XTranslateCoordinates() - translate window coordinates
Bool XTranslateCoordinates (Display *display,
Window src_w, Window dest_w,
int src_x, int src_y,
int *dest_x_return, int *dest_y_return,
Window *child_return)
If XTranslateCoordinates(3) returns True, it takes the src_x and src_y coordinates relative to the source window's origin and returns these coordinates to dest_x_return and dest_y_return relative to the destination window's origin. If XTranslateCoordinates(3) returns False, src_w and dest_w are on different screens, and dest_x_return and dest_y_return are zero. If the coordinates are contained in a mapped child of dest_w, that child is returned to child_return. Otherwise, child_return is set to None.
XTranslateCoordinates(3) can generate a BadWindow error.
Xlib