Created attachment 362707 [details] Test case See the attached test case. In this example we initially run a transition for 5 seconds, and 2 seconds into its run we change its to-value. In our implementation both the initial and the retargeted transition have the same duration: 5 seconds. However, the retargeted transition should compute its duration by factoring the transformed progress (accounting for the timing-function) of the initial duration when it's interrupted and the transition-duration.