If w is PointerWindow , the destination window is the window that contains the pointer.
If w is InputFocus and if the focus window contains the pointer, the destination window is the window that contains the pointer; otherwise, the destination window is the focus window.
To determine which clients should receive the specified events, XSendExtensionEvent uses the propagate argument as follows:
If event_list is the empty set, the event is sent to the client that created the destination window. If that client no longer exists, no event is sent.
If propagate is False, the event is sent to every client selecting on destination any of the event types specified by the event_list array.
If propagate is True and no clients have selected on destination any of the events specified by the event_list array, the destination is replaced with the closest ancestor of destination for which some client has selected a type specified by the event-list array and for which no intervening window has that type in its do-not-propagate-mask. If no such window exists or if the window is an ancestor of the focus window and InputFocus was originally specified as the destination, the event is not sent to any clients. Otherwise, the event is reported to every client selecting on the final destination any of the events specified in the event_list array.
The event in the XEvent structure must be one of the events defined by the input extension (or a BadValue error results) so that the X server can correctly byte-swap the contents as necessary. The contents of the event are otherwise unaltered and unchecked by the X server except to force send_event to True in the forwarded event and to set the serial number in the event correctly.
XSendExtensionEvent returns zero if the conversion to wire protocol format failed and returns nonzero otherwise. XSendExtensionEvent can generate BadClass, BadDevice, BadValue, and BadWindow errors.