Add download progress support to ASNetworkImageNode (#1489)

Source/ASNetworkImageNode.h

@@ -133,6 +133,13 @@ NS_ASSUME_NONNULL_BEGIN
  */
 @property (readonly) CGFloat renderedImageQuality;
 
+/**
+ * Download progress of the current image.
+ * When downloading a network image, this value would be updated to track download progress (value between 0 and 1)
+ * This is 1 if image load from cache or network successfully.
+ */
+@property (readonly) CGFloat downloadProgress;
+
 @end
 
 

Source/ASNetworkImageNode.mm

@@ -39,6 +39,7 @@
 
   CGFloat _currentImageQuality;
   CGFloat _renderedImageQuality;
+  CGFloat _downloadProgress;
 
     // Immutable and set on init only. We don't need to lock in this case.
   __weak id<ASImageDownloaderProtocol> _downloader;
@@ -151,6 +152,7 @@ static std::atomic_bool _useMainThreadDelegateCallbacks(true);
   // If our image is being set externally, the image quality is 100%
   if (imageWasSetExternally) {
     [self _setCurrentImageQuality:1.0];
+    [self _setDownloadProgress:1.0];
   }
   
   [self _locked__setImage:image];
@@ -202,7 +204,9 @@ static std::atomic_bool _useMainThreadDelegateCallbacks(true);
     _networkImageNodeFlags.imageWasSetExternally = NO;
     
     [self _locked_cancelImageDownloadWithResumePossibility:NO];
-
+    
+    [self _setDownloadProgress:0.0];
+    
     _networkImageNodeFlags.imageLoaded = NO;
     
     _URL = URL;
@@ -273,6 +277,30 @@ static std::atomic_bool _useMainThreadDelegateCallbacks(true);
   });
 }
 
+- (void)setDownloadProgress:(CGFloat)downloadProgress
+{
+  ASLockScopeSelf();
+  _downloadProgress = downloadProgress;
+}
+
+- (CGFloat)downloadProgress
+{
+  return ASLockedSelf(_downloadProgress);
+}
+
+/**
+ * Always use these methods internally to update the current download progress
+ * We want to maintain the order that downloadProgress is set regardless of the calling thread,
+ * so we always have to dispatch to the main thread to ensure that we queue the operations in the correct order.
+ * (see comment in displayDidFinish)
+ */
+- (void)_setDownloadProgress:(CGFloat)downloadProgress
+{
+  dispatch_async(dispatch_get_main_queue(), ^{
+    self.downloadProgress = downloadProgress;
+  });
+}
+
 - (void)setRenderedImageQuality:(CGFloat)renderedImageQuality
 {
   ASLockScopeSelf();
@@ -363,6 +391,7 @@ static std::atomic_bool _useMainThreadDelegateCallbacks(true);
       UIImage *result = [[_cache synchronouslyFetchedCachedImageWithURL:url] asdk_image];
       if (result) {
         [self _setCurrentImageQuality:1.0];
+        [self _setDownloadProgress:1.0];
         [self _locked__setImage:result];
         _networkImageNodeFlags.imageLoaded = YES;
         
@@ -438,6 +467,17 @@ static std::atomic_bool _useMainThreadDelegateCallbacks(true);
 
 #pragma mark - Progress
 
+- (void)_updateDownloadedProgress:(CGFloat)progress
+              downloadIdentifier:(nullable id)downloadIdentifier
+{
+  ASLockScopeSelf();
+  // Getting a result back for a different download identifier, download must not have been successfully canceled
+  if (ASObjectIsEqual(_downloadIdentifier, downloadIdentifier) == NO && downloadIdentifier != nil) {
+    return;
+  }
+  [self _setDownloadProgress:progress];
+}
+
 - (void)handleProgressImage:(UIImage *)progressImage progress:(CGFloat)progress downloadIdentifier:(nullable id)downloadIdentifier
 {
   ASLockScopeSelf();
@@ -536,6 +576,7 @@ static std::atomic_bool _useMainThreadDelegateCallbacks(true);
   
   [self _locked_setAnimatedImage:nil];
   [self _setCurrentImageQuality:0.0];
+  [self _setDownloadProgress:0.0];
   [self _locked__setImage:_defaultImage];
 
   _networkImageNodeFlags.imageLoaded = NO;
@@ -593,7 +634,13 @@ static std::atomic_bool _useMainThreadDelegateCallbacks(true);
     }
 
     dispatch_queue_t callbackQueue = [self callbackQueue];
-    ASImageDownloaderProgress downloadProgress = NULL;
+    __weak __typeof__(self) weakSelf = self;
+    ASImageDownloaderProgress downloadProgress = ^(CGFloat progress){
+      __typeof__(self) strongSelf = weakSelf;
+      if (strongSelf) {
+        [strongSelf _updateDownloadedProgress:progress downloadIdentifier:downloadIdentifier];
+      }
+    };
     ASImageDownloaderCompletion completion = ^(id <ASImageContainerProtocol> _Nullable imageContainer, NSError * _Nullable error, id  _Nullable downloadIdentifier, id _Nullable userInfo) {
       if (finished != NULL) {
         finished(imageContainer, error, downloadIdentifier, userInfo);
@@ -727,6 +774,7 @@ static std::atomic_bool _useMainThreadDelegateCallbacks(true);
         self->_networkImageNodeFlags.imageLoaded = YES;
 
         [self _setCurrentImageQuality:1.0];
+        [self _setDownloadProgress:1.0];
 
         if (self->_networkImageNodeFlags.delegateDidLoadImageWithInfo) {
           ASUnlockScope(self);
@@ -766,6 +814,7 @@ static std::atomic_bool _useMainThreadDelegateCallbacks(true);
           UIImage *newImage;
           if (imageContainer != nil) {
             [strongSelf _setCurrentImageQuality:1.0];
+            [strongSelf _setDownloadProgress:1.0];
             NSData *animatedImageData = [imageContainer asdk_animatedImageData];
             if (animatedImageData && strongSelf->_networkImageNodeFlags.downloaderImplementsAnimatedImage) {
               id animatedImage = [strongSelf->_downloader animatedImageWithData:animatedImageData];