Add an experimental "no-copy" renderer (TextureGroup#741)

* Add "ASGraphicsContext" to skip copying our rendered images

* Zero the buffer before making a context

* Update license header

* Update dangerfile

* Make it a runtime flag

* Restore GState for good measure

* Free buffer if end without image

* Enable the experiment, and cut out the middle-man

* Fix typo

AsyncDisplayKit.xcodeproj/project.pbxproj

@@ -402,6 +402,8 @@
 		CCCCCCE41EC3EF060087FE10 /* NSParagraphStyle+ASText.m in Sources */ = {isa = PBXBuildFile; fileRef = CCCCCCD41EC3EF060087FE10 /* NSParagraphStyle+ASText.m */; };
 		CCCCCCE71EC3F0FC0087FE10 /* NSAttributedString+ASText.h in Headers */ = {isa = PBXBuildFile; fileRef = CCCCCCE51EC3F0FC0087FE10 /* NSAttributedString+ASText.h */; };
 		CCCCCCE81EC3F0FC0087FE10 /* NSAttributedString+ASText.m in Sources */ = {isa = PBXBuildFile; fileRef = CCCCCCE61EC3F0FC0087FE10 /* NSAttributedString+ASText.m */; };
+		CCDC9B4D200991D10063C1F8 /* ASGraphicsContext.h in Headers */ = {isa = PBXBuildFile; fileRef = CCDC9B4B200991D10063C1F8 /* ASGraphicsContext.h */; settings = {ATTRIBUTES = (Public, ); }; };
+		CCDC9B4E200991D10063C1F8 /* ASGraphicsContext.m in Sources */ = {isa = PBXBuildFile; fileRef = CCDC9B4C200991D10063C1F8 /* ASGraphicsContext.m */; };
 		CCDD148B1EEDCD9D0020834E /* ASCollectionModernDataSourceTests.m in Sources */ = {isa = PBXBuildFile; fileRef = CCDD148A1EEDCD9D0020834E /* ASCollectionModernDataSourceTests.m */; };
 		CCE4F9B31F0D60AC00062E4E /* ASIntegerMapTests.m in Sources */ = {isa = PBXBuildFile; fileRef = CCE4F9B21F0D60AC00062E4E /* ASIntegerMapTests.m */; };
 		CCE4F9B51F0DA4F300062E4E /* ASLayoutEngineTests.mm in Sources */ = {isa = PBXBuildFile; fileRef = CCE4F9B41F0DA4F300062E4E /* ASLayoutEngineTests.mm */; };
@@ -895,6 +897,8 @@
 		CCCCCCD41EC3EF060087FE10 /* NSParagraphStyle+ASText.m */ = {isa = PBXFileReference; fileEncoding = 4; lastKnownFileType = sourcecode.c.objc; path = "NSParagraphStyle+ASText.m"; sourceTree = "<group>"; };
 		CCCCCCE51EC3F0FC0087FE10 /* NSAttributedString+ASText.h */ = {isa = PBXFileReference; fileEncoding = 4; lastKnownFileType = sourcecode.c.h; path = "NSAttributedString+ASText.h"; sourceTree = "<group>"; };
 		CCCCCCE61EC3F0FC0087FE10 /* NSAttributedString+ASText.m */ = {isa = PBXFileReference; fileEncoding = 4; lastKnownFileType = sourcecode.c.objc; path = "NSAttributedString+ASText.m"; sourceTree = "<group>"; };
+		CCDC9B4B200991D10063C1F8 /* ASGraphicsContext.h */ = {isa = PBXFileReference; lastKnownFileType = sourcecode.c.h; path = ASGraphicsContext.h; sourceTree = "<group>"; };
+		CCDC9B4C200991D10063C1F8 /* ASGraphicsContext.m */ = {isa = PBXFileReference; lastKnownFileType = sourcecode.c.objc; path = ASGraphicsContext.m; sourceTree = "<group>"; };
 		CCDD148A1EEDCD9D0020834E /* ASCollectionModernDataSourceTests.m */ = {isa = PBXFileReference; fileEncoding = 4; lastKnownFileType = sourcecode.c.objc; path = ASCollectionModernDataSourceTests.m; sourceTree = "<group>"; };
 		CCE04B1E1E313EA7006AEBBB /* ASSectionController.h */ = {isa = PBXFileReference; fileEncoding = 4; lastKnownFileType = sourcecode.c.h; path = ASSectionController.h; sourceTree = "<group>"; };
 		CCE04B201E313EB9006AEBBB /* IGListAdapter+AsyncDisplayKit.h */ = {isa = PBXFileReference; fileEncoding = 4; lastKnownFileType = sourcecode.c.h; path = "IGListAdapter+AsyncDisplayKit.h"; sourceTree = "<group>"; };
@@ -1270,6 +1274,8 @@
 		058D09E1195D050800B7D73C /* Details */ = {
 			isa = PBXGroup;
 			children = (
+				CCDC9B4B200991D10063C1F8 /* ASGraphicsContext.h */,
+				CCDC9B4C200991D10063C1F8 /* ASGraphicsContext.m */,
 				CC5601391F06E9A700DC4FBE /* ASIntegerMap.h */,
 				CC56013A1F06E9A700DC4FBE /* ASIntegerMap.mm */,
 				CC0F885E1E4280B800576FED /* _ASCollectionViewCell.h */,
@@ -1836,6 +1842,7 @@
 				68EE0DBE1C1B4ED300BA1B99 /* ASMainSerialQueue.h in Headers */,
 				CCCCCCE11EC3EF060087FE10 /* ASTextUtilities.h in Headers */,
 				B350624B1B010EFD0018CF92 /* _ASPendingState.h in Headers */,
+				CCDC9B4D200991D10063C1F8 /* ASGraphicsContext.h in Headers */,
 				E5C347B11ECB3D9200EC4BE4 /* ASBatchFetchingDelegate.h in Headers */,
 				CC54A81C1D70079800296A24 /* ASDispatch.h in Headers */,
 				B350624D1B010EFD0018CF92 /* _ASScopeTimer.h in Headers */,
@@ -2268,6 +2275,7 @@
 				E5B078001E69F4EB00C24B5B /* ASElementMap.m in Sources */,
 				9C8898BC1C738BA800D6B02E /* ASTextKitFontSizeAdjuster.mm in Sources */,
 				690ED59B1E36D118000627C0 /* ASImageNode+tvOS.m in Sources */,
+				CCDC9B4E200991D10063C1F8 /* ASGraphicsContext.m in Sources */,
 				CCCCCCD81EC3EF060087FE10 /* ASTextInput.m in Sources */,
 				34EFC7621B701CA400AD841F /* ASBackgroundLayoutSpec.mm in Sources */,
 				DE8BEAC41C2DF3FC00D57C12 /* ASDelegateProxy.m in Sources */,

