* indent.c (Fvertical_motion): Do move back if the Lisp string

	being displayed contains newlines.

2 files changed, 28 insertions, 7 deletions

diff --git a/src/ChangeLog b/src/ChangeLog
index 147d3533886..5f919ffedef 100644
--- a/src/ChangeLog
+++ b/src/ChangeLog
@@ -1,3 +1,8 @@
+2006-09-26  Chong Yidong  <cyd@stupidchicken.com>
+
+        * indent.c (Fvertical_motion): Do move back if the Lisp string
+        being displayed contains newlines.
+
 2006-09-26  YAMAMOTO Mitsuharu  <mituharu@math.s.chiba-u.ac.jp>
 
         * macterm.c (mac_compute_glyph_string_overhangs, XLoadQueryFont)
diff --git a/src/indent.c b/src/indent.c
index c302c5313e7..3cbb105e80f 100644
--- a/src/indent.c
+++ b/src/indent.c
@@ -2074,7 +2074,7 @@ whether or not it is currently displayed in some window.  */)
     {
       int it_start;
       int oselective;
-      int start_on_image_or_stretch_or_string_p;
+      int it_overshoot_expected_p;
 
       SET_TEXT_POS (pt, PT, PT_BYTE);
       start_display (&it, w, pt);
@@ -2086,9 +2086,26 @@ whether or not it is currently displayed in some window.  */)
          while the end position is really at some X > 0, the same X that
          PT had.  */
       it_start = IT_CHARPOS (it);
-      start_on_image_or_stretch_or_string_p = (it.method == GET_FROM_IMAGE
-                                               || it.method == GET_FROM_STRETCH
-                                               || it.method == GET_FROM_STRING);
+
+      /* We expect the call to move_it_to, further down, to overshoot
+         if the starting point is on an image, stretch glyph, or Lisp
+         string.  We won't need to backtrack in this situation, except
+         for one corner case: when the Lisp string contains a
+         newline.  */
+      if (it.method == GET_FROM_STRING)
+        {
+          const char *s = SDATA (it.string);
+          const char *e = s + SBYTES (it.string);
+
+          while (s < e && *s != '\n')
+            ++s;
+
+          it_overshoot_expected_p = (s == e);
+        }
+      else
+        it_overshoot_expected_p = (it.method == GET_FROM_IMAGE
+                                   || it.method == GET_FROM_STRETCH);
+
       reseat_at_previous_visible_line_start (&it);
       it.current_x = it.hpos = 0;
       /* Temporarily disable selective display so we don't move too far */
@@ -2099,10 +2116,9 @@ whether or not it is currently displayed in some window.  */)
 
       /* Move back if we got too far.  This may happen if
          truncate-lines is on and PT is beyond right margin.
-         It may also happen if it_start is on an image, stretch
-         glyph, or string -- in that case, don't go back.  */
+         Don't go back if the overshoot is expected (see above).  */
       if (IT_CHARPOS (it) > it_start && XINT (lines) > 0
-          && !start_on_image_or_stretch_or_string_p)
+          && !it_overshoot_expected_p)
         move_it_by_lines (&it, -1, 0);
 
       it.vpos = 0;