Merge branch 'charlesmchen/messageViewScrollStateRevisited'

Podfile.lock

@@ -139,7 +139,7 @@ CHECKOUT OPTIONS:
     :commit: 6e9d5e8c3dc87e397b4b7485172507b0990a22dd
     :git: https://github.com/WhisperSystems/SignalProtocolKit.git
   JSQMessagesViewController:
-    :commit: 9e452ee59cbcebf2c67f0dc499988b6725de776e
+    :commit: 868cf70fae0f3b54c3cfa7773ef03578d209b668
     :git: https://github.com/WhisperSystems/JSQMessagesViewController.git
   OpenSSL:
     :commit: b2d3c149102032a09aefbfb470885db4aa83efad

Signal.xcodeproj/project.pbxproj

@@ -2580,11 +2580,7 @@
 					"DEBUG=1",
 					"$(inherited)",
 				);
-				"GCC_PREPROCESSOR_DEFINITIONS[arch=*]" = (
-					"DEBUG=1",
-					"$(inherited)",
-					"SSK_BUILDING_FOR_TESTS=1",
-				);
+				"GCC_PREPROCESSOR_DEFINITIONS[arch=*]" = "DEBUG=1 $(inherited) SSK_BUILDING_FOR_TESTS=1";
 				GCC_TREAT_IMPLICIT_FUNCTION_DECLARATIONS_AS_ERRORS = YES;
 				GCC_TREAT_INCOMPATIBLE_POINTER_TYPE_WARNINGS_AS_ERRORS = YES;
 				GCC_WARN_64_TO_32_BIT_CONVERSION = YES;

Signal/src/ViewControllers/ConversationView/MessagesViewController.m

@@ -243,6 +243,7 @@ typedef NS_ENUM(NSInteger, MessagesRangeSizeMode) {
 @property (nonatomic) BOOL isViewVisible;
 @property (nonatomic) BOOL isAppInBackground;
 @property (nonatomic) BOOL shouldObserveDBModifications;
+@property (nonatomic) BOOL viewHasEverAppeared;
 
 @end
 
@@ -639,7 +640,11 @@ typedef NS_ENUM(NSInteger, MessagesRangeSizeMode) {
     [((OWSMessagesToolbarContentView *)self.inputToolbar.contentView)ensureSubviews];
 
     [self.view layoutSubviews];
-    [self scrollToDefaultPosition];
+
+    // We want to set the initial scroll state the first time we enter the view.
+    if (!self.viewHasEverAppeared) {
+        [self scrollToDefaultPosition];
+    }
 }
 
 - (NSIndexPath *_Nullable)indexPathOfUnreadMessagesIndicator
@@ -1059,6 +1064,8 @@ typedef NS_ENUM(NSInteger, MessagesRangeSizeMode) {
     [ProfileFetcherJob runWithThread:self.thread networkManager:self.networkManager];
 
     [self markVisibleMessagesAsRead];
+
+    self.viewHasEverAppeared = YES;
 }
 
 - (void)viewWillDisappear:(BOOL)animated
@@ -3506,6 +3513,14 @@ typedef NS_ENUM(NSInteger, MessagesRangeSizeMode) {
 
 - (BOOL)isScrolledToBottom
 {
+    if (self.collectionView.contentSize.height < 1) {
+        // If the collection view hasn't determined its content size yet,
+        // scroll state is not yet coherent. Therefore we can't (and don't
+        // need to) determine whether we're "scrolled to the bottom" until
+        // the collection view has determined its content size.
+        return NO;
+    }
+
     const CGFloat kIsAtBottomTolerancePts = 5;
     return (self.collectionView.contentOffset.y + self.collectionView.bounds.size.height + kIsAtBottomTolerancePts
         >= self.collectionView.contentSize.height);
@@ -4149,6 +4164,7 @@ typedef NS_ENUM(NSInteger, MessagesRangeSizeMode) {
 
 - (void)scrollToBottomAnimated:(BOOL)animated
 {
+    OWSAssert([NSThread isMainThread]);
 
     if (self.isUserScrolling) {
         return;