[PATCH inputproto 2/2] Document smooth-scrolling support

[Peter Hutterer]

On Thu, Jun 23, 2011 at 10:50:41AM +0100, Daniel Stone wrote:
> Hi,
> 
> On Thu, Jun 23, 2011 at 10:44:44AM +1000, Peter Hutterer wrote:
> > On Thu, Jun 09, 2011 at 06:26:01PM +0100, Daniel Stone wrote:
> > > Two new axes are added to support smooth scrolling: Rel Vert Scroll and
> > > Rel Horiz Scroll.  Cumulative values of 1.0 with either magnitude on
> > > these axes are considered to be equivalent to one legacy ButtonPress
> > > event on the scroll buttons.
> > 
> > one more question:
> > What do we do for backwards compatibility? 2.0 clients get both events?
> > 2.0 clients won't see the flag after all and would be lead to think that
> > there's movement _and_ scrolling.
> 
> A 2.0 client which listens for 2.1 axes but doesn't pay attention to 2.1
> flags? I think we can just put that one in the 'well, don't do that'
> basket, to be honest.

you can't choose which axes you listen to, you get all of them. with smooth
scrolling, a 1.x/2.0 client (built before the addition of the scrolling
labels) would see motion events on two unknown/unlabelled axes and button
4-7
events.

Now, of course there's the argument that you shouldn't be handling axes that
you don't know what they are but that doesn't help 1.x clients at all (plus,
we have e.g. in the wacom driver several axes that are still "unknown").

Cheers,
  Peter