New approach to multitouch using DIDs and bitmasked events

[Chase Douglas]

On Mon, 2010-07-05 at 13:48 -0400, Rafi Rubin wrote:
> On 07/05/2010 01:31 PM, Chase Douglas wrote:
> > On Mon, 2010-07-05 at 13:20 -0400, Rafi Rubin wrote:
> >> On 07/05/2010 12:54 PM, Chase Douglas wrote:
> >>> The reason we can't pass DIDs as XI1 events is because an XI1 client
> >>> also doesn't see "floating" input devices that aren't attached to master
> >>> pointers. Only XI2 can see events from "floating" input devices.
> >>
> >> Would vestigial valuators enable us to support XI1?  Do we care about XI1?
> >
> > Heh, I feel like we're returning to the conversation I had with Peter
> > about legacy client support. Essentially, you need XI2 for multitouch,
> > and the toolkit layer should use XI2 and translate to toolkit events as
> > required. XI1 just isn't extensible enough for multitouch.
> 
> Yup, I was thinking of what you said before with something watching all the MT 
> contacts moving around and producing conventional pointer events where they are 
> needed.  It sounds like a great idea.

Yeah, the problem is that the X architecture really just does not allow
this to happen. The *aha* moment for me was when I was reading the
wikipedia article about X :). It quoted some early principles of X, one
of which was:

Provide mechanism rather than policy. In particular, place user
interface policy in the clients' hands.

Thus, it makes sense why X is architected as it is, but it also means we
have to solve issues like MT pointing above X itself.

> However, it is yet another obstacle in the path of getting MT to the X desktop. 
>   When you say toolkit, I hope you mean just some separate piece of code, and 
> not requiring gtk/qt to get conventional pointer events.  I'd hate to loose 
> support for some real legacy apps (which I actually use for my work), where it 
> really is standard X events or nothing (programs written in straight xlib, 
> statically compiled, obscure toolkits, etc).

I think the real solution is getting the MT to pointer translation in
all the toolkits. If you build your programs right, they shouldn't be
statically linked to toolkits. A toolkit upgrade should just magically
make things work in older applications.

Now, if you've really written stuff in xlib, then you'll have to fix it
up manually. How many applications are really written in xlib though?

-- Chase