Fix bug #18276 with vertical motion through a display property.

 src/indent.c (Fvertical_motion): Fix vertical motion up through a
 display property after a newline.

2 files changed, 28 insertions, 8 deletions

diff --git a/src/ChangeLog b/src/ChangeLog
index 8c89f693bca..3a2e03aa99c 100644
--- a/src/ChangeLog
+++ b/src/ChangeLog
@@ -1,3 +1,8 @@
+2014-08-18  Eli Zaretskii  <eliz@gnu.org>
+
+        * indent.c (Fvertical_motion): Fix vertical motion up through a
+        display property after a newline.  (Bug#18276)
+
 2014-08-17  Eli Zaretskii  <eliz@gnu.org>
 
         * xdisp.c (display_line): Don't assume that the call to
diff --git a/src/indent.c b/src/indent.c
index 711792f75cd..026f44ccf9c 100644
--- a/src/indent.c
+++ b/src/indent.c
@@ -2004,6 +2004,8 @@ whether or not it is currently displayed in some window.  */)
       int first_x;
       bool overshoot_handled = 0;
       bool disp_string_at_start_p = 0;
+      ptrdiff_t nlines = XINT (lines);
+      int vpos_init = 0;
 
       itdata = bidi_shelve_cache ();
       SET_TEXT_POS (pt, PT, PT_BYTE);
@@ -2093,18 +2095,31 @@ whether or not it is currently displayed in some window.  */)
 
           overshoot_handled = 1;
         }
-      if (XINT (lines) <= 0)
+      else if (IT_CHARPOS (it) == PT - 1
+               && FETCH_BYTE (PT - 1) == '\n'
+               && nlines < 0)
         {
-          it.vpos = 0;
+          /* The position we started from was covered by a display
+             property, so we moved to position before the string, and
+             backed up one line, because the character at PT - 1 is a
+             newline.  So we need one less line to go up.  */
+          nlines++;
+          /* But we still need to record that one line, in order to
+             return the correct value to the caller.  */
+          vpos_init = -1;
+        }
+      if (nlines <= 0)
+        {
+          it.vpos = vpos_init;
           /* Do this even if LINES is 0, so that we move back to the
              beginning of the current line as we ought.  */
-          if (XINT (lines) == 0 || IT_CHARPOS (it) > 0)
-            move_it_by_lines (&it, max (PTRDIFF_MIN, XINT (lines)));
+          if (nlines == 0 || IT_CHARPOS (it) > 0)
+            move_it_by_lines (&it, max (PTRDIFF_MIN, nlines));
         }
       else if (overshoot_handled)
         {
           it.vpos = 0;
-          move_it_by_lines (&it, min (PTRDIFF_MAX, XINT (lines)));
+          move_it_by_lines (&it, min (PTRDIFF_MAX, nlines));
         }
       else
         {
@@ -2119,13 +2134,13 @@ whether or not it is currently displayed in some window.  */)
                   it.vpos = 0;
                   move_it_by_lines (&it, 1);
                 }
-              if (XINT (lines) > 1)
-                move_it_by_lines (&it, min (PTRDIFF_MAX, XINT (lines) - 1));
+              if (nlines > 1)
+                move_it_by_lines (&it, min (PTRDIFF_MAX, nlines - 1));
             }
           else
             {
               it.vpos = 0;
-              move_it_by_lines (&it, min (PTRDIFF_MAX, XINT (lines)));
+              move_it_by_lines (&it, min (PTRDIFF_MAX, nlines));
             }
         }