diff --git a/src/xdisp.c b/src/xdisp.c
index 0f842b8673e..6ba92f3ed79 100644
--- a/src/xdisp.c
+++ b/src/xdisp.c
@@ -6441,6 +6441,8 @@ get_next_display_element (struct it *it)
 
 	      c = ' ';
 	      for (i = 0; i < cmp->glyph_len; i++)
+		/* TAB in a composition means display glyphs with
+		   padding space on the left or right.  */
 		if ((c = COMPOSITION_GLYPH (cmp, i)) != '\t')
 		  break;
 	    }
@@ -11916,7 +11918,7 @@ hscroll_window_tree (Lisp_Object window)
 		}
 	      hscroll = max (hscroll, XFASTINT (w->min_hscroll));
 
-	      /* Don't will prevent redisplay optimizations if hscroll
+	      /* Don't prevent redisplay optimizations if hscroll
 		 hasn't changed, as it will unnecessarily slow down
 		 redisplay.  */
 	      if (XFASTINT (w->hscroll) != hscroll)
@@ -21726,6 +21728,8 @@ fill_composite_glyph_string (struct glyph_string *s, struct face *base_face,
     {
       int c = COMPOSITION_GLYPH (s->cmp, i);
 
+      /* TAB in a composition means display glyphs with padding space
+	 on the left or right.  */
       if (c != '\t')
 	{
 	  int face_id = FACE_FOR_CHAR (s->f, base_face->ascii_face, c,