Add reported application state.

Signal/src/util/MainAppContext.m

@@ -11,6 +11,14 @@
 
 NS_ASSUME_NONNULL_BEGIN
 
+@interface MainAppContext ()
+
+@property (atomic) UIApplicationState reportedApplicationState;
+
+@end
+
+#pragma mark -
+
 @implementation MainAppContext
 
 @synthesize mainWindow = _mainWindow;
@@ -23,6 +31,8 @@ NS_ASSUME_NONNULL_BEGIN
         return self;
     }
 
+    self.reportedApplicationState = UIApplicationStateInactive;
+
     [[NSNotificationCenter defaultCenter] addObserver:self
                                              selector:@selector(applicationWillEnterForeground:)
                                                  name:UIApplicationWillEnterForegroundNotification
@@ -58,6 +68,8 @@ NS_ASSUME_NONNULL_BEGIN
 {
     OWSAssertIsOnMainThread();
 
+    self.reportedApplicationState = UIApplicationStateInactive;
+
     DDLogInfo(@"%@ %s", self.logTag, __PRETTY_FUNCTION__);
 
     [NSNotificationCenter.defaultCenter postNotificationName:OWSApplicationWillEnterForegroundNotification object:nil];
@@ -67,6 +79,8 @@ NS_ASSUME_NONNULL_BEGIN
 {
     OWSAssertIsOnMainThread();
 
+    self.reportedApplicationState = UIApplicationStateBackground;
+
     DDLogInfo(@"%@ %s", self.logTag, __PRETTY_FUNCTION__);
     [DDLog flushLog];
 
@@ -77,6 +91,8 @@ NS_ASSUME_NONNULL_BEGIN
 {
     OWSAssertIsOnMainThread();
 
+    self.reportedApplicationState = UIApplicationStateInactive;
+
     DDLogInfo(@"%@ %s", self.logTag, __PRETTY_FUNCTION__);
     [DDLog flushLog];
 
@@ -87,6 +103,8 @@ NS_ASSUME_NONNULL_BEGIN
 {
     OWSAssertIsOnMainThread();
 
+    self.reportedApplicationState = UIApplicationStateActive;
+
     DDLogInfo(@"%@ %s", self.logTag, __PRETTY_FUNCTION__);
 
     [NSNotificationCenter.defaultCenter postNotificationName:OWSApplicationDidBecomeActiveNotification object:nil];
@@ -135,12 +153,7 @@ NS_ASSUME_NONNULL_BEGIN
 
 - (BOOL)isInBackground
 {
-    return [UIApplication sharedApplication].applicationState == UIApplicationStateBackground;
-}
-
-- (UIApplicationState)mainApplicationState
-{
-    return [UIApplication sharedApplication].applicationState;
+    return self.reportedApplicationState == UIApplicationStateBackground;
 }
 
 - (UIBackgroundTaskIdentifier)beginBackgroundTaskWithExpirationHandler:

SignalServiceKit/src/Storage/OWSStorage.m

@@ -720,9 +720,9 @@ NSString *const kNSUserDefaults_DatabaseExtensionVersionMap = @"kNSUserDefaults_
             stringWithFormat:@"CipherKeySpec inaccessible. New install or no unlock since device restart? Error: %@",
             error];
         if (CurrentAppContext().isMainApp) {
-            UIApplicationState applicationState = CurrentAppContext().mainApplicationState;
-            errorDescription =
-                [errorDescription stringByAppendingFormat:@", ApplicationState: %d", (int)applicationState];
+            UIApplicationState applicationState = CurrentAppContext().reportedApplicationState;
+            errorDescription = [errorDescription
+                stringByAppendingFormat:@", ApplicationState: %@", NSStringForUIApplicationState(applicationState)];
         }
         DDLogError(@"%@ %@", self.logTag, errorDescription);
         [DDLog flushLog];

SignalServiceKit/src/Util/AppContext.h

@@ -33,13 +33,26 @@ NSString *NSStringForUIApplicationState(UIApplicationState value);
 
 @property (atomic, nullable) UIWindow *mainWindow;
 
