multi-touch-dev team mailing list archive

[Peter Hutterer <peter.hutterer@xxxxxxxxx>]

On Mon, Oct 18, 2010 at 09:39:36AM +0200, Henrik Rydberg wrote:
> On 10/18/2010 03:29 AM, Peter Hutterer wrote:
> [...]
> >>
> 
> >> From what I gather, tentative events are passed during the time when an event is
> >> neither replayed nor consumed. For gestures, this is exactly the time when
> >> nothing at all should happen. 
> > 
> > Then don't do anything with the events? That's kinda what you're supposed to
> > do anyway until you get the OK that the event sequence isn't tentative
> > anymore.
> 
> 
> The client would not know that the touches landing within its realm are
> part of a global gesture, and thus would not know when to display
> something, and when not to.
> 
> >> If the gesture is accepted, the action will be
> >> controlled by the entity detecting the gesture, and it is up to that entity to
> >> make sure some kind of feedback is given. Nota bene, the *gesture* may very well
> >> be tentative at this stage. If the gesture is cancelled, the real events will be
> >> replayed and things will continue as normal. Thus, I see no reason at all to
> >> introduce tentative events.
> > 
> > There's a reasonable technical argument for them - to avoid buffering a
> > possibly huge number of events in the server. Seriously, the tentative
> > events, whether they will be added or not, add virtually nothing to the
> > client-side semantics.
> 
> 
> The way they are discussed here suggests they do. If they did not carry
> information, I would have no objection. Currently, however, they do.

they carry information, but the client is explicitly requested to not use
that information until it gets the green light for it. if a client misuses
that, well, meh.

> > In fact, if you always wait until the "use-it-now event" before doing the
> > handling of touch events and discard those you get a "discard this sequence"
> > event for, there is no semantical change at all.
> 
> 
> I believe you said yourself that it is hard to constrain the semantics of
> these events.

from a technical point of view, yes. grab replaying when you've sent events
to clients already is quite interesting, since you need to track which
clients you sent the events to, who's next in line to use them, and send the 
"discard" events to all clients.

Cheers,
  Peter