[pitivi] Make PropertyChangeTracker reusable.

[Edward Hervey <edwardrv src gnome org>]

commit 4b26229ba420cca49b94cfaea05378bba19a22a3
Author: Alessandro Decina <alessandro d gmail com>
Date:   Tue Jun 9 18:50:53 2009 +0200

    Make PropertyChangeTracker reusable.

 pitivi/timeline/timeline.py |    4 +++-
 pitivi/utils.py             |   15 ++++++++++-----
 2 files changed, 13 insertions(+), 6 deletions(-)
---
diff --git a/pitivi/timeline/timeline.py b/pitivi/timeline/timeline.py
index 1438193..56d1daf 100644
--- a/pitivi/timeline/timeline.py
+++ b/pitivi/timeline/timeline.py
@@ -558,7 +558,8 @@ class Link(object):
 
         self.timeline_objects.add(timeline_object)
 
-        tracker = LinkPropertyChangeTracker(timeline_object)
+        tracker = LinkPropertyChangeTracker()
+        tracker.connectToObject(timeline_object)
         self.property_trackers[timeline_object] = tracker
 
         tracker.connect('start-changed', self._startChangedCb)
@@ -579,6 +580,7 @@ class Link(object):
             raise TimelineError()
 
         tracker = self.property_trackers.pop(timeline_object)
+        tracker.disconnectFromObject(timeline_object)
         tracker.disconnect_by_function(self._startChangedCb)
 
         timeline_object.link = None
diff --git a/pitivi/utils.py b/pitivi/utils.py
index 72328f8..b1c067a 100644
--- a/pitivi/utils.py
+++ b/pitivi/utils.py
@@ -237,21 +237,26 @@ def uri_is_reachable(uri):
     return os.path.isfile(gst.uri_get_location(uri))
 
 class PropertyChangeTracker(Signallable):
-    def __init__(self, timeline_object):
+    def __init__(self):
         self.properties = {}
 
+    def connectToObject(self, obj):
         for property_name in self.property_names:
             self.properties[property_name] = \
-                    getattr(timeline_object, property_name)
+                    getattr(obj, property_name)
 
-            timeline_object.connect(property_name + '-changed',
+            obj.connect(property_name + '-changed',
                     self._propertyChangedCb, property_name)
 
-    def _propertyChangedCb(self, timeline_object, value, property_name):
+
+    def disconnectFromObject(self, obj):
+        obj.disconnect_by_func(self._propertyChangedCb)
+
+    def _propertyChangedCb(self, object, value, property_name):
         old_value = self.properties[property_name]
         self.properties[property_name] = value
 
-        self.emit(property_name + '-changed', timeline_object, old_value, value)
+        self.emit(property_name + '-changed', object, old_value, value)
 
 class Seeker(Signallable):
     __signals__ = {'seek': ['position', 'format']}