信号“接收到拖动数据”的回调称为两次

Question

当我将文件拖放到条目时，gtk.entry.connect('drag-data-received', callback)回调方法运行两次。但是它应该只运行一次。为什么叫两次？

#!/usr/bin/env python3
#
# 2019-05-04 19:29:22

import gi
gi.require_version('Gtk', '3.0')

from gi.repository import Gtk as g, Gdk as d


class Window(g.Window):
  def __init__(self):
    super().__init__(title = 'hi')
    self.grid = g.Grid()
    self.add(self.grid)

    self.count = 1

    entry = g.Entry()
    entry.drag_dest_set(g.DestDefaults.ALL,
                        [g.TargetEntry.new("text/uri-list", 0, 80)],
                        d.DragAction.COPY)
    entry.connect('drag-data-received', self.set_path_by_drag)

    self.grid.add(entry)

  def set_path_by_drag(self, entry, context, x, y, data, info, time):
    '''
    reference: https://stackoverflow.com/questions/24094186/drag-and-drop-file-example-in-pygobject
    '''
    print(self.count)
    self.count += 1

    return True


def main():
  win = Window()
  win.connect('destroy', g.main_quit)
  win.show_all()

  g.main()


if __name__ == '__main__':
  main()

输出：

1
2

我已经安装了以下libgtk-3软件包：

$ dpkg -l | grep libgtk-3
ii  libgtk-3-0:amd64                           3.22.30-1ubuntu3                            amd64        GTK+ graphical user interface library
ii  libgtk-3-bin                               3.22.30-1ubuntu3                            amd64        programs for the GTK+ graphical user interface library
ii  libgtk-3-common                            3.22.30-1ubuntu3                            all          common files for the GTK+ graphical user interface library