Committing patches from Lubomir Marinov (moving isRegistered() to AbstractProtocolProviderService) and Keio Kraaner (implementation of message filtering).

21 files changed, 240 insertions, 128 deletions

diff --git a/src/net/java/sip/communicator/impl/protocol/dict/ProtocolProviderServiceDictImpl.java b/src/net/java/sip/communicator/impl/protocol/dict/ProtocolProviderServiceDictImpl.java
index 97dc631..edf97f4 100644
--- a/src/net/java/sip/communicator/impl/protocol/dict/ProtocolProviderServiceDictImpl.java
+++ b/src/net/java/sip/communicator/impl/protocol/dict/ProtocolProviderServiceDictImpl.java
@@ -267,17 +267,6 @@ public class ProtocolProviderServiceDictImpl
     }
 
     /**
-     * Indicates whether or not this provider is registered
-     *
-     * @return true if the provider is currently registered and false
-     *   otherwise.
-     */
-    public boolean isRegistered()
-    {
-        return currentRegistrationState.equals(RegistrationState.REGISTERED);
-    }
-
-    /**
      * Starts the registration process.
      *
      * @param authority the security authority that will be used for
diff --git a/src/net/java/sip/communicator/impl/protocol/gibberish/ProtocolProviderServiceGibberishImpl.java b/src/net/java/sip/communicator/impl/protocol/gibberish/ProtocolProviderServiceGibberishImpl.java
index 8b8ccc7..714d5e5 100644
--- a/src/net/java/sip/communicator/impl/protocol/gibberish/ProtocolProviderServiceGibberishImpl.java
+++ b/src/net/java/sip/communicator/impl/protocol/gibberish/ProtocolProviderServiceGibberishImpl.java
@@ -195,17 +195,6 @@ public class ProtocolProviderServiceGibberishImpl
     }
 
     /**
-     * Indicates whether or not this provider is registered
-     *
-     * @return true if the provider is currently registered and false
-     *   otherwise.
-     */
-    public boolean isRegistered()
-    {
-        return currentRegistrationState.equals(RegistrationState.REGISTERED);
-    }
-
-    /**
      * Starts the registration process.
      *
      * @param authority the security authority that will be used for
diff --git a/src/net/java/sip/communicator/impl/protocol/icq/ProtocolProviderServiceIcqImpl.java b/src/net/java/sip/communicator/impl/protocol/icq/ProtocolProviderServiceIcqImpl.java
index df19848..07ad09a 100644
--- a/src/net/java/sip/communicator/impl/protocol/icq/ProtocolProviderServiceIcqImpl.java
+++ b/src/net/java/sip/communicator/impl/protocol/icq/ProtocolProviderServiceIcqImpl.java
@@ -402,16 +402,6 @@ public class ProtocolProviderServiceIcqImpl
     }
 
     /**
-     * Indicates whether or not this provider is signed on the icq service
-     * @return true if the provider is currently signed on (and hence online)
-     * and false otherwise.
-     */
-    public boolean isRegistered()
-    {
-        return getRegistrationState().equals(RegistrationState.REGISTERED);
-    }
-
-    /**
      * Returns the short name of the protocol that the implementation of this
      * provider is based upon (like SIP, Jabber, ICQ/AIM, or others for
      * example).
diff --git a/src/net/java/sip/communicator/impl/protocol/irc/ProtocolProviderServiceIrcImpl.java b/src/net/java/sip/communicator/impl/protocol/irc/ProtocolProviderServiceIrcImpl.java
index 8b19522..f0a6cf0 100644
--- a/src/net/java/sip/communicator/impl/protocol/irc/ProtocolProviderServiceIrcImpl.java
+++ b/src/net/java/sip/communicator/impl/protocol/irc/ProtocolProviderServiceIrcImpl.java
@@ -174,18 +174,6 @@ public class ProtocolProviderServiceIrcImpl
     }
 
     /**
-     * Indicates whether or not this provider is registered
-     *
-     * @return true if the provider is currently registered and false
-     *   otherwise.
-     */
-    public boolean isRegistered()
-    {
-        return currentRegistrationState
-            .equals(RegistrationState.REGISTERED);
-    }
-
-    /**
      * Starts the registration process.
      *
      * @param authority the security authority that will be used for
diff --git a/src/net/java/sip/communicator/impl/protocol/jabber/ProtocolProviderServiceJabberImpl.java b/src/net/java/sip/communicator/impl/protocol/jabber/ProtocolProviderServiceJabberImpl.java
index 149abe8..289e2d4 100644
--- a/src/net/java/sip/communicator/impl/protocol/jabber/ProtocolProviderServiceJabberImpl.java
+++ b/src/net/java/sip/communicator/impl/protocol/jabber/ProtocolProviderServiceJabberImpl.java
@@ -440,16 +440,6 @@ public class ProtocolProviderServiceJabberImpl
     }
 
     /**
-     * Indicates whether or not this provider is signed on the service
-     * @return true if the provider is currently signed on (and hence online)
-     * and false otherwise.
-     */
-    public boolean isRegistered()
-    {
-        return getRegistrationState().equals(RegistrationState.REGISTERED);
-    }
-
-    /**
      * Returns the short name of the protocol that the implementation of this
      * provider is based upon (like SIP, Jabber, ICQ/AIM, or others for
      * example).
diff --git a/src/net/java/sip/communicator/impl/protocol/msn/ProtocolProviderServiceMsnImpl.java b/src/net/java/sip/communicator/impl/protocol/msn/ProtocolProviderServiceMsnImpl.java
index 904ffba..e988695 100644
--- a/src/net/java/sip/communicator/impl/protocol/msn/ProtocolProviderServiceMsnImpl.java
+++ b/src/net/java/sip/communicator/impl/protocol/msn/ProtocolProviderServiceMsnImpl.java
@@ -237,16 +237,6 @@ public class ProtocolProviderServiceMsnImpl
     }
 
     /**
-     * Indicates whether or not this provider is signed on the service
-     * @return true if the provider is currently signed on (and hence online)
-     * and false otherwise.
-     */
-    public boolean isRegistered()
-    {
-        return getRegistrationState().equals(RegistrationState.REGISTERED);
-    }
-
-    /**
      * Returns the short name of the protocol that the implementation of this
      * provider is based upon (like SIP, Msn, ICQ/AIM, or others for
      * example).
diff --git a/src/net/java/sip/communicator/impl/protocol/rss/ProtocolProviderServiceRssImpl.java b/src/net/java/sip/communicator/impl/protocol/rss/ProtocolProviderServiceRssImpl.java
index 5642d07..073a50f 100644
--- a/src/net/java/sip/communicator/impl/protocol/rss/ProtocolProviderServiceRssImpl.java
+++ b/src/net/java/sip/communicator/impl/protocol/rss/ProtocolProviderServiceRssImpl.java
@@ -195,17 +195,6 @@ public class ProtocolProviderServiceRssImpl
     }
 
     /**
-     * Indicates whether or not this provider is registered
-     *
-     * @return true if the provider is currently registered and false
-     *   otherwise.
-     */
-    public boolean isRegistered()
-    {
-        return currentRegistrationState.equals(RegistrationState.REGISTERED);
-    }
-
-    /**
      * Starts the registration process.
      *
      * @param authority the security authority that will be used for
diff --git a/src/net/java/sip/communicator/impl/protocol/sip/CallParticipantSipImpl.java b/src/net/java/sip/communicator/impl/protocol/sip/CallParticipantSipImpl.java
index 77197ac..73b08d1 100644
--- a/src/net/java/sip/communicator/impl/protocol/sip/CallParticipantSipImpl.java
+++ b/src/net/java/sip/communicator/impl/protocol/sip/CallParticipantSipImpl.java
@@ -88,6 +88,12 @@ public class CallParticipantSipImpl
      * address of our sip registrar).
      */
     private InetSocketAddress transportAddress = null;
+    
+    /**
+     * A URL pointing to a location with call information or a call control
+     * web interface related to this participant. 
+     */
+    private URL callControlURL = null;
 
     /**
      * Creates a new call participant with address <tt>participantAddress</tt>.
@@ -457,4 +463,29 @@ public class CallParticipantSipImpl
         return opSetPresence.findContactByID(getAddress());
     }
 
+    /**
+     * Returns a URL pointing ta a location with call control information for 
+     * this participant or <tt>null</tt> if no such URL is available for this 
+     * call participant.
+     * 
+     * @return a URL link to a location with call information or a call control
+     * web interface related to this participant or <tt>null</tt> if no such URL
+     * is available.
+     */
+    public URL getCallInfoURL()
+    {
+        return this.callControlURL;
+    }
+    
+    /**
+     * Returns a URL pointing ta a location with call control information for 
+     * this participant.
+     * 
+     * @param callControlURL a URL link to a location with call information or 
+     * a call control web interface related to this participant.
+     */
+    public void setCallInfoURL(URL callControlURL)
+    {
+        this.callControlURL = callControlURL;
+    }
 }
diff --git a/src/net/java/sip/communicator/impl/protocol/sip/OperationSetBasicTelephonySipImpl.java b/src/net/java/sip/communicator/impl/protocol/sip/OperationSetBasicTelephonySipImpl.java
index c2d09a3..3ea5a51 100644
--- a/src/net/java/sip/communicator/impl/protocol/sip/OperationSetBasicTelephonySipImpl.java
+++ b/src/net/java/sip/communicator/impl/protocol/sip/OperationSetBasicTelephonySipImpl.java
@@ -754,6 +754,12 @@ public class OperationSetBasicTelephonySipImpl
                         callParticipant
                         , callParticipant.getSdpDescription());
                     ack.setContent(sdp, contentTypeHeader);
+                    
+                    //set the call url in case there was one
+                    /** @todo this should be done in CallSession, once we move 
+                     * it here.*/
+                    callParticipant.setCallInfoURL(
+                            callSession.getCallInfoURL());
                 }
 
             }
@@ -775,6 +781,10 @@ public class OperationSetBasicTelephonySipImpl
        
             callSession.processSdpAnswer(callParticipant
                                          , callParticipant.getSdpDescription());
+            //set the call url in case there was one
+            /** @todo this should be done in CallSession, once we move 
+             * it here.*/
+            callParticipant.setCallInfoURL(callSession.getCallInfoURL());
         }
         catch (ParseException exc)
         {
@@ -1840,6 +1850,11 @@ public class OperationSetBasicTelephonySipImpl
                 sdp = callSession.processSdpOffer(
                         callParticipant
                         , callParticipant.getSdpDescription());
+                
+                //set the call url in case there was one
+                /** @todo this should be done in CallSession, once we move 
+                 * it here.*/
+                callParticipant.setCallInfoURL(callSession.getCallInfoURL());
             }
             //if there was no offer in the invite - create an offer
             else
diff --git a/src/net/java/sip/communicator/impl/protocol/sip/ProtocolProviderServiceSipImpl.java b/src/net/java/sip/communicator/impl/protocol/sip/ProtocolProviderServiceSipImpl.java
index d89c511..c379681 100644
--- a/src/net/java/sip/communicator/impl/protocol/sip/ProtocolProviderServiceSipImpl.java
+++ b/src/net/java/sip/communicator/impl/protocol/sip/ProtocolProviderServiceSipImpl.java
@@ -197,7 +197,7 @@ public class ProtocolProviderServiceSipImpl
      * A String indicating the default debug level for the jain-sip-ri (must be
      * log4j compatible).
      */
-    private static final String NSPVALUE_TRACE_LEVEL = "DEBUG";
+    private static final String NSPVALUE_TRACE_LEVEL = "ERROR";
 
