Merge branch 'charlesmchen/reportedApplicationState'

Signal/src/ViewControllers/ConversationView/ConversationViewController.m

@@ -233,7 +233,6 @@ typedef enum : NSUInteger {
 
 @property (nonatomic) BOOL isViewCompletelyAppeared;
 @property (nonatomic) BOOL isViewVisible;
-@property (nonatomic) BOOL isAppInBackground;
 @property (nonatomic) BOOL shouldObserveDBModifications;
 @property (nonatomic) BOOL viewHasEverAppeared;
 @property (nonatomic) BOOL hasUnreadMessages;
@@ -594,12 +593,12 @@ typedef enum : NSUInteger {
 - (void)applicationWillEnterForeground:(NSNotification *)notification
 {
     [self startReadTimer];
-    self.isAppInBackground = NO;
+    [self updateCellsVisible];
 }
 
 - (void)applicationDidEnterBackground:(NSNotification *)notification
 {
-    self.isAppInBackground = YES;
+    [self updateCellsVisible];
     if (self.hasClearedUnreadMessagesIndicator) {
         self.hasClearedUnreadMessagesIndicator = NO;
         [self.dynamicInteractions clearUnreadIndicatorState];
@@ -609,6 +608,7 @@ typedef enum : NSUInteger {
 
 - (void)applicationWillResignActive:(NSNotification *)notification
 {
+    [self updateShouldObserveDBModifications];
     [self cancelVoiceMemo];
     self.isUserScrolling = NO;
     [self saveDraft];
@@ -620,6 +620,7 @@ typedef enum : NSUInteger {
 
 - (void)applicationDidBecomeActive:(NSNotification *)notification
 {
+    [self updateShouldObserveDBModifications];
     [self startReadTimer];
 }
 
@@ -1530,7 +1531,8 @@ typedef enum : NSUInteger {
 
 - (void)autoLoadMoreIfNecessary
 {
-    if (self.isUserScrolling || !self.isViewVisible || self.isAppInBackground) {
+    BOOL isMainAppAndActive = CurrentAppContext().isMainAppAndActive;
+    if (self.isUserScrolling || !self.isViewVisible || !isMainAppAndActive) {
         return;
     }
     if (!self.showLoadMoreHeader) {
@@ -4428,17 +4430,10 @@ typedef enum : NSUInteger {
     [self updateCellsVisible];
 }
 
-- (void)setIsAppInBackground:(BOOL)isAppInBackground
-{
-    _isAppInBackground = isAppInBackground;
-
-    [self updateShouldObserveDBModifications];
-    [self updateCellsVisible];
-}
-
 - (void)updateCellsVisible
 {
-    BOOL isCellVisible = self.isViewVisible && !self.isAppInBackground;
+    BOOL isAppInBackground = CurrentAppContext().isInBackground;
+    BOOL isCellVisible = self.isViewVisible && !isAppInBackground;
     for (ConversationViewCell *cell in self.collectionView.visibleCells) {
         cell.isCellVisible = isCellVisible;
     }
@@ -4446,7 +4441,8 @@ typedef enum : NSUInteger {
 
 - (void)updateShouldObserveDBModifications
 {
-    self.shouldObserveDBModifications = self.isViewVisible && !self.isAppInBackground;
+    BOOL isAppForegroundAndActive = CurrentAppContext().isAppForegroundAndActive;
+    self.shouldObserveDBModifications = self.isViewVisible && isAppForegroundAndActive;
 }
 
 - (void)setShouldObserveDBModifications:(BOOL)shouldObserveDBModifications

Signal/src/ViewControllers/HomeView/HomeViewController.m

@@ -51,7 +51,6 @@ NSString *const kArchivedConversationsReuseIdentifier = @"kArchivedConversations
 @property (nonatomic) NSSet<NSString *> *blockedPhoneNumberSet;
 @property (nonatomic, readonly) NSCache<NSString *, ThreadViewModel *> *threadViewModelCache;
 @property (nonatomic) BOOL isViewVisible;
-@property (nonatomic) BOOL isAppInBackground;
 @property (nonatomic) BOOL shouldObserveDBModifications;
 @property (nonatomic) BOOL hasBeenPresented;
 
@@ -131,14 +130,14 @@ NSString *const kArchivedConversationsReuseIdentifier = @"kArchivedConversations
                                              selector:@selector(applicationWillEnterForeground:)
                                                  name:OWSApplicationWillEnterForegroundNotification
                                                object:nil];
-    [[NSNotificationCenter defaultCenter] addObserver:self
-                                             selector:@selector(applicationDidEnterBackground:)
-                                                 name:OWSApplicationDidEnterBackgroundNotification
-                                               object:nil];
     [[NSNotificationCenter defaultCenter] addObserver:self
                                              selector:@selector(applicationDidBecomeActive:)
                                                  name:OWSApplicationDidBecomeActiveNotification
                                                object:nil];
+    [[NSNotificationCenter defaultCenter] addObserver:self
+                                             selector:@selector(applicationWillResignActive:)
+                                                 name:OWSApplicationWillResignActiveNotification
+                                               object:nil];
     [[NSNotificationCenter defaultCenter] addObserver:self
                                              selector:@selector(yapDatabaseModified:)
                                                  name:YapDatabaseModifiedNotification
@@ -484,16 +483,10 @@ NSString *const kArchivedConversationsReuseIdentifier = @"kArchivedConversations
     [self updateShouldObserveDBModifications];
 }
 
