Question Getting back to a previous visualStree keeps instance state?

Hi there,
And don't get me wrong, I think it is a lovely feature but I am not sure if it is intended (and if so maybe the naming is a bit off) or if it is unintended (so it is just a nice bug that's likely to disappear)

So take this code:

Code (CSharp):

1.     public void ShowUI()
2.     {
3.         GetComponent<UIDocument>().visualTreeAsset = thisVisualTree;
4.         rootVisualElement = GetComponent<UIDocument>().rootVisualElement;
5.         listView = rootVisualElement.Q<ListView>();
6. //..and add stuff to the list
7.         var button = rootVisualElement.Q<Button>("configure");
8.         button.clicked += ()=> {
9.             var logConfig = GetComponent<LogConfig>();
10.             logConfig.ShowUI(ShowUI); //inside this call we swap the UIDocument's visualTreeAsset
11.         };

I have two VisualTrees, the one I am on (assigned to the UIDocument) and a second one, when the 'clicked' code above is executed I assign a new VisualTree to the UIDocument component.
Now, I assumed that VisualTrees where assets that would live in disk or somesuch. If so, I don't quite get what happens: I assign a new VisualTree, I stop seeing the old one and get to see the new one (all good), then I assign the old VisualTree asset back and the contents of the instance of that VisualTree happens to pop back in place <-so the listView carries whatever was there before the visualTreeAsset was assigned
Is that by design?

PS: My guess is that VisualTree (as in the inspector) is not an asset but a sort of instance already, but yeah, is that the case?
thanks!

 

hi @JuliaP_Unity!
To clarify thing a bit, this is what I see:
I have an UIDocument that's get a visual tree assigned in the inspector:

Code (CSharp):

1.     public VisualTreeAsset firstVisualTree;

That tree contains a ListView that I populate with a few things
Then I assign the UIDocument's VisualTree to a different .uxml asset:

Code (CSharp):

1.         GetComponent<UIDocument>().visualTreeAsset = secondVisualTree;

and add stuff to that (well, to the rootVisualElement of the UIDocument)

What seems magic is that I can assign the old tree again:

Code (CSharp):

1.         GetComponent<UIDocument>().visualTreeAsset = firstVisualTree;

and I get the previous content! including the populated ListView, which appears as I left it *which is a nice thing* but which follows a mechanism I don't understand
My guess here is that setter of the visualTreeAsset keeps a map of visualTrees (assets) and rootVisualElements (instances) but it seems not documented anywhere. Hence the question

About the hint about GetComponent<>, I am familiar with those but they are handy when trying stuff out

Thanks!