Clean up #468:

- -layoutSpecThatFits: must return an ASLayoutSpec.
- Move ASDisplayNode's -measureWithSizeRange: redeclaration to ASDisplayNode.h.
- Rename ASStackLayoutChild.h to ASStackLayoutDefines.h.
- Rename ASStaticLayoutSpecDimension.h to ASRelativeSize.h.
- Don't import ASLayout.h in other headers to prevent circular inclusions.
- Explain use cases of ASLayout's initializers.
- Clean up ASInternalHelpers.h.

AsyncDisplayKit.xcodeproj/project.pbxproj

@@ -187,13 +187,13 @@
 		509E68661B3AEDD7009B9150 /* CGRect+ASConvenience.m in Sources */ = {isa = PBXBuildFile; fileRef = 205F0E201B376416007741D0 /* CGRect+ASConvenience.m */; };
 		6BDC61F61979037800E50D21 /* AsyncDisplayKit.h in Headers */ = {isa = PBXBuildFile; fileRef = 6BDC61F51978FEA400E50D21 /* AsyncDisplayKit.h */; settings = {ATTRIBUTES = (Public, ); }; };
 		9F06E5CD1B4CAF4200F015D8 /* ASCollectionViewTests.m in Sources */ = {isa = PBXBuildFile; fileRef = 9F06E5CC1B4CAF4200F015D8 /* ASCollectionViewTests.m */; };
-		AC21EC101B3D0BF600C8B19A /* ASStackLayoutChild.h in Headers */ = {isa = PBXBuildFile; fileRef = AC21EC0F1B3D0BF600C8B19A /* ASStackLayoutChild.h */; settings = {ATTRIBUTES = (Public, ); }; };
+		AC21EC101B3D0BF600C8B19A /* ASStackLayoutDefines.h in Headers */ = {isa = PBXBuildFile; fileRef = AC21EC0F1B3D0BF600C8B19A /* ASStackLayoutDefines.h */; settings = {ATTRIBUTES = (Public, ); }; };
 		AC3C4A511A1139C100143C57 /* ASCollectionView.h in Headers */ = {isa = PBXBuildFile; fileRef = AC3C4A4F1A1139C100143C57 /* ASCollectionView.h */; settings = {ATTRIBUTES = (Public, ); }; };
 		AC3C4A521A1139C100143C57 /* ASCollectionView.mm in Sources */ = {isa = PBXBuildFile; fileRef = AC3C4A501A1139C100143C57 /* ASCollectionView.mm */; };
 		AC3C4A541A113EEC00143C57 /* ASCollectionViewProtocols.h in Headers */ = {isa = PBXBuildFile; fileRef = AC3C4A531A113EEC00143C57 /* ASCollectionViewProtocols.h */; settings = {ATTRIBUTES = (Public, ); }; };
 		AC47D9421B3B891B00AAEE9D /* ASCellNode.m in Sources */ = {isa = PBXBuildFile; fileRef = AC6456071B0A335000CF11B8 /* ASCellNode.m */; };
-		AC47D9451B3BB41900AAEE9D /* ASStaticLayoutSpecDimension.h in Headers */ = {isa = PBXBuildFile; fileRef = AC47D9431B3BB41900AAEE9D /* ASStaticLayoutSpecDimension.h */; settings = {ATTRIBUTES = (Public, ); }; };
+		AC47D9451B3BB41900AAEE9D /* ASRelativeSize.h in Headers */ = {isa = PBXBuildFile; fileRef = AC47D9431B3BB41900AAEE9D /* ASRelativeSize.h */; settings = {ATTRIBUTES = (Public, ); }; };
-		AC47D9461B3BB41900AAEE9D /* ASStaticLayoutSpecDimension.mm in Sources */ = {isa = PBXBuildFile; fileRef = AC47D9441B3BB41900AAEE9D /* ASStaticLayoutSpecDimension.mm */; };
+		AC47D9461B3BB41900AAEE9D /* ASRelativeSize.mm in Sources */ = {isa = PBXBuildFile; fileRef = AC47D9441B3BB41900AAEE9D /* ASRelativeSize.mm */; };
 		AC6456091B0A335000CF11B8 /* ASCellNode.m in Sources */ = {isa = PBXBuildFile; fileRef = AC6456071B0A335000CF11B8 /* ASCellNode.m */; };
