cairo:device-to-user-distance (cr dx dy)

cr -- a cairo:context-t instance

dx -- a double float for the x component of the distance vector
dy -- a double float for the y component of the distance vector

Transform a distance vector from device space to user space. This function is similar to the cairo:device-to-user function except that the translation components of the inverse CTM will be ignored when transforming (dx,dy).