Add cache and scheduling parameters to image loaders

facebook · Jun 14, 2016 · e837958 · e837958
1 parent 654778c
commit e837958
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Showing 3 changed files with 62 additions and 24 deletions.
diff --git a/Libraries/Image/RCTImageLoader.h b/Libraries/Image/RCTImageLoader.h
@@ -185,6 +185,18 @@ __deprecated_msg("Use getImageSizeWithURLRequest:block: instead");
  */
 - (float)loaderPriority;
 
+/**
+ * If the loader must be called on the serial url cache queue. If this is NO,
+ * the loader will be called from the main queue. Defaults to YES.
+ */
+- (BOOL)requiresScheduling;
+
+/**
+ * If images loaded by the loader should be cached in the decoded image cache.
+ * Defaults to YES.
+ */
+- (BOOL)shouldCacheLoadedImages;
+
 @end
 
 /**

diff --git a/Libraries/Image/RCTImageLoader.m b/Libraries/Image/RCTImageLoader.m
@@ -290,27 +290,44 @@ - (RCTImageLoaderCancellationBlock)loadImageOrDataWithURLRequest:(NSURLRequest *
                                                            scale:(CGFloat)scale
                                                       resizeMode:(RCTResizeMode)resizeMode
                                                    progressBlock:(RCTImageLoaderProgressBlock)progressHandler
-                                                 completionBlock:(void (^)(NSError *error, id imageOrData))completionBlock
+                                                 completionBlock:(void (^)(NSError *error, id imageOrData, BOOL cacheResult))completionBlock
 {
   __block volatile uint32_t cancelled = 0;
   __block void(^cancelLoad)(void) = nil;
   __weak RCTImageLoader *weakSelf = self;
+  // Find suitable image URL loader
+  __block id<RCTImageURLLoader> loadHandler = [self imageURLLoaderForURL:imageURLRequest.URL];
+  __block BOOL cacheResult = [loadHandler respondsToSelector:@selector(shouldCacheLoadedImages)] ?
+      [loadHandler shouldCacheLoadedImages] : YES;
+  BOOL requiresScheduling = [loadHandler respondsToSelector:@selector(requiresScheduling)] ?
+      [loadHandler requiresScheduling] : YES;
 
   void (^completionHandler)(NSError *error, id imageOrData) = ^(NSError *error, id imageOrData) {
-    if (RCTIsMainQueue()) {
+    if (RCTIsMainQueue() && requiresScheduling) {
 
       // Most loaders do not return on the main thread, so caller is probably not
       // expecting it, and may do expensive post-processing in the callback
       dispatch_async(dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_DEFAULT, 0), ^{
         if (!cancelled) {
-          completionBlock(error, imageOrData);
+          completionBlock(error, imageOrData, cacheResult);
         }
       });
     } else if (!cancelled) {
-      completionBlock(error, imageOrData);
+      completionBlock(error, imageOrData, cacheResult);
     }
   };
 
+  // If the loader doesn't require scheduling we call it directly on
+  // the main queue.
+  if (loadHandler && !requiresScheduling) {
+    return [loadHandler loadImageForURL:imageURLRequest.URL
+                                   size:size
+                                  scale:scale
+                             resizeMode:resizeMode
+                        progressHandler:progressHandler
+                      completionHandler:completionHandler] ?: ^{};
+  }
+
   // All access to URL cache must be serialized
   if (!_URLCacheQueue) {
     [self setUp];
@@ -328,9 +345,18 @@ - (RCTImageLoaderCancellationBlock)loadImageOrDataWithURLRequest:(NSURLRequest *
       return;
     }
 
-    // Find suitable image URL loader
     NSURLRequest *request = imageURLRequest; // Use a local variable so we can reassign it in this block
 
