Refine 'new message' animations.

Signal/src/ViewControllers/ConversationView/Cells/OWSMessageBubbleView.m

@@ -508,12 +508,18 @@ NS_ASSUME_NONNULL_BEGIN
     [self.bubbleView addPartnerView:shadowView];
     [self.bubbleView addPartnerView:clipView];
 
+    // Prevent the layer from animating changes.
+    [CATransaction begin];
+    [CATransaction setDisableActions:YES];
+
     OWSAssert(buttonsView.backgroundColor);
     shadowView.fillColor = buttonsView.backgroundColor;
     shadowView.layer.shadowColor = [UIColor blackColor].CGColor;
     shadowView.layer.shadowOpacity = 0.12f;
     shadowView.layer.shadowOffset = CGSizeZero;
     shadowView.layer.shadowRadius = 1.f;
+
+    [CATransaction commit];
 }
 
 - (BOOL)contactShareHasSpacerTop

Signal/src/ViewControllers/ConversationView/ConversationViewController.m

@@ -3489,55 +3489,40 @@ typedef enum : NSUInteger {
     OWSAssert(rowChanges);
 
     // If user sends a new outgoing message, don't animate the change.
-    BOOL isOnlyInsertingNewOutgoingMessages = YES;
-    BOOL isOnlyUpdatingLastOutgoingMessage = YES;
-    NSNumber *_Nullable lastUpdateRow = nil;
-    NSNumber *_Nullable lastNonUpdateRow = nil;
+    BOOL isOnlyModifyingLastMessage = YES;
     for (YapDatabaseViewRowChange *rowChange in rowChanges) {
         switch (rowChange.type) {
             case YapDatabaseViewChangeDelete:
-                isOnlyInsertingNewOutgoingMessages = NO;
-                isOnlyUpdatingLastOutgoingMessage = NO;
-                if (!lastNonUpdateRow || lastNonUpdateRow.integerValue < rowChange.indexPath.row) {
-                    lastNonUpdateRow = @(rowChange.indexPath.row);
-                }
+                isOnlyModifyingLastMessage = NO;
                 break;
             case YapDatabaseViewChangeInsert: {
-                isOnlyUpdatingLastOutgoingMessage = NO;
                 ConversationViewItem *_Nullable viewItem = [self viewItemForIndex:(NSInteger)rowChange.finalIndex];
-                if ([viewItem.interaction isKindOfClass:[TSOutgoingMessage class]]
+                if (([viewItem.interaction isKindOfClass:[TSIncomingMessage class]] ||
+                        [viewItem.interaction isKindOfClass:[TSOutgoingMessage class]])
                     && rowChange.finalIndex >= oldViewItemCount) {
                     continue;
                 }
-                if (!lastNonUpdateRow || lastNonUpdateRow.unsignedIntegerValue < rowChange.finalIndex) {
-                    lastNonUpdateRow = @(rowChange.finalIndex);
-                }
+                isOnlyModifyingLastMessage = NO;
             }
             case YapDatabaseViewChangeMove:
-                isOnlyInsertingNewOutgoingMessages = NO;
-                isOnlyUpdatingLastOutgoingMessage = NO;
-                if (!lastNonUpdateRow || lastNonUpdateRow.integerValue < rowChange.indexPath.row) {
-                    lastNonUpdateRow = @(rowChange.indexPath.row);
-                }
-                if (!lastNonUpdateRow || lastNonUpdateRow.unsignedIntegerValue < rowChange.finalIndex) {
-                    lastNonUpdateRow = @(rowChange.finalIndex);
-                }
+                isOnlyModifyingLastMessage = NO;
                 break;
             case YapDatabaseViewChangeUpdate: {
-                isOnlyInsertingNewOutgoingMessages = NO;
-                ConversationViewItem *_Nullable viewItem = [self viewItemForIndex:(NSInteger)rowChange.finalIndex];
-                if (![viewItem.interaction isKindOfClass:[TSOutgoingMessage class]]
-                    || rowChange.indexPath.row != (NSInteger)(oldViewItemCount - 1)) {
-                    isOnlyUpdatingLastOutgoingMessage = NO;
+                if (rowChange.changes == YapDatabaseViewChangedDependency) {
+                    continue;
                 }
-                if (!lastUpdateRow || lastUpdateRow.integerValue < rowChange.indexPath.row) {
-                    lastUpdateRow = @(rowChange.indexPath.row);
+                ConversationViewItem *_Nullable viewItem = [self viewItemForIndex:(NSInteger)rowChange.finalIndex];
+                if (([viewItem.interaction isKindOfClass:[TSIncomingMessage class]] ||
+                        [viewItem.interaction isKindOfClass:[TSOutgoingMessage class]])
+                    && rowChange.finalIndex >= oldViewItemCount) {
+                    continue;
                 }
+                isOnlyModifyingLastMessage = NO;
                 break;
             }
         }
     }
-    BOOL shouldAnimateRowUpdates = !(isOnlyInsertingNewOutgoingMessages || isOnlyUpdatingLastOutgoingMessage);
+    BOOL shouldAnimateRowUpdates = !isOnlyModifyingLastMessage;
     return shouldAnimateRowUpdates;
 }
 

Signal/src/ViewControllers/ConversationView/ConversationViewLayout.m

@@ -172,6 +172,26 @@ NS_ASSUME_NONNULL_BEGIN
     return self.collectionView.bounds.size.width != newBounds.size.width;
 }
 
+- (nullable UICollectionViewLayoutAttributes *)initialLayoutAttributesForAppearingItemAtIndexPath:
+    (NSIndexPath *)indexPath
+{
+    UICollectionViewLayoutAttributes *_Nullable layoutAttributes =
+        [super initialLayoutAttributesForAppearingItemAtIndexPath:indexPath];
+    // Don't fade in new cells.
+    layoutAttributes.alpha = 1.f;
+    return layoutAttributes;
+}
+
+- (nullable UICollectionViewLayoutAttributes *)finalLayoutAttributesForDisappearingItemAtIndexPath:
+    (NSIndexPath *)indexPath
+{
+    UICollectionViewLayoutAttributes *_Nullable layoutAttributes =
+        [super finalLayoutAttributesForDisappearingItemAtIndexPath:indexPath];
+    // Don't fade in new cells.
+    layoutAttributes.alpha = 1.f;
+    return layoutAttributes;
+}
+
 @end
 
 NS_ASSUME_NONNULL_END