     /**
      * The name of the property under which the jain-sip-ri would expect to find
@@ -357,7 +357,8 @@ public class ProtocolProviderServiceSipImpl
      *
      * @param event The event to register
      */
-    public void registerEvent(String event) {
+    public void registerEvent(String event) 
+	{
         synchronized (this.registeredEvents) {
             if (!this.registeredEvents.contains(event)) {
                 this.registeredEvents.add(event);
@@ -370,25 +371,12 @@ public class ProtocolProviderServiceSipImpl
      *
      * @return The list of all the registered events
      */
-    public List getKnownEventsList() {
+    public List getKnownEventsList() 
+	{
         return this.registeredEvents;
     }
 
     /**
-     * Indicates whether or not this provider is registered
-     * @return true if the provider is currently registered and false otherwise.
-     */
-    public boolean isRegistered()
-    {
-        if(this.sipRegistrarConnection == null )
-        {
-            return false;
-        }
-        return sipRegistrarConnection.getRegistrationState()
-            .equals(RegistrationState.REGISTERED);
-    }
-
-    /**
      * Returns an array containing all operation sets supported by the current
      * implementation. When querying this method users must be prepared to
      * receive any sybset of the OperationSet-s defined by this service. They
diff --git a/src/net/java/sip/communicator/impl/protocol/ssh/ProtocolProviderServiceSSHImpl.java b/src/net/java/sip/communicator/impl/protocol/ssh/ProtocolProviderServiceSSHImpl.java
index e8a17b9..428ffc9 100644
--- a/src/net/java/sip/communicator/impl/protocol/ssh/ProtocolProviderServiceSSHImpl.java
+++ b/src/net/java/sip/communicator/impl/protocol/ssh/ProtocolProviderServiceSSHImpl.java
@@ -568,17 +568,6 @@ public class ProtocolProviderServiceSSHImpl
     }
     
     /**
-     * Indicates whether or not this provider is registered
-     *
-     * @return true if the provider is currently registered and false
-     *   otherwise.
-     */
-    public boolean isRegistered()
-    {
-        return currentRegistrationState.equals(RegistrationState.REGISTERED);
-    }
-    
-    /**
      * Starts the registration process.
      *
      * @param authority the security authority that will be used for
diff --git a/src/net/java/sip/communicator/impl/protocol/yahoo/OperationSetBasicInstantMessagingYahooImpl.java b/src/net/java/sip/communicator/impl/protocol/yahoo/OperationSetBasicInstantMessagingYahooImpl.java
index 1fcd95a..9e54276 100644
--- a/src/net/java/sip/communicator/impl/protocol/yahoo/OperationSetBasicInstantMessagingYahooImpl.java
+++ b/src/net/java/sip/communicator/impl/protocol/yahoo/OperationSetBasicInstantMessagingYahooImpl.java
@@ -21,9 +21,11 @@ import ymsg.support.*;
  * set.
  *
  * @author Damian Minkov
+ * @author Keio Kraaner
  */
 public class OperationSetBasicInstantMessagingYahooImpl
-    implements OperationSetBasicInstantMessaging
+    implements OperationSetBasicInstantMessaging,
+    OperationSetInstantMessageFiltering
 {
     /**
      * Logger for this class
@@ -45,9 +47,15 @@ public class OperationSetBasicInstantMessagingYahooImpl
     /**
      * A list of listeneres registered for message events.
      */
-    private Vector messageListeners = new Vector();
+    private Vector<MessageListener> messageListeners 
+                                            = new Vector<MessageListener>();
 
