C++ supports sketched, but not finalized yet. Slic3r is still using

the old Perl supports, but this time with the C++ fillers.

xs/src/libslic3r/Layer.hpp

@@ -26,7 +26,8 @@ class LayerRegion
 
     public:
     Layer* layer();
-    PrintRegion* region();
+    PrintRegion* region() { return this->_region; }
+    const PrintRegion* region() const { return this->_region; }
 
     // collection of surfaces generated by slicing the original geometry
     // divided by type top/bottom/internal