Fix bug #11063 with move_it_by_lines when there's a before-string at bol.

 src/xdisp.c (move_it_by_lines): When DVPOS is positive, and the
 position we get to after a call to move_it_to fails the
 IS_POS_VALID_AFTER_MOVE_P test, move to the next buffer position
 only if we wind up in a string from display property.

2 files changed, 19 insertions, 1 deletions

diff --git a/src/ChangeLog b/src/ChangeLog
index 33c93a30b08..9be289c42bb 100644
--- a/src/ChangeLog
+++ b/src/ChangeLog
@@ -1,5 +1,10 @@
 2012-03-31  Eli Zaretskii  <eliz@gnu.org>
 
+        * xdisp.c (move_it_by_lines): When DVPOS is positive, and the
+        position we get to after a call to move_it_to fails the
+        IS_POS_VALID_AFTER_MOVE_P test, move to the next buffer position
+        only if we wind up in a string from display property.  (Bug#11063)
+
         * window.c (Fdelete_other_windows_internal): Invalidate the row
         and column information about mouse highlight, so that redisplay
         restores it after reallocating the glyph matrices.  (Bug#7464)
diff --git a/src/xdisp.c b/src/xdisp.c
index 54379a2e99f..dcd14a1792a 100644
--- a/src/xdisp.c
+++ b/src/xdisp.c
@@ -8973,7 +8973,20 @@ move_it_by_lines (struct it *it, int dvpos)
     {
       move_it_to (it, -1, -1, -1, it->vpos + dvpos, MOVE_TO_VPOS);
       if (!IT_POS_VALID_AFTER_MOVE_P (it))
-        move_it_to (it, IT_CHARPOS (*it) + 1, -1, -1, -1, MOVE_TO_POS);
+        {
+          /* Only move to the next buffer position if we ended up in a
+             string from display property, not in an overlay string
+             (before-string or after-string).  That is because the
+             latter don't conceal the underlying buffer position, so
+             we can ask to move the iterator to the exact position we
+             are interested in.  Note that, even if we are already at
+             IT_CHARPOS (*it), the call below is not a no-op, as it
+             will detect that we are at the end of the string, pop the
+             iterator, and compute it->current_x and it->hpos
+             correctly.  */
+          move_it_to (it, IT_CHARPOS (*it) + it->string_from_display_prop_p,
+                      -1, -1, -1, MOVE_TO_POS);
+        }
     }
   else
     {