gdk:cairo-set-source-window (cr window x y)

cr -- a cairo:context-t context
window -- a gdk:window object
x -- a number coerced to a double float for the x coordinate of the location to place the upper left corner of window
y -- a number coerced to a double float for the y coordinate of the location to place the upper left corner of window

Sets the given window as the source pattern for cr. The pattern has a :none extend mode of the cairo:extend-t enumeration and is aligned so that the origin of window is (x,y). The window contains all its subwindows when rendering.

Note that the contents of window are undefined outside of the visible part of the window, so use this function with care.