Basic implementation of transitioning API for layout specs

AsyncDisplayKit.xcodeproj/project.pbxproj

@@ -460,6 +460,10 @@
 		CC7FD9E21BB603FF005CCB2B /* ASPhotosFrameworkImageRequest.h in Headers */ = {isa = PBXBuildFile; fileRef = CC7FD9DC1BB5E962005CCB2B /* ASPhotosFrameworkImageRequest.h */; settings = {ATTRIBUTES = (Public, ); }; };
 		D785F6621A74327E00291744 /* ASScrollNode.h in Headers */ = {isa = PBXBuildFile; fileRef = D785F6601A74327E00291744 /* ASScrollNode.h */; settings = {ATTRIBUTES = (Public, ); }; };
 		D785F6631A74327E00291744 /* ASScrollNode.m in Sources */ = {isa = PBXBuildFile; fileRef = D785F6611A74327E00291744 /* ASScrollNode.m */; };
+		DB55C2611C6408D6004EDCF5 /* _ASTransitionContext.h in Headers */ = {isa = PBXBuildFile; fileRef = DB55C25F1C6408D6004EDCF5 /* _ASTransitionContext.h */; };
+		DB55C2631C6408D6004EDCF5 /* _ASTransitionContext.m in Sources */ = {isa = PBXBuildFile; fileRef = DB55C2601C6408D6004EDCF5 /* _ASTransitionContext.m */; };
+		DB55C2661C641AE4004EDCF5 /* ASContextTransitioning.h in Headers */ = {isa = PBXBuildFile; fileRef = DB55C2651C641AE4004EDCF5 /* ASContextTransitioning.h */; settings = {ATTRIBUTES = (Public, ); }; };
+		DB55C2671C641AE4004EDCF5 /* ASContextTransitioning.h in Headers */ = {isa = PBXBuildFile; fileRef = DB55C2651C641AE4004EDCF5 /* ASContextTransitioning.h */; settings = {ATTRIBUTES = (Public, ); }; };
 		DB7121BCD50849C498C886FB /* libPods-AsyncDisplayKitTests.a in Frameworks */ = {isa = PBXBuildFile; fileRef = EFA731F0396842FF8AB635EE /* libPods-AsyncDisplayKitTests.a */; };
 		DBC452DB1C5BF64600B16017 /* NSArray+Diffing.h in Headers */ = {isa = PBXBuildFile; fileRef = DBC452D91C5BF64600B16017 /* NSArray+Diffing.h */; };
 		DBC452DC1C5BF64600B16017 /* NSArray+Diffing.m in Sources */ = {isa = PBXBuildFile; fileRef = DBC452DA1C5BF64600B16017 /* NSArray+Diffing.m */; };
@@ -781,6 +785,9 @@
 		D3779BCFF841AD3EB56537ED /* Pods-AsyncDisplayKitTests.release.xcconfig */ = {isa = PBXFileReference; includeInIndex = 1; lastKnownFileType = text.xcconfig; name = "Pods-AsyncDisplayKitTests.release.xcconfig"; path = "Pods/Target Support Files/Pods-AsyncDisplayKitTests/Pods-AsyncDisplayKitTests.release.xcconfig"; sourceTree = "<group>"; };
 		D785F6601A74327E00291744 /* ASScrollNode.h */ = {isa = PBXFileReference; fileEncoding = 4; lastKnownFileType = sourcecode.c.h; path = ASScrollNode.h; sourceTree = "<group>"; };
 		D785F6611A74327E00291744 /* ASScrollNode.m */ = {isa = PBXFileReference; fileEncoding = 4; lastKnownFileType = sourcecode.c.objc; path = ASScrollNode.m; sourceTree = "<group>"; };
+		DB55C25F1C6408D6004EDCF5 /* _ASTransitionContext.h */ = {isa = PBXFileReference; fileEncoding = 4; lastKnownFileType = sourcecode.c.h; name = _ASTransitionContext.h; path = ../_ASTransitionContext.h; sourceTree = "<group>"; };
+		DB55C2601C6408D6004EDCF5 /* _ASTransitionContext.m */ = {isa = PBXFileReference; fileEncoding = 4; lastKnownFileType = sourcecode.c.objc; name = _ASTransitionContext.m; path = ../_ASTransitionContext.m; sourceTree = "<group>"; };
+		DB55C2651C641AE4004EDCF5 /* ASContextTransitioning.h */ = {isa = PBXFileReference; fileEncoding = 4; lastKnownFileType = sourcecode.c.h; path = ASContextTransitioning.h; sourceTree = "<group>"; };