 		ACF6ED1A1B17843500DA7C62 /* ASBackgroundLayoutSpec.h in Headers */ = {isa = PBXBuildFile; fileRef = ACF6ED011B17843500DA7C62 /* ASBackgroundLayoutSpec.h */; settings = {ATTRIBUTES = (Public, ); }; };
 		ACF6ED1B1B17843500DA7C62 /* ASBackgroundLayoutSpec.mm in Sources */ = {isa = PBXBuildFile; fileRef = ACF6ED021B17843500DA7C62 /* ASBackgroundLayoutSpec.mm */; };
@@ -526,12 +526,12 @@
 		4640521F1A3F83C40061C0BA /* ASMultidimensionalArrayUtils.mm */ = {isa = PBXFileReference; fileEncoding = 4; lastKnownFileType = sourcecode.cpp.objcpp; path = ASMultidimensionalArrayUtils.mm; sourceTree = "<group>"; };
 		6BDC61F51978FEA400E50D21 /* AsyncDisplayKit.h */ = {isa = PBXFileReference; lastKnownFileType = sourcecode.c.h; path = AsyncDisplayKit.h; sourceTree = "<group>"; };
 		9F06E5CC1B4CAF4200F015D8 /* ASCollectionViewTests.m */ = {isa = PBXFileReference; fileEncoding = 4; lastKnownFileType = sourcecode.c.objc; path = ASCollectionViewTests.m; sourceTree = "<group>"; };
-		AC21EC0F1B3D0BF600C8B19A /* ASStackLayoutChild.h */ = {isa = PBXFileReference; fileEncoding = 4; lastKnownFileType = sourcecode.c.h; name = ASStackLayoutChild.h; path = AsyncDisplayKit/Layout/ASStackLayoutChild.h; sourceTree = "<group>"; };
+		AC21EC0F1B3D0BF600C8B19A /* ASStackLayoutDefines.h */ = {isa = PBXFileReference; fileEncoding = 4; lastKnownFileType = sourcecode.c.h; name = ASStackLayoutDefines.h; path = AsyncDisplayKit/Layout/ASStackLayoutDefines.h; sourceTree = "<group>"; };
 		AC3C4A4F1A1139C100143C57 /* ASCollectionView.h */ = {isa = PBXFileReference; fileEncoding = 4; lastKnownFileType = sourcecode.c.h; path = ASCollectionView.h; sourceTree = "<group>"; };
 		AC3C4A501A1139C100143C57 /* ASCollectionView.mm */ = {isa = PBXFileReference; fileEncoding = 4; lastKnownFileType = sourcecode.cpp.objcpp; path = ASCollectionView.mm; sourceTree = "<group>"; };
 		AC3C4A531A113EEC00143C57 /* ASCollectionViewProtocols.h */ = {isa = PBXFileReference; fileEncoding = 4; lastKnownFileType = sourcecode.c.h; path = ASCollectionViewProtocols.h; sourceTree = "<group>"; };
-		AC47D9431B3BB41900AAEE9D /* ASStaticLayoutSpecDimension.h */ = {isa = PBXFileReference; fileEncoding = 4; lastKnownFileType = sourcecode.c.h; name = ASStaticLayoutSpecDimension.h; path = AsyncDisplayKit/Layout/ASStaticLayoutSpecDimension.h; sourceTree = "<group>"; };
+		AC47D9431B3BB41900AAEE9D /* ASRelativeSize.h */ = {isa = PBXFileReference; fileEncoding = 4; lastKnownFileType = sourcecode.c.h; name = ASRelativeSize.h; path = AsyncDisplayKit/Layout/ASRelativeSize.h; sourceTree = "<group>"; };
-		AC47D9441B3BB41900AAEE9D /* ASStaticLayoutSpecDimension.mm */ = {isa = PBXFileReference; fileEncoding = 4; lastKnownFileType = sourcecode.cpp.objcpp; name = ASStaticLayoutSpecDimension.mm; path = AsyncDisplayKit/Layout/ASStaticLayoutSpecDimension.mm; sourceTree = "<group>"; };
+		AC47D9441B3BB41900AAEE9D /* ASRelativeSize.mm */ = {isa = PBXFileReference; fileEncoding = 4; lastKnownFileType = sourcecode.cpp.objcpp; name = ASRelativeSize.mm; path = AsyncDisplayKit/Layout/ASRelativeSize.mm; sourceTree = "<group>"; };
