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From: rws@expo.lcs.mit.EDU (Bob Scheifler)
Newsgroups: comp.windows.x
Subject: Re: Possible Event Handler Bug
Message-ID: <9101122032.AA28066@expire.lcs.mit.edu>
Date: 12 Jan 91 20:32:33 GMT
References: <9101122029.AA08824@kiwi.lgc.com>
Sender: daemon@athena.mit.edu (Mr Background)
Organization: The Internet
Lines: 20


    The problem here is the implicit pointer grab that the server starts when
    the pointer button goes down (see 8.4.1.1 of the Scheifler/Gettys/Newman
    book).

Good work!  I was just about to send a message saying the same thing.

    I think if you call XChangeActivePointerGrab in your button press
    event handler with a mask that includes PointerMotionMask and
    ButtonReleaseMask, your problem will go away (but I haven't actually
    run the test).

I have.  To do it right, you should also specify the time from the event in
the call:

	...
	XtAddEventHandler(canvas, PointerMotionMask, FALSE, motion, NULL);
	XChangeActivePointerGrab(XtDisplay(canvas),
				 PointerMotionMask|ButtonReleaseMask,
				 None, evt->xbutton.time);