 		DBC452D91C5BF64600B16017 /* NSArray+Diffing.h */ = {isa = PBXFileReference; fileEncoding = 4; lastKnownFileType = sourcecode.c.h; path = "NSArray+Diffing.h"; sourceTree = "<group>"; };
 		DBC452DA1C5BF64600B16017 /* NSArray+Diffing.m */ = {isa = PBXFileReference; fileEncoding = 4; lastKnownFileType = sourcecode.c.objc; path = "NSArray+Diffing.m"; sourceTree = "<group>"; };
 		DBC452DD1C5C6A6A00B16017 /* ArrayDiffingTests.m */ = {isa = PBXFileReference; fileEncoding = 4; lastKnownFileType = sourcecode.c.objc; path = ArrayDiffingTests.m; sourceTree = "<group>"; };
@@ -959,6 +966,7 @@
 				ACC945A81BA9E7A0005E1FB8 /* ASViewController.h */,
 				ACC945AA1BA9E7C1005E1FB8 /* ASViewController.m */,
 				6BDC61F51978FEA400E50D21 /* AsyncDisplayKit.h */,
+				DB55C2651C641AE4004EDCF5 /* ASContextTransitioning.h */,
 				058D09E1195D050800B7D73C /* Details */,
 				058D0A01195D050800B7D73C /* Private */,
 				AC6456051B0A333200CF11B8 /* Layout */,
@@ -1102,6 +1110,8 @@
 		058D0A01195D050800B7D73C /* Private */ = {
 			isa = PBXGroup;
 			children = (
+				DB55C25F1C6408D6004EDCF5 /* _ASTransitionContext.h */,
+				DB55C2601C6408D6004EDCF5 /* _ASTransitionContext.m */,
 				AC026B6D1BD57DBF00BBC17E /* _ASHierarchyChangeSet.h */,
 				AC026B6E1BD57DBF00BBC17E /* _ASHierarchyChangeSet.m */,
 				9C65A7291BA8EA4D0084DA91 /* ASLayoutOptionsPrivate.h */,
@@ -1343,6 +1353,7 @@
 				DE6EA3221C14000600183B10 /* ASDisplayNode+FrameworkPrivate.h in Headers */,
 				1950C4491A3BB5C1005C8279 /* ASEqualityHelpers.h in Headers */,
 				257754A81BEE44CD00737CA5 /* ASTextKitContext.h in Headers */,
+				DB55C2611C6408D6004EDCF5 /* _ASTransitionContext.h in Headers */,
 				464052221A3F83C40061C0BA /* ASFlowLayoutController.h in Headers */,
 				257754AF1BEE44CD00737CA5 /* ASTextKitRenderer+TextChecking.h in Headers */,
 				058D0A57195D05DC00B7D73C /* ASHighlightOverlayLayer.h in Headers */,
@@ -1352,6 +1363,7 @@
 				430E7C8F1B4C23F100697A4C /* ASIndexPath.h in Headers */,
 				ACF6ED221B17843500DA7C62 /* ASInsetLayoutSpec.h in Headers */,
 				ACF6ED4B1B17847A00DA7C62 /* ASInternalHelpers.h in Headers */,
+				DB55C2661C641AE4004EDCF5 /* ASContextTransitioning.h in Headers */,
 				ACF6ED241B17843500DA7C62 /* ASLayout.h in Headers */,
 				251B8EFB1BBB3D690087C538 /* ASDataController+Subclasses.h in Headers */,
 				ACF6ED2A1B17843500DA7C62 /* ASLayoutable.h in Headers */,
@@ -1501,6 +1513,7 @@
 				34EFC76E1B701CF400AD841F /* ASRatioLayoutSpec.h in Headers */,
 				34EFC7651B701CCC00AD841F /* ASRelativeSize.h in Headers */,
 				254C6B741BF94DF4003EC431 /* ASTextNodeWordKerner.h in Headers */,
+				DB55C2671C641AE4004EDCF5 /* ASContextTransitioning.h in Headers */,
 				68B0277B1C1A79D60041016B /* ASDisplayNode+Beta.h in Headers */,
 				B350622D1B010EFD0018CF92 /* ASScrollDirection.h in Headers */,
 				254C6B751BF94DF4003EC431 /* ASTextKitHelpers.h in Headers */,
@@ -1775,6 +1788,7 @@
 				ACF6ED231B17843500DA7C62 /* ASInsetLayoutSpec.mm in Sources */,
 				ACF6ED4C1B17847A00DA7C62 /* ASInternalHelpers.mm in Sources */,
 				ACF6ED251B17843500DA7C62 /* ASLayout.mm in Sources */,
+				DB55C2631C6408D6004EDCF5 /* _ASTransitionContext.m in Sources */,
 				9C5FA3531B8F6ADF00A62714 /* ASLayoutOptions.mm in Sources */,
 				9C5FA35F1B90C9A500A62714 /* ASLayoutOptionsPrivate.mm in Sources */,
 				251B8EFA1BBB3D690087C538 /* ASCollectionViewFlowLayoutInspector.m in Sources */,

