class_docstr: Instances of this class are delivered to items in a :class:`GraphicsScene <pyqtgraph.GraphicsScene>` via their mouseDragEvent() method when the item is being mouse-dragged. 
docstr: Return the position of the mouse at the time the drag was initiated
  in the coordinate system of the item that the event was delivered to.
docstr_tok: ["Return","the","position","of","the","mouse","at","the","time","the","drag","was","initiated","in","the","coordinate","system","of","the","item","that","the","event","was","delivered","to","."]
code: def buttonDownPos(self, btn=None):
      """
      Return the position of the mouse at the time the drag was initiated
      in the coordinate system of the item that the event was delivered to.
      """
      if btn is None:
          btn = self.button()
      return Point(
          self.currentItem.mapFromScene(self._buttonDownScenePos[btn])
      )
  
imports: import weakref
  from time import perf_counter
  from ..Point import Point
  from ..Qt import QtCore
label_desc: Use image node_id 15 for calling the MouseDragEvent obj's underlying member method code with example usage: obj.buttonDownPos(btn) and returns: Point