Fix crash with invisible text and overlays (Bug#7016).

* src/dispextern.h (struct it): New member overlay_strings_charpos.

* src/xdisp.c (next_overlay_string, load_overlay_strings): Record the
charpos where we computed n_overlay_strings.
(next_overlay_string): Load overlay strings at recorded position,
which may not be the same as the iterator's charpos (Bug#7016).

3 files changed, 22 insertions, 3 deletions

diff --git a/src/ChangeLog b/src/ChangeLog
index d10b5d194a9..3293ec08da5 100644
--- a/src/ChangeLog
+++ b/src/ChangeLog
@@ -1,3 +1,12 @@
+2010-12-06  Chong Yidong  <cyd@stupidchicken.com>
+
+        * dispextern.h (struct it): New member overlay_strings_charpos.
+
+        * xdisp.c (next_overlay_string, load_overlay_strings): Record the
+        charpos where we computed n_overlay_strings.
+        (next_overlay_string): Load overlay strings at recorded position,
+        which may not be the same as the iterator's charpos (Bug#7016).
+
 2010-12-05  Jan Djärv  <jan.h.d@swipnet.se>
 
         * nsterm.m (ns_dumpglyphs_image): If drawing cursor, fill background
diff --git a/src/dispextern.h b/src/dispextern.h
index bc34aec2dd5..b43565739ea 100644
--- a/src/dispextern.h
+++ b/src/dispextern.h
@@ -1989,6 +1989,12 @@ struct it
      OVERLAY_STRING_CHUNK_SIZE.  */
   int n_overlay_strings;
 
+  /* The charpos where n_overlay_strings was calculated.  This should
+     be set at the same time as n_overlay_strings.  It is needed
+     because we show before-strings at the start of invisible text;
+     see handle_invisible_prop in xdisp.c.  */
+  int overlay_strings_charpos;
+
   /* Vector of overlays to process.  Overlay strings are processed
      OVERLAY_STRING_CHUNK_SIZE at a time.  */
 #define OVERLAY_STRING_CHUNK_SIZE 16
diff --git a/src/xdisp.c b/src/xdisp.c
index dbe3e443c67..161e2b1cc4d 100644
--- a/src/xdisp.c
+++ b/src/xdisp.c
@@ -4717,6 +4717,7 @@ next_overlay_string (it)
                    && it->stop_charpos <= it->end_charpos));
       it->current.overlay_string_index = -1;
       it->n_overlay_strings = 0;
+      it->overlay_strings_charpos = -1;
 
       /* If we're at the end of the buffer, record that we have
          processed the overlay strings there already, so that
@@ -4729,11 +4730,13 @@ next_overlay_string (it)
       /* There are more overlay strings to process.  If
          IT->current.overlay_string_index has advanced to a position
          where we must load IT->overlay_strings with more strings, do
-         it.  */
+         it.  We must load at the IT->overlay_strings_charpos where
+         IT->n_overlay_strings was originally computed; when invisible
+         text is present, this might not be IT_CHARPOS (Bug#7016).  */
       int i = it->current.overlay_string_index % OVERLAY_STRING_CHUNK_SIZE;
 
       if (it->current.overlay_string_index && i == 0)
-        load_overlay_strings (it, 0);
+        load_overlay_strings (it, it->overlay_strings_charpos);
 
       /* Initialize IT to deliver display elements from the overlay
          string.  */
@@ -4949,8 +4952,9 @@ load_overlay_strings (it, charpos)
   if (n > 1)
     qsort (entries, n, sizeof *entries, compare_overlay_entries);
 
-  /* Record the total number of strings to process.  */
+  /* Record number of overlay strings, and where we computed it.  */
   it->n_overlay_strings = n;
+  it->overlay_strings_charpos = charpos;
 
   /* IT->current.overlay_string_index is the number of overlay strings
      that have already been consumed by IT.  Copy some of the