[ASRelativeLayoutSpec] New core layout spec type: Relative Position, now powers Center as well.

This spec allows positioning a child at any 9-part box position (corners, edges, or center).

AsyncDisplayKit.xcodeproj/project.pbxproj

@@ -268,6 +268,11 @@
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 		81EE38501C8E94F000456208 /* ASRunLoopQueue.mm in Sources */ = {isa = PBXBuildFile; fileRef = 81EE384E1C8E94F000456208 /* ASRunLoopQueue.mm */; };
+		7A06A73A1C35F08800FE8DAA /* ASRelativeLayoutSpec.mm in Sources */ = {isa = PBXBuildFile; fileRef = 7A06A7381C35F08800FE8DAA /* ASRelativeLayoutSpec.mm */; };
+		7A06A73B1C35F08800FE8DAA /* ASRelativeLayoutSpec.h in Headers */ = {isa = PBXBuildFile; fileRef = 7A06A7391C35F08800FE8DAA /* ASRelativeLayoutSpec.h */; settings = {ATTRIBUTES = (Public, ); }; };
+		7AB338661C55B3420055FDE8 /* ASRelativeLayoutSpec.mm in Sources */ = {isa = PBXBuildFile; fileRef = 7A06A7381C35F08800FE8DAA /* ASRelativeLayoutSpec.mm */; };
+		7AB338671C55B3460055FDE8 /* ASRelativeLayoutSpec.h in Headers */ = {isa = PBXBuildFile; fileRef = 7A06A7391C35F08800FE8DAA /* ASRelativeLayoutSpec.h */; settings = {ATTRIBUTES = (Public, ); }; };
+		7AB338691C55B97B0055FDE8 /* ASRelativeLayoutSpecSnapshotTests.mm in Sources */ = {isa = PBXBuildFile; fileRef = 7AB338681C55B97B0055FDE8 /* ASRelativeLayoutSpecSnapshotTests.mm */; };
 		92DD2FE31BF4B97E0074C9DD /* ASMapNode.h in Headers */ = {isa = PBXBuildFile; fileRef = 92DD2FE11BF4B97E0074C9DD /* ASMapNode.h */; settings = {ATTRIBUTES = (Public, ); }; };
 		92DD2FE41BF4B97E0074C9DD /* ASMapNode.mm in Sources */ = {isa = PBXBuildFile; fileRef = 92DD2FE21BF4B97E0074C9DD /* ASMapNode.mm */; };
 		92DD2FE61BF4D05E0074C9DD /* MapKit.framework in Frameworks */ = {isa = PBXBuildFile; fileRef = 92DD2FE51BF4D05E0074C9DD /* MapKit.framework */; };
@@ -739,6 +744,9 @@
 		764D83D31C8EA515009B4FB8 /* AsyncDisplayKit+Debug.m */ = {isa = PBXFileReference; fileEncoding = 4; lastKnownFileType = sourcecode.c.objc; path = "AsyncDisplayKit+Debug.m"; sourceTree = "<group>"; };
 		81EE384D1C8E94F000456208 /* ASRunLoopQueue.h */ = {isa = PBXFileReference; fileEncoding = 4; lastKnownFileType = sourcecode.c.h; name = ASRunLoopQueue.h; path = ../ASRunLoopQueue.h; sourceTree = "<group>"; };
 		81EE384E1C8E94F000456208 /* ASRunLoopQueue.mm */ = {isa = PBXFileReference; fileEncoding = 4; lastKnownFileType = sourcecode.cpp.objcpp; name = ASRunLoopQueue.mm; path = ../ASRunLoopQueue.mm; sourceTree = "<group>"; };
+		7A06A7381C35F08800FE8DAA /* ASRelativeLayoutSpec.mm */ = {isa = PBXFileReference; fileEncoding = 4; lastKnownFileType = sourcecode.cpp.objcpp; name = ASRelativeLayoutSpec.mm; path = AsyncDisplayKit/Layout/ASRelativeLayoutSpec.mm; sourceTree = "<group>"; };
+		7A06A7391C35F08800FE8DAA /* ASRelativeLayoutSpec.h */ = {isa = PBXFileReference; fileEncoding = 4; lastKnownFileType = sourcecode.c.h; name = ASRelativeLayoutSpec.h; path = AsyncDisplayKit/Layout/ASRelativeLayoutSpec.h; sourceTree = "<group>"; };
+		7AB338681C55B97B0055FDE8 /* ASRelativeLayoutSpecSnapshotTests.mm */ = {isa = PBXFileReference; fileEncoding = 4; lastKnownFileType = sourcecode.cpp.objcpp; path = ASRelativeLayoutSpecSnapshotTests.mm; sourceTree = "<group>"; };
 		92DD2FE11BF4B97E0074C9DD /* ASMapNode.h */ = {isa = PBXFileReference; fileEncoding = 4; lastKnownFileType = sourcecode.c.h; path = ASMapNode.h; sourceTree = "<group>"; };
 		92DD2FE21BF4B97E0074C9DD /* ASMapNode.mm */ = {isa = PBXFileReference; fileEncoding = 4; lastKnownFileType = sourcecode.cpp.objcpp; path = ASMapNode.mm; sourceTree = "<group>"; };
 		92DD2FE51BF4D05E0074C9DD /* MapKit.framework */ = {isa = PBXFileReference; lastKnownFileType = wrapper.framework; name = MapKit.framework; path = System/Library/Frameworks/MapKit.framework; sourceTree = SDKROOT; };
