Finds the destination window and DND protocol to use at the given pointer position.
This function is called by the drag source to obtain the dest_window and protocol parameters for
drag_motion.
| context | |
| drag_window |
a window which may be at the pointer position, but should be ignored, since it is put up by the drag source as an icon |
| screen |
the screen where the destination window is sought |
| x_root |
the x position of the pointer in root coordinates |
| y_root |
the y position of the pointer in root coordinates |
| dest_window |
location to store the destination window in |
| protocol |
location to store the DND protocol in |