@@ -877,10 +877,17 @@ class DotWidget(gtk.DrawingArea):

         state = event.state

         if state & gtk.gdk.BUTTON2_MASK or state & gtk.gdk.BUTTON1_MASK:

-            # pan the image

-            self.x += (self.prevmousex - x)/self.zoom_ratio

-            self.y += (self.prevmousey - y)/self.zoom_ratio

-            self.queue_draw()

+            deltax = self.prevmousex - event.x

+            deltay = self.prevmousey - event.y

+            if state & gtk.gdk.CONTROL_MASK:

+                # zoom the image

+                self.zoom_ratio *= 1.005 ** (deltax + deltay)

+                self.queue_draw()

+            else:

+                # pan the image

+                self.x += deltax/self.zoom_ratio

+                self.y += deltay/self.zoom_ratio

+                self.queue_draw()

             self.prevmousex = x

             self.prevmousey = y

             self.animation.stop()