@@ -1057,6 +1065,7 @@
 				05EA6FE61AC0966E00E35788 /* ASSnapshotTestCase.mm */,
 				056D21541ABCEF50001107EF /* ASImageNodeSnapshotTests.m */,
 				ACF6ED531B178DC700DA7C62 /* ASCenterLayoutSpecSnapshotTests.mm */,
+				7AB338681C55B97B0055FDE8 /* ASRelativeLayoutSpecSnapshotTests.mm */,
 				ACF6ED551B178DC700DA7C62 /* ASInsetLayoutSpecSnapshotTests.mm */,
 				ACF6ED591B178DC700DA7C62 /* ASOverlayLayoutSpecSnapshotTests.mm */,
 				ACF6ED5A1B178DC700DA7C62 /* ASRatioLayoutSpecSnapshotTests.mm */,
@@ -1316,6 +1325,8 @@
 				ACF6ED131B17843500DA7C62 /* ASOverlayLayoutSpec.mm */,
 				ACF6ED141B17843500DA7C62 /* ASRatioLayoutSpec.h */,
 				ACF6ED151B17843500DA7C62 /* ASRatioLayoutSpec.mm */,
+				7A06A7391C35F08800FE8DAA /* ASRelativeLayoutSpec.h */,
+				7A06A7381C35F08800FE8DAA /* ASRelativeLayoutSpec.mm */,
 				9C49C36E1B853957000B0DD5 /* ASStackLayoutable.h */,
 				AC21EC0F1B3D0BF600C8B19A /* ASStackLayoutDefines.h */,
 				ACF6ED161B17843500DA7C62 /* ASStackLayoutSpec.h */,
@@ -1377,6 +1388,7 @@
 				058D0A6B195D05EC00B7D73C /* _ASAsyncTransactionContainer.h in Headers */,
 				058D0A6D195D05EC00B7D73C /* _ASAsyncTransactionGroup.h in Headers */,
 				058D0A72195D05F800B7D73C /* _ASCoreAnimationExtras.h in Headers */,
+				7A06A73B1C35F08800FE8DAA /* ASRelativeLayoutSpec.h in Headers */,
 				058D0A53195D05DC00B7D73C /* _ASDisplayLayer.h in Headers */,
 				058D0A55195D05DC00B7D73C /* _ASDisplayView.h in Headers */,
 				B13CA0F71C519E9400E031AB /* ASCollectionViewLayoutFacilitatorProtocol.h in Headers */,
@@ -1570,6 +1582,7 @@
 				AC7A2C181BDE11DF0093FE1A /* ASTableViewInternal.h in Headers */,
 				B35062531B010EFD0018CF92 /* ASImageNode+CGExtras.h in Headers */,
 				254C6B7F1BF94DF4003EC431 /* ASTextKitTruncating.h in Headers */,
+				7AB338671C55B3460055FDE8 /* ASRelativeLayoutSpec.h in Headers */,
 				B35062021B010EFD0018CF92 /* ASImageNode.h in Headers */,
 				B350621F1B010EFD0018CF92 /* ASImageProtocols.h in Headers */,
 				430E7C901B4C23F100697A4C /* ASIndexPath.h in Headers */,
@@ -1912,6 +1925,7 @@
 				CC3B20851C3F76D600798563 /* ASPendingStateController.mm in Sources */,
 				ACF6ED2C1B17843500DA7C62 /* ASOverlayLayoutSpec.mm in Sources */,
 				0442850F1BAA64EC00D16268 /* ASMultidimensionalArrayUtils.mm in Sources */,
+				7A06A73A1C35F08800FE8DAA /* ASRelativeLayoutSpec.mm in Sources */,
 				257754921BED28F300737CA5 /* ASEqualityHashHelpers.mm in Sources */,
 				E52405B31C8FEF03004DC8E7 /* ASDisplayNodeLayoutContext.mm in Sources */,
 				257754AB1BEE44CD00737CA5 /* ASTextKitEntityAttribute.m in Sources */,
@@ -1975,6 +1989,7 @@
 				058D0A3C195D057000B7D73C /* ASMutableAttributedStringBuilderTests.m in Sources */,
 				ACF6ED611B178DC700DA7C62 /* ASOverlayLayoutSpecSnapshotTests.mm in Sources */,
 				ACF6ED621B178DC700DA7C62 /* ASRatioLayoutSpecSnapshotTests.mm in Sources */,
+				7AB338691C55B97B0055FDE8 /* ASRelativeLayoutSpecSnapshotTests.mm in Sources */,
 				254C6B541BF8FF2A003EC431 /* ASTextKitTests.mm in Sources */,
 				05EA6FE71AC0966E00E35788 /* ASSnapshotTestCase.mm in Sources */,
 				ACF6ED631B178DC700DA7C62 /* ASStackLayoutSpecSnapshotTests.mm in Sources */,
@@ -2075,6 +2090,8 @@
 				9C8221981BA237B80037F19A /* ASStackBaselinePositionedLayout.mm in Sources */,
 				34EFC7721B701D0300AD841F /* ASStackLayoutSpec.mm in Sources */,
 				34EFC7761B701D2A00AD841F /* ASStackPositionedLayout.mm in Sources */,
+				DECC2ED01C35C1C600388446 /* ASRangeControllerBeta.mm in Sources */,
+				7AB338661C55B3420055FDE8 /* ASRelativeLayoutSpec.mm in Sources */,
 				34EFC7781B701D3100AD841F /* ASStackUnpositionedLayout.mm in Sources */,
 				DE84918E1C8FFF9F003D89E9 /* ASRunLoopQueue.mm in Sources */,
 				AC026B6C1BD57D6F00BBC17E /* ASChangeSetDataController.m in Sources */,