AsyncDisplayKit/ASContextTransitioning.h

@@ -0,0 +1,33 @@
+//
+//  ASContextTransitioning.h
+//  AsyncDisplayKit
+//
+//  Created by Levi McCallum on 2/4/16.
+//  Copyright © 2016 Facebook. All rights reserved.
+//
+
+#import <AsyncDisplayKit/AsyncDisplayKit.h>
+
+@protocol ASContextTransitioning <NSObject>
+
+/**
+ @abstract The frame for the given node before the transition began.
+ @discussion Returns CGRectNull if the node was not in the hierarchy before the transition.
+ */
+- (CGRect)initialFrameForNode:(ASDisplayNode *)node;
+
+/**
+ @abstract The frame for the given node when the transition completes.
+ @discussion Returns CGRectNull if the node is no longer in the hierarchy after the transition.
+ */
+- (CGRect)finalFrameForNode:(ASDisplayNode *)node;
+
+- (NSArray<ASLayout *> *)sublayouts;
+
+/**
+ @abstract Invoke this method when the transition is completed in `transitionLayout:`
+ @discussion Passing NO to `didComplete` will set the original layout as the new layout.
+ */
+- (void)completeTransition:(BOOL)didComplete;
+
+@end

AsyncDisplayKit/ASDisplayNode+Subclasses.h

@@ -14,6 +14,7 @@
 #import <AsyncDisplayKit/ASThread.h>
 
 @class ASLayoutSpec;
+@protocol ASContextTransitioning;
 
 NS_ASSUME_NONNULL_BEGIN
 
@@ -155,6 +156,24 @@ NS_ASSUME_NONNULL_BEGIN
 - (void)invalidateCalculatedLayout;
 
 
+/** @name Layout Transitioning */
+
+/**
+ @discussion Called right before new nodes are inserted. A great place to setup layer attributes before animation.
+ */
+- (void)willTransitionLayout:(id<ASContextTransitioning>)context;
+
+/**
+ @discussion A place to perform your animation. New nodes have been inserted here. You can also use this time to re-order the hierarchy.
+ */
+- (void)transitionLayout:(id<ASContextTransitioning>)context;
+
+/**
+ @discussion A place to clean up your nodes after the transition
+ */
+- (void)didCompleteTransitionLayout:(id<ASContextTransitioning>)context;
+
+
 /** @name Drawing */
 
 

AsyncDisplayKit/ASDisplayNode.h

@@ -571,6 +571,17 @@ NS_ASSUME_NONNULL_BEGIN
 
 @end
 
+@interface ASDisplayNode (Transitioning)
+
+/**
+ @abstract Invalidates the current layout and begins a relayout of the node to the new layout returned in `calculateLayoutThatFits:`.
+
+ @discussion Animation is optional, but will still proceed through the `transitionLayout` methods with `isAnimated == NO`.
+ */
+- (void)transitionLayoutWithAnimation:(BOOL)animated;
+
+@end
+
 
 /**
  * Convenience methods for debugging.

AsyncDisplayKit/ASDisplayNode.mm

@@ -84,7 +84,7 @@ NSString * const ASRenderingEngineDidDisplayNodesScheduledBeforeTimestamp = @"AS
 #define TIME_SCOPED(outVar)
 #endif
 
-@interface ASDisplayNode () <_ASDisplayLayerDelegate>
+@interface ASDisplayNode () <_ASDisplayLayerDelegate, _ASTransitionContextDelegate>
 
 @property (assign, nonatomic) BOOL implicitNodeHierarchyManagement;
 
@@ -996,6 +996,119 @@ static inline CATransform3D _calculateTransformFromReferenceToTarget(ASDisplayNo
   return CGRectApplyAffineTransform(rect, flattenedTransform);
 }
 
+#pragma mark - Layout Transition
+
+- (void)transitionLayoutWithAnimation:(BOOL)animated
+{
+  [self transitionLayoutToFit:_constrainedSize animated:animated];
+}
+
+- (void)transitionLayoutToFit:(ASSizeRange)constrainedSize animated:(BOOL)animated
+{
+  [self invalidateCalculatedLayout];
+  [self measureWithSizeRange:constrainedSize]; // Generate a new layout
+  [self __transitionLayoutWithAnimation:animated];
+}
+
+- (void)__transitionLayoutWithAnimation:(BOOL)animated
+{
+  _transitionContext = [[_ASTransitionContext alloc] initWithAnimation:animated delegate:self];
+
+  [self willTransitionLayout:_transitionContext];
+  if ([_insertedSubnodes count]) {
+    for (_ASDisplayNodePosition *position in _insertedSubnodes) {
+      [self _implicitlyInsertSubnode:position.node atIndex:position.index];
+    }
+    _insertedSubnodes = @[];
+  }
+
+  [self transitionLayout:_transitionContext];
+}
+
+- (void)willTransitionLayout:(id<ASContextTransitioning>)context
+{
+}
+
+- (void)transitionLayout:(id<ASContextTransitioning>)context
+{
+  for (ASLayout *subnodeLayout in [context sublayouts]) {
+    ((ASDisplayNode *)subnodeLayout.layoutableObject).frame = [self _adjustedFrameForLayout:subnodeLayout];
+  }
+
+  [context completeTransition:YES];
+}
+
+- (void)didCompleteTransitionLayout:(id<ASContextTransitioning>)context
+{
+  if ([_deletedSubnodes count]) {
+    for (_ASDisplayNodePosition *position in _deletedSubnodes) {
+      [self _implicitlyRemoveSubnode:position.node atIndex:position.index];
+    }
+    _deletedSubnodes = @[];
+  }
+}
+
+- (CGRect)_adjustedFrameForLayout:(ASLayout *)layout
+{
+  CGRect subnodeFrame = CGRectZero;
+  CGPoint adjustedOrigin = layout.position;
+  if (isfinite(adjustedOrigin.x) == NO) {
+    ASDisplayNodeAssert(0, @"subnodeLayout has an invalid position");
+    adjustedOrigin.x = 0;
+  }
+  if (isfinite(adjustedOrigin.y) == NO) {
+    ASDisplayNodeAssert(0, @"subnodeLayout has an invalid position");
+    adjustedOrigin.y = 0;
+  }
+  subnodeFrame.origin = adjustedOrigin;
+  
+  CGSize adjustedSize = layout.size;
+  if (isfinite(adjustedSize.width) == NO) {
+    ASDisplayNodeAssert(0, @"subnodeLayout has an invalid size");
+    adjustedSize.width = 0;
+  }
+  if (isfinite(adjustedSize.height) == NO) {
+    ASDisplayNodeAssert(0, @"subnodeLayout has an invalid position");
+    adjustedSize.height = 0;
+  }
+  subnodeFrame.size = adjustedSize;
+  
+  return subnodeFrame;
+}
+
+#pragma mark - _ASTransitionContextDelegate
+
+- (void)transitionContext:(_ASTransitionContext *)context didComplete:(BOOL)didComplete
+{
+  [self didCompleteTransitionLayout:context];
+  _transitionContext = nil;
+}
+
+- (CGRect)transitionContext:(_ASTransitionContext *)context initialFrameForNode:(ASDisplayNode *)node
+{
+  for (ASDisplayNode *subnode in _subnodes) {
+    if (ASObjectIsEqual(node, subnode)) {
+      return node.frame;
+    }
+  }
+  return CGRectNull;
+}
+
+- (CGRect)transitionContext:(_ASTransitionContext *)context finalFrameForNode:(ASDisplayNode *)node
+{
+  for (ASLayout *layout in _layout.sublayouts) {
+    if (ASObjectIsEqual(node, layout.layoutableObject)) {
+      return [self _adjustedFrameForLayout:layout];
+    }
+  }
+  return CGRectNull;
+}
+
+- (NSArray<ASLayout *> *)sublayoutsForTransitioningContext:(_ASTransitionContext *)context
+{
+  return _layout.sublayouts;
+}
+
 #pragma mark - _ASDisplayLayerDelegate
 
 - (void)willDisplayAsyncLayer:(_ASDisplayLayer *)layer
@@ -2053,77 +2166,27 @@ void recursivelyTriggerDisplayForLayer(CALayer *layer, BOOL shouldBlock)
   if (!_flags.isMeasured) {
     return;
   }
-
-  // Assume that _layout was flattened and is 1-level deep.
-  ASDisplayNode *subnode = nil;
-  CGRect subnodeFrame = CGRectZero;
-  for (ASLayout *subnodeLayout in _layout.sublayouts) {
-    if (![[self class] usesImplicitHierarchyManagement]) {
-      ASDisplayNodeAssert([_subnodes containsObject:subnodeLayout.layoutableObject], @"Sublayouts must only contain subnodes' layout.  self = %@, subnodes = %@", self, _subnodes);
-    }
-    CGPoint adjustedOrigin = subnodeLayout.position;
-    if (isfinite(adjustedOrigin.x) == NO) {
-      ASDisplayNodeAssert(0, @"subnodeLayout has an invalid position");
-      adjustedOrigin.x = 0;
-    }
-    if (isfinite(adjustedOrigin.y) == NO) {
-      ASDisplayNodeAssert(0, @"subnodeLayout has an invalid position");
-      adjustedOrigin.y = 0;
-    }
-    subnodeFrame.origin = adjustedOrigin;
-    
-    CGSize adjustedSize = subnodeLayout.size;
-    if (isfinite(adjustedSize.width) == NO) {
-      ASDisplayNodeAssert(0, @"subnodeLayout has an invalid size");
-      adjustedSize.width = 0;
-    }
-    if (isfinite(adjustedSize.height) == NO) {
-      ASDisplayNodeAssert(0, @"subnodeLayout has an invalid position");
-      adjustedSize.height = 0;
-    }
-    subnodeFrame.size = adjustedSize;
-    
-    subnode = ((ASDisplayNode *)subnodeLayout.layoutableObject);
-    [subnode setFrame:subnodeFrame];
-  }
   
   if ([[self class] usesImplicitHierarchyManagement]) {
-    for (_ASDisplayNodePosition *position in _deletedSubnodes) {
-      [self _implicitlyRemoveSubnode:position.node atIndex:position.index];
-    }
-    
-    for (_ASDisplayNodePosition *position in _insertedSubnodes) {
-      [self _implicitlyInsertSubnode:position.node atIndex:position.index];
+    [self __transitionLayoutWithAnimation:NO];
+  } else {
+    // Assume that _layout was flattened and is 1-level deep.
+    CGRect subnodeFrame = CGRectZero;
+    for (ASLayout *subnodeLayout in _layout.sublayouts) {
+      ASDisplayNodeAssert([_subnodes containsObject:subnodeLayout.layoutableObject], @"Sublayouts must only contain subnodes' layout. self = %@, subnodes = %@", self, _subnodes);
+      subnodeFrame = [self _adjustedFrameForLayout:subnodeLayout];
+      ((ASDisplayNode *)subnodeLayout.layoutableObject).frame = subnodeFrame;
     }
   }
 }
 
 - (void)_implicitlyInsertSubnode:(ASDisplayNode *)node atIndex:(NSUInteger)idx
 {
-  ASDisplayNodeAssertThreadAffinity(self);
-
-  if (!_managedSubnodes) {
-    _managedSubnodes = [NSMutableArray array];
-  }
-
-  ASDisplayNodeAssert(idx <= [_managedSubnodes count], @"index needs to be in range of the current managed subnodes");
-  if (idx == [_managedSubnodes count]) {
-    [_managedSubnodes addObject:node];
-  } else {
-    [_managedSubnodes insertObject:node atIndex:idx];
-  }
-  [self addSubnode:node];
+  [self insertSubnode:node atIndex:idx];
 }
 
 - (void)_implicitlyRemoveSubnode:(ASDisplayNode *)node atIndex:(NSUInteger)idx
 {
-  ASDisplayNodeAssertThreadAffinity(self);
-
-  if (!_managedSubnodes) {
-    _managedSubnodes = [NSMutableArray array];
-  }
-
-  [_managedSubnodes removeObjectAtIndex:idx];
   [node removeFromSupernode];
 }
 

AsyncDisplayKit/AsyncDisplayKit.h

@@ -68,3 +68,4 @@
 #import <AsyncDisplayKit/NSMutableAttributedString+TextKitAdditions.h>
 #import <AsyncDisplayKit/UICollectionViewLayout+ASConvenience.h>
 #import <AsyncDisplayKit/UIView+ASConvenience.h>
+#import <AsyncDisplayKit/ASContextTransitioning.h>

