multi-touch-dev team mailing list archive

[Chase Douglas <chase.douglas@xxxxxxxxxxxxx>]

On Tue, 2010-10-12 at 16:02 +0200, Zeno Albisser wrote:
> On 10/12/2010 03:49 PM, ext Chase Douglas wrote:
> > This leads us to the gesture recognition mechanism Peter and I have been
> > discussing. Since we can't perform gesture recognition in the server, we
> > have to potentially perform recognition twice: first at the system-wide
> > level, then potentially at the application level if no system-wide
> > gestures were recognized. One method for doing this is XI 2.1 passive
> > grabbing.
> I don't understand why we hear that often about these different levels 
> of gesture recognition.
> Shouldn't all subscribers of input events be handled exactly the same way?
> And consuming such input/gesture events should be solved by event 
> propagation?
> Or do you want "system wide gestures" to have precedence over 
> "application level gestures"?
> In case you want that kind of precedence, shouldn't just the window 
> manager be the instance to decide if this is a "system wide gesture" or 
> if the raw events should be propagated to the next client? - In that 
> case i think it boils down to the same solution again. Am I missing 
> something?

Nope, I think we're in agreement here :). The XI 2.1 passive grabs only
come into play as far as the window manager is concerned. We (Canonical)
believe that system wide gestures take precedence over application
gestures until the user performs an action, per application, telling us
otherwise. So we need a mechanism for the window manager to receive all
MT events and decide whether they are system-wide gestures and consume
them, or to "replay" them to the underlying applications.

Outside of this usage scenario, we (Canonical again :) don't foresee a
need for MT grabbing for our purposes. Of course, others may have their
own needs, so XI 2.1 should still support active grabs and other
semantics as required.

-- Chase