AsyncDisplayKit/AsyncDisplayKit.h

@@ -45,6 +45,7 @@
 #import <AsyncDisplayKit/ASLayoutSpec.h>
 #import <AsyncDisplayKit/ASBackgroundLayoutSpec.h>
 #import <AsyncDisplayKit/ASCenterLayoutSpec.h>
+#import <AsyncDisplayKit/ASRelativeLayoutSpec.h>
 #import <AsyncDisplayKit/ASInsetLayoutSpec.h>
 #import <AsyncDisplayKit/ASOverlayLayoutSpec.h>
 #import <AsyncDisplayKit/ASRatioLayoutSpec.h>

AsyncDisplayKit/Layout/ASCenterLayoutSpec.h

@@ -8,7 +8,7 @@
  *
  */
 
-#import <AsyncDisplayKit/ASLayoutSpec.h>
+#import <AsyncDisplayKit/ASRelativeLayoutSpec.h>
 
 /** How the child is centered within the spec. */
 typedef NS_OPTIONS(NSUInteger, ASCenterLayoutSpecCenteringOptions) {
@@ -25,19 +25,22 @@ typedef NS_OPTIONS(NSUInteger, ASCenterLayoutSpecCenteringOptions) {
 /** How much space the spec will take up. */
 typedef NS_OPTIONS(NSUInteger, ASCenterLayoutSpecSizingOptions) {
   /** The spec will take up the maximum size possible */
-  ASCenterLayoutSpecSizingOptionDefault,
+  ASCenterLayoutSpecSizingOptionDefault = ASRelativeLayoutSpecSizingOptionDefault,
   /** The spec will take up the minimum size possible along the X axis */
-  ASCenterLayoutSpecSizingOptionMinimumX = 1 << 0,
+  ASCenterLayoutSpecSizingOptionMinimumX = ASRelativeLayoutSpecSizingOptionMinimumWidth,
   /** The spec will take up the minimum size possible along the Y axis */
-  ASCenterLayoutSpecSizingOptionMinimumY = 1 << 1,
+  ASCenterLayoutSpecSizingOptionMinimumY = ASRelativeLayoutSpecSizingOptionMinimumHeight,
   /** Convenience option to take up the minimum size along both the X and Y axis */
-  ASCenterLayoutSpecSizingOptionMinimumXY = ASCenterLayoutSpecSizingOptionMinimumX | ASCenterLayoutSpecSizingOptionMinimumY,
+  ASCenterLayoutSpecSizingOptionMinimumXY = ASRelativeLayoutSpecSizingOptionMinimumSize
 };
 