CHANGELOG.md

@@ -11,6 +11,7 @@
 - Add new unit testing to the layout engine. [Adlai Holler](https://github.com/Adlai-Holler) [#424](https://github.com/TextureGroup/Texture/pull/424)
 - [Automatic Subnode Management] Nodes with ASM enabled now insert/delete their subnodes as soon as they enter preload state, so the subnodes can preload too. [Huy Nguyen](https://github.com/nguyenhuy) [#706](https://github.com/TextureGroup/Texture/pull/706)
 - [ASCollectionNode] Added support for interactive item movement. [Adlai Holler](https://github.com/Adlai-Holler)
+- Added an experimental "no-copy" rendering API. See ASGraphicsContext.h for info. [Adlai Holler](https://github.com/Adlai-Holler)
 
 ## 2.6
 - [Xcode 9] Updated to require Xcode 9 (to fix warnings) [Garrett Moon](https://github.com/garrettmoon)

Dangerfile

@@ -67,7 +67,7 @@ end
 
 # Ensure new files have proper header
 new_source_license_header = <<-HEREDOC
-//  Copyright (c) 2017-present, Pinterest, Inc.  All rights reserved.
+//  Copyright (c) 2018-present, Pinterest, Inc.  All rights reserved.
 //  Licensed under the Apache License, Version 2.0 (the "License");
 //  you may not use this file except in compliance with the License.
 //  You may obtain a copy of the License at

Source/ASDisplayNode.mm

@@ -36,6 +36,7 @@
 #import <AsyncDisplayKit/ASDimension.h>
 #import <AsyncDisplayKit/ASDisplayNodeExtras.h>
 #import <AsyncDisplayKit/ASEqualityHelpers.h>
+#import <AsyncDisplayKit/ASGraphicsContext.h>
 #import <AsyncDisplayKit/ASInternalHelpers.h>
 #import <AsyncDisplayKit/ASLayoutElementStylePrivate.h>
 #import <AsyncDisplayKit/ASLayoutSpec.h>
@@ -1507,7 +1508,7 @@ - (void)_updateClipCornerLayerContentsWithRadius:(CGFloat)radius backgroundColor
       BOOL isRight = (idx == 1 || idx == 2);
 
