XSetTransientForHint(display, w, prop_window)
      Display *display;
      Window w;
      Window prop_window;
| display | Specifies the connection to the X server. | 
| w | Specifies the window. | 
| prop_window | Specifies the window that the WM_TRANSIENT_FOR property is to be set to. | 
XSetTransientForHint() can generate BadAlloc and BadWindow errors.
| BadAlloc | The server failed to allocate the requested source or server memory. | 
| BadWindow | A value for a Window argument does not name a defined Window. |