Jumbomoji.

// FREEBIE

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

@@ -132,8 +132,6 @@ NS_ASSUME_NONNULL_BEGIN
     [self.bubbleImageView autoPinToSuperviewEdges];
 
     self.textView = [UITextView new];
-    // Honor dynamic type in the message bodies.
-    self.textView.font = [self textMessageFont];
     self.textView.backgroundColor = [UIColor clearColor];
     self.textView.opaque = NO;
     self.textView.editable = NO;
@@ -182,6 +180,23 @@ NS_ASSUME_NONNULL_BEGIN
 
 - (UIFont *)textMessageFont
 {
+    OWSAssert(DisplayableText.kMaxJumbomojiCount == 5);
+
+    if (self.displayableText.jumbomojiCount) {
+        switch (self.displayableText.jumbomojiCount.integerValue) {
+            case 1:
+                return [UIFont ows_regularFontWithSize:35.f];
+            case 2:
+                return [UIFont ows_regularFontWithSize:30.f];
+            case 3:
+            case 4:
+            case 5:
+                return [UIFont ows_regularFontWithSize:25.f];
+            default:
+                break;
+        }
+    }
+
     return [UIFont ows_dynamicTypeBodyFont];
 }
 
@@ -627,6 +642,7 @@ NS_ASSUME_NONNULL_BEGIN
     self.textView.text = self.displayableText.displayText;
     UIColor *textColor = [self textColor];
     self.textView.textColor = textColor;
+    // Honor dynamic type in the message bodies.
     self.textView.font = [self textMessageFont];
 
     // Don't link outgoing messages that haven't been sent yet, as
@@ -848,6 +864,7 @@ NS_ASSUME_NONNULL_BEGIN
             const int maxTextWidth = (int)floor(maxMessageWidth - (leftMargin + rightMargin));
 
             self.textView.text = self.displayableText.displayText;
+            // Honor dynamic type in the message bodies.
             self.textView.font = [self textMessageFont];
             CGSize textSize = [self.textView sizeThatFits:CGSizeMake(maxTextWidth, CGFLOAT_MAX)];
             CGFloat tapForMoreHeight = (self.displayableText.isTextTruncated ? [self tapForMoreHeight] : 0.f);

Signal/src/ViewControllers/ConversationView/ConversationViewItem.m

@@ -323,8 +323,12 @@ NSString *NSStringForOWSMessageCellType(OWSMessageCellType cellType)
             displayText = @"";
         }
 
-        displayableText =
-            [[DisplayableText alloc] initWithFullText:fullText displayText:displayText isTextTruncated:isTextTruncated];
+        NSNumber *_Nullable jumbomojiCount = [DisplayableText jumbomojiCountTo:fullText];
+
+        displayableText = [[DisplayableText alloc] initWithFullText:fullText
+                                                        displayText:displayText
+                                                    isTextTruncated:isTextTruncated
+                                                     jumbomojiCount:jumbomojiCount];
 
         [[self displayableTextCache] setObject:displayableText forKey:interactionId];
     }

Signal/src/util/DisplayableText.swift

@@ -11,13 +11,83 @@ import Foundation
     let fullText: String
     let displayText: String
     let isTextTruncated: Bool
+    let jumbomojiCount: NSNumber?
+
+    static let kMaxJumbomojiCount: UInt = 5
 
     // MARK: Initializers
 
-    init(fullText: String, displayText: String, isTextTruncated: Bool) {
+    init(fullText: String, displayText: String, isTextTruncated: Bool, jumbomojiCount: NSNumber?) {
         self.fullText = fullText
         self.displayText = displayText
         self.isTextTruncated = isTextTruncated
+        self.jumbomojiCount = jumbomojiCount
+    }
+
+    // MARK: Emoji
+
+    private class func canDetectEmoji() -> Bool {
+        if #available(iOS 10.0, *) {
+            return true
+        } else {
+            return false
+        }
+    }
+
+    // If the string is...
+    //
+    // * Non-empty
+    // * Only contains emoji
+    // * Contains <= maxEmojiCount emoji
+    //
+    // ...return the number of emoji in the string.  Otherwise return nil.
+    //
+    // On iOS 9 and earler, always returns nil.
+    @objc public class func jumbomojiCount(to string: String) -> NSNumber? {
+        if string == "" {
+            return nil
+        }
+        if string.characters.count > Int(kMaxJumbomojiCount) {
+            return nil
+        }
+        if !canDetectEmoji() {
+            return nil
+        }
+        var didFail = false
+        var emojiCount: UInt = 0
+        let attributes = [NSFontAttributeName: UIFont.systemFont(ofSize:12)]
+        let attributedString = NSMutableAttributedString(string: string, attributes: attributes)
+        let range = NSRange(location: 0, length: string.characters.count)
+        attributedString.fixAttributes(in: range)
+        attributedString.enumerateAttribute(NSFontAttributeName,
+                                            in: range,
+                                            options: [],
+                                            using: {(_ value: Any?, range: NSRange, stop: UnsafeMutablePointer<ObjCBool>) -> Void in
+                                                guard emojiCount < kMaxJumbomojiCount else {
+                                                    didFail = true
+                                                    stop.pointee = true
+                                                    return
+                                                }
+                                                guard let rangeFont = value as? UIFont else {
+                                                    didFail = true
+                                                    stop.pointee = true
+                                                    return
+                                                }
+                                                guard rangeFont.fontName == ".AppleColorEmojiUI" else {
+                                                    didFail = true
+                                                    stop.pointee = true
+                                                    return
+                                                }
+                                                if rangeFont.fontName == ".AppleColorEmojiUI" {
+                                                    Logger.verbose("Detected Emoji at location: \(range.location), for length: \(range.length)")
+                                                    emojiCount += UInt(range.length)
+                                                }
+        })
+
+        guard !didFail else {
+            return nil
+        }
+        return NSNumber(value: emojiCount)
     }
 
     // MARK: Filter Methods