-- (void)setIsAppInBackground:(BOOL)isAppInBackground
-{
-    _isAppInBackground = isAppInBackground;
-
-    [self updateShouldObserveDBModifications];
-}
-
 - (void)updateShouldObserveDBModifications
 {
-    self.shouldObserveDBModifications = self.isViewVisible && !self.isAppInBackground;
+    BOOL isAppForegroundAndActive = CurrentAppContext().isAppForegroundAndActive;
+    self.shouldObserveDBModifications = self.isViewVisible && isAppForegroundAndActive;
 }
 
 - (void)setShouldObserveDBModifications:(BOOL)shouldObserveDBModifications
@@ -550,15 +543,9 @@ NSString *const kArchivedConversationsReuseIdentifier = @"kArchivedConversations
 
 - (void)applicationWillEnterForeground:(NSNotification *)notification
 {
-    self.isAppInBackground = NO;
     [self checkIfEmptyView];
 }
 
-- (void)applicationDidEnterBackground:(NSNotification *)notification
-{
-    self.isAppInBackground = YES;
-}
-
 - (BOOL)hasAnyMessagesWithTransaction:(YapDatabaseReadTransaction *)transaction
 {
     return [TSThread numberOfKeysInCollectionWithTransaction:transaction] > 0;
@@ -566,6 +553,8 @@ NSString *const kArchivedConversationsReuseIdentifier = @"kArchivedConversations
 
 - (void)applicationDidBecomeActive:(NSNotification *)notification
 {
+    [self updateShouldObserveDBModifications];
+
     // It's possible a thread was created while we where in the background. But since we don't honor contact
     // requests unless the app is in the foregrond, we must check again here upon becoming active.
     __block BOOL hasAnyMessages;
@@ -582,6 +571,11 @@ NSString *const kArchivedConversationsReuseIdentifier = @"kArchivedConversations
     }
 }
 
+- (void)applicationWillResignActive:(NSNotification *)notification
+{
+    [self updateShouldObserveDBModifications];
+}
+
 #pragma mark - startup
 
 - (NSArray<ExperienceUpgrade *> *)unseenUpgradeExperiences

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 +153,12 @@ NS_ASSUME_NONNULL_BEGIN
 
 - (BOOL)isInBackground
 {
-    return [UIApplication sharedApplication].applicationState == UIApplicationStateBackground;
+    return self.reportedApplicationState == UIApplicationStateBackground;
 }
 
-- (UIApplicationState)mainApplicationState
+- (BOOL)isAppForegroundAndActive
 {
-    return [UIApplication sharedApplication].applicationState;
+    return self.reportedApplicationState == UIApplicationStateActive;
 }
 
 - (UIBackgroundTaskIdentifier)beginBackgroundTaskWithExpirationHandler:

SignalMessaging/Views/ThreadViewHelper.m

@@ -56,25 +56,30 @@ NS_ASSUME_NONNULL_BEGIN
     [self.uiDatabaseConnection beginLongLivedReadTransaction];
 
     [[NSNotificationCenter defaultCenter] addObserver:self
-                                             selector:@selector(applicationWillEnterForeground:)
-                                                 name:OWSApplicationWillEnterForegroundNotification
+                                             selector:@selector(applicationDidBecomeActive:)
+                                                 name:OWSApplicationDidBecomeActiveNotification
                                                object:nil];
     [[NSNotificationCenter defaultCenter] addObserver:self
-                                             selector:@selector(applicationDidEnterBackground:)
-                                                 name:OWSApplicationDidEnterBackgroundNotification
+                                             selector:@selector(applicationWillResignActive:)
+                                                 name:OWSApplicationWillResignActiveNotification
                                                object:nil];
 
-    self.shouldObserveDBModifications = !CurrentAppContext().isInBackground;
+    [self updateShouldObserveDBModifications];
 }
 
-- (void)applicationWillEnterForeground:(NSNotification *)notification
+- (void)applicationDidBecomeActive:(NSNotification *)notification
 {
-    self.shouldObserveDBModifications = YES;
+    [self updateShouldObserveDBModifications];
 }
 
-- (void)applicationDidEnterBackground:(NSNotification *)notification
+- (void)applicationWillResignActive:(NSNotification *)notification
 {
-    self.shouldObserveDBModifications = NO;
+    [self updateShouldObserveDBModifications];
+}
+
+- (void)updateShouldObserveDBModifications
+{
+    self.shouldObserveDBModifications = CurrentAppContext().isAppForegroundAndActive;
 }
 
 // Don't observe database change notifications when the app is in the background.

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

@@ -33,15 +33,33 @@ 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.
+//
+// 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.
 //
-// Wherever possible, use isMainAppAndActive or isInBackground instead.
-// This should only be used by debugging/logging code.
-- (UIApplicationState)mainApplicationState;
+// 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;
 
+// A convenience accessor for reportedApplicationState.
+//
+// This method is thread-safe.
+- (BOOL)isAppForegroundAndActive;
+
 // Should start a background task if isMainApp is YES.
 // Should just return UIBackgroundTaskInvalid if isMainApp is NO.
 - (UIBackgroundTaskIdentifier)beginBackgroundTaskWithExpirationHandler:

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 +148,12 @@ NS_ASSUME_NONNULL_BEGIN
 
 - (BOOL)isInBackground
 {
-    return self.isSAEInBackground;
+    return self.reportedApplicationState == UIApplicationStateBackground;
 }
 
-- (UIApplicationState)mainApplicationState
+- (BOOL)isAppForegroundAndActive
 {
-    OWSFail(@"%@ called %s.", self.logTag, __PRETTY_FUNCTION__);
-    return UIApplicationStateBackground;
+    return self.reportedApplicationState == UIApplicationStateActive;
 }
 
 - (UIBackgroundTaskIdentifier)beginBackgroundTaskWithExpirationHandler: