Modify CesiumSubScene to use parent CesiumGeoreference's coordinates when added in-editor.

[azrogers]

Fixes #343.

When CesiumSubScene::OnEnable is called, it sets the coordinates of the parent CesiumGeoreference to the coordinates it has set. This means when adding a new CesiumSubScene component as a child of an existing CesiumGeoreference, it would reset the coordinates of the parent to the default coordinates. This change uses the Reset event to restore the georeference's original coordinates without changing the behavior outside of the editor.

[j9liu]

Thanks @azrogers ! I hadn't realized that OnEnable runs before Reset, so I can see how this became more complicated than anticipated.

Still I wonder if this can be simplified (ish)? Instead of storing the parent coordinates, is it possible to have a bool variable called isInitialized? (name can be improved if possible)

Then in OnEnable, you could have this code towards the end

if (Application.isPlaying)
  // In play mode, the subscene coordinates should be used as-is.
  this.isInitialized = true;

if (isInitialized) {
 this.UpdateOrigin()
 }

Then Reset could look something like this:

this.UpdateParentReference();
if(this._parentGeoreference != null) {
  // adopt parent georeference coordinates here
  isInitialized = true;
}

How does that sound? If it helps with clarity, we could potentially surround these segments with #if EDITOR statements.

I confirmed that this implementation works otherwise. I just think the internal state management is a little confusing.

[j9liu]

Actually, the solution in my previous comment fails to account for existing sub-scenes when they're enabled in the editor. 🙃 And I don't know if the call is to make that isInitialized variable [Serialized]. So ignore what I wrote. I think the solution you found is fine; I'd like to add a bit of clarity to the comment but I'll put a suggestion tomorrow morning.

Just because it was driving me crazy, I looked up if there was an event for any time a component was added in the editor. I found that the ObjectFactory class exists and has a componentWasAdded event on it, but I have no idea when this event is called in relation to the component's event cycle. It's probably not worth exploring at this point.

[j9liu]

@azrogers I left a few more comments, just for code clarity + organization.

[azrogers]

@j9liu Updated review based on feedback - let me know if I missed anything!

[j9liu]

Looks great, thanks @azrogers !