
+          
+          /* Disable lines in the current matrix which are now
+             below the window.  */
+          for (; row < bottom_row; ++row)
+            row->enabled_p = 0;
         }
 
       /* Update window_end_pos etc.; last_reused_text_row is the last