diff --git a/x0vncserver/PollingManager.h b/x0vncserver/PollingManager.h
index 59eb22e..253c237 100644
--- a/x0vncserver/PollingManager.h
+++ b/x0vncserver/PollingManager.h
@@ -43,10 +43,14 @@
 
 protected:
 
-  void poll_DetectVideo();
-  void poll_SkipCycles();
-  void poll_Traditional();
-  void poll_Dumb();
+  //
+  // Implementations of different polling algorithms.
+  // Return value of true reports that some changes were detected.
+  //
+  bool poll_DetectVideo();
+  bool poll_SkipCycles();
+  bool poll_Traditional();
+  bool poll_Dumb();
 
   Display *m_dpy;
   VNCServer *m_server;