AsyncDisplayKit/Private/ASDisplayNodeInternal.h

@@ -17,6 +17,7 @@
 #import "ASSentinel.h"
 #import "ASThread.h"
 #import "ASLayoutOptions.h"
+#import "_ASTransitionContext.h"
 
 @protocol _ASDisplayLayerDelegate;
 @class _ASDisplayLayer;
@@ -63,10 +64,8 @@ FOUNDATION_EXPORT NSString * const ASRenderingEngineDidDisplayNodesScheduledBefo
   ASSizeRange _constrainedSize;
   UIEdgeInsets _hitTestSlop;
   NSMutableArray *_subnodes;
-
-  // Subnodes implicitly managed by layout changes
-  NSMutableArray<ASDisplayNode *> *_managedSubnodes;
   
+  _ASTransitionContext *_transitionContext;
   NSArray<_ASDisplayNodePosition *> *_insertedSubnodes;
   NSArray<_ASDisplayNodePosition *> *_deletedSubnodes;
 
@@ -149,6 +148,11 @@ FOUNDATION_EXPORT NSString * const ASRenderingEngineDidDisplayNodesScheduledBefo
 - (void)__layout;
 - (void)__setSupernode:(ASDisplayNode *)supernode;
 
+/**
+ Clamps the layout's origin or position to 0 if any of the calculated values are infinite.
+ */
+- (CGRect)_adjustedFrameForLayout:(ASLayout *)layout;
+
 // Private API for helper functions / unit tests.  Use ASDisplayNodeDisableHierarchyNotifications() to control this.
 - (BOOL)__visibilityNotificationsDisabled;
 - (BOOL)__selfOrParentHasVisibilityNotificationsDisabled;

AsyncDisplayKit/_ASTransitionContext.h

@@ -0,0 +1,32 @@
+//
+//  _ASTransitionContext.h
+//  AsyncDisplayKit
+//
+//  Created by Levi McCallum on 2/4/16.
+//  Copyright © 2016 Facebook. All rights reserved.
+//
+
+#import <Foundation/Foundation.h>
+
+#import "ASContextTransitioning.h"
+
+@class ASLayout;
+@class _ASTransitionContext;
+
+@protocol _ASTransitionContextDelegate <NSObject>
+
+- (void)transitionContext:(_ASTransitionContext *)context didComplete:(BOOL)didComplete;
+- (CGRect)transitionContext:(_ASTransitionContext *)context initialFrameForNode:(ASDisplayNode *)node;
+- (CGRect)transitionContext:(_ASTransitionContext *)context finalFrameForNode:(ASDisplayNode *)node;
+
+- (NSArray<ASLayout *> *)sublayoutsForTransitioningContext:(_ASTransitionContext *)context;
+
+@end
+
+@interface _ASTransitionContext : NSObject <ASContextTransitioning>
+
+@property (assign, readonly, nonatomic, getter=isAnimated) BOOL animated;
+
+- (instancetype)initWithAnimation:(BOOL)animated delegate:(id<_ASTransitionContextDelegate>)delegate;
+
+@end

AsyncDisplayKit/_ASTransitionContext.m

@@ -0,0 +1,49 @@
+//
+//  _ASTransitionContext.m
+//  AsyncDisplayKit
+//
+//  Created by Levi McCallum on 2/4/16.
+//  Copyright © 2016 Facebook. All rights reserved.
+//
+
+#import "_ASTransitionContext.h"
+
+@interface _ASTransitionContext ()
+
+@property (weak, nonatomic) id<_ASTransitionContextDelegate> delegate;
+
+@end
+
+@implementation _ASTransitionContext
+
+- (instancetype)initWithAnimation:(BOOL)animated delegate:(id<_ASTransitionContextDelegate>)delegate
+{
+  self = [super init];
+  if (self) {
+    _animated = animated;
+    _delegate = delegate;
+  }
+  return self;
+}
+
+- (CGRect)initialFrameForNode:(ASDisplayNode *)node
+{
+  return [_delegate transitionContext:self initialFrameForNode:node];
+}
+
+- (CGRect)finalFrameForNode:(ASDisplayNode *)node
+{
+  return [_delegate transitionContext:self finalFrameForNode:node];
+}
+
+- (NSArray<ASLayout *> *)sublayouts
+{
+  return [_delegate sublayoutsForTransitioningContext:self];
+}
+
+- (void)completeTransition:(BOOL)didComplete
+{
+  [_delegate transitionContext:self didComplete:didComplete];
+}
+
+@end