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From: ellis@audi.mit.EDU (Ellis Cohen)
Newsgroups: comp.windows.x
Subject: Relative Warp
Message-ID: <8708102109.AA00666@audi.siemens.uucp>
Date: Mon, 10-Aug-87 17:09:05 EDT
Article-I.D.: audi.8708102109.AA00666
Posted: Mon Aug 10 17:09:05 1987
Date-Received: Tue, 11-Aug-87 06:30:23 EDT
Sender: daemon@ucbvax.BERKELEY.EDU
Distribution: world
Organization: The ARPA Internet
Lines: 43


    
        In our tiled window manager, we have a move gadget
        to the right of the title bar.
        Clicking on the gadget warps the pointer to the
        middle of the window.
        The user then moves the pointer to another place
        on the screen and clicks again, and this location
        becomes the new center location of the window.
    
    This seems like a perfect example of where a relative warp is a bad
    idea, and a conditional absolute warp is a good idea.  The position you
    ideally want to end up at (the center of the window) is known
    absolutely.  If the window manager suffers a delay in warping, and the
    user has since moved the pointer off to the new center and is about to
    click, I find it hard to imagine that it is desirable to suddenly do a
    relative warp.
    
    What am I missing?

Well, suppose that the user wants to move the window a bit to the right.
He could click in the move gadget, wait for the manager to warp the pointer
to the center of the window, move the pointer to the right, and then click.

However, our experience is that users like to "point ahead".  That is,
the user clicks the move gadget, and immediately starts moving the
pointer to the right.  In the middle of moving it to the right, the
server catches up, and the pointer is warped relative to its current
location (i.e. if it was not moved at all, it is moved to the window
center; if it was moved slightly to the right, it is warped slightly to
the right of the window center, etc.). This is the way our 1 year old
Sunview implementation works, and it is just fine.

The problem is, without the relative warp, even when the user has moved
the pointer slightly, the cursor is warped back to the original window
center, which is pretty annoying.




Ellis Cohen
Ellis.Cohen@a.gp.cs.cmu.edu
princeton!siemens!ellis