Did some debugging in trackers.

src/geometry.py

@@ -52,6 +52,9 @@ class Positionable(object):
         ox, oy = other
         return ((ox - self.x) ** 2 + (oy - self.y) ** 2) ** .5
 
+    def translate(self, x, y):
+        self.set_position(self.x + x, self.y + y)
+
 
 class MovingPositionable(Positionable):
     """

src/trackers/tap.py

@@ -36,8 +36,8 @@ class TapTracker(GestureTracker):
     configurable = ['tap_distance', 'tap_time', 'double_tap_time',
                     'double_tap_distance', 'update_rate', 'propagate_up_event']
 
-    def __init__(self, window=None):
-        super(TapTracker, self).__init__(window)
+    def __init__(self, widget):
+        super(TapTracker, self).__init__(widget)
 
         # Map of touch object id to tuple (timestamp, position) of point down
         self.reg = {}

src/trackers/transform.py

@@ -59,6 +59,9 @@ class DragGesture(Gesture, Positionable):
         return '<DragGesture at (%s, %s) translation=(%s, %s)>' \
                % (self.get_position() + self.translation.get_position())
 
+    def get_translation(self):
+        return self.translation
+
 
 class TransformationTracker(GestureTracker):
     """
@@ -67,7 +70,7 @@ class TransformationTracker(GestureTracker):
     """
     supported_gestures = [RotationGesture, PinchGesture, DragGesture]
 
-    def __init__(self, widget=None):
+    def __init__(self, widget):
         super(TransformationTracker, self).__init__(widget)
 
         # All touch points performing the transformation
@@ -116,12 +119,16 @@ class TransformationTracker(GestureTracker):
             scale = dist / prev
             self.trigger(PinchGesture(event, self.centroid, scale))
 
-        # Update centroid before movement can be detected
-        self.update_centroid()
-
-        # Movement
+            # Movement using multiple touch points
             self.trigger(DragGesture(event, self.centroid,
                                     self.centroid.translation()))
+        else:
+            # Movement using one touch point
+            self.trigger(DragGesture(event, event.point,
+                                     event.point.translation()))
+
+        # Update centroid before movement can be detected
+        self.update_centroid()
 
     def on_point_up(self, event):
         self.points.remove(event.point)