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From: cflatter@ZIA.AOC.NRAO.EDU (Chris Flatters)
Newsgroups: comp.windows.x
Subject: Re:  XView XV_KEY_DATA problem
Message-ID: <9009172352.AA24028@zia.aoc.nrao.edu>
Date: 17 Sep 90 23:52:51 GMT
Sender: root@athena.mit.edu (Wizard A. Root)
Organization: The Internet
Lines: 25


> I just ran into a problem with XView's XV_KEY_DATA attribute.  It seems
> the XView toolkit attaches data to some of the object it creates.
> This is fine until you happen to choose the same key as the toolkit.
> I attached a pointer with KEY=1 to a panel which is what XView uses to
> attach the panel's private structure.

There is an (apparently) undocumented function in XView:

      xv_unique_key()

which returns an unused attribute key.  Xv_unique_key is used extensively
inside XView objects to allocate keys but there are at least two instances
(panel and text) where keys are #define'd to 1.  I don't know if there is
a good reason for these exceptions or whether they are oversites.  In practice
it makes no difference since xv_unique_key does not return 1 if you have
created some XView objects.

It is possible that xv_unique_key() is intended for internal use only but
it does have uses at the application level.  In addition to guaranteeing
a unique key for XV_KEY_DATA it is also a good way of assigning client IDs
for the notifier.

			Chris Flatters
			cflatter@nrao.edu