FWIW, I just added a keychain sharing entitlement using Xcode 12.5, and it added the entitlements file with $(AppIdentifierPrefix)groupname (groupname is what I put in the entitlements UI). I don't know what value it's actually putting in there, as I can't find AppIdentifierPrefix anywhere else in the project. Update: It's really hard to know what the string in my code should be to match what Xcode is generating for the entitlement.

Well, I can't show all the code, but I can show a bit more: swift class ChatStream { @Published var messages = OrderedSetMessage() func add(messages inMsgs: [IncomingMessage]) { for msg in inMsgs { let msg = Message(fromIncoming: msg, user: user) self.messages.append(msg) } self.messages.sort() } } ... struct ChatView: View { @ObservedObject public var stream : ChatStream var body: some View { ScrollViewReader { scrollView in ScrollView { LazyVStack(alignment: .leading, spacing: 0.0) { ForEach(self.stream.messages) { inMsg in ChatMessageCell(message: inMsg) } .onChange(of: self.stream.messages, perform: { inMessages in --- called multiple times for each update below. if inMessages.count 1 { return } withAnimation(.linear(duration: 0.25)) { scrollView.scrollTo(inMessages.last!.id, anchor: .bottom) } }) } } } } }

Oh never mind, I'm wrong about that.

The range of position is the same for both interpolatedValueAtPosition and valueAtPosition. What happens if you don't divide x by 256?

Did you ever find a solution to this? BTW when I try that sample code on Big Sur 11.2.3, it barely works. I can't pinch-zoom without also clicking the trackpad, and even then it doesn't really change size nicely.

Unfortunately that only works while the mouse button is held down. I found an amazing solution, though, but the forum won't let me include a link to it. It's the SwiftUI-Lab (dot com) website, article The Power of the Hosting+Representable Combo.” It's unfortunate that Apple seems to have completely omitted mouse tracking in views.

I, too, would like this source code. This was an extremely informative talk, and demonstrated some non-trivial SwiftUI. In so doing, it went beyond just showing how to use documents.

Yes, that was the first thing I checked. As I mentioned, optimizations are off.