 NS_ASSUME_NONNULL_BEGIN
 
-/** Lays out a single layoutable child and position it so that it is centered into the layout bounds. */
-@interface ASCenterLayoutSpec : ASLayoutSpec
+/** Lays out a single layoutable child and position it so that it is centered into the layout bounds.
+  * NOTE: ASRelativeLayoutSpec offers all of the capabilities of Center, and more.
+  * Check it out if you would like to be able to position the child at any corner or the middle of an edge.
+ */
+@interface ASCenterLayoutSpec : ASRelativeLayoutSpec
 
 @property (nonatomic, assign) ASCenterLayoutSpecCenteringOptions centeringOptions;
 @property (nonatomic, assign) ASCenterLayoutSpecSizingOptions sizingOptions;

AsyncDisplayKit/Layout/ASCenterLayoutSpec.mm

@@ -23,13 +23,14 @@
                            sizingOptions:(ASCenterLayoutSpecSizingOptions)sizingOptions
                                    child:(id<ASLayoutable>)child;
 {
-  if (!(self = [super init])) {
+  ASRelativeLayoutSpecPosition verticalPosition = [self verticalPositionFromCenteringOptions:centeringOptions];
+  ASRelativeLayoutSpecPosition horizontalPosition = [self horizontalPositionFromCenteringOptions:centeringOptions];
+  
+  if (!(self = [super initWithHorizontalPosition:horizontalPosition verticalPosition:verticalPosition sizingOption:sizingOptions child:child])) {
     return nil;
   }
-  ASDisplayNodeAssertNotNil(child, @"Child cannot be nil");
   _centeringOptions = centeringOptions;
   _sizingOptions = sizingOptions;
-  [self setChild:child];
   return self;
 }
 
@@ -44,61 +45,36 @@
 {
   ASDisplayNodeAssert(self.isMutable, @"Cannot set properties when layout spec is not mutable");
   _centeringOptions = centeringOptions;
+  
+  [self setHorizontalPosition:[self horizontalPositionFromCenteringOptions:centeringOptions]];
+  [self setVerticalPosition:[self verticalPositionFromCenteringOptions:centeringOptions]];
 }
 
 - (void)setSizingOptions:(ASCenterLayoutSpecSizingOptions)sizingOptions
 {
   ASDisplayNodeAssert(self.isMutable, @"Cannot set properties when layout spec is not mutable");
   _sizingOptions = sizingOptions;
+  [self setSizingOption:sizingOptions];
 }
 
-- (ASLayout *)measureWithSizeRange:(ASSizeRange)constrainedSize
+- (ASRelativeLayoutSpecPosition)horizontalPositionFromCenteringOptions:(ASCenterLayoutSpecCenteringOptions)centeringOptions
 {
-  CGSize size = {
-    constrainedSize.max.width,
-    constrainedSize.max.height
-  };
-
-  // Layout the child
-  const CGSize minChildSize = {
-    (_centeringOptions & ASCenterLayoutSpecCenteringX) != 0 ? 0 : constrainedSize.min.width,
-    (_centeringOptions & ASCenterLayoutSpecCenteringY) != 0 ? 0 : constrainedSize.min.height,
-  };
-  ASLayout *sublayout = [self.child measureWithSizeRange:ASSizeRangeMake(minChildSize, constrainedSize.max)];
-
-  // If we have an undetermined height or width, use the child size to define the layout
-  // size
-  size = ASSizeRangeClamp(constrainedSize, {
-    isnan(size.width) ? sublayout.size.width : size.width,
-    isnan(size.height) ? sublayout.size.height : size.height
-  });
-
-  // If minimum size options are set, attempt to shrink the size to the size of the child
-  size = ASSizeRangeClamp(constrainedSize, {
-    MIN(size.width, (_sizingOptions & ASCenterLayoutSpecSizingOptionMinimumX) != 0 ? sublayout.size.width : size.width),
-    MIN(size.height, (_sizingOptions & ASCenterLayoutSpecSizingOptionMinimumY) != 0 ? sublayout.size.height : size.height)
-  });
-
-  // Compute the centered position for the child
-  BOOL shouldCenterAlongX = (_centeringOptions & ASCenterLayoutSpecCenteringX);
-  BOOL shouldCenterAlongY = (_centeringOptions & ASCenterLayoutSpecCenteringY);
-  sublayout.position = {
-    ASRoundPixelValue(shouldCenterAlongX ? (size.width - sublayout.size.width) * 0.5f : 0),
-    ASRoundPixelValue(shouldCenterAlongY ? (size.height - sublayout.size.height) * 0.5f : 0)
-  };
-
-  return [ASLayout layoutWithLayoutableObject:self size:size sublayouts:@[sublayout]];
+  BOOL centerX =  (centeringOptions & ASCenterLayoutSpecCenteringX) != 0;
+  if (centerX) {
+    return ASRelativeLayoutSpecPositionCenter;
+  } else {
+    return ASRelativeLayoutSpecPositionStart;
+  }
 }
 
