Fix vertical cursor motion when there are overlay strings at EOL.

 src/indent.c (Fvertical_motion): Don't consider display strings on
 overlay strings as display strings on the buffer position we
 started from.  This prevents vertical cursor motion from jumping
 more than one line when there's an overlay string with a display
 property at end of line.
 Reported by Karl Chen <Karl.Chen@quarl.org> in
 http://lists.gnu.org/archive/html/emacs-devel/2013-04/msg00362.html.

1 files changed, 6 insertions, 2 deletions

diff --git a/src/indent.c b/src/indent.c
index 67796ab8a8f..47358e17db8 100644
--- a/src/indent.c
+++ b/src/indent.c
@@ -2006,11 +2006,15 @@ whether or not it is currently displayed in some window.  */)
           const char *s = SSDATA (it.string);
           const char *e = s + SBYTES (it.string);
 
+          disp_string_at_start_p =
           /* If it.area is anything but TEXT_AREA, we need not bother
              about the display string, as it doesn't affect cursor
              positioning.  */
-          disp_string_at_start_p =
-            it.string_from_display_prop_p && it.area == TEXT_AREA;
+            it.area == TEXT_AREA
+            && it.string_from_display_prop_p
+            /* A display string on anything but buffer text (e.g., on
+               an overlay string) doesn't affect cursor positioning.  */
+            && (it.sp > 0 && it.stack[it.sp - 1].method == GET_FROM_BUFFER);
           while (s < e)
             {
               if (*s++ == '\n')