       CGSize size = CGSizeMake(radius + 1, radius + 1);
-      UIGraphicsBeginImageContextWithOptions(size, NO, self.contentsScaleForDisplay);
+      ASGraphicsBeginImageContextWithOptions(size, NO, self.contentsScaleForDisplay);
 
       CGContextRef ctx = UIGraphicsGetCurrentContext();
       if (isRight == YES) {
@@ -1524,11 +1525,9 @@ - (void)_updateClipCornerLayerContentsWithRadius:(CGFloat)radius backgroundColor
 
       // No lock needed, as _clipCornerLayers is only modified on the main thread.
       CALayer *clipCornerLayer = _clipCornerLayers[idx];
-      clipCornerLayer.contents = (id)(UIGraphicsGetImageFromCurrentImageContext().CGImage);
+      clipCornerLayer.contents = (id)(ASGraphicsGetImageAndEndCurrentContext().CGImage);
       clipCornerLayer.bounds = CGRectMake(0.0, 0.0, size.width, size.height);
       clipCornerLayer.anchorPoint = CGPointMake(isRight ? 1.0 : 0.0, isTop ? 1.0 : 0.0);
-
-      UIGraphicsEndImageContext();
     }
     [self _layoutClipCornersIfNeeded];
   });

Source/ASImageNode.mm

@@ -25,6 +25,7 @@
 #import <AsyncDisplayKit/ASDisplayNode+FrameworkSubclasses.h>
 #import <AsyncDisplayKit/ASDisplayNodeExtras.h>
 #import <AsyncDisplayKit/ASDisplayNode+Beta.h>
+#import <AsyncDisplayKit/ASGraphicsContext.h>
 #import <AsyncDisplayKit/ASLayout.h>
 #import <AsyncDisplayKit/ASTextNode.h>
 #import <AsyncDisplayKit/ASImageNode+AnimatedImagePrivate.h>
@@ -213,11 +214,10 @@ - (UIImage *)placeholderImage
 
   ASDN::MutexLocker l(__instanceLock__);
 
-  UIGraphicsBeginImageContext(size);
+  ASGraphicsBeginImageContextWithOptions(size, NO, 1);
   [self.placeholderColor setFill];
   UIRectFill(CGRectMake(0, 0, size.width, size.height));
-  UIImage *image = UIGraphicsGetImageFromCurrentImageContext();
-  UIGraphicsEndImageContext();
+  UIImage *image = ASGraphicsGetImageAndEndCurrentContext();
 
   return image;
 }
@@ -472,7 +472,7 @@ + (ASWeakMapEntry *)contentsForkey:(ASImageNodeContentsKey *)key drawParameters:
 
 + (UIImage *)createContentsForkey:(ASImageNodeContentsKey *)key drawParameters:(id)drawParameters isCancelled:(asdisplaynode_iscancelled_block_t)isCancelled
 {
-  // The following `UIGraphicsBeginImageContextWithOptions` call will sometimes take take longer than 5ms on an
+  // The following `ASGraphicsBeginImageContextWithOptions` call will sometimes take take longer than 5ms on an
   // A5 processor for a 400x800 backingSize.
   // Check for cancellation before we call it.
   if (isCancelled()) {
@@ -481,7 +481,7 @@ + (UIImage *)createContentsForkey:(ASImageNodeContentsKey *)key drawParameters:(
 
   // Use contentsScale of 1.0 and do the contentsScale handling in boundsSizeInPixels so ASCroppedImageBackingSizeAndDrawRectInBounds
   // will do its rounding on pixel instead of point boundaries
-  UIGraphicsBeginImageContextWithOptions(key.backingSize, key.isOpaque, 1.0);
+  ASGraphicsBeginImageContextWithOptions(key.backingSize, key.isOpaque, 1.0);
 
   BOOL contextIsClean = YES;
 
@@ -529,9 +529,7 @@ + (UIImage *)createContentsForkey:(ASImageNodeContentsKey *)key drawParameters:(
     return nil;
   }
 
-  UIImage *result = UIGraphicsGetImageFromCurrentImageContext();
-
-  UIGraphicsEndImageContext();
+  UIImage *result = ASGraphicsGetImageAndEndCurrentContext();
 
   if (key.imageModificationBlock) {
     result = key.imageModificationBlock(result);
@@ -742,7 +740,7 @@ - (NSDictionary *)debugLabelAttributes
 extern asimagenode_modification_block_t ASImageNodeRoundBorderModificationBlock(CGFloat borderWidth, UIColor *borderColor)
 {
   return ^(UIImage *originalImage) {
-    UIGraphicsBeginImageContextWithOptions(originalImage.size, NO, originalImage.scale);
+    ASGraphicsBeginImageContextWithOptions(originalImage.size, NO, originalImage.scale);
     UIBezierPath *roundOutline = [UIBezierPath bezierPathWithOvalInRect:(CGRect){CGPointZero, originalImage.size}];
 
     // Make the image round
@@ -758,24 +756,21 @@ extern asimagenode_modification_block_t ASImageNodeRoundBorderModificationBlock(
       [roundOutline stroke];
     }
 
-    UIImage *modifiedImage = UIGraphicsGetImageFromCurrentImageContext();
-    UIGraphicsEndImageContext();
-    return modifiedImage;
+    return ASGraphicsGetImageAndEndCurrentContext();
   };
 }
 
 extern asimagenode_modification_block_t ASImageNodeTintColorModificationBlock(UIColor *color)
 {
   return ^(UIImage *originalImage) {
-    UIGraphicsBeginImageContextWithOptions(originalImage.size, NO, originalImage.scale);
+    ASGraphicsBeginImageContextWithOptions(originalImage.size, NO, originalImage.scale);
 
     // Set color and render template
     [color setFill];
     UIImage *templateImage = [originalImage imageWithRenderingMode:UIImageRenderingModeAlwaysTemplate];
     [templateImage drawAtPoint:CGPointZero blendMode:kCGBlendModeCopy alpha:1];
 
-    UIImage *modifiedImage = UIGraphicsGetImageFromCurrentImageContext();
-    UIGraphicsEndImageContext();
+    UIImage *modifiedImage = ASGraphicsGetImageAndEndCurrentContext();
 
     // if the original image was stretchy, keep it stretchy
     if (!UIEdgeInsetsEqualToEdgeInsets(originalImage.capInsets, UIEdgeInsetsZero)) {

Source/ASMapNode.mm

@@ -24,6 +24,7 @@
 
 #import <AsyncDisplayKit/ASDisplayNode+FrameworkSubclasses.h>
 #import <AsyncDisplayKit/ASDisplayNodeExtras.h>
+#import <AsyncDisplayKit/ASGraphicsContext.h>
 #import <AsyncDisplayKit/ASInsetLayoutSpec.h>
 #import <AsyncDisplayKit/ASInternalHelpers.h>
 #import <AsyncDisplayKit/ASLayout.h>
@@ -222,7 +223,7 @@ - (void)takeSnapshot
 
                     CGRect finalImageRect = CGRectMake(0, 0, image.size.width, image.size.height);
 
-                    UIGraphicsBeginImageContextWithOptions(image.size, YES, image.scale);
+                    ASGraphicsBeginImageContextWithOptions(image.size, YES, image.scale);
                     [image drawAtPoint:CGPointZero];
 
                     UIImage *pinImage;
@@ -254,8 +255,7 @@ - (void)takeSnapshot
                       }
                     }
 
-                    image = UIGraphicsGetImageFromCurrentImageContext();
-                    UIGraphicsEndImageContext();
+                    image = ASGraphicsGetImageAndEndCurrentContext();
                   }
 
                   strongSelf.image = image;

Source/ASTextNode.mm

@@ -28,6 +28,7 @@
 #import <AsyncDisplayKit/ASDisplayNode+FrameworkSubclasses.h>
 #import <AsyncDisplayKit/ASHighlightOverlayLayer.h>
 #import <AsyncDisplayKit/ASDisplayNodeExtras.h>
+#import <AsyncDisplayKit/ASGraphicsContext.h>
 
 #import <AsyncDisplayKit/ASTextKitCoreTextAdditions.h>
 #import <AsyncDisplayKit/ASTextKitRenderer+Positioning.h>
@@ -907,7 +908,7 @@ - (UIImage *)placeholderImage
 
   ASDN::MutexLocker l(__instanceLock__);
 
-  UIGraphicsBeginImageContext(size);
+  ASGraphicsBeginImageContextWithOptions(size, NO, 1.0);
   [self.placeholderColor setFill];
 
   ASTextKitRenderer *renderer = [self _locked_renderer];
@@ -926,8 +927,7 @@ - (UIImage *)placeholderImage
     }
   }
 
-  UIImage *image = UIGraphicsGetImageFromCurrentImageContext();
-  UIGraphicsEndImageContext();
+  UIImage *image = ASGraphicsGetImageAndEndCurrentContext();
   return image;
 }
 

