XGrabKey can generate BadAccess , BadValue , and BadWindow errors. The XUngrabKey function releases the key combination on the specified window if it was grabbed by this client. It has no effect on an active grab. A keycode argument of AnyKey is equivalent to issuing the request for all possible key codes. XUngrabKey can generate BadValue and BadWindow error.
Some numeric value falls outside the range of values accepted by the request.
Unless a specific range is specified for an argument, the full range defined by the argument's type is accepted. Any argument defined as a set of alternatives can generate this error. BadWindow A value for a Window argument does not name a defined Window.