Restore full-screen thumbnails.

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

@@ -837,9 +837,8 @@ NS_ASSUME_NONNULL_BEGIN
     stillImageView.backgroundColor = [UIColor whiteColor];
     [self addAttachmentUploadViewIfNecessary];
 
-    __weak UIImageView *weakImageView = stillImageView;
-
     __weak OWSMessageBubbleView *weakSelf = self;
+    __weak UIImageView *weakImageView = stillImageView;
     self.loadCellContentBlock = ^{
         OWSMessageBubbleView *strongSelf = weakSelf;
         if (!strongSelf) {
@@ -980,6 +979,7 @@ NS_ASSUME_NONNULL_BEGIN
     }];
 
     __weak OWSMessageBubbleView *weakSelf = self;
+    __weak UIImageView *weakImageView = stillImageView;
     self.loadCellContentBlock = ^{
         OWSMessageBubbleView *strongSelf = weakSelf;
         if (!strongSelf) {
@@ -990,6 +990,22 @@ NS_ASSUME_NONNULL_BEGIN
             return;
         }
         stillImageView.image = [strongSelf
+            tryToLoadCellMedia:^{
+                OWSCAssert([strongSelf.attachmentStream isImage]);
+                return [strongSelf.attachmentStream
+                    thumbnailImageMediumWithSuccess:^(UIImage *image) {
+                        weakImageView.image = image;
+                    }
+                    failure:^{
+                        DDLogError(@"Could not load thumbnail.");
+                    }];
+            }
+                     mediaView:stillImageView
+                      cacheKey:strongSelf.attachmentStream.uniqueId
+               shouldSkipCache:shouldSkipCache
+                  canLoadAsync:YES];
+
+
             tryToLoadCellMedia:^{
                 OWSCAssert([strongSelf.attachmentStream isVideo]);
 

SignalServiceKit/src/Messages/Attachments/TSAttachmentStream.h

@@ -89,6 +89,7 @@ typedef void (^OWSThumbnailFailure)(void);
                                          failure:(OWSThumbnailFailure)failure;
 - (nullable UIImage *)thumbnailImageSmallWithSuccess:(OWSThumbnailSuccess)success failure:(OWSThumbnailFailure)failure;
 - (nullable UIImage *)thumbnailImageMediumWithSuccess:(OWSThumbnailSuccess)success failure:(OWSThumbnailFailure)failure;
+- (nullable UIImage *)thumbnailImageLargeWithSuccess:(OWSThumbnailSuccess)success failure:(OWSThumbnailFailure)failure;
 - (nullable UIImage *)thumbnailImageSmallSync;
 
 // This method should only be invoked by OWSThumbnailService.

SignalServiceKit/src/Messages/Attachments/TSAttachmentStream.m

@@ -15,6 +15,13 @@ NS_ASSUME_NONNULL_BEGIN
 
 const NSUInteger kThumbnailDimensionPointsSmall = 200;
 const NSUInteger kThumbnailDimensionPointsMedium = 450;
+// This size is large enough to render full screen.
+const NSUInteger ThumbnailDimensionPointsLarge()
+{
+    CGSize screenSizePoints = UIScreen.mainScreen.bounds.size;
+    const CGFloat kMinZoomFactor = 2.f;
+    return MAX(screenSizePoints.width * kMinZoomFactor, screenSizePoints.height * kMinZoomFactor);
+}
 
 typedef void (^OWSLoadedThumbnailSuccess)(OWSLoadedThumbnail *loadedThumbnail);
 
@@ -625,8 +632,10 @@ typedef void (^OWSLoadedThumbnailSuccess)(OWSLoadedThumbnail *loadedThumbnail);
     NSUInteger thumbnailDimensionPoints;
     if (maxDimensionHint <= kThumbnailDimensionPointsSmall) {
         thumbnailDimensionPoints = kThumbnailDimensionPointsSmall;
-    } else {
+    } else if (maxDimensionHint <= kThumbnailDimensionPointsMedium) {
         thumbnailDimensionPoints = kThumbnailDimensionPointsMedium;
+    } else {
+        thumbnailDimensionPoints = ThumbnailDimensionPointsLarge();
     }
 
     return [self thumbnailImageWithThumbnailDimensionPoints:thumbnailDimensionPoints success:success failure:failure];
@@ -646,6 +655,13 @@ typedef void (^OWSLoadedThumbnailSuccess)(OWSLoadedThumbnail *loadedThumbnail);
                                                     failure:failure];
 }
 
+- (nullable UIImage *)thumbnailImageLargeWithSuccess:(OWSThumbnailSuccess)success failure:(OWSThumbnailFailure)failure
+{
+    return [self thumbnailImageWithThumbnailDimensionPoints:ThumbnailDimensionPointsLarge()
+                                                    success:success
+                                                    failure:failure];
+}
+
 - (nullable UIImage *)thumbnailImageWithThumbnailDimensionPoints:(NSUInteger)thumbnailDimensionPoints
                                                          success:(OWSThumbnailSuccess)success
                                                          failure:(OWSThumbnailFailure)failure