Reset the unread indicator state if possible while app is in the background.

* Clean up timer usage.

// FREEBIE

Signal/src/ViewControllers/MessagesViewController.m

@@ -585,6 +585,7 @@ typedef enum : NSUInteger {
             }
         }];
 
+    [self.voiceMemoUpdateTimer invalidate];
     self.voiceMemoUpdateTimer = [NSTimer weakScheduledTimerWithTimeInterval:0.1f
                                                                      target:self
                                                                    selector:@selector(updateVoiceMemo)
@@ -971,6 +972,10 @@ typedef enum : NSUInteger {
                                                  selector:@selector(applicationWillEnterForeground:)
                                                      name:UIApplicationWillEnterForegroundNotification
                                                    object:nil];
+        [[NSNotificationCenter defaultCenter] addObserver:self
+                                                 selector:@selector(applicationDidEnterBackground:)
+                                                     name:UIApplicationDidEnterBackgroundNotification
+                                                   object:nil];
         [[NSNotificationCenter defaultCenter] addObserver:self
                                                  selector:@selector(applicationWillResignActive:)
                                                      name:UIApplicationWillResignActiveNotification
@@ -1006,6 +1011,16 @@ typedef enum : NSUInteger {
     [self ensureThreadOffersAndIndicators];
 }
 
+- (void)applicationDidEnterBackground:(NSNotification *)notification
+{
+    //    self.hasEnteredBackground = YES;
+
+    if (self.hasClearedUnreadMessagesIndicator) {
+        self.hasClearedUnreadMessagesIndicator = NO;
+        self.offersAndIndicators = nil;
+    }
+}
+
 - (void)applicationWillResignActive:(NSNotification *)notification
 {
     [self cancelVoiceMemo];
@@ -1279,7 +1294,8 @@ typedef enum : NSUInteger {
 }
 
 - (void)startReadTimer {
-    self.readTimer = [NSTimer scheduledTimerWithTimeInterval:1
+    [self.readTimer invalidate];
+    self.readTimer = [NSTimer weakScheduledTimerWithTimeInterval:2
                                                           target:self
                                                         selector:@selector(readTimerDidFire)
                                                         userInfo:nil
@@ -2972,8 +2988,12 @@ typedef enum : NSUInteger {
     // make sure we don't show it again.
     self.hasClearedUnreadMessagesIndicator = YES;
 
+    if (self.offersAndIndicators.unreadIndicatorPosition) {
+        // If we've just cleared the "unread messages" indicator,
+        // update the dynamic interactions.
         [self ensureThreadOffersAndIndicators];
     }
+}
 
 #pragma mark - Attachment Picking: Documents
 

Signal/src/ViewControllers/OWSAudioAttachmentPlayer.m

@@ -127,6 +127,7 @@ NS_ASSUME_NONNULL_BEGIN
 
     [self.audioPlayer prepareToPlay];
     [self.audioPlayer play];
+    [self.audioPlayerPoller invalidate];
     self.audioPlayerPoller = [NSTimer weakScheduledTimerWithTimeInterval:.05f
                                                                   target:self
                                                                 selector:@selector(audioPlayerUpdated:)

Signal/src/ViewControllers/OWSLinkedDevicesTableViewController.m

@@ -6,6 +6,7 @@
 #import "OWSDeviceTableViewCell.h"
 #import "OWSLinkDeviceViewController.h"
 #import "UIViewController+CameraPermissions.h"
+#import <SignalServiceKit/NSTimer+OWS.h>
 #import <SignalServiceKit/OWSDevice.h>
 #import <SignalServiceKit/OWSDevicesService.h>
 #import <SignalServiceKit/TSDatabaseView.h>
@@ -100,8 +101,8 @@ int const OWSLinkedDevicesTableViewControllerSectionAddDevice = 1;
     self.editing = NO;
 
     __weak typeof(self) wself = self;
-    self.pollingRefreshTimer = [NSTimer scheduledTimerWithTimeInterval:(10.0)
+    [self.pollingRefreshTimer invalidate];
-                                                                target:wself
+    self.pollingRefreshTimer = [NSTimer weakScheduledTimerWithTimeInterval:(10.0)target:wself
                                                                   selector:@selector(refreshDevices)
                                                                   userInfo:nil
                                                                    repeats:YES];

Signal/src/ViewControllers/SignalsNavigationController.m

@@ -4,6 +4,7 @@
 
 #import "SignalsNavigationController.h"
 #import "UIUtil.h"
+#import <SignalServiceKit/NSTimer+OWS.h>
 #import <SignalServiceKit/OWSSignalService.h>
 #import <SignalServiceKit/TSSocketManager.h>
 
@@ -87,7 +88,8 @@ static double const STALLED_PROGRESS = 0.9;
         case SocketManagerStateClosed:
             if (_socketStatusView == nil) {
                 [self initializeSocketStatusBar];
-                _updateStatusTimer = [NSTimer scheduledTimerWithTimeInterval:0.5
+                [_updateStatusTimer invalidate];
+                _updateStatusTimer = [NSTimer weakScheduledTimerWithTimeInterval:0.5
                                                                           target:self
                                                                         selector:@selector(updateProgress)
                                                                         userInfo:nil

Signal/src/util/ThreadUtil.m

@@ -155,7 +155,7 @@ NS_ASSUME_NONNULL_BEGIN
         // have been marked as read.
         //
         // IFF this variable is non-null, there are unseen messages in the thread.
-        __block NSNumber *firstUnseenInteractionTimestamp = nil;
+        NSNumber *firstUnseenInteractionTimestamp = nil;
         if (firstUnseenInteractionTimestampParameter) {
             firstUnseenInteractionTimestamp = firstUnseenInteractionTimestampParameter;
         } else {