Animations in transitions do not set running property, transitions do not have running property

Run sample.qml and press the red rectangle.

The problem is: Animations which run in transitions do not propagate the fact that they are running in their "running" property. A second problem is, that the Transition itself does not have a read-only running property.

Why is this a problem? We sometimes want to enable special GL effects when a transition is happening.

The current workaround is to set a special property to true when the transition starts with PropertyAction{}, and have that set to false in the target state. But this is ugly and mixes states and transisions.
It's necessary to set the property in the state's PropertyChanges, because state-changing transitions can be aborted at any time.

sample_workaround.qml shows this workaround.