 		AC6456071B0A335000CF11B8 /* ASCellNode.m */ = {isa = PBXFileReference; fileEncoding = 4; lastKnownFileType = sourcecode.c.objc; path = ASCellNode.m; sourceTree = "<group>"; };
 		ACF6ED011B17843500DA7C62 /* ASBackgroundLayoutSpec.h */ = {isa = PBXFileReference; fileEncoding = 4; lastKnownFileType = sourcecode.c.h; name = ASBackgroundLayoutSpec.h; path = AsyncDisplayKit/Layout/ASBackgroundLayoutSpec.h; sourceTree = "<group>"; };
 		ACF6ED021B17843500DA7C62 /* ASBackgroundLayoutSpec.mm */ = {isa = PBXFileReference; fileEncoding = 4; lastKnownFileType = sourcecode.cpp.objcpp; lineEnding = 0; name = ASBackgroundLayoutSpec.mm; path = AsyncDisplayKit/Layout/ASBackgroundLayoutSpec.mm; sourceTree = "<group>"; };
@@ -914,6 +914,8 @@
 				ACF6ED041B17843500DA7C62 /* ASCenterLayoutSpec.mm */,
 				ACF6ED071B17843500DA7C62 /* ASDimension.h */,
 				ACF6ED081B17843500DA7C62 /* ASDimension.mm */,
+				AC47D9431B3BB41900AAEE9D /* ASRelativeSize.h */,
+				AC47D9441B3BB41900AAEE9D /* ASRelativeSize.mm */,
 				ACF6ED091B17843500DA7C62 /* ASInsetLayoutSpec.h */,
 				ACF6ED0A1B17843500DA7C62 /* ASInsetLayoutSpec.mm */,
 				ACF6ED0B1B17843500DA7C62 /* ASLayout.h */,
@@ -925,13 +927,11 @@
 				ACF6ED131B17843500DA7C62 /* ASOverlayLayoutSpec.mm */,
 				ACF6ED141B17843500DA7C62 /* ASRatioLayoutSpec.h */,
 				ACF6ED151B17843500DA7C62 /* ASRatioLayoutSpec.mm */,
-				AC21EC0F1B3D0BF600C8B19A /* ASStackLayoutChild.h */,
+				AC21EC0F1B3D0BF600C8B19A /* ASStackLayoutDefines.h */,
 				ACF6ED161B17843500DA7C62 /* ASStackLayoutSpec.h */,
 				ACF6ED171B17843500DA7C62 /* ASStackLayoutSpec.mm */,
 				ACF6ED181B17843500DA7C62 /* ASStaticLayoutSpec.h */,
 				ACF6ED191B17843500DA7C62 /* ASStaticLayoutSpec.mm */,
-				AC47D9431B3BB41900AAEE9D /* ASStaticLayoutSpecDimension.h */,
-				AC47D9441B3BB41900AAEE9D /* ASStaticLayoutSpecDimension.mm */,
 			);
 			name = Layout;
 			path = ..;
@@ -971,8 +971,8 @@
 			isa = PBXHeadersBuildPhase;
 			buildActionMask = 2147483647;
 			files = (
-				AC21EC101B3D0BF600C8B19A /* ASStackLayoutChild.h in Headers */,
+				AC21EC101B3D0BF600C8B19A /* ASStackLayoutDefines.h in Headers */,
-				AC47D9451B3BB41900AAEE9D /* ASStaticLayoutSpecDimension.h in Headers */,
+				AC47D9451B3BB41900AAEE9D /* ASRelativeSize.h in Headers */,
 				ACF6ED511B17847A00DA7C62 /* ASStackUnpositionedLayout.h in Headers */,
 				ACF6ED2D1B17843500DA7C62 /* ASRatioLayoutSpec.h in Headers */,
 				ACF6ED261B17843500DA7C62 /* ASLayoutSpec.h in Headers */,
@@ -1374,7 +1374,7 @@
 				ACF6ED1B1B17843500DA7C62 /* ASBackgroundLayoutSpec.mm in Sources */,
 				055F1A3519ABD3E3004DAFF1 /* ASTableView.mm in Sources */,
 				205F0E121B371BD7007741D0 /* ASScrollDirection.m in Sources */,
-				AC47D9461B3BB41900AAEE9D /* ASStaticLayoutSpecDimension.mm in Sources */,
+				AC47D9461B3BB41900AAEE9D /* ASRelativeSize.mm in Sources */,
 				ACF6ED271B17843500DA7C62 /* ASLayoutSpec.mm in Sources */,
 				ACF6ED211B17843500DA7C62 /* ASDimension.mm in Sources */,
 				464052261A3F83C40061C0BA /* ASMultidimensionalArrayUtils.mm in Sources */,

