Okay, so by adding a .navigationDestination(for:) to the sidebar column, it fixes the content to detail column animation.

However, now the sidebar to content column animation is broken. I've tried fiddling around with .navigationBarTitleDisplayMode(.large), etc. Nada.

I need to lay down.

I refuse to sleep until I have found a solution to this, which is unfortunate, as it means I may never sleep again 🥲

I've now officially arrived in crazy town, and started wrapping UINavigationController myself.

What's interesting is that the SwiftUI environment is still automatically adding nav items to the controller, so I've actually got the same broken animations as with NavigationStack. At least it’s…consistent.

Running out of ideas now 😅

Hallelujah! 🙌

Finally got a workaround for the NavigationSplitView regression in iOS 16.4.

Transitions stop working when the content column no longer contains a List (say you have a “Select Mailbox" view, a Grid, etc).

Here's a gist of the issue: https://gist.github.com/phillipcaudell/6d4d0efac6a22cd42bf75f3acd7a033b

It seems to suddenly start behaving like a NavigationStack, which is why adding a navigationDestination sorta works (except now you've got wonky nav animations, and it still sometimes fails)…

…so instead, I'm switching to a Stack when compact. Only issue is getting NavigationLink, SplitView and Stack to play together.

In the end I found it was easier to remove NavigationLinks all together, and instead use tags. Lists then use this as their selection value.

Then, using those selections, I'm computing a path to drive the Stack. Once I caught EditMode, it all worked.

No jittery toolbars. Smooth transitions. Consistent and predictable across iPhone/iPad/Mac.

Thank god.

If there's any poor souls stumbling across this in the future, here's a gist to my solution: https://gist.github.com/phillipcaudell/085580a9412284f381a4730930c7d52f

Now to refactor this back into Big Mail 🥲 #SwiftUI