Fix rendering of composed caharacters on the mode line. (Bug#19435)

 src/xdisp.c (set_iterator_to_next) <GET_FROM_STRING>: Limit search in
 composition_compute_stop_pos to the number of characters in the
 string.
 <GET_FROM_BUFFER, GET_FROM_STRING>: Simplify code.
 src/composite.c (composition_compute_stop_pos): If no composition
 was found in a string before ENDPOS, and ENDPOS is the string end,
 no need to back up to a safe point.
 src/dispextern.h (struct it) <end_charpos>: Improve commentary.

4 files changed, 93 insertions, 99 deletions

diff --git a/src/ChangeLog b/src/ChangeLog
index 2840109ac1c..2df83082fbd 100644
--- a/src/ChangeLog
+++ b/src/ChangeLog
@@ -1,3 +1,16 @@
+2014-12-25  Eli Zaretskii  <eliz@gnu.org>
+
+	* xdisp.c (set_iterator_to_next) <GET_FROM_STRING>: Limit search in
+	composition_compute_stop_pos to the number of characters in the
+	string.  (Bug#19435)
+	<GET_FROM_BUFFER, GET_FROM_STRING>: Simplify code.
+
+	* composite.c (composition_compute_stop_pos): If no composition
+	was found in a string before ENDPOS, and ENDPOS is the string end,
+	no need to back up to a safe point.
+
+	* dispextern.h (struct it) <end_charpos>: Improve commentary.
+
 2014-12-24  Jan Djärv  <jan.h.d@swipnet.se>
 
 	* nsimage.m (allocInitFromFile:): Initialize bmRep.
diff --git a/src/composite.c b/src/composite.c
index fa882141908..a1282103972 100644
--- a/src/composite.c
+++ b/src/composite.c
@@ -1036,7 +1036,8 @@ composition_compute_stop_pos (struct composition_it *cmp_it, ptrdiff_t charpos,
 		}
 	    }
 	}
-      if (charpos == endpos)
+      if (charpos == endpos
+	  && !(STRINGP (string) && endpos == SCHARS (string)))
 	{
 	  /* We couldn't find a composition point before ENDPOS.  But,
 	     some character after ENDPOS may be composed with
diff --git a/src/dispextern.h b/src/dispextern.h
index 576f22870c2..0e5a73a929c 100644
--- a/src/dispextern.h
+++ b/src/dispextern.h
@@ -2222,7 +2222,10 @@ struct it
   ptrdiff_t base_level_stop;
 
   /* Maximum string or buffer position + 1.  ZV when iterating over
-     current_buffer.  */
+     current_buffer.  When iterating over a string in display_string,
+     this can be smaller or greater than the number of string
+     characters, depending on the values of PRECISION and FIELD_WIDTH
+     with which display_string was called.  */
   ptrdiff_t end_charpos;
 
   /* C string to iterate over.  Non-null means get characters from
diff --git a/src/xdisp.c b/src/xdisp.c
index e3e00357ed0..173df5d011b 100644
--- a/src/xdisp.c
+++ b/src/xdisp.c
@@ -7330,27 +7330,15 @@ set_iterator_to_next (struct it *it, int reseat_p)
       else if (it->cmp_it.id >= 0)
 	{
 	  /* We are currently getting glyphs from a composition.  */
-	  int i;
-
 	  if (! it->bidi_p)
 	    {
 	      IT_CHARPOS (*it) += it->cmp_it.nchars;
 	      IT_BYTEPOS (*it) += it->cmp_it.nbytes;
-	      if (it->cmp_it.to < it->cmp_it.nglyphs)
-		{
-		  it->cmp_it.from = it->cmp_it.to;
-		}
-	      else
-		{
-		  it->cmp_it.id = -1;
-		  composition_compute_stop_pos (&it->cmp_it, IT_CHARPOS (*it),
-						IT_BYTEPOS (*it),
-						it->end_charpos, Qnil);
-		}
 	    }
-	  else if (! it->cmp_it.reversed_p)
+	  else
 	    {
-	      /* Composition created while scanning forward.  */
+	      int i;
+
 	      /* Update IT's char/byte positions to point to the first
 		 character of the next grapheme cluster, or to the
 		 character visually after the current composition.  */
@@ -7358,52 +7346,34 @@ set_iterator_to_next (struct it *it, int reseat_p)
 		bidi_move_to_visually_next (&it->bidi_it);
 	      IT_BYTEPOS (*it) = it->bidi_it.bytepos;
 	      IT_CHARPOS (*it) = it->bidi_it.charpos;
+	    }
 
