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What's the latest way to hook into the "back" button? I see some older posts but they seem outdated. I'm experimenting with writing a custom nav controller, since the official NavController does not do what I want. It seems relatively easy thanks to Compose, but the back button is a question mark... maybe more difficultly is hiding there.

`BackHandler` with an event handler that pops your backstack

Okay, I found `BackHandler`. Perfect, thanks! By "backstack" do you mean something in the system API that I need to hook into, or do you just mean whatever stack/nav system I'm implementing?  I'm clear how to implement _my_ version of "back", but I'm not sure how to know when the user intends to go "back" out of my app.

Yea whatever your nav system is. ~If you don’t specify a back handler then back will back out of your app, so just don’t call `BackHandler` if your stack is size 1~

Actually, you'd want to use the `enabled` parameter of `BackHandler` for the stack size, not just conditionally including the `BackHandler`. As per the custom back docs (<https://developer.android.com/guide/navigation/navigation-custom-back>), the ordering of `BackHandler`s is important for dispatch - you'd want to maintain the correct place in the list as it were compared to parent, sibling, and child `BackHandler` instances

Conditionally adding a `BackHandler` does have its use cases (say, for a side nav drawer that needs to be at the top of the dispatch queue when it is open, no matter what `BackHandler`s the underlying content have), it just isn't the right one for the back stack size case