     /**
+     * A list of filters registered for message events.
+     */
+    private Vector<EventFilter> eventFilters = new Vector<EventFilter>();
+    
+    /**
      * The provider that created us.
      */
     private ProtocolProviderServiceYahooImpl yahooProvider = null;
@@ -310,6 +318,36 @@ public class OperationSetBasicInstantMessagingYahooImpl
      */
     private void fireMessageEvent(EventObject evt)
     {
+        // check if this event should be filtered out
+        Iterator<EventFilter> filters = null;
+        synchronized (eventFilters)
+        {
+            filters = new ArrayList<EventFilter>(eventFilters).iterator();
+        }
+        // return if a filter has filtered this event out
+        boolean filtered = false;
+        while (filters.hasNext())
+        {
+            try
+            {
+                if (filters.next().filterEvent(evt))
+                {
+                    filtered = true;
+                }
+            }
+            catch(Exception exc) 
+            {
+                logger.error("An exception occurred while filtering an event.", 
+                             exc);
+            }
+        }
+        
+        if (filtered) 
+        {
+            logger.trace("Message event filtered.");
+            return;
+        }
+
         Iterator listeners = null;
         synchronized (messageListeners)
         {
@@ -627,4 +665,35 @@ public class OperationSetBasicInstantMessagingYahooImpl
 
         return linkBuffer.toString();
     }
+    
+    /**
+     * Registers an <tt>EventFilter</tt> with this operation set so that 
+     * events, that do not need processing, are filtered out.
+     *
+     * @param filter the <tt>EventFilter</tt> to register.
+     */
+    public void addEventFilter(EventFilter filter)
+    {
+        synchronized(eventFilters)
+        {
+            if(!eventFilters.contains(filter))
+            {
+                eventFilters.add(filter);
+            }
+        }
+    }
+
+    /**
+     * Unregisteres an <tt>EventFilter</tt> so that it won't check any more 
+     * if an event should be filtered out.
+     *
+     * @param filter the <tt>EventFilter</tt> to unregister.
+     */
+    public void removeEventFilter(EventFilter filter)
+    {
+        synchronized(eventFilters)
+        {
+            eventFilters.remove(filter);
+        }
+    }
 }
diff --git a/src/net/java/sip/communicator/impl/protocol/yahoo/ProtocolProviderServiceYahooImpl.java b/src/net/java/sip/communicator/impl/protocol/yahoo/ProtocolProviderServiceYahooImpl.java
index 004752c..a8e5fdc 100644
--- a/src/net/java/sip/communicator/impl/protocol/yahoo/ProtocolProviderServiceYahooImpl.java
+++ b/src/net/java/sip/communicator/impl/protocol/yahoo/ProtocolProviderServiceYahooImpl.java
@@ -266,16 +266,6 @@ public class ProtocolProviderServiceYahooImpl
     }
 
     /**
-     * Indicates whether or not this provider is signed on the service
-     * @return true if the provider is currently signed on (and hence online)
-     * and false otherwise.
-     */
-    public boolean isRegistered()
-    {
-        return getRegistrationState().equals(RegistrationState.REGISTERED);
-    }
-
-    /**
      * Returns the short name of the protocol that the implementation of this
      * provider is based upon (like SIP, Msn, ICQ/AIM, or others for
      * example).
diff --git a/src/net/java/sip/communicator/impl/protocol/zeroconf/ProtocolProviderServiceZeroconfImpl.java b/src/net/java/sip/communicator/impl/protocol/zeroconf/ProtocolProviderServiceZeroconfImpl.java
index 78af46e..9b479aa 100644
--- a/src/net/java/sip/communicator/impl/protocol/zeroconf/ProtocolProviderServiceZeroconfImpl.java
+++ b/src/net/java/sip/communicator/impl/protocol/zeroconf/ProtocolProviderServiceZeroconfImpl.java
@@ -206,17 +206,6 @@ public class ProtocolProviderServiceZeroconfImpl
         //Copy the map so that the caller is not able to modify it.
         return (Map)supportedOperationSets.clone();
     }
-
-    /**
-     * Indicates whether or not this provider is registered
-     *
-     * @return true if the provider is currently registered and false
-     *   otherwise.
-     */
-    public boolean isRegistered()
-    {
-        return currentRegistrationState.equals(RegistrationState.REGISTERED);
-    }
     
