[ASImageNode] An ASImageNode debug feature showing pixel scaling amount

AsyncDisplayKit.xcodeproj/project.pbxproj

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+		764D83D21C8EA515009B4FB8 /* AsyncDisplayKit+Debug.h */ = {isa = PBXFileReference; fileEncoding = 4; lastKnownFileType = sourcecode.c.h; path = "AsyncDisplayKit+Debug.h"; sourceTree = "<group>"; };
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@@ -1010,6 +1016,8 @@
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 				ACC945AA1BA9E7C1005E1FB8 /* ASViewController.m */,
 				6BDC61F51978FEA400E50D21 /* AsyncDisplayKit.h */,
+				764D83D21C8EA515009B4FB8 /* AsyncDisplayKit+Debug.h */,
+				764D83D31C8EA515009B4FB8 /* AsyncDisplayKit+Debug.m */,
 				DB55C2651C641AE4004EDCF5 /* ASContextTransitioning.h */,
 				058D09E1195D050800B7D73C /* Details */,
 				058D0A01195D050800B7D73C /* Private */,
@@ -1404,6 +1412,7 @@
 				AC7A2C171BDE11DF0093FE1A /* ASTableViewInternal.h in Headers */,
 				058D0A4D195D05CB00B7D73C /* ASDisplayNodeExtras.h in Headers */,
 				68B0277A1C1A79CC0041016B /* ASDisplayNode+Beta.h in Headers */,
+				767E7F8D1C9019130066C000 /* AsyncDisplayKit+Debug.h in Headers */,
 				257754B11BEE44CD00737CA5 /* ASTextKitShadower.h in Headers */,
 				058D0A7B195D05F900B7D73C /* ASDisplayNodeInternal.h in Headers */,
 				0587F9BD1A7309ED00AFF0BA /* ASEditableTextNode.h in Headers */,
@@ -1592,6 +1601,7 @@
 				9C49C3701B853961000B0DD5 /* ASStackLayoutable.h in Headers */,
 				DE040EF91C2B40AC004692FF /* ASCollectionViewFlowLayoutInspector.h in Headers */,
 				34EFC7701B701CFA00AD841F /* ASStackLayoutDefines.h in Headers */,
+				764D83D51C8EA515009B4FB8 /* AsyncDisplayKit+Debug.h in Headers */,
 				E5711A2C1C840C81009619D4 /* ASIndexedNodeContext.h in Headers */,
 				254C6B7B1BF94DF4003EC431 /* ASTextKitRenderer+Positioning.h in Headers */,
 				CC7FD9E21BB603FF005CCB2B /* ASPhotosFrameworkImageRequest.h in Headers */,
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 				058D09BA195D04C000B7D73C /* Resources */,
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 			);
@@ -1794,6 +1805,21 @@
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 			showEnvVarsInLog = 0;
 		};
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+			shellPath = /bin/sh;
+			shellScript = "\"${SRCROOT}/Pods/Target Support Files/Pods-AsyncDisplayKitTests/Pods-AsyncDisplayKitTests-frameworks.sh\"\n";
+			showEnvVarsInLog = 0;
+		};
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@@ -1842,6 +1868,7 @@
 				ACF6ED211B17843500DA7C62 /* ASDimension.mm in Sources */,
 				058D0A28195D050800B7D73C /* ASDisplayNode+AsyncDisplay.mm in Sources */,
 				058D0A29195D050800B7D73C /* ASDisplayNode+DebugTiming.mm in Sources */,
+				764D83D61C8EA515009B4FB8 /* AsyncDisplayKit+Debug.m in Sources */,
 				058D0A2A195D050800B7D73C /* ASDisplayNode+UIViewBridge.mm in Sources */,
 				25E327581C16819500A2170C /* ASPagerNode.m in Sources */,
 				058D0A14195D050800B7D73C /* ASDisplayNode.mm in Sources */,
@@ -1986,6 +2013,7 @@
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 				B35062181B010EFD0018CF92 /* ASDataController.mm in Sources */,
 				B350621A1B010EFD0018CF92 /* ASDealloc2MainObject.m in Sources */,
+				767E7F8E1C90191D0066C000 /* AsyncDisplayKit+Debug.m in Sources */,
 				34EFC75C1B701BD200AD841F /* ASDimension.mm in Sources */,
 				B350624E1B010EFD0018CF92 /* ASDisplayNode+AsyncDisplay.mm in Sources */,
 				25E327591C16819500A2170C /* ASPagerNode.m in Sources */,

AsyncDisplayKit/ASImageNode.mm

@@ -15,8 +15,10 @@
 #import <AsyncDisplayKit/ASDisplayNodeInternal.h>
 #import <AsyncDisplayKit/ASDisplayNodeExtras.h>
 #import <AsyncDisplayKit/ASDisplayNode+Beta.h>
+#import <AsyncDisplayKit/ASTextNode.h>
 
 #import "ASImageNode+CGExtras.h"
+#import "AsyncDisplayKit+Debug.h"
 
 #import "ASInternalHelpers.h"
 #import "ASEqualityHelpers.h"
@@ -55,7 +57,6 @@ - (NSString *)description
 
 @end
 
-
 @implementation ASImageNode
 {
 @private
@@ -69,6 +70,8 @@ @implementation ASImageNode
   BOOL _forceUpscaling; //Defaults to NO.
   CGRect _cropRect; // Defaults to CGRectMake(0.5, 0.5, 0, 0)
   CGRect _cropDisplayBounds;
+
+  ASTextNode *_debugLabelNode;
 }
 
