pointer #GdkDevice to query to.
return location for the X coordinate of @device, or %NULL.
return location for the Y coordinate of @device, or %NULL.
return location for the modifier mask, or %NULL.
The window underneath @device (as with gdk_device_get_window_at_position()), or %NULL if the window is not known to GDK.
3.10
Obtains the current device position in doubles and modifier state. The position is given in coordinates relative to the upper left corner of @window.