     /**
      * Starts the registration process.
diff --git a/src/net/java/sip/communicator/service/media/CallSession.java b/src/net/java/sip/communicator/service/media/CallSession.java
index 84baf46..de7cac5 100644
--- a/src/net/java/sip/communicator/service/media/CallSession.java
+++ b/src/net/java/sip/communicator/service/media/CallSession.java
@@ -109,4 +109,14 @@ public interface CallSession
      * <tt>CallSession</tt>.
      */
     public int getAudioPort();
+    
+    /**
+     * Returns a URL pointing ta a location with call control information for 
+     * this call or <tt>null</tt> if no such URL is available.
+     * 
+     * @return a URL link to a location with call information or a call control
+     * web interface for the specified participant or <tt>null</tt> if no such 
+     * URL is available.
+     */
+    public URL getCallInfoURL();
 }
diff --git a/src/net/java/sip/communicator/service/media/event/MediaEvent.java b/src/net/java/sip/communicator/service/media/event/MediaEvent.java
index b84bbcc..6192832 100644
--- a/src/net/java/sip/communicator/service/media/event/MediaEvent.java
+++ b/src/net/java/sip/communicator/service/media/event/MediaEvent.java
@@ -11,7 +11,7 @@ import net.java.sip.communicator.service.protocol.*;
 
 /**
  * 
- * @author Martin Andre
+ * @author Symphorien Wanko
  */
 public class MediaEvent
     extends java.util.EventObject
diff --git a/src/net/java/sip/communicator/service/protocol/AbstractCallParticipant.java b/src/net/java/sip/communicator/service/protocol/AbstractCallParticipant.java
index 656652f..d38ab5c 100644
--- a/src/net/java/sip/communicator/service/protocol/AbstractCallParticipant.java
+++ b/src/net/java/sip/communicator/service/protocol/AbstractCallParticipant.java
@@ -7,6 +7,7 @@
 package net.java.sip.communicator.service.protocol;
 
 import java.util.*;
+import java.net.*;
 
 import net.java.sip.communicator.service.protocol.event.*;
 import net.java.sip.communicator.util.*;
@@ -143,4 +144,20 @@ public abstract class AbstractCallParticipant
         return getDisplayName() + " <" + getAddress()
             + ">;status=" + getState().getStateString();
     }
+    
+    /**
+     * Returns a URL pointing ta a location with call control information for 
+     * this participant or <tt>null</tt> if no such URL is available for this 
+     * call participant.
+     * 
+     * @return a URL link to a location with call information or a call control
+     * web interface related to this participant or <tt>null</tt> if no such URL
+     * is available.
+     */
+    public URL getCallInfoURL()
+    {
+        //if signaling protocols (such as SIP) know where to get this URL from 
+        //they should override this method
+        return null;
+    }
 }
diff --git a/src/net/java/sip/communicator/service/protocol/AbstractProtocolProviderService.java b/src/net/java/sip/communicator/service/protocol/AbstractProtocolProviderService.java
index 800b537..2a7334e 100644
--- a/src/net/java/sip/communicator/service/protocol/AbstractProtocolProviderService.java
+++ b/src/net/java/sip/communicator/service/protocol/AbstractProtocolProviderService.java
@@ -12,7 +12,7 @@ import net.java.sip.communicator.service.protocol.event.*;
 import net.java.sip.communicator.util.*;
 
 /**
- * Implements "standard" functionality of <tt>ProtocolProviderService</code> in
+ * Implements "standard" functionality of <tt>ProtocolProviderService</tt> in
  * order to make it easier for implementers to provide complete solutions while
  * focusing on protocol-specific details.
  */
@@ -105,6 +105,17 @@ public abstract class AbstractProtocolProviderService
     }
 
