XTranslateCoordinates - translate window coordinates
Bool XTranslateCoordinates(Display *display, Window
    src_w, dest_w, int src_x, int src_y, int
    *dest_x_return, int *dest_y_return, Window
    *child_return);
  - child_return
- Returns the child if the coordinates are contained in a mapped child of
      the destination window.
- dest_w
- Specifies the destination window.
- dest_x_return
- 
    
 
- dest_y_return
- Return the x and y coordinates within the destination window.
- display
- Specifies the connection to the X server.
- src_w
- Specifies the source window.
- src_x
- 
    
 
- src_y
- Specify the x and y coordinates within the source window.
If XTranslateCoordinates 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 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 can generate a BadWindow
    error.
  - BadWindow
- A value for a Window argument does not name a defined Window.
Xlib - C Language X Interface