Currently, 3rd party Transitions are very limited comparing to Transitions in javafx.animation package.

There are several reasons for this.

1) impl_sync, impl_startable methods are package-private and cannot be used by them. Making these methods protected would allow 3rd party Transitions to synchronize with the current state of things at the beginning of an animation

2) Transitions are not object agnostic currently. Although it's not visible in the public API, they inherit Node from their parent Transitions (Sequential/Parallel). This should be changed to some general Object or generic parameter.

3) Explicit call to setCycleDuration is needed. Should be probably added to Transition constructor so that some reasonable default is set at the start.