gdk:window-device-position (window device)

window -- a gdk:window object
device -- a gdk:device object to query

win -- a gdk:window object underneath device, as with the gdk:device-window-at-position function, or nil if the window is not known to GDK
x -- an integer with the x coordinate of the device
y -- an integer with the y coordinate of the device
mask -- a gdk:modifier-type value

Obtains the current device position and modifier state. The position is given in coordinates relative to the upper left corner of window. Use the gdk:window-device-position-double function if you need subpixel precision.