multi-touch-dev team mailing list archive

[Henrik Rydberg <rydberg@xxxxxxxxxxx>]

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.

> 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.

Cheers,
Henrik