-- (void)setChildren:(NSArray *)children
+- (ASRelativeLayoutSpecPosition)verticalPositionFromCenteringOptions:(ASCenterLayoutSpecCenteringOptions)centeringOptions
 {
-  ASDisplayNodeAssert(NO, @"not supported by this layout spec");
-}
-
-- (NSArray *)children
-{
-  ASDisplayNodeAssert(NO, @"not supported by this layout spec");
-  return nil;
+  BOOL centerY =  (centeringOptions & ASCenterLayoutSpecCenteringY) != 0;
+  if (centerY) {
+    return ASRelativeLayoutSpecPositionCenter;
+  } else {
+    return ASRelativeLayoutSpecPositionStart;
+  }
 }
 
 @end

AsyncDisplayKit/Layout/ASRelativeLayoutSpec.h

@@ -0,0 +1,73 @@
+//
+//  ASRelativeLayoutSpec.h
+//  AsyncDisplayKit
+//
+//  Created by Samuel Stow on 12/31/15.
+//
+
+#import <AsyncDisplayKit/ASLayoutSpec.h>
+
+/** How the child is positioned within the spec. */
+typedef NS_OPTIONS(NSUInteger, ASRelativeLayoutSpecPosition) {
+    /** The child is positioned at point 0 relatively to the layout axis (ie left / top most) */
+    ASRelativeLayoutSpecPositionStart = 0,
+    /** The child is centered along the specified axis */
+    ASRelativeLayoutSpecPositionCenter = 1 << 0,
+    /** The child is positioned at the maximum point of the layout axis (ie right / bottom most) */
+    ASRelativeLayoutSpecPositionEnd = 1 << 1,
+};
+
+/** How much space the spec will take up. */
+typedef NS_OPTIONS(NSUInteger, ASRelativeLayoutSpecSizingOption) {
+    /** The spec will take up the maximum size possible */
+    ASRelativeLayoutSpecSizingOptionDefault,
+    /** The spec will take up the minimum size possible along the X axis */
+    ASRelativeLayoutSpecSizingOptionMinimumWidth = 1 << 0,
+    /** The spec will take up the minimum size possible along the Y axis */
+    ASRelativeLayoutSpecSizingOptionMinimumHeight = 1 << 1,
+    /** Convenience option to take up the minimum size along both the X and Y axis */
+    ASRelativeLayoutSpecSizingOptionMinimumSize = ASRelativeLayoutSpecSizingOptionMinimumWidth | ASRelativeLayoutSpecSizingOptionMinimumHeight,
+};
+
+NS_ASSUME_NONNULL_BEGIN
+
+/** Lays out a single layoutable child and positions it within the layout bounds according to vertical and horizontal positional specifiers.
+ *  Can position the child at any of the 4 corners, or the middle of any of the 4 edges, as well as the center - similar to "9-part" image areas.
+ */
+@interface ASRelativeLayoutSpec : ASLayoutSpec
+
+// You may create a spec with alloc / init, then set any non-default properties; or use a convenience initialize that accepts all properties.
+@property (nonatomic, assign) ASRelativeLayoutSpecPosition horizontalPosition;
+@property (nonatomic, assign) ASRelativeLayoutSpecPosition verticalPosition;
+@property (nonatomic, assign) ASRelativeLayoutSpecSizingOption sizingOption;
+
+/*!
+ * @discussion convenience constructor for a ASRelativeLayoutSpec
+ * @param horizontalPosition how to position the item on the horizontal (x) axis
+ * @param verticalPosition how to position the item on the vertical (y) axis
+ * @param sizingOption how