The XSendExtensionEvent request identifies the destination
window, determines which clients should receive the specified
events, and ignores any active grabs. This request requires you
to pass an event class list. For a discussion of the valid
event class names, see XOpenDevice(3) This
request uses the w argument to identify the destination window
as follows:
  * 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.

BadDevice
       An invalid device was specified. The specified device
       does not exist or has not been opened by this client via
       XOpenInputDevice. This error may also occur if the
       specified device is the X keyboard or X pointer device.

BadValue
       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.