allow casting bitmasks to their integer type, and make sure that bool(bitmask) is False when all bits are off

panda/src/putil/bitMask.I

@@ -821,6 +821,29 @@ operator >>= (int shift) {
   _word >>= shift;
 }
 
+////////////////////////////////////////////////////////////////////
+//     Function: BitMask::operator WType
+//       Access: Published
+//  Description: Used to cast this BitMask back into the
+//               underlying integer type.
+////////////////////////////////////////////////////////////////////
+template<class WType, int nbits>
+INLINE BitMask<WType, nbits>::
+operator WType () const {
+  return _word;
+}
+
+////////////////////////////////////////////////////////////////////
+//     Function: BitMask::operator bool
+//       Access: Published
+//  Description: Will return true, unless all bits are off.
+////////////////////////////////////////////////////////////////////
+template<class WType, int nbits>
+INLINE BitMask<WType, nbits>::
+operator bool () const {
+  return (_word != 0);
+}
+
 ////////////////////////////////////////////////////////////////////
 //     Function: BitMask::get_key
 //       Access: Published