* xdisp.c (draw_glyphs): Set clipping to highlight boundaries.

src/ChangeLog

+2014-05-12  YAMAMOTO Mitsuharu  <mituharu@math.s.chiba-u.ac.jp>
+
+	* xdisp.c (draw_glyphs): Set clipping to highlight boundaries.
+
 2014-05-12  Glenn Morris  <rgm@gnu.org>
 
 	* fileio.c (Ffile_executable_p): Doc tweak.

src/xdisp.c

@@ -24589,13 +24589,16 @@ draw_glyphs (struct window *w, int x, struct glyph_row *row,
 	  else
 	    overlap_hl = DRAW_NORMAL_TEXT;
+	  if (hl != overlap_hl)
+	    clip_head = head;
 	  j = i;
 	  BUILD_GLYPH_STRINGS (j, start, h, t,
 			       overlap_hl, dummy_x, last_x);
 	  start = i;
 	  compute_overhangs_and_x (t, head->x, 1);
 	  prepend_glyph_string_lists (&head, &tail, h, t);
-	  clip_head = head;
+	  if (clip_head == NULL)
+	    clip_head = head;
 	}
       /* Prepend glyph strings for glyphs in front of the first glyph
@@ -24616,7 +24619,8 @@ draw_glyphs (struct window *w, int x, struct glyph_row *row,
 	  else
 	    overlap_hl = DRAW_NORMAL_TEXT;
-	  clip_head = head;
+	  if (hl == overlap_hl || clip_head == NULL)
+	    clip_head = head;
 	  BUILD_GLYPH_STRINGS (i, start, h, t,
 			       overlap_hl, dummy_x, last_x);
 	  for (s = h; s; s = s->next)
@@ -24640,13 +24644,16 @@ draw_glyphs (struct window *w, int x, struct glyph_row *row,
 	  else
 	    overlap_hl = DRAW_NORMAL_TEXT;
+	  if (hl != overlap_hl)
+	    clip_tail = tail;
 	  BUILD_GLYPH_STRINGS (end, i, h, t,
 			       overlap_hl, x, last_x);
 	  /* Because BUILD_GLYPH_STRINGS updates the first argument,
 	     we don't have `end = i;' here.  */
 	  compute_overhangs_and_x (h, tail->x + tail->width, 0);
 	  append_glyph_string_lists (&head, &tail, h, t);
-	  clip_tail = tail;
+	  if (clip_tail == NULL)
+	    clip_tail = tail;
 	}
       /* Append glyph strings for glyphs following the last glyph
@@ -24664,7 +24671,8 @@ draw_glyphs (struct window *w, int x, struct glyph_row *row,
 	  else
 	    overlap_hl = DRAW_NORMAL_TEXT;
-	  clip_tail = tail;
+	  if (hl == overlap_hl || clip_tail == NULL)
+	    clip_tail = tail;
 	  i++;			/* We must include the Ith glyph.  */
 	  BUILD_GLYPH_STRINGS (end, i, h, t,
 			       overlap_hl, x, last_x);