AsyncDisplayKit/ASCellNode.m

@@ -106,7 +106,7 @@ static const CGFloat kFontSize = 18.0f;
   return self;
 }
 
-- (id<ASLayoutable>)layoutSpecThatFits:(ASSizeRange)constrainedSize
+- (ASLayoutSpec *)layoutSpecThatFits:(ASSizeRange)constrainedSize
 {
   static const CGFloat kHorizontalPadding = 15.0f;
   static const CGFloat kVerticalPadding = 11.0f;

AsyncDisplayKit/ASDisplayNode+Subclasses.h

@@ -13,8 +13,7 @@
 #import <AsyncDisplayKit/ASDisplayNode.h>
 #import <AsyncDisplayKit/ASThread.h>
 
-#import <AsyncDisplayKit/ASLayout.h>
+@class ASLayoutSpec;
-#import <AsyncDisplayKit/ASLayoutable.h>
 
 /**
  * The subclass header _ASDisplayNode+Subclasses_ defines the following methods that either must or can be overriden by
@@ -36,7 +35,7 @@
  * variables.
  */
 
-@interface ASDisplayNode (Subclassing) <ASLayoutable>
+@interface ASDisplayNode (Subclassing)
 
 
 /** @name View Configuration */
@@ -120,23 +119,6 @@
 
 /** @name Layout calculation */
 
-/**
- * @abstract Asks the node to measure a layout based on given size range.
- *
- * @param constrainedSize The minimum and maximum sizes the receiver should fit in.
- *
- * @return An ASLayout instance defining the layout of the receiver (and its children, if the box layout model is used).
- *
- * @discussion Though this method does not set the bounds of the view, it does have side effects--caching both the
- * constraint and the result.
- *
- * @warning Subclasses must not override this; it caches results from -calculateLayoutThatFits:.  Calling this method may
- * be expensive if result is not cached.
- *
- * @see [ASDisplayNode(Subclassing) calculateLayoutThatFits:]
- */
-- (ASLayout *)measureWithSizeRange:(ASSizeRange)constrainedSize;
-
 /**
  * @abstract Calculate a layout based on given size range.
  *
@@ -180,7 +162,7 @@
  *
  * @note This method should not be called directly outside of ASDisplayNode; use -measure: or -calculatedLayout instead.
  */
-- (id<ASLayoutable>)layoutSpecThatFits:(ASSizeRange)constrainedSize;
+- (ASLayoutSpec *)layoutSpecThatFits:(ASSizeRange)constrainedSize;
 
 /**
  * @abstract Invalidate previously measured and cached layout.

AsyncDisplayKit/ASDisplayNode.h

@@ -13,6 +13,8 @@
 #import <AsyncDisplayKit/ASDealloc2MainObject.h>
 #import <AsyncDisplayKit/ASDimension.h>
 
+#import <AsyncDisplayKit/ASLayoutable.h>
+
 typedef UIView *(^ASDisplayNodeViewBlock)();
 typedef CALayer *(^ASDisplayNodeLayerBlock)();
 
@@ -32,7 +34,7 @@ typedef CALayer *(^ASDisplayNodeLayerBlock)();
  *
  */
 
-@interface ASDisplayNode : ASDealloc2MainObject
+@interface ASDisplayNode : ASDealloc2MainObject <ASLayoutable>
 
 
 /** @name Initializing a node object */
@@ -137,6 +139,23 @@ typedef CALayer *(^ASDisplayNodeLayerBlock)();
  */
 - (CGSize)measure:(CGSize)constrainedSize;
 
+/**
+ * @abstract Asks the node to measure a layout based on given size range.
+ *
+ * @param constrainedSize The minimum and maximum sizes the receiver should fit in.
+ *
+ * @return An ASLayout instance defining the layout of the receiver (and its children, if the box layout model is used).
+ *
+ * @discussion Though this method does not set the bounds of the view, it does have side effects--caching both the
+ * constraint and the result.
+ *
+ * @warning Subclasses must not override this; it caches results from -calculateLayoutThatFits:.  Calling this method may
+ * be expensive if result is not cached.
+ *
+ * @see [ASDisplayNode(Subclassing) calculateLayoutThatFits:]
+ */
+- (ASLayout *)measureWithSizeRange:(ASSizeRange)constrainedSize;
+
 /** 
  * @abstract Return the calculated size.
  *

AsyncDisplayKit/ASDisplayNode.mm

@@ -19,6 +19,8 @@
 #import "ASDisplayNodeExtras.h"
 
 #import "ASInternalHelpers.h"
+#import "ASLayout.h"
+#import "ASLayoutSpec.h"
 
 @interface ASDisplayNode () <UIGestureRecognizerDelegate>
 
@@ -1307,10 +1309,10 @@ static NSInteger incrementIfFound(NSInteger i) {
   return CGSizeZero;
 }
 
-- (id<ASLayoutable>)layoutSpecThatFits:(ASSizeRange)constrainedSize
+- (ASLayoutSpec *)layoutSpecThatFits:(ASSizeRange)constrainedSize
 {
   ASDisplayNodeAssertThreadAffinity(self);
-  return nil;
+  return [ASLayoutSpec new];
 }
 
 - (ASLayout *)calculatedLayout

AsyncDisplayKit/AsyncDisplayKit.h

@@ -35,5 +35,5 @@
 #import <AsyncDisplayKit/ASOverlayLayoutSpec.h>
 #import <AsyncDisplayKit/ASRatioLayoutSpec.h>
 #import <AsyncDisplayKit/ASStaticLayoutSpec.h>
-#import <AsyncDisplayKit/ASStackLayoutChild.h>
+#import <AsyncDisplayKit/ASStackLayoutDefines.h>
 #import <AsyncDisplayKit/ASStackLayoutSpec.h>

AsyncDisplayKit/Layout/ASBackgroundLayoutSpec.mm

@@ -12,6 +12,7 @@
 
 #import "ASAssert.h"
 #import "ASBaseDefines.h"
+#import "ASLayout.h"
 
 @interface ASBackgroundLayoutSpec ()
 {

AsyncDisplayKit/Layout/ASCenterLayoutSpec.mm

@@ -11,6 +11,7 @@
 #import "ASCenterLayoutSpec.h"
 
 #import "ASInternalHelpers.h"
+#import "ASLayout.h"
 
 @implementation ASCenterLayoutSpec
 {

AsyncDisplayKit/Layout/ASInsetLayoutSpec.mm

@@ -14,6 +14,7 @@
 #import "ASBaseDefines.h"
 
 #import "ASInternalHelpers.h"
+#import "ASLayout.h"
 
 @interface ASInsetLayoutSpec ()
 {

AsyncDisplayKit/Layout/ASLayout.h

@@ -39,6 +39,9 @@ extern BOOL CGPointIsNull(CGPoint point);
 
 /**
  * Convenience that has CGPointNull position. 
+ * Best used by ASDisplayNode subclasses that are manually creating a layout for -calculateLayoutThatFits:,
+ * or for ASLayoutSpec subclasses that are referencing the "self" level in the layout tree,
+ * or for creating a sublayout of which the position is yet to be determined.
  */
 + (instancetype)newWithLayoutableObject:(id<ASLayoutable>)layoutableObject
                                    size:(CGSize)size
@@ -46,6 +49,8 @@ extern BOOL CGPointIsNull(CGPoint point);
 