+    if (loadHandler && requiresScheduling) {
+      cancelLoad = [loadHandler loadImageForURL:imageURLRequest.URL
+                                     size:size
+                                    scale:scale
+                               resizeMode:resizeMode
+                          progressHandler:progressHandler
+                        completionHandler:completionHandler] ?: ^{};
+      return;
+    }
+
     // Check if networking module is available
     if (RCT_DEBUG && ![_bridge respondsToSelector:@selector(networking)]) {
       RCTLogError(@"No suitable image URL loader found for %@. You may need to "
@@ -470,18 +496,6 @@ - (RCTImageLoaderCancellationBlock)loadImageWithURLRequest:(NSURLRequest *)image
   __block void(^cancelLoad)(void) = nil;
   __weak RCTImageLoader *weakSelf = self;
 
-  // Load handlers are executed before the generic caching logic so they are responsible
-  // for caching the images if necessary.
-  id<RCTImageURLLoader> loadHandler = [self imageURLLoaderForURL:imageURLRequest.URL];
-  if (loadHandler) {
-    return [loadHandler loadImageForURL:imageURLRequest.URL
-                                   size:size
-                                  scale:scale
-                             resizeMode:resizeMode
-                        progressHandler:progressHandler
-                      completionHandler:completionBlock] ?: ^{};
-  }
-
   // Check decoded image cache
   NSString *cacheKey = RCTCacheKeyForImage(imageURLRequest.URL.absoluteString, size, scale, resizeMode);
   {
@@ -506,17 +520,18 @@ - (RCTImageLoaderCancellationBlock)loadImageWithURLRequest:(NSURLRequest *)image
     completionBlock(error, image);
   };
 
-  void (^completionHandler)(NSError *, id) = ^(NSError *error, id imageOrData) {
+  void (^completionHandler)(NSError *, id, BOOL) = ^(NSError *error, id imageOrData, BOOL cacheResult) {
     if (!cancelled) {
+      RCTImageLoaderCompletionBlock resultHandler = cacheResult ? cacheResultHandler : completionBlock;
       if (!imageOrData || [imageOrData isKindOfClass:[UIImage class]]) {
-        cacheResultHandler(error, imageOrData);
+        resultHandler(error, imageOrData);
       } else {
         cancelLoad = [weakSelf decodeImageData:imageOrData
                                           size:size
                                          scale:scale
                                        clipped:clipped
                                     resizeMode:resizeMode
-                               completionBlock:cacheResultHandler];
+                               completionBlock:resultHandler];
       }
     }
   };
@@ -654,7 +669,7 @@ - (RCTImageLoaderCancellationBlock)getImageSizeForURLRequest:(NSURLRequest *)ima
                                 scale:1
                            resizeMode:RCTResizeModeStretch
                         progressBlock:nil
-                      completionBlock:^(NSError *error, id imageOrData) {
+                      completionBlock:^(NSError *error, id imageOrData, __unused BOOL cacheResult) {
                         CGSize size;
                         if ([imageOrData isKindOfClass:[NSData class]]) {
                           NSDictionary *meta = RCTGetImageMetadata(imageOrData);

diff --git a/Libraries/Image/RCTLocalAssetImageLoader.m b/Libraries/Image/RCTLocalAssetImageLoader.m
@@ -22,6 +22,20 @@ - (BOOL)canLoadImageURL:(NSURL *)requestURL
   return RCTIsLocalAssetURL(requestURL);
 }
 
+- (BOOL)requiresScheduling
+{
+  // Don't schedule this loader on the URL queue so we can load the
+  // local assets synchronously to avoid flickers.
+  return NO;
+}
+
+- (BOOL)shouldCacheLoadedImages
+{
+  // UIImage imageNamed handles the caching automatically so we don't want
+  // to add it to the image cache.
+  return NO;
+}
+
  - (RCTImageLoaderCancellationBlock)loadImageForURL:(NSURL *)imageURL
                                                size:(CGSize)size
                                               scale:(CGFloat)scale
@@ -37,9 +51,6 @@ - (RCTImageLoaderCancellationBlock)loadImageForURL:(NSURL *)imageURL
     }
 
     NSString *imageName = RCTBundlePathForURL(imageURL);
-
-    // imageNamed handles the caching automatically so there is no
-    // need to do any manual caching.
     UIImage *image = [UIImage imageNamed:imageName];
     if (image) {
       if (progressHandler) {