Reduced work done on main thread by RCTImageLoader

Summary: public

Removed redundant calls to [RCTNetwork canHandleRequest] in release mode when loading images, and improved perf for handler lookups when running in debug mode.

Reviewed By: tadeuzagallo

Differential Revision: D2663307

fb-gh-sync-id: 13285154c1c3773b32dba7894d86d14992e2fd7d

Libraries/Image/RCTImageLoader.m

@@ -99,8 +99,11 @@ RCT_EXPORT_MODULE()
     float previousPriority = 0;
     id<RCTImageURLLoader> previousLoader = nil;
     for (id<RCTImageURLLoader> loader in _loaders) {
-      if ([loader canLoadImageURL:URL]) {
       float priority = [loader respondsToSelector:@selector(loaderPriority)] ? [loader loaderPriority] : 0;
+      if (previousLoader && priority < previousPriority) {
+        return previousLoader;
+      }
+      if ([loader canLoadImageURL:URL]) {
         if (previousLoader) {
           if (priority == previousPriority) {
             RCTLogError(@"The RCTImageURLLoaders %@ and %@ both reported that"
@@ -114,6 +117,7 @@ RCT_EXPORT_MODULE()
         }
       }
     }
+    return previousLoader;
   }
 
   // Normal code path
@@ -132,8 +136,11 @@ RCT_EXPORT_MODULE()
     float previousPriority = 0;
     id<RCTImageDataDecoder> previousDecoder = nil;
     for (id<RCTImageDataDecoder> decoder in _decoders) {
-      if ([decoder canDecodeImageData:data]) {
       float priority = [decoder respondsToSelector:@selector(decoderPriority)] ? [decoder decoderPriority] : 0;
+      if (previousDecoder && priority < previousPriority) {
+        return previousDecoder;
+      }
+      if ([decoder canDecodeImageData:data]) {
         if (previousDecoder) {
           if (priority == previousPriority) {
             RCTLogError(@"The RCTImageDataDecoders %@ and %@ both reported that"
@@ -148,6 +155,7 @@ RCT_EXPORT_MODULE()
         }
       }
     }
+    return previousDecoder;
   }
 
   // Normal code path
@@ -211,16 +219,20 @@ RCT_EXPORT_MODULE()
   }
 
   // Check if networking module is available
-  if (![_bridge respondsToSelector:@selector(networking)]) {
+  if (RCT_DEBUG && ![_bridge respondsToSelector:@selector(networking)]) {
     RCTLogError(@"No suitable image URL loader found for %@. You may need to "
                 " import the RCTNetworking library in order to load images.",
                 imageTag);
     return ^{};
   }
 
-  // Use networking module to load image
-  if ([_bridge.networking canHandleRequest:request]) {
+  // Check if networking module can load image
+  if (RCT_DEBUG && ![_bridge.networking canHandleRequest:request]) {
+    RCTLogError(@"No suitable image URL loader found for %@", imageTag);
+    return ^{};
+  }
 
+  // Use networking module to load image
   __weak RCTImageLoader *weakSelf = self;
   __block RCTImageLoaderCancellationBlock decodeCancel = nil;
   RCTURLRequestCompletionBlock processResponse =
@@ -304,16 +316,17 @@ RCT_EXPORT_MODULE()
   };
 }
 
-  RCTLogError(@"No suitable image URL loader found for %@", imageTag);
-  return ^{};
-}
-
 - (RCTImageLoaderCancellationBlock)decodeImageData:(NSData *)data
                                               size:(CGSize)size
                                              scale:(CGFloat)scale
                                         resizeMode:(UIViewContentMode)resizeMode
                                    completionBlock:(RCTImageLoaderCompletionBlock)completionHandler
 {
+  if (data.length == 0) {
+    completionHandler(RCTErrorWithMessage(@"No image data"), nil);
+    return ^{};
+  }
+
   id<RCTImageDataDecoder> imageDecoder = [self imageDataDecoderForData:data];
   if (imageDecoder) {
 

Libraries/Image/RCTImageView.m

@@ -183,13 +183,6 @@ RCT_NOT_IMPLEMENTED(- (instancetype)init)
                                                                resizeMode:self.contentMode
                                                             progressBlock:progressHandler
                                                           completionBlock:^(NSError *error, UIImage *image) {
-      dispatch_async(dispatch_get_main_queue(), ^{
-        if (image.reactKeyframeAnimation) {
-          [self.layer addAnimation:image.reactKeyframeAnimation forKey:@"contents"];
-        } else {
-          [self.layer removeAnimationForKey:@"contents"];
-          self.image = image;
-        }
       if (error) {
         if (_onError) {
           _onError(@{ @"error": error.localizedDescription });
@@ -202,6 +195,14 @@ RCT_NOT_IMPLEMENTED(- (instancetype)init)
       if (_onLoadEnd) {
          _onLoadEnd(nil);
       }
+
+      dispatch_async(dispatch_get_main_queue(), ^{
+        if (image.reactKeyframeAnimation) {
+          [self.layer addAnimation:image.reactKeyframeAnimation forKey:@"contents"];
+        } else {
+          [self.layer removeAnimationForKey:@"contents"];
+          self.image = image;
+        }
       });
     }];
   } else {

Libraries/Network/RCTNetworking.m

@@ -165,8 +165,11 @@ RCT_EXPORT_MODULE()
     float previousPriority = 0;
     id<RCTURLRequestHandler> previousHandler = nil;
     for (id<RCTURLRequestHandler> handler in _handlers) {
-      if ([handler canHandleRequest:request]) {
       float priority = [handler respondsToSelector:@selector(handlerPriority)] ? [handler handlerPriority] : 0;
+      if (previousHandler && priority < previousPriority) {
+        return previousHandler;
+      }
+      if ([handler canHandleRequest:request]) {
         if (previousHandler) {
           if (priority == previousPriority) {
             RCTLogError(@"The RCTURLRequestHandlers %@ and %@ both reported that"
@@ -180,6 +183,7 @@ RCT_EXPORT_MODULE()
         }
       }
     }
+    return previousHandler;
   }
 
   // Normal code path

React/Base/RCTAssert.h

@@ -79,6 +79,12 @@ typedef void (^RCTFatalHandler)(NSError *error);
 #define RCTAssertMainThread() RCTAssert([NSThread isMainThread], \
   @"This function must be called on the main thread")
 
+/**
+ * Convenience macro for asserting that we're running off the main thread.
+ */
+#define RCTAssertNotMainThread() RCTAssert(![NSThread isMainThread], \
+@"This function must not be called on the main thread")
+
 /**
  * These methods get and set the current assert function called by the RCTAssert
  * macros. You can use these to replace the standard behavior with custom assert