Obtains the surface underneath device, returning the location of the device in win_x and win_y.
Returns null if the surface tree under device is not known to GDK (for example, belongs to another application).
return location for the X coordinate of the device location relative to the surface origin
return location for the Y coordinate of the device location relative to the surface origin
the gdk.surface.Surface under the device position
Obtains the surface underneath device, returning the location of the device in win_x and win_y.
Returns null if the surface tree under device is not known to GDK (for example, belongs to another application).