code: func Initialize(xu *xgbutil.XUtil) {
  	xevent.MotionNotifyFun(dragStep).Connect(xu, xu.Dummy())
  	xevent.ButtonReleaseFun(DragEnd).Connect(xu, xu.Dummy())
  }
docs: // Initialize attaches the appropriate callbacks to make mouse bindings easier.
  // i.e., prep the dummy window to handle mouse dragging events