System messsages can show timestamp

added the JSQCollectionViewCell cellTopLabel to the system message
layout

// FREEBIE

Signal/src/ViewControllers/ConversationView/MessagesViewController.m

@@ -1723,6 +1723,9 @@ typedef enum : NSUInteger {
         [self.collectionView dequeueReusableCellWithReuseIdentifier:[OWSSystemMessageCell cellReuseIdentifier]
                                                        forIndexPath:indexPath];
     [cell configureWithInteraction:interaction];
+    cell.cellTopLabel.attributedText =
+        [self collectionView:self.collectionView attributedTextForCellTopLabelAtIndexPath:indexPath];
+
     cell.systemMessageCellDelegate = self;
 
     return cell;

Signal/src/views/OWSSystemMessageCell.m

@@ -24,6 +24,7 @@ NS_ASSUME_NONNULL_BEGIN
 
 @property (nonatomic) UIImageView *imageView;
 @property (nonatomic) UILabel *titleLabel;
+@property (nonatomic) UILabel *cellTopLabel;
 
 @end
 
@@ -31,6 +32,9 @@ NS_ASSUME_NONNULL_BEGIN
 
 @implementation OWSSystemMessageCell
 
+// override from JSQMessagesCollectionViewCell
+@synthesize cellTopLabel = _cellTopLabel;
+
 // `[UIView init]` invokes `[self initWithFrame:...]`.
 - (instancetype)initWithFrame:(CGRect)frame
 {
@@ -49,6 +53,12 @@ NS_ASSUME_NONNULL_BEGIN
 
     self.backgroundColor = [UIColor whiteColor];
 
+    self.cellTopLabel = [UILabel new];
+    self.cellTopLabel.textAlignment = NSTextAlignmentCenter;
+    self.cellTopLabel.font = self.topLabelFont;
+    self.cellTopLabel.textColor = [UIColor lightGrayColor];
+    [self.contentView addSubview:self.cellTopLabel];
+
     self.imageView = [UIImageView new];
     [self.contentView addSubview:self.imageView];
 
@@ -84,6 +94,11 @@ NS_ASSUME_NONNULL_BEGIN
     [self setNeedsLayout];
 }
 
+- (UIFont *)topLabelFont
+{
+    return [UIFont boldSystemFontOfSize:12.0f];
+}
+
 - (UIColor *)textColor
 {
     return [UIColor colorWithRGBHex:0x303030];
@@ -227,6 +242,12 @@ NS_ASSUME_NONNULL_BEGIN
     return 20.f;
 }
 
+/// The default layout spacing for the top label (e.g. timestamp) feels a little too close for the system messages.
+- (CGFloat)topLabelBottomMargin
+{
+    return 4.f;
+}
+
 - (void)layoutSubviews
 {
     [super layoutSubviews];
@@ -235,12 +256,19 @@ NS_ASSUME_NONNULL_BEGIN
     CGSize titleSize = [self.titleLabel sizeThatFits:CGSizeMake(maxTitleWidth, CGFLOAT_MAX)];
 
     CGFloat contentWidth = ([self iconSize] + [self hSpacing] + titleSize.width);
+
+    CGSize topLabelSize = [self.cellTopLabel sizeThatFits:CGSizeMake(self.contentView.width, CGFLOAT_MAX)];
+    self.cellTopLabel.frame = CGRectMake(0, 0, self.contentView.frame.size.width, topLabelSize.height);
+
+    CGFloat topLabelSpacing = topLabelSize.height + [self topLabelBottomMargin];
+
     self.imageView.frame = CGRectMake(round((self.contentView.width - contentWidth) * 0.5f),
-        round((self.contentView.height - [self iconSize]) * 0.5f),
+        round((self.contentView.height - [self iconSize] + topLabelSpacing) * 0.5f),
         [self iconSize],
         [self iconSize]);
+
     self.titleLabel.frame = CGRectMake(round(self.imageView.right + [self hSpacing]),
-        round((self.contentView.height - titleSize.height) * 0.5f),
+        round((self.contentView.height - titleSize.height + topLabelSpacing) * 0.5f),
         ceil(titleSize.width + 1.f),
         ceil(titleSize.height + 1.f));
 }
@@ -254,9 +282,12 @@ NS_ASSUME_NONNULL_BEGIN
     [self applyTitleForInteraction:interaction label:self.titleLabel];
     CGFloat maxTitleWidth = (collectionViewWidth - ([self hMargin] * 2.f + [self hSpacing] + [self iconSize]));
     CGSize titleSize = [self.titleLabel sizeThatFits:CGSizeMake(maxTitleWidth, CGFLOAT_MAX)];
+
     CGFloat contentHeight = ceil(MAX([self iconSize], titleSize.height));
     result.height += contentHeight;
 
+    result.height += [self topLabelBottomMargin];
+
     return result;
 }