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 scene position of the mouse at the time *btn* was pressed.
  If *btn* is omitted, then the button that initiated the drag is assumed.
docstr_tok: ["Return","the","scene","position","of","the","mouse","at","the","time","*","btn","*","was","pressed",".","If","*","btn","*","is","omitted",",","then","the","button","that","initiated","the","drag","is","assumed","."]
code: def buttonDownScenePos(self, btn=None):
      """
      Return the scene position of the mouse at the time *btn* was pressed.
      If *btn* is omitted, then the button that initiated the drag is assumed.
      """
      if btn is None:
          btn = self.button()
      return Point(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 7 for calling the MouseDragEvent obj's underlying member method code with example usage: obj.buttonDownScenePos(btn) and returns: Point