Fix the row number mistakenly reported by pos_visible_p in rare cases.

 src/xdisp.c (pos_visible_p): Properly save and restore the iterator
 state around the call to line_bottom, since it can move the
 iterator to another screen line.  This fixes off-by-one errors in
 the reported row in some rare cases.

2 files changed, 16 insertions, 6 deletions

diff --git a/src/ChangeLog b/src/ChangeLog
index e834a2cc161..274817d8262 100644
--- a/src/ChangeLog
+++ b/src/ChangeLog
@@ -1,3 +1,10 @@
+2014-09-09  Eli Zaretskii  <eliz@gnu.org>
+
+        * xdisp.c (pos_visible_p): Properly save and restore the iterator
+        state around the call to line_bottom, since it can move the
+        iterator to another screen line.  This fixes off-by-one errors in
+        the reported row in some rare cases.
+
 2014-09-07  Eli Zaretskii  <eliz@gnu.org>
 
         * dispnew.c (prepare_desired_row): When MODE_LINE_P is zero,
diff --git a/src/xdisp.c b/src/xdisp.c
index d435bf148a0..6991e44b931 100644
--- a/src/xdisp.c
+++ b/src/xdisp.c
@@ -1452,11 +1452,15 @@ pos_visible_p (struct window *w, ptrdiff_t charpos, int *x, int *y,
          glyph.  */
       int top_x = it.current_x;
       int top_y = it.current_y;
-      /* Calling line_bottom_y may change it.method, it.position, etc.  */
-      enum it_method it_method = it.method;
-      int bottom_y = (last_height = 0, line_bottom_y (&it));
       int window_top_y = WINDOW_HEADER_LINE_HEIGHT (w);
+      int bottom_y;
+      struct it save_it;
+      void *save_it_data = NULL;
 
+      /* Calling line_bottom_y may change it.method, it.position, etc.  */
+      SAVE_IT (save_it, it, save_it_data);
+      last_height = 0;
+      bottom_y = line_bottom_y (&it);
       if (top_y < window_top_y)
         visible_p = bottom_y > window_top_y;
       else if (top_y < it.last_visible_y)
@@ -1473,7 +1477,6 @@ pos_visible_p (struct window *w, ptrdiff_t charpos, int *x, int *y,
              move_it_to again with a slightly larger vertical limit,
              and see if it actually moved vertically; if it did, we
              didn't really reach CHARPOS, which is beyond window end.  */
-          struct it save_it = it;
           /* Why 10? because we don't know how many canonical lines
              will the height of the next line(s) be.  So we guess.  */
           int ten_more_lines = 10 * default_line_pixel_height (w);
@@ -1483,11 +1486,11 @@ pos_visible_p (struct window *w, ptrdiff_t charpos, int *x, int *y,
           if (it.current_y > top_y)
             visible_p = 0;
 
-          it = save_it;
         }
+      RESTORE_IT (&it, &save_it, save_it_data);
       if (visible_p)
         {
-          if (it_method == GET_FROM_DISPLAY_VECTOR)
+          if (it.method == GET_FROM_DISPLAY_VECTOR)
             {
               /* We stopped on the last glyph of a display vector.
                  Try and recompute.  Hack alert!  */