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From: mouse@lightning.mcrcim.mcgill.EDU
Newsgroups: comp.windows.x
Subject: Re:  Can an application know a DESTROY/KILL is applied on itself?
Message-ID: <9101220259.AA12732@lightning.McRCIM.McGill.EDU>
Date: 22 Jan 91 02:59:20 GMT
Sender: daemon@athena.mit.edu (Mr Background)
Organization: The Internet
Lines: 38

> By far I understand, to destroy a window in a WM, such as using
> "destroy/kill" in twm, "close" in mwm, is to tell X server to close
> the connection with the application which creates the window.

This is how it has traditionally been done.  The ICCCM defines the
DELETE_WINDOW protocol, with others under discussion, to address this
perceived need.  I won't describe this here; it would make this posting
excessively large and I probably wouldn't get it right, unless I quoted
directly from the ICCC document itself.  And you can read it for
yourself....

> My question is, is there any way an application can be notified or
> get to know a DESTROY/KILL instruction is applied to the application.
> The purpose to do that is for safty.  For example, a drawing program
> certainly wants to save the contents before terminated by an
> acciendly DESTROY/KILL from the WM.

Not to address the problem, but "certainly" is too strong a word.  In
my case, for example, doing a kill in my window manager is sufficiently
difficult that it does not happen by accident; if I kill the window I
do *not* want it to auto-save what is probably a botched drawing.
(Auto-checkpoint would be a reasonable compromise.)

> The DestroyNotify in Xlib doesn't work because

Because DestroyNotify is for something else: notifying applications of
window destruction.  And as you noticed, while the window is destroyed
by the forced connection close, the client can't get the event.  It
would work to open a second connection and have that connection do
nothing but select for DestroyNotify on the windows created on the
first connection.  (This qualifies as a gross kludge.  Besides, it
really doesn't tell you anything more than the first connection being
broken does.)

					der Mouse

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