Show the lock screen placeholder on willResignActive. (#2086)

ElementX/Sources/Services/AppLock/AppLockService.swift

@@ -111,8 +111,8 @@ class AppLockService: AppLockServiceProtocol {
         timer.applicationDidEnterBackground()
     }
     
-    func computeNeedsUnlock(willEnterForegroundAt date: Date) -> Bool {
-        timer.computeLockState(willEnterForegroundAt: date)
+    func computeNeedsUnlock(didBecomeActiveAt date: Date) -> Bool {
+        timer.computeLockState(didBecomeActiveAt: date)
     }
     
     func unlock(with pinCode: String) -> Bool {

ElementX/Sources/Services/AppLock/AppLockServiceProtocol.swift

@@ -59,7 +59,7 @@ protocol AppLockServiceProtocol: AnyObject {
     /// Informs the service that the app has entered the background.
     func applicationDidEnterBackground()
     /// Decides whether the app should be unlocked with a PIN code/biometrics on foregrounding.
-    func computeNeedsUnlock(willEnterForegroundAt date: Date) -> Bool
+    func computeNeedsUnlock(didBecomeActiveAt date: Date) -> Bool
     
     /// Attempt to unlock the app with the supplied PIN code.
     func unlock(with pinCode: String) -> Bool

ElementX/Sources/Services/AppLock/AppLockTimer.swift

@@ -21,13 +21,18 @@ class AppLockTimer {
     /// The amount of time the app should remain unlocked for whilst backgrounded.
     let gracePeriod: TimeInterval
     
-    /// Whether the timer considers the app to be locked or not.
+    /// Whether the timer considers the app to be locked or not. Always starts with a locked app.
     ///
     /// Internally this value may be incorrect, always call `needsUnlock` to get the correct value.
     private var isLocked = true
     /// The date when the app was last backgrounded whilst in an unlocked state.
     private var lastUnlockedBackground: Date?
     
+    /// Whether or not the app has moved to the background.
+    ///
+    /// This allows us to distinguish between `willResignActive` and `didEnterBackground`.
+    private var isInBackground = false
+    
     /// Creates a new timer.
     /// - Parameter gracePeriod: The amount of time the app should remain unlocked for whilst backgrounded.
     init(gracePeriod: TimeInterval) {
@@ -36,13 +41,18 @@ class AppLockTimer {
     
     /// Signals to the timer to track how long the app will be backgrounded for.
     func applicationDidEnterBackground(date: Date = .now) {
+        isInBackground = true
         // Only update the last background date if the app is currently unlocked.
         guard !isLocked else { return }
         lastUnlockedBackground = date
     }
     
-    /// Asks the timer to recompute the lock state on foregrounding.
-    func computeLockState(willEnterForegroundAt date: Date) -> Bool {
+    /// Asks the timer to recompute the lock state when active. If ``applicationDidEnterBackground`` hasn't been
+    /// called since the last computation, then this method won't recompute it, instead directly returning the previous state.
+    func computeLockState(didBecomeActiveAt date: Date) -> Bool {
+        guard isInBackground else { return isLocked }
+        isInBackground = false
+        
         guard !isLocked, let lastUnlockedBackground else { return true }
         
         isLocked = date.timeIntervalSince(lastUnlockedBackground) >= gracePeriod