Updated the display controllers to use state controls

src/dawn/state/StateProperty.hpp

@@ -58,7 +58,7 @@ namespace Dawn {
        * Creates a new state property and listens for its change.
        * @param initial The initial value of this state.
        */
-      StateProperty(V initial) : _realValue(initial) {}
+      StateProperty(V initial) : _realValue(initial), previous(initial) {}
 
       const StateProperty& operator += (const V &value) {
         this->setInternal(this->_realValue + value);
@@ -78,6 +78,10 @@ namespace Dawn {
         return *this;
       }
 
+      const V operator->() const {
+        return this->_realValue;
+      }
+
       operator V() const {
         return this->_realValue;
       }