Avoid unnecessariy flashing avatars

Make avatar building sync

Tests on a iPhone5 with 1k threads, 3k contacts show no noticeable lag.

Profiling shows ~4% of usage goes to contact avatar building, but once
cached, even that goes towards zero.

// FREEBIE

Signal/src/Models/OWSAvatarBuilder.h

@@ -11,8 +11,8 @@ NS_ASSUME_NONNULL_BEGIN
 @interface OWSAvatarBuilder : NSObject
 
 + (UIImage *)buildImageForThread:(TSThread *)thread
-                 contactsManager:(OWSContactsManager *)contactsManager
-                        diameter:(NSUInteger)diameter;
+                        diameter:(NSUInteger)diameter
+                 contactsManager:(OWSContactsManager *)contactsManager NS_SWIFT_NAME(buildImage(thread:diameter:contactsManager:));
 
 - (nullable UIImage *)buildSavedImage;
 - (UIImage *)buildDefaultImage;

Signal/src/Models/OWSAvatarBuilder.m

@@ -13,8 +13,8 @@ NS_ASSUME_NONNULL_BEGIN
 @implementation OWSAvatarBuilder
 
 + (UIImage *)buildImageForThread:(TSThread *)thread
-                 contactsManager:(OWSContactsManager *)contactsManager
                         diameter:(NSUInteger)diameter
+                 contactsManager:(OWSContactsManager *)contactsManager
 {
     OWSAvatarBuilder *avatarBuilder;
     if ([thread isKindOfClass:[TSContactThread class]]) {

Signal/src/Models/OWSContactAvatarBuilder.m

@@ -95,7 +95,7 @@ NS_ASSUME_NONNULL_BEGIN
                                                                        textColor:[UIColor whiteColor]
                                                                             font:[UIFont ows_boldFontWithSize:fontSize]
                                                                         diameter:self.diameter] avatarImage];
-    [self.contactsManager.avatarCache setObject:image forKey:self.signalId];
+    [self.contactsManager.avatarCache setObject:image forKey:cacheKey];
     return image;
 }
 

Signal/src/Models/OWSGroupAvatarBuilder.m

@@ -1,5 +1,6 @@
-//  Created by Michael Kirk on 9/26/16.
-//  Copyright © 2016 Open Whisper Systems. All rights reserved.
+//
+//  Copyright (c) 2017 Open Whisper Systems. All rights reserved.
+//
 
 #import "OWSGroupAvatarBuilder.h"
 #import "TSGroupThread.h"
@@ -32,7 +33,12 @@ NS_ASSUME_NONNULL_BEGIN
 
 - (UIImage *)buildDefaultImage
 {
-    return [UIImage imageNamed:@"empty-group-avatar"];
+    static UIImage *defaultGroupImage;
+    static dispatch_once_t onceToken;
+    dispatch_once(&onceToken, ^{
+        defaultGroupImage = [UIImage imageNamed:@"empty-group-avatar"];
+    });
+    return defaultGroupImage;
 }
 
 @end

Signal/src/ViewControllers/CallViewController.swift

@@ -399,7 +399,7 @@ class CallViewController: OWSViewController, CallObserver, CallServiceObserver,
     }
 
     func updateAvatarImage() {
-        contactAvatarView.image = OWSAvatarBuilder.buildImage(for: thread, contactsManager: contactsManager, diameter:400)
+        contactAvatarView.image = OWSAvatarBuilder.buildImage(thread: thread, diameter: 400, contactsManager: contactsManager)
     }
 
     func createIncomingCallControls() {

Signal/src/ViewControllers/InboxTableViewCell.m

@@ -20,7 +20,7 @@ NS_ASSUME_NONNULL_BEGIN
 #define DATE_LABEL_SIZE 13
 #define SWIPE_ARCHIVE_OFFSET -50
 
-const NSUInteger kavatarViewDiameter = 52;
+const NSUInteger kAvatarViewDiameter = 52;
 
 @interface InboxTableViewCell ()
 
@@ -227,16 +227,8 @@ const NSUInteger kavatarViewDiameter = 52;
         self.unreadLabel.hidden = YES;
     }
 
-    NSString *threadIdCopy = thread.uniqueId;
-    dispatch_async(dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_DEFAULT, 0), ^{
-        UIImage *avatar =
-            [OWSAvatarBuilder buildImageForThread:thread contactsManager:contactsManager diameter:kavatarViewDiameter];
-        dispatch_async(dispatch_get_main_queue(), ^{
-            if ([_threadId isEqualToString:threadIdCopy]) {
-                self.avatarView.image = avatar;
-            }
-        });
-    });
+    self.avatarView.image =
+        [OWSAvatarBuilder buildImageForThread:thread diameter:kAvatarViewDiameter contactsManager:contactsManager];
 }
 
 - (void)updateCellForUnreadMessage {

Signal/src/ViewControllers/OWSConversationSettingsTableViewController.m

@@ -575,11 +575,11 @@ NS_ASSUME_NONNULL_BEGIN
     [threadInfoView autoPinHeightToSuperviewWithMargin:16.f];
 
     const NSUInteger kAvatarSize = 68;
-    UIImage *avatar =
-        [OWSAvatarBuilder buildImageForThread:self.thread contactsManager:self.contactsManager diameter:kAvatarSize];
-    OWSAssert(avatar);
+    UIImage *avatarImage =
+        [OWSAvatarBuilder buildImageForThread:self.thread diameter:kAvatarSize contactsManager:self.contactsManager];
+    OWSAssert(avatarImage);
 
-    AvatarImageView *avatarView = [[AvatarImageView alloc] initWithImage:avatar];
+    AvatarImageView *avatarView = [[AvatarImageView alloc] initWithImage:avatarImage];
     _avatarView = avatarView;
     [threadInfoView addSubview:avatarView];
     [avatarView autoVCenterInSuperview];

Signal/src/views/ContactTableViewCell.m

@@ -139,8 +139,8 @@ const NSUInteger kContactTableViewCellAvatarSize = 40;
     self.nameLabel.attributedText = attributedText;
 
     self.avatarView.image = [OWSAvatarBuilder buildImageForThread:thread
-                                                  contactsManager:contactsManager
-                                                         diameter:kContactTableViewCellAvatarSize];
+                                                         diameter:kContactTableViewCellAvatarSize
+                                                  contactsManager:contactsManager];
 
     // Force layout, since imageView isn't being initally rendered on App Store optimized build.
     [self layoutSubviews];