Why invent a new notification schema. Just enable notification in the IDE in the timeline panel. And then receive the update as HypeTimelineUpdate with the regular way Hype handles updates like HypeSceneLoad etc. only difference is that this event has to be enabled.
Do you mind describing your specific use case? I know generally why someone wants this but it is useful to grab a corpus of needs for the design - for example one open question is if it should be called before or after Hype does its animation work. Thanks!
Many cases we need mutation observer for could be supported natively. Act when the timeline progresses or on specific value changes. Currently we need to watch timeline offsets or values that are connected to a timeline. I could even see it not firing on every value change in a timeline. To narrow notifications even further down it could be attached to a attribute in the timeline.
If that not an option and we keep it simple and notify about all events in a timeline (it’s certainly a simpler UI then the previous suggestion) meta information like the timeline name, attribute name and value and other meta information could be provided in the event object passed by notify. Also the element is part of this call.
I actually hacked the runtime once todo just that but it did fire on any value change and passed in the unresolved attributes.
It seems there are times when we want to know when a timeline is at a particular stage so we can do a few things.
My original thoughts were in the scope of questions like these.
The main thing is we have to poll or request the currenttime in a time line manually or write our own code using mutation observer, poll via setInteval or/and requestanimationFrame to run code when the time is right.
The closest thing to a timeline onupdate is using a Math Equation within an easing to run a hype function ( outside its own scope) aliased to a global. ( also which cannot be accessed within a sprite )
An on event or as @MaxZieb suggests an optional registration to a HypeTimelineUpdate event would possibly make it easier to innovate and understand and writ for the masses. In particular doing away with the cumbersome setInteval and complex mutation observer.
This is not saying it will not have it’s own challanges…