Resolve crash within NavigationSplitView in v2.3.4

[julianschiavo]

Hey! Per your recommendation, we (Bitrig) updated STTextView to v2.3.4 today. Unfortunately, this caused our app to crash on launch when using STTextView within a SwiftUI.NavigationSplitView.

Sample code:

struct ContentView: View {
    var body: some View {
        NavigationSplitView {
            Spacer()
        } detail: {
            TextView(
                text: .constant(.init("Wow"))
            )
            .font(.system(size: 12, weight: .regular, design: .monospaced))
        }
    }
}

I investigated the crash and believe it was caused by an invalidation loop from NavigationSplitView while STTextView is resizing during layout.

I found that implementing sizeThatFits to accept SwiftUI's size proposal resolves the crash.

We have already made this change in our internal source editor package. I'm making this PR to share the fix with other users as well in case it's helpful. Thank you!

[CLAassistant]

All committers have signed the CLA.

[krzyzanowskim]

fantastic! thank you