Re: Drag and drop is dead, long live grab and throw :)

[Toby Jaffey <psystrj unix ccc nottingham ac uk>]

On Fri, Jun 18, 1999 at 01:32:18PM +0100, Mark R. Bowyer wrote:

> >From: Alastair B Roberts <abr@tardis.ed.ac.uk>
> >To: gnome-devel-list@gnome.org

> >On Fri, 18 Jun 1999, Mark R. Bowyer wrote:

> >> Surely we can take a leaf from Gesture research here.  For a drag, the mouse 
> >> has started to decelerate before we release the button.  For a throw, the 
> >> button is released while the mouse is still accelerating.  This is how we 
> >> drop and throw in real life, it should work that way on-screen, too.

> >Sounds like a good idea, but

> >(a) how easy would this be to implement?

> It's been a long time since I've done this kind of code, but I think you just 
> record the difference between each positional value you read and note the delta. 
> It's used to calculate how far to move the mouse if acceleration is on in 
> Windoze and many Xservers already...

Hmm.. If you look in the example code that I posted, this was exactly
the problem that I had. Because of the mouse acceleration the drag was
considered to first hit the background some way away from the source
site. Can this be overcome within gtk (without resorting to the bare
metal of X). I guess that the gimp must do it while the brush is being
moved..

> >(b) it was mentioned previously in this thread about the inaccuracy of
> >    the modern mouse (especially after its been used for a while). I
> >    fear that the average mouse will not accelerate and deaccelerate
> >    accurately enough to reliably detect. Remember the basic HCI
> >    (human computer interaction) principle: speed and accuracy are
> >    tradeoffs. If one has to accelerate the mouse to throw an icon,
> >    the accuracy of the placement will be very much decreased. Just
> >    a thought.

> Not sure if this is true or not.  But it should be possible to allow for a 
> tunable huristic so that the user can slide a slider to differentiate between a 
> drop and a throw for their own setup and hand movements?

If you consider the case that you have a file selector or something in
the middle of the screen that supports dnd (or rather gnt) and the drop
sites are positioned around the outside of the screen, it would be fine.

The best idea I have heard so far though is that when a drag begin, a
line should be drawn as a guide for the user, so they can see the place
it will land if they continue with the current path. This could even
'snap' between targets.

-- 
(o_   | Toby Jaffey : www.nott.ac.uk/~psystrj/
//\   | Real Programmers don't comment their code.  If it was hard  
V_/_  | to write, it should be hard to understand.