     /**
+     * Indicates whether or not this provider is registered
+     *
+     * @return true if the provider is currently registered and false
+     *   otherwise.
+     */
+    public boolean isRegistered()
+    {
+        return getRegistrationState().equals(RegistrationState.REGISTERED);
+    }
+
+    /**
      * Removes the specified registration state change listener so that it does
      * not receive any further notifications upon changes of the
      * RegistrationState of this provider.
diff --git a/src/net/java/sip/communicator/service/protocol/CallParticipant.java b/src/net/java/sip/communicator/service/protocol/CallParticipant.java
index 1fd94c5..0c18065 100644
--- a/src/net/java/sip/communicator/service/protocol/CallParticipant.java
+++ b/src/net/java/sip/communicator/service/protocol/CallParticipant.java
@@ -122,4 +122,14 @@ public interface CallParticipant
      * if no particular contact has been associated.
      */
     public Contact getContact();
+    
+    /**
+     * Returns a URL pointing ta a location with call control information or 
+     * null if such an URL is not available for the current call participant.
+     * 
+     * @return a URL link to a location with call information or a call control
+     * web interface related to this participant or <tt>null</tt> if no such URL
+     * is available.
+     */
+    public URL getCallInfoURL();
 }
diff --git a/src/net/java/sip/communicator/service/protocol/OperationSetInstantMessageFiltering.java b/src/net/java/sip/communicator/service/protocol/OperationSetInstantMessageFiltering.java
new file mode 100644
index 0000000..de2b6d0
--- /dev/null
+++ b/src/net/java/sip/communicator/service/protocol/OperationSetInstantMessageFiltering.java
@@ -0,0 +1,36 @@
+/*
+ * To change this template, choose Tools | Templates
+ * and open the template in the editor.
+ */
+package net.java.sip.communicator.service.protocol;
+
+/**
+ * An operation set that allows plugins to register filters which could 
+ * intercept instant messages and determine whether or not they should be 
+ * dispatched to regular listeners. <tt>EventFilter</tt>-s allow implementating
+ * features that use standard instant messaging channels to exchange 
+ * 
+ * @author Keio Kraaner
+ */
+
+import net.java.sip.communicator.service.protocol.event.*;
+
+public interface OperationSetInstantMessageFiltering
+    extends OperationSet
+{
+    /**
+     * Registeres an <tt>EventFilter</tt> with this operation set so that 
+     * events, that do not need processing, are filtered out.
+     *
+     * @param filter the <tt>EventFilter</tt> to register.
+     */
+    public void addEventFilter(EventFilter filter);
+
+    /**
+     * Unregisteres an <tt>EventFilter</tt> so that it won't check any more 
+     * if an event should be filtered out.
+     *
+     * @param filter the <tt>EventFilter</tt> to unregister.
+     */
+    public void removeEventFilter(EventFilter filter);
+}
diff --git a/src/net/java/sip/communicator/service/protocol/event/EventFilter.java b/src/net/java/sip/communicator/service/protocol/event/EventFilter.java
new file mode 100644
index 0000000..8ea7ad9
--- /dev/null
+++ b/src/net/java/sip/communicator/service/protocol/event/EventFilter.java
@@ -0,0 +1,32 @@
+/*
+ * SIP Communicator, the OpenSource Java VoIP and Instant Messaging client.
+ *
+ * Distributable under LGPL license.
+ * See terms of license at gnu.org.
+ */
+package net.java.sip.communicator.service.protocol.event;
+
+import java.util.*;
+
+/**
+ * An event filter that decides whether an instant message event should be 
+ * filtered or not. For instance, maybe some type of received messages should not be 
+ * shown in the chat windows. In such cases implementations of this filter would block
+ * this message before it is delivered to other IM listeners.
+ * <p>
+ * Note that in order to be able to use this Filter, protocols should implement 
+ * <tt>OperationSetMessageFiltering</tt>.
+ * <p>
+ * @author Keio Kraaner
+ */
+public interface EventFilter
+{
+    /**
+     * Checks if an event should be filtered out or processed.
+     * 
+     * @param msg The event that should be checked
+     * @return <tt>true</tt> if the event was filtered out, otherwise 
+     * <tt>false</tt>.
+     */
+    public boolean filterEvent(EventObject msg);
+}