Source/AsyncDisplayKit.h

@@ -119,6 +119,7 @@
 #import <AsyncDisplayKit/UICollectionViewLayout+ASConvenience.h>
 #import <AsyncDisplayKit/UIView+ASConvenience.h>
 #import <AsyncDisplayKit/UIImage+ASConvenience.h>
+#import <AsyncDisplayKit/ASGraphicsContext.h>
 #import <AsyncDisplayKit/NSArray+Diffing.h>
 #import <AsyncDisplayKit/ASObjectDescriptionHelpers.h>
 #import <AsyncDisplayKit/UIResponder+AsyncDisplayKit.h>

Source/Debug/AsyncDisplayKit+Debug.m

@@ -17,6 +17,7 @@
 
 #import <AsyncDisplayKit/AsyncDisplayKit+Debug.h>
 #import <AsyncDisplayKit/ASAbstractLayoutController.h>
+#import <AsyncDisplayKit/ASGraphicsContext.h>
 #import <AsyncDisplayKit/ASLayout.h>
 #import <AsyncDisplayKit/ASWeakSet.h>
 #import <AsyncDisplayKit/UIImage+ASConvenience.h>
@@ -148,16 +149,15 @@ - (void)layout
       UIColor *clipsBorderColor = [UIColor colorWithRed:30/255.0 green:90/255.0 blue:50/255.0 alpha:0.7];
       CGRect imgRect            = CGRectMake(0, 0, 2.0 * borderWidth + 1.0, 2.0 * borderWidth + 1.0);
 
-      UIGraphicsBeginImageContext(imgRect.size);
+      ASGraphicsBeginImageContextWithOptions(imgRect.size, NO, 1);
 
       [fillColor setFill];
       UIRectFill(imgRect);
 
       [self drawEdgeIfClippedWithEdges:clippedEdges color:clipsBorderColor borderWidth:borderWidth imgRect:imgRect];
       [self drawEdgeIfClippedWithEdges:clipsToBoundsClippedEdges color:borderColor borderWidth:borderWidth imgRect:imgRect];
 
-      UIImage *debugHighlightImage = UIGraphicsGetImageFromCurrentImageContext();
-      UIGraphicsEndImageContext();
+      UIImage *debugHighlightImage = ASGraphicsGetImageAndEndCurrentContext();
 
       UIEdgeInsets edgeInsets = UIEdgeInsetsMake(borderWidth, borderWidth, borderWidth, borderWidth);
       debugOverlay.image = [debugHighlightImage resizableImageWithCapInsets:edgeInsets resizingMode:UIImageResizingModeStretch];

Source/Details/ASGraphicsContext.h

@@ -0,0 +1,62 @@
+//
+//  ASGraphicsContext.h
+//  Texture
+//
+//  Copyright (c) 2018-present, Pinterest, Inc.  All rights reserved.
+//  Licensed under the Apache License, Version 2.0 (the "License");
+//  you may not use this file except in compliance with the License.
+//  You may obtain a copy of the License at
+//
+//      http://www.apache.org/licenses/LICENSE-2.0
+//
+
+#import <Foundation/Foundation.h>
+#import <AsyncDisplayKit/ASBaseDefines.h>
+#import <CoreGraphics/CoreGraphics.h>
+
+@class UIImage;
+
+/**
+ * Functions for creating one-shot graphics contexts that do not have to copy
+ * their contents when an image is generated from them. This is efficient
+ * for our use, since we do not reuse graphics contexts.
+ *
+ * The API mirrors the UIGraphics API, with the exception that forming an image
+ * ends the context as well.
+ */
+
+NS_ASSUME_NONNULL_BEGIN
+ASDISPLAYNODE_EXTERN_C_BEGIN
+
+/**
+ * Call this to enable the experimental no-copy rendering.
+ *
+ * Returns YES if it was enabled, or NO + assert if it's too late because
+ * rendering has already started. In practice it's fine to call this
+ * during -didFinishLaunchingWithOptions:.
+ */
+extern BOOL ASEnableNoCopyRendering(void);
+
+/**
+ * Creates a one-shot context.
+ *
+ * Behavior is the same as UIGraphicsBeginImageContextWithOptions.
+ */
+extern void ASGraphicsBeginImageContextWithOptions(CGSize size, BOOL opaque, CGFloat scale);
+
+/**
+ * Generates and image and ends the current one-shot context.
+ *
+ * Behavior is the same as UIGraphicsGetImageFromCurrentImageContext followed by UIGraphicsEndImageContext.
+ */
+extern UIImage * _Nullable ASGraphicsGetImageAndEndCurrentContext(void);
+
+/**
+ * Call this if you want to end the current context without making an image.
+ *
+ * Behavior is the same as UIGraphicsEndImageContext.
+ */
+extern void ASGraphicsEndImageContext(void);
+
+ASDISPLAYNODE_EXTERN_C_END
+NS_ASSUME_NONNULL_END