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From: mouse@larry.mcrcim.mcgill.EDU
Newsgroups: comp.windows.x
Subject: Re: XWarpPointer revisited.....
Message-ID: <9101241054.AA16132@Larry.McRCIM.McGill.EDU>
Date: 24 Jan 91 10:54:08 GMT
Sender: daemon@athena.mit.edu (Mr Background)
Organization: The Internet
Lines: 29

>> Can someone explain why warping the pointer *within* the client
>> using XWarpPointer is discouraged?

> Speaking from personal experience, one real good reason is that the
> pointing device might be an absolute one (like a tablet) rather than
> a relative one (like a mouse), in which case warping the pointer is
> completely ineffective!

Not necessarily so.  I brought this point up in an email exchange with
someone a while ago and the other person pointed out that it is fairly
easy to take absolute positions from a tablet-style device and turn
them into deltas, which are then applied to the cursor the same way
deltas from a mouse would be.  Then, when the pen is lifted off the
pad, the next point does not generate a delta.  This way the tablet
behaves very much the way a mouse does: keep the pen down and move it
around and it tracks; pick it up and put it down elsewhere and it
doesn't notice the motion.

Not that you always want this.  I recall a video game we had (years
ago) that used a tablet as an absolute positioning device.  That game
would have been unplayable if the tablet coordinates had been processed
this way; it depended on getting absolute positions.  (Which is why
I've never rewritten it to run on the machines we have now - we have no
absolute pointing devices.)

					der Mouse

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