Improve ASNetworkImageNode delegate callout behavior

CHANGELOG.md

@@ -19,6 +19,7 @@
   - Modified `ASImageDownloaderCompletion` to add an optional `id userInfo` field. Your custom downloader can pass `nil`.
   - Modified the last argument to `-[ASNetworkImageNodeDelegate imageNode:didLoadImage:info:]` method from a struct to an object of new class `ASNetworkImageLoadInfo` which includes other metadata about the load operation.
 - Removed +load static initializer from ASDisplayNode. [Adlai Holler](https://github.com/Adlai-Holler)
+- Optimized ASNetworkImageNode loading and resolved edge cases where the image provided to the delegate was not the image that was loaded. [Adlai Holler](https://github.com/Adlai-Holler) [#778](https://github.com/TextureGroup/Texture/pull/778/)
 
 ## 2.6
 - [Xcode 9] Updated to require Xcode 9 (to fix warnings) [Garrett Moon](https://github.com/garrettmoon)

Source/ASNetworkImageNode.mm

@@ -703,47 +703,49 @@ - (void)_lazilyLoadImageIfNecessary
             return;
           }
 
+          UIImage *newImage;
           if (imageContainer != nil) {
             [strongSelf _locked_setCurrentImageQuality:1.0];
             NSData *animatedImageData = [imageContainer asdk_animatedImageData];
             if (animatedImageData && strongSelf->_downloaderFlags.downloaderImplementsAnimatedImage) {
               id animatedImage = [strongSelf->_downloader animatedImageWithData:animatedImageData];
               [strongSelf _locked_setAnimatedImage:animatedImage];
             } else {
-              [strongSelf _locked__setImage:[imageContainer asdk_image]];
+              newImage = [imageContainer asdk_image];
+              [strongSelf _locked__setImage:newImage];
             }
             strongSelf->_imageLoaded = YES;
           }
 
           strongSelf->_downloadIdentifier = nil;
           strongSelf->_cacheUUID = nil;
 
-          // TODO: Why dispatch to main here?
-          // The docs say the image node delegate methods
-          // are called from background.
-          ASPerformBlockOnMainThread(^{
-            __typeof__(self) strongSelf = weakSelf;
-            if (strongSelf == nil) {
-              return;
-            }
-
-            // Grab the lock for the rest of the block
-            ASDN::MutexLocker l(strongSelf->__instanceLock__);
-
-            if (imageContainer != nil) {
-              if (strongSelf->_delegateFlags.delegateDidLoadImageWithInfo) {
-                ASDN::MutexUnlocker u(strongSelf->__instanceLock__);
+          void (^calloutBlock)(ASNetworkImageNode *inst);
+
+          if (newImage) {
+            if (_delegateFlags.delegateDidLoadImageWithInfo) {
+              calloutBlock = ^(ASNetworkImageNode *strongSelf) {
                 auto info = [[ASNetworkImageLoadInfo alloc] initWithURL:URL sourceType:imageSource downloadIdentifier:downloadIdentifier userInfo:userInfo];
-                [delegate imageNode:strongSelf didLoadImage:strongSelf.image info:info];
-              } else if (strongSelf->_delegateFlags.delegateDidLoadImage) {
-                ASDN::MutexUnlocker u(strongSelf->__instanceLock__);
-                [delegate imageNode:strongSelf didLoadImage:strongSelf.image];
-              }
-            } else if (error && strongSelf->_delegateFlags.delegateDidFailWithError) {
-              ASDN::MutexUnlocker u(strongSelf->__instanceLock__);
-              [delegate imageNode:strongSelf didFailWithError:error];
+                [delegate imageNode:strongSelf didLoadImage:newImage info:info];
+              };
+            } else if (_delegateFlags.delegateDidLoadImage) {
+              calloutBlock = ^(ASNetworkImageNode *strongSelf) {
+                [delegate imageNode:strongSelf didLoadImage:newImage];
+              };
             }
-          });
+          } else if (error && _delegateFlags.delegateDidFailWithError) {
+            calloutBlock = ^(ASNetworkImageNode *strongSelf) {
+              [delegate imageNode:strongSelf didFailWithError:error];
+            };
+          }
+
+          if (calloutBlock) {
+            ASPerformBlockOnMainThread(^{
+              if (auto strongSelf = weakSelf) {
+                calloutBlock(strongSelf);
+              }
+            });
+          }
         });
       };