The drag_drop signal is emitted on the drop site when the user drops the data onto the widget.
The signal handler must determine whether the cursor position is in a drop zone or not. If it is not in a drop zone, it returns false and no further processing is necessary. Otherwise, the handler returns true . In this case, the handler must ensure that drag_finish is called to let the source know that the drop is done. The call to drag_finish can be done either directly or in a drag_data_received handler which gets triggered by calling drag_get_data to receive the data for one or more of the supported targets.
the drag context
the x coordinate of the current cursor position
the y coordinate of the current cursor position
the timestamp of the motion event
whether the cursor position is in a drop zone