 @synthesize image = _image;
@@ -89,6 +92,12 @@ - (id)init
   _cropRect = CGRectMake(0.5, 0.5, 0, 0);
   _cropDisplayBounds = CGRectNull;
   _placeholderColor = ASDisplayNodeDefaultPlaceholderColor();
+
+  if ([ASImageNode shouldShowImageScalingOverlay]) {
+    _debugLabelNode = [[ASTextNode alloc] init];
+    _debugLabelNode.layerBacked = YES;
+    [self addSubnode:_debugLabelNode];
+  }
 
   return self;
 }
@@ -152,6 +161,12 @@ - (NSObject *)drawParametersForAsyncLayer:(_ASDisplayLayer *)layer
                                                 contentMode:self.contentMode];
 }
 
+- (NSDictionary *)debugLabelAttributes
+{
+  return @{ NSFontAttributeName: [UIFont systemFontOfSize:15.0],
+            NSForegroundColorAttributeName: [UIColor redColor] };
+}
+
 - (UIImage *)displayWithParameters:(_ASImageNodeDrawParameters *)parameters isCancelled:(asdisplaynode_iscancelled_block_t)isCancelled
 {
   UIImage *image;
@@ -202,6 +217,19 @@ - (UIImage *)displayWithParameters:(_ASImageNodeDrawParameters *)parameters isCa
   CGSize imageSizeInPixels = CGSizeMake(imageSize.width * image.scale, imageSize.height * image.scale);
   CGSize boundsSizeInPixels = CGSizeMake(floorf(bounds.size.width * contentsScale), floorf(bounds.size.height * contentsScale));
 
+  if (_debugLabelNode) {
+    CGFloat pixelCountRatio            = (imageSizeInPixels.width * imageSizeInPixels.height) / (boundsSizeInPixels.width * boundsSizeInPixels.height);
+    if (pixelCountRatio != 1.0) {
+      NSString *scaleString            = [NSString stringWithFormat:@"%.2fx", pixelCountRatio];
+      _debugLabelNode.attributedString = [[NSAttributedString alloc] initWithString:scaleString attributes:[self debugLabelAttributes]];
+      _debugLabelNode.hidden           = NO;
+      [self setNeedsLayout];
+    } else {
+      _debugLabelNode.hidden           = YES;
+      _debugLabelNode.attributedString = nil;
+    }
+  }
+
   BOOL contentModeSupported =    contentMode == UIViewContentModeScaleAspectFill
   || contentMode == UIViewContentModeScaleAspectFit
   || contentMode == UIViewContentModeCenter;
@@ -410,9 +438,21 @@ - (void)setImageModificationBlock:(asimagenode_modification_block_t)imageModific
   _imageModificationBlock = imageModificationBlock;
 }
 
+#pragma mark - Debug
+- (void)layout
+{
+  [super layout];
+
+  if (_debugLabelNode) {
+    CGSize boundsSize        = self.bounds.size;
+    CGSize debugLabelSize    = [_debugLabelNode measure:boundsSize];
+    CGPoint debugLabelOrigin = CGPointMake(boundsSize.width - debugLabelSize.width,
+                                           boundsSize.height - debugLabelSize.height);
+    _debugLabelNode.frame    = (CGRect) {debugLabelOrigin, debugLabelSize};
+  }
+}
 @end
 
-
 #pragma mark - Extras
 extern asimagenode_modification_block_t ASImageNodeRoundBorderModificationBlock(CGFloat borderWidth, UIColor *borderColor)
 {
@@ -460,4 +500,3 @@ extern asimagenode_modification_block_t ASImageNodeTintColorModificationBlock(UI
     return modifiedImage;
   };
 }
-

AsyncDisplayKit/AsyncDisplayKit+Debug.h

@@ -0,0 +1,23 @@
+//
+//  AsyncDisplayKit+Debug.h
+//  AsyncDisplayKit
+//
+//  Created by Hannah Troisi on 3/7/16.
+//  Copyright © 2016 Facebook. All rights reserved.
+//
+
+#import <Foundation/Foundation.h>
+#import "ASImageNode.h"
+
+@interface ASImageNode (Debugging)
+
+/**
+* Enables an ASImageNode debug label that shows the ratio of pixels in the source image to those in
+* the displayed bounds (including cropRect).  This helps detect excessive image fetching / downscaling,
+* as well as upscaling (such as providing a URL not suitable for a Retina device).  For dev purposes only.
+* @param enabled Specify YES to show the label on all ASImageNodes with non-1.0x source-to-bounds pixel ratio.
+*/
++ (void)setShouldShowImageScalingOverlay:(BOOL)show;
++ (BOOL)shouldShowImageScalingOverlay;
+
+@end

AsyncDisplayKit/AsyncDisplayKit+Debug.m

@@ -0,0 +1,26 @@
+//
+//  AsyncDisplayKit+Debug.m
+//  AsyncDisplayKit
+//
+//  Created by Hannah Troisi on 3/7/16.
+//  Copyright © 2016 Facebook. All rights reserved.
+//
+
+#import "AsyncDisplayKit+Debug.h"
+#import "ASDisplayNode+Subclasses.h"
+
+static BOOL __shouldShowImageScalingOverlay = NO;
+
+@implementation ASImageNode (Debugging)
+
++ (void)setShouldShowImageScalingOverlay:(BOOL)show;
+{
+  __shouldShowImageScalingOverlay = show;
+}
+
++ (BOOL)shouldShowImageScalingOverlay
+{
+  return __shouldShowImageScalingOverlay;
+}
+
+@end

AsyncDisplayKit/AsyncDisplayKit.h

@@ -74,3 +74,5 @@
 #import <AsyncDisplayKit/NSMutableAttributedString+TextKitAdditions.h>
 #import <AsyncDisplayKit/UICollectionViewLayout+ASConvenience.h>
 #import <AsyncDisplayKit/UIView+ASConvenience.h>
+
+#import <AsyncDisplayKit/AsyncDisplayKit+Debug.h>