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>6. Window Manager Protocols</A
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><A
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>6.1. _NET_WM_PING</A
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><P
>This protocol allows the Window Manager to determine if the Client is still
processing X events.  This can be used by the Window Manager to determine if a
window which fails to close after being sent WM_DELETE_WINDOW has stopped
responding, or has stalled for some other reason, such as waiting for user
confirmation.  A Client SHOULD indicate that it is willing to participate in
this protocol by listing _NET_WM_PING in the WM_PROTOCOLS property of the
client window.
		</P
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>A Window Manager can use this protocol at any time by sending a client message
as follows:
		</P
><PRE
CLASS="PROGRAMLISTING"
>type = ClientMessage
window = the respective client window
message_type = WM_PROTOCOLS
format = 32
data.l[0] = _NET_WM_PING
data.l[1] = timestamp</PRE
><P
>A participating Client receiving this message MUST send it back to the root
window immediately, by setting window = root, and calling XSendEvent.  The
Client MUST NOT alter the timestamp, as this can be used by the Window Manager
to uniquely identify the ping.
		</P
><P
>The Window Manager MAY kill the Client (using _NET_WM_PID) if it fails to
respond to this protocol within a reasonable time.
		</P
><P
>See also the implementation notes on <A
HREF="x351.html#KILLINGWINDOWS"
>killing hung processes</A
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