Fix assertion violation in redisplay.

 src/xdisp.c (try_cursor_movement): Don't use cursor position if
 set_cursor_from_row failed to compute it.  This avoids assertion
 violations in MATRIX_ROW.

2 files changed, 28 insertions, 22 deletions

diff --git a/src/ChangeLog b/src/ChangeLog
index b46650a76db..3c063ca3c0b 100644
--- a/src/ChangeLog
+++ b/src/ChangeLog
@@ -2,6 +2,9 @@
 
         * xdisp.c (init_iterator): Don't dereference a bogus face
         pointer.  (Bug#16819)
+        (try_cursor_movement): Don't use cursor position if
+        set_cursor_from_row failed to compute it.  This avoids assertion
+        violations in MATRIX_ROW.
 
 2014-02-20  Glenn Morris  <rgm@gnu.org>
 
diff --git a/src/xdisp.c b/src/xdisp.c
index 6d5b9d18260..94dd65c5d0b 100644
--- a/src/xdisp.c
+++ b/src/xdisp.c
@@ -15470,29 +15470,32 @@ try_cursor_movement (Lisp_Object window, struct text_pos startp, int *scroll_ste
                   /* As soon as we've found the exact match for point,
                      or the first suitable row whose ends_at_zv_p flag
                      is set, we are done.  */
-                  at_zv_p =
-                    MATRIX_ROW (w->current_matrix, w->cursor.vpos)->ends_at_zv_p;
-                  if (rv && !at_zv_p
-                      && w->cursor.hpos >= 0
-                      && w->cursor.hpos < MATRIX_ROW_USED (w->current_matrix,
-                                                           w->cursor.vpos))
+                  if (rv)
                     {
-                      struct glyph_row *candidate =
-                        MATRIX_ROW (w->current_matrix, w->cursor.vpos);
-                      struct glyph *g =
-                        candidate->glyphs[TEXT_AREA] + w->cursor.hpos;
-                      ptrdiff_t endpos = MATRIX_ROW_END_CHARPOS (candidate);
-
-                      exact_match_p =
-                        (BUFFERP (g->object) && g->charpos == PT)
-                        || (INTEGERP (g->object)
-                            && (g->charpos == PT
-                                || (g->charpos == 0 && endpos - 1 == PT)));
-                    }
-                  if (rv && (at_zv_p || exact_match_p))
-                    {
-                      rc = CURSOR_MOVEMENT_SUCCESS;
-                      break;
+                      at_zv_p = MATRIX_ROW (w->current_matrix,
+                                            w->cursor.vpos)->ends_at_zv_p;
+                      if (!at_zv_p
+                          && w->cursor.hpos >= 0
+                          && w->cursor.hpos < MATRIX_ROW_USED (w->current_matrix,
+                                                               w->cursor.vpos))
+                        {
+                          struct glyph_row *candidate =
+                            MATRIX_ROW (w->current_matrix, w->cursor.vpos);
+                          struct glyph *g =
+                            candidate->glyphs[TEXT_AREA] + w->cursor.hpos;
+                          ptrdiff_t endpos = MATRIX_ROW_END_CHARPOS (candidate);
+
+                          exact_match_p =
+                            (BUFFERP (g->object) && g->charpos == PT)
+                            || (INTEGERP (g->object)
+                                && (g->charpos == PT
+                                    || (g->charpos == 0 && endpos - 1 == PT)));
+                        }
+                      if (at_zv_p || exact_match_p)
+                        {
+                          rc = CURSOR_MOVEMENT_SUCCESS;
+                          break;
+                        }
                     }
                   if (MATRIX_ROW_BOTTOM_Y (row) == last_y)
                     break;