Duplicated tap-and-hold events and DontStartGesturesOnChilden problem

There are several issues in the gesture system affected by tiny commit added back in the 5.0 development cycle. The commit is 602ea84f44ab507e5603ed0808bf4a5dd145d773 and surprisingly, it was done to fix tap and hold, but what it does for certain applications (that grab a gesture in the top level widget) is cause duplicated tap and hold events.

It also causes that the Qt::DontStartGestureOnChildren flag is not honored, at least in some cases.

I can confirm that in a large, complex, and heavy user of the gesture system, unapplying said commit fixes several issues, and causes no apparent regressions.

I'm also attaching a self contained test case that proves the two issues, and how removing those lines fixes them.