Add Key description for Key D which displays the domain.

Periodic_2_triangulation_2/examples/Periodic_2_triangulation_2/draw_periodic_2_triangulation_2.cpp

@@ -6,7 +6,6 @@
 
 typedef CGAL::Exact_predicates_inexact_constructions_kernel K;
 typedef CGAL::Periodic_2_triangulation_traits_2<K>          GT;
-
 typedef CGAL::Periodic_2_triangulation_2<GT>                PDT;
 
 typedef PDT::Point                                          Point;

Periodic_2_triangulation_2/include/CGAL/draw_periodic_2_triangulation_2.h

@@ -90,6 +90,7 @@ public:
     setKeyDescription(::Qt::Key_4, "UNIQUE_COVER_DOMAIN: Same as UNIQUE but also display "
                                    "all primitives whose intersection with the original "
                                    "domain of the current covering space is non-empty");
+    setKeyDescription(::Qt::Key_D, "Toggle 9-sheeted domain display");
 
     compute_elements();
   }