 /**
  * Convenience that has CGPointNull position and no sublayouts. 
+ * Best used for creating a layout that has no sublayouts, and is either a root one
+ * or a sublayout of which the position is yet to be determined.
  */
 + (instancetype)newWithLayoutableObject:(id<ASLayoutable>)layoutableObject size:(CGSize)size;
 

AsyncDisplayKit/Layout/ASLayoutSpec.h

@@ -9,7 +9,6 @@
  */
 
 #import <AsyncDisplayKit/ASLayoutable.h>
-#import <AsyncDisplayKit/ASLayout.h>
 
 /** A layout spec is an immutable object that describes a layout, loosely inspired by React. */
 @interface ASLayoutSpec : NSObject <ASLayoutable>

AsyncDisplayKit/Layout/ASLayoutable.h

@@ -9,7 +9,7 @@
  */
 
 #import <AsyncDisplayKit/ASDimension.h>
-#import <AsyncDisplayKit/ASStackLayoutChild.h>
+#import <AsyncDisplayKit/ASStackLayoutDefines.h>
 
 @class ASLayout;
 

AsyncDisplayKit/Layout/ASOverlayLayoutSpec.mm

@@ -12,6 +12,7 @@
 
 #import "ASAssert.h"
 #import "ASBaseDefines.h"
+#import "ASLayout.h"
 
 @implementation ASOverlayLayoutSpec
 {

AsyncDisplayKit/Layout/ASRatioLayoutSpec.mm

@@ -17,6 +17,7 @@
 #import "ASBaseDefines.h"
 
 #import "ASInternalHelpers.h"
+#import "ASLayout.h"
 
 @implementation ASRatioLayoutSpec
 {

AsyncDisplayKit/Layout/ASRelativeSize.mm

@@ -8,7 +8,7 @@
  *
  */
 
-#import "ASStaticLayoutSpecDimension.h"
+#import "ASRelativeSize.h"
 #import "ASAssert.h"
 
 ASRelativeSizeRange const ASRelativeSizeRangeUnconstrained = {};

AsyncDisplayKit/Layout/ASStaticLayoutSpec.h

@@ -9,7 +9,7 @@
  */
 
 #import <AsyncDisplayKit/ASLayoutSpec.h>
-#import <AsyncDisplayKit/ASStaticLayoutSpecDimension.h>
+#import <AsyncDisplayKit/ASRelativeSize.h>
 
 @interface ASStaticLayoutSpecChild : NSObject
 

AsyncDisplayKit/Layout/ASStaticLayoutSpec.mm

@@ -12,6 +12,7 @@
 
 #import "ASLayoutSpecUtilities.h"
 #import "ASInternalHelpers.h"
+#import "ASLayout.h"
 
 @implementation ASStaticLayoutSpecChild
 

AsyncDisplayKit/Private/ASDisplayNodeInternal.h

@@ -17,7 +17,6 @@
 #import "ASDisplayNode.h"
 #import "ASSentinel.h"
 #import "ASThread.h"
-#import "ASLayout.h"
 
 BOOL ASDisplayNodeSubclassOverridesSelector(Class subclass, SEL selector);
 void ASDisplayNodePerformBlockOnMainThread(void (^block)());

AsyncDisplayKit/Private/ASInternalHelpers.h

@@ -8,11 +8,9 @@
  *
  */
 
-#import <UIKit/UIKit.h>
+#include <CoreGraphics/CGBase.h>
 #import "ASBaseDefines.h"
 
-@class ASLayoutChild;
-
 ASDISPLAYNODE_EXTERN_C_BEGIN
 
 BOOL ASSubclassOverridesSelector(Class superclass, Class subclass, SEL selector);

AsyncDisplayKitTests/ASLayoutSpecSnapshotTestsHelper.m

@@ -12,6 +12,7 @@
 
 #import "ASDisplayNode.h"
 #import "ASLayoutSpec.h"
+#import "ASLayout.h"
 
 @interface ASTestNode : ASDisplayNode
 - (void)setLayoutSpecUnderTest:(ASLayoutSpec *)layoutSpecUnderTest sizeRange:(ASSizeRange)sizeRange;