Support calling methods from timers

We can't safely use the normal timers in base classes as we cannot
guarantee that subclasses will call the base class' handleTimeout()
properly if the subclass overrides it.

common/rfb/Timer.h

@@ -35,6 +35,8 @@ namespace rfb {
      dispatch elapsed Timer callbacks and to determine how long to wait in select() for
      the next timeout to occur.
 
+     For classes that can be derived it's best to use MethodTimer which can call a specific
+     method on the class, thus avoiding conflicts when subclassing.
   */
 
   struct Timer {
@@ -101,6 +103,19 @@ namespace rfb {
     static std::list<Timer*> pending;
   };
 
+  template<class T> class MethodTimer
+    : public Timer, public Timer::Callback {
+  public:
+    MethodTimer(T* obj_, bool (T::*cb_)(Timer*))
+      : Timer(this), obj(obj_), cb(cb_) {}
+
+    virtual bool handleTimeout(Timer* t) { return (obj->*cb)(t); }
+
+  private:
+    T* obj;
+    bool (T::*cb)(Timer*);
+  };
+
 };
 
 #endif