-// Should only be called if isMainApp is YES.
+// Unlike UIApplication.applicationState, this is thread-safe.
+// It contains the "last known" application state.
 //
-// Wherever possible, use isMainAppAndActive or isInBackground instead.
-// This should only be used by debugging/logging code.
-- (UIApplicationState)mainApplicationState;
+// Because it is updated in response to "will/did-style" events, it is
+// conservative and skews toward less-active and not-foreground:
+//
+// * It doesn't report "is active" until the app is active
+//   and reports "inactive" as soon as it _will become_ inactive.
+// * It doesn't report "is foreground (but inactive)" until the app is
+//   foreground & inactive and reports "background" as soon as it _will
+//   enter_ background.
+//
+// This conservatism is useful, since we want to err on the side of
+// caution when, for example, we do work that should only be done
+// when the app is foreground and active.
+@property (atomic, readonly) UIApplicationState reportedApplicationState;
 
-// Similar to UIApplicationStateBackground, but works in SAE.
+// A convenience accessor for reportedApplicationState.
+//
+// This method is thread-safe.
 - (BOOL)isInBackground;
 
 // Should start a background task if isMainApp is YES.

SignalShareExtension/utils/ShareAppExtensionContext.m

@@ -11,7 +11,8 @@ NS_ASSUME_NONNULL_BEGIN
 @interface ShareAppExtensionContext ()
 
 @property (nonatomic) UIViewController *rootViewController;
-@property (atomic) BOOL isSAEInBackground;
+
+@property (atomic) UIApplicationState reportedApplicationState;
 
 @end
 
@@ -33,6 +34,8 @@ NS_ASSUME_NONNULL_BEGIN
 
     _rootViewController = rootViewController;
 
+    self.reportedApplicationState = UIApplicationStateInactive;
+
     [[NSNotificationCenter defaultCenter] addObserver:self
                                              selector:@selector(extensionHostDidBecomeActive:)
                                                  name:NSExtensionHostDidBecomeActiveNotification
@@ -66,7 +69,7 @@ NS_ASSUME_NONNULL_BEGIN
 
     DDLogInfo(@"%@ %s", self.logTag, __PRETTY_FUNCTION__);
 
-    self.isSAEInBackground = NO;
+    self.reportedApplicationState = UIApplicationStateActive;
 
     [NSNotificationCenter.defaultCenter postNotificationName:OWSApplicationDidBecomeActiveNotification object:nil];
 }
@@ -75,6 +78,8 @@ NS_ASSUME_NONNULL_BEGIN
 {
     OWSAssertIsOnMainThread();
 
+    self.reportedApplicationState = UIApplicationStateInactive;
+
     DDLogInfo(@"%@ %s", self.logTag, __PRETTY_FUNCTION__);
     [DDLog flushLog];
 
@@ -88,7 +93,7 @@ NS_ASSUME_NONNULL_BEGIN
     DDLogInfo(@"%@ %s", self.logTag, __PRETTY_FUNCTION__);
     [DDLog flushLog];
 
-    self.isSAEInBackground = YES;
+    self.reportedApplicationState = UIApplicationStateBackground;
 
     [NSNotificationCenter.defaultCenter postNotificationName:OWSApplicationDidEnterBackgroundNotification object:nil];
 }
@@ -99,7 +104,7 @@ NS_ASSUME_NONNULL_BEGIN
 
     DDLogInfo(@"%@ %s", self.logTag, __PRETTY_FUNCTION__);
 
-    self.isSAEInBackground = NO;
+    self.reportedApplicationState = UIApplicationStateInactive;
 
     [NSNotificationCenter.defaultCenter postNotificationName:OWSApplicationWillEnterForegroundNotification object:nil];
 }
@@ -143,13 +148,7 @@ NS_ASSUME_NONNULL_BEGIN
 
 - (BOOL)isInBackground
 {
-    return self.isSAEInBackground;
-}
-
-- (UIApplicationState)mainApplicationState
-{
-    OWSFail(@"%@ called %s.", self.logTag, __PRETTY_FUNCTION__);
-    return UIApplicationStateBackground;
+    return self.reportedApplicationState == UIApplicationStateBackground;
 }
 
 - (UIBackgroundTaskIdentifier)beginBackgroundTaskWithExpirationHandler: