Fix bug #11261 with cursor movement in a continued line when header line is present.

 src/xdisp.c (string_buffer_position_lim): Limit starting position to BEGV.
 (set_cursor_from_row): If called for a mode-line or header-line
 row, return zero immediately.
 (try_cursor_movement): If inside continuation line, don't back up
 farther than the first row after the header line, if any.  Don't
 consider the header-line row as "partially visible", even if
 MATRIX_ROW_PARTIALLY_VISIBLE_P returns non-zero.

2 files changed, 28 insertions, 4 deletions

diff --git a/src/ChangeLog b/src/ChangeLog
index 73c67125257..42c582994cf 100644
--- a/src/ChangeLog
+++ b/src/ChangeLog
@@ -1,3 +1,14 @@
+2012-04-17  Eli Zaretskii  <eliz@gnu.org>
+
+        * xdisp.c (string_buffer_position_lim): Limit starting position to
+        BEGV.
+        (set_cursor_from_row): If called for a mode-line or header-line
+        row, return zero immediately.
+        (try_cursor_movement): If inside continuation line, don't back up
+        farther than the first row after the header line, if any.  Don't
+        consider the header-line row as "partially visible", even if
+        MATRIX_ROW_PARTIALLY_VISIBLE_P returns non-zero.  (Bug#11261)
+
 2012-04-13  Atsuo Ohki  <ohki@gssm.otsuka.tsukuba.ac.jp>  (tiny change)
 
         * lread.c (lisp_file_lexically_bound_p): Fix hang at ";-*-\n" (bug#11238).
diff --git a/src/xdisp.c b/src/xdisp.c
index 61b0b9df5e1..9881adfa34d 100644
--- a/src/xdisp.c
+++ b/src/xdisp.c
@@ -4979,7 +4979,7 @@ string_buffer_position_lim (Lisp_Object string,
   Lisp_Object limit, prop, pos;
   int found = 0;
 
-  pos = make_number (from);
+  pos = make_number (max (from, BEGV));
 
   if (!back_p)  /* looking forward */
     {
@@ -13690,6 +13690,13 @@ set_cursor_from_row (struct window *w, struct glyph_row *row,
      comes from a text property, not from an overlay.  */
   int string_from_text_prop = 0;
 
+  /* Don't even try doing anything if called for a mode-line or
+     header-line row, since the rest of the code isn't prepared to
+     deal with such calamities.  */
+  xassert (!row->mode_line_p);
+  if (row->mode_line_p)
+    return 0;
+
   /* Skip over glyphs not having an object at the start and the end of
      the row.  These are special glyphs like truncation marks on
      terminal frames.  */
@@ -14906,6 +14913,8 @@ try_cursor_movement (Lisp_Object window, struct text_pos startp, int *scroll_ste
           else if (rc != CURSOR_MOVEMENT_SUCCESS
                    && !NILP (BVAR (XBUFFER (w->buffer), bidi_display_reordering)))
             {
+              struct glyph_row *row1;
+
               /* If rows are bidi-reordered and point moved, back up
                  until we find a row that does not belong to a
                  continuation line.  This is because we must consider
@@ -14916,24 +14925,28 @@ try_cursor_movement (Lisp_Object window, struct text_pos startp, int *scroll_ste
               /* FIXME: Revisit this when glyph ``spilling'' in
                  continuation lines' rows is implemented for
                  bidi-reordered rows.  */
-              while (MATRIX_ROW_CONTINUATION_LINE_P (row))
+              for (row1 = MATRIX_FIRST_TEXT_ROW (w->current_matrix);
+                   MATRIX_ROW_CONTINUATION_LINE_P (row);
+                   --row)
                 {
                   /* If we hit the beginning of the displayed portion
                      without finding the first row of a continued
                      line, give up.  */
-                  if (row <= w->current_matrix->rows)
+                  if (row <= row1)
                     {
                       rc = CURSOR_MOVEMENT_MUST_SCROLL;
                       break;
                     }
                   xassert (row->enabled_p);
-                  --row;
                 }
             }
           if (must_scroll)
             ;
           else if (rc != CURSOR_MOVEMENT_SUCCESS
               && MATRIX_ROW_PARTIALLY_VISIBLE_P (w, row)
+              /* Make sure this isn't a header line by any chance, since
+                 then MATRIX_ROW_PARTIALLY_VISIBLE_P might yield non-zero.  */
+              && !row->mode_line_p
               && make_cursor_line_fully_visible_p)
             {
               if (PT == MATRIX_ROW_END_CHARPOS (row)