gdk:surface-device-position (surface device)

surface -- a gdk:surface object
device -- a gdk:device object
x -- a double float for the x coordinate of device
y -- a double float for the y coordinate of device
mask -- a gdk:modifier-type value

Obtains the current device position in doubles and modifier state. The position is given in coordinates relative to the upper left corner of surface. Returns false if the device is not over the surface.