-	      if (it->cmp_it.to < it->cmp_it.nglyphs)
-		{
-		  /* Proceed to the next grapheme cluster.  */
-		  it->cmp_it.from = it->cmp_it.to;
-		}
-	      else
-		{
-		  /* No more grapheme clusters in this composition.
-		     Find the next stop position.  */
-		  ptrdiff_t stop = it->end_charpos;
-		  if (it->bidi_it.scan_dir < 0)
-		    /* Now we are scanning backward and don't know
-		       where to stop.  */
-		    stop = -1;
-		  composition_compute_stop_pos (&it->cmp_it, IT_CHARPOS (*it),
-						IT_BYTEPOS (*it), stop, Qnil);
-		}
+	  if ((! it->bidi_p || ! it->cmp_it.reversed_p)
+	      && it->cmp_it.to < it->cmp_it.nglyphs)
+	    {
+	      /* Composition created while scanning forward.  Proceed
+		 to the next grapheme cluster.  */
+	      it->cmp_it.from = it->cmp_it.to;
+	    }
+	  else if ((it->bidi_p && it->cmp_it.reversed_p)
+		   && it->cmp_it.from > 0)
+	    {
+	      /* Composition created while scanning backward.  Proceed
+		 to the previous grapheme cluster.  */
+	      it->cmp_it.to = it->cmp_it.from;
 	    }
 	  else
 	    {
-	      /* Composition created while scanning backward.  */
-	      /* Update IT's char/byte positions to point to the last
-		 character of the previous grapheme cluster, or the
-		 character visually after the current composition.  */
-	      for (i = 0; i < it->cmp_it.nchars; i++)
-		bidi_move_to_visually_next (&it->bidi_it);
-	      IT_BYTEPOS (*it) = it->bidi_it.bytepos;
-	      IT_CHARPOS (*it) = it->bidi_it.charpos;
-	      if (it->cmp_it.from > 0)
-		{
-		  /* Proceed to the previous grapheme cluster.  */
-		  it->cmp_it.to = it->cmp_it.from;
-		}
-	      else
-		{
-		  /* No more grapheme clusters in this composition.
-		     Find the next stop position.  */
-		  ptrdiff_t stop = it->end_charpos;
-		  if (it->bidi_it.scan_dir < 0)
-		    /* Now we are scanning backward and don't know
-		       where to stop.  */
-		    stop = -1;
-		  composition_compute_stop_pos (&it->cmp_it, IT_CHARPOS (*it),
-						IT_BYTEPOS (*it), stop, Qnil);
-		}
+	      /* No more grapheme clusters in this composition.
+		 Find the next stop position.  */
+	      ptrdiff_t stop = it->end_charpos;
+
+	      if (it->bidi_it.scan_dir < 0)
+		/* Now we are scanning backward and don't know
+		   where to stop.  */
+		stop = -1;
+	      composition_compute_stop_pos (&it->cmp_it, IT_CHARPOS (*it),
+					    IT_BYTEPOS (*it), stop, Qnil);
 	    }
 	}
       else
@@ -7532,61 +7502,63 @@ set_iterator_to_next (struct it *it, int reseat_p)
 	}
       if (it->cmp_it.id >= 0)
 	{
-	  int i;
-
+	  /* We are delivering display elements from a composition.
+	     Update the string position past the grapheme cluster
+	     we've just processed.  */
 	  if (! it->bidi_p)
 	    {
 	      IT_STRING_CHARPOS (*it) += it->cmp_it.nchars;
 	      IT_STRING_BYTEPOS (*it) += it->cmp_it.nbytes;
-	      if (it->cmp_it.to < it->cmp_it.nglyphs)
-		it->cmp_it.from = it->cmp_it.to;
-	      else
-		{
-		  it->cmp_it.id = -1;
-		  composition_compute_stop_pos (&it->cmp_it,
-						IT_STRING_CHARPOS (*it),
-						IT_STRING_BYTEPOS (*it),
-						it->end_charpos, it->string);
-		}
 	    }
-	  else if (! it->cmp_it.reversed_p)
+	  else
 	    {
+	      int i;
+
 	      for (i = 0; i < it->cmp_it.nchars; i++)
 		bidi_move_to_visually_next (&it->bidi_it);
 	      IT_STRING_BYTEPOS (*it) = it->bidi_it.bytepos;
 	      IT_STRING_CHARPOS (*it) = it->bidi_it.charpos;
+	    }
 
-	      if (it->cmp_it.to < it->cmp_it.nglyphs)
-		it->cmp_it.from = it->cmp_it.to;
-	      else
-		{
-		  ptrdiff_t stop = it->end_charpos;
-		  if (it->bidi_it.scan_dir < 0)
-		    stop = -1;
-		  composition_compute_stop_pos (&it->cmp_it,
-						IT_STRING_CHARPOS (*it),
-						IT_STRING_BYTEPOS (*it), stop,
-						it->string);
-		}
+	  /* Did we exhaust all the grapheme clusters of this
+	     composition?  */
+	  if ((! it->bidi_p || ! it->cmp_it.reversed_p)
+	      && (it->cmp_it.to < it->cmp_it.nglyphs))
+	    {
+	      /* Not all the grapheme clusters were processed yet;
+		 advance to the next cluster.  */
+	      it->cmp_it.from = it->cmp_it.to;
+	    }
+	  else if ((it->bidi_p && it->cmp_it.reversed_p)
+		   && it->cmp_it.from > 0)
+	    {
+	      /* Likewise: advance to the next cluster, but going in
+		 the reverse direction.  */
+	      it->cmp_it.to = it->cmp_it.from;
 	    }
 	  else
 	    {
-	      for (i = 0; i < it->cmp_it.nchars; i++)
-		bidi_move_to_visually_next (&it->bidi_it);
-	      IT_STRING_BYTEPOS (*it) = it->bidi_it.bytepos;
-	      IT_STRING_CHARPOS (*it) = it->bidi_it.charpos;
-	      if (it->cmp_it.from > 0)
-		it->cmp_it.to = it->cmp_it.from;
-	      else
+	      /* This composition was fully processed; find the next
+		 candidate place for checking for composed
+		 characters.  */
+	      /* Always limit string searches to the string length;
+		 any padding spaces are not part of the string, and
+		 there cannot be any compositions in that padding.  */
+	      ptrdiff_t stop = SCHARS (it->string);
+
+	      if (it->bidi_p && it->bidi_it.scan_dir < 0)
+		stop = -1;
+	      else if (it->end_charpos < stop)
 		{
-		  ptrdiff_t stop = it->end_charpos;
-		  if (it->bidi_it.scan_dir < 0)
-		    stop = -1;
-		  composition_compute_stop_pos (&it->cmp_it,
-						IT_STRING_CHARPOS (*it),
-						IT_STRING_BYTEPOS (*it), stop,
-						it->string);
+		  /* Cf. PRECISION in reseat_to_string: we might be
+		     limited in how many of the string characters we
+		     need to deliver.  */
+		  stop = it->end_charpos;
 		}
+	      composition_compute_stop_pos (&it->cmp_it,
+					    IT_STRING_CHARPOS (*it),
+					    IT_STRING_BYTEPOS (*it), stop,
+					    it->string);
 	    }
 	}
       else
@@ -7609,12 +7581,17 @@ set_iterator_to_next (struct it *it, int reseat_p)
 	      bidi_move_to_visually_next (&it->bidi_it);
 	      IT_STRING_BYTEPOS (*it) = it->bidi_it.bytepos;
 	      IT_STRING_CHARPOS (*it) = it->bidi_it.charpos;
+	      /* If the scan direction changes, we may need to update
+		 the place where to check for composed characters.  */
 	      if (prev_scan_dir != it->bidi_it.scan_dir)
 		{
-		  ptrdiff_t stop = it->end_charpos;
+		  ptrdiff_t stop = SCHARS (it->string);
 
 		  if (it->bidi_it.scan_dir < 0)
 		    stop = -1;
+		  else if (it->end_charpos < stop)
+		    stop = it->end_charpos;
+
 		  composition_compute_stop_pos (&it->cmp_it,
 						IT_STRING_CHARPOS (*it),
 						IT_STRING_BYTEPOS (*it), stop,