[Development] Should gestures consume events?

[Shawn Rutledge]

On Thu, Nov 08, 2012 at 08:07:31PM -0200, Rafael Roquetto wrote:
> Hello,
> 
> I was wondering if some gestures, such as QTapGesture or QTapAndHoldGesture
> should consume QEvent::TouchBegin || QEvent::TouchEnd. The reason I am asking
> this is that, if these events are not consumed somewhere along the chain, Qt
> assumes that the touch events haven't been handled at all, and then
> synthethizes and delivers corresponding MouseEvents (using
> QApplicationPrivate::translateTouchToMouse), causing additional mouse events
> to be delivered. Now, I am not sure if this is the intended behavior, but
> I am assuming that applications watching for GestureEvents are not monitoring
> TouchEvent directly, and thus receiving wasted mouse events. On the other
> hand, "provide mechanism, not policy".
> 
> Any thoughts?

Maybe if the recipient of the gesture accepts it, it should accept all the 
touches that contributed to the gesture?

I guess I should try it to understand better how it works.

> The reason I am bringing this up is that currently on Qt5,
> QApplicationPrivate::translateTouchToMouse (or something related) is broken,
> causing these mouse events that are synthethized from touch events to have a
> position() of (0, 0). These mouse events are then also handled by the gesture

That's surprising.   I was working on it a couple of months ago, but mostly from the
QML perspective.  How do you reproduce the problem?

> recognizers, which update the gesture position to that of this event - (0 ,0),
> in a cascading effect. I am working on fixing that, patch will be in gerrit
> soon.
> 
> Thanks a lot,
> Rafael
> -- 
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> 
> Rafael Roquetto | rafael.roquetto at kdab.com | Software Engineer
> Klarälvdalens Datakonsult AB, a KDAB Group company
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