Add an iPhone client sharing the macOS app's SwiftUI code

mac/Sources/Byre/PaneFocus.swift

@@ -1,11 +1,9 @@
-import AppKit
 import ByreAPI
 import SwiftUI
 
 @MainActor
 final class PaneFocus {
     private let api: API
-    private weak var window: NSWindow?
     private var paneFrame: CGRect = .zero
     private var taskSheetFrame: CGRect = .zero
     private var leadSheetFrame: CGRect = .zero
@@ -15,13 +13,57 @@ final class PaneFocus {
     private(set) var drafting = false
     private var sending: Task<Void, Never>?
     private var observers: [NotificationCenter.ObservationToken] = []
+    #if os(macOS)
+    private weak var window: NSWindow?
     private var responder: NSKeyValueObservation?
     private var clicks: Any?
+    #endif
 
     init(api: API) {
         self.api = api
     }
 
+    #if os(iOS)
+    func attach() {
+        if !observers.isEmpty {
+            return
+        }
+        let center = NotificationCenter.default
+        observers = [
+            center.addObserver(of: UIApplication.self, for: .didBecomeActive) { [weak self] _ in
+                self?.update()
+            },
+            center.addObserver(of: UIApplication.self, for: .willResignActive) { [weak self] _ in
+                self?.update()
+            },
+        ]
+    }
+
+    let shown = Listeners<Void>()
+
+    func setShown(_ shown: Bool) {
+        inside = shown
+        update()
+        if shown {
+            self.shown.send(())
+        }
+    }
+
+    func detach() {
+        for o in observers {
+            NotificationCenter.default.removeObserver(o)
+        }
+        observers = []
+    }
+
+    private var active: Bool {
+        UIApplication.shared.applicationState == .active
+    }
+    #else
+    private var active: Bool {
+        (window?.isKeyWindow ?? false) && NSApp.isActive
+    }
+
     func attach(_ window: NSWindow) {
         if self.window === window {
             return
@@ -73,9 +115,14 @@ final class PaneFocus {
         clicks = nil
         window = nil
     }
+    #endif
 
-    var windowKey: Bool {
-        (window?.isKeyWindow ?? false) && NSApp.isActive
+    var taskVisible: Bool {
+        #if os(iOS)
+        active && inside
+        #else
+        active
+        #endif
     }
 
     func setFrame(_ frame: CGRect) {
@@ -123,6 +170,7 @@ final class PaneFocus {
         }
     }
 
+    #if os(macOS)
     private func contentPoint(_ rect: CGRect, in view: NSView) -> CGPoint? {
         guard let content = window?.contentView else {
             return nil
@@ -157,9 +205,10 @@ final class PaneFocus {
             self?.responderChanged()
         }
     }
+    #endif
 
     private func update() {
-        let now = (window?.isKeyWindow ?? false) && NSApp.isActive && inside
+        let now = active && inside
         let draft = !drafts.isEmpty
         if now == focused && draft == drafting {
             return
@@ -183,6 +232,7 @@ final class PaneFocus {
     }
 }
 
+#if os(macOS)
 struct WindowReader: NSViewRepresentable {
     let found: (NSWindow) -> Void
 
@@ -212,3 +262,4 @@ final class WindowReaderView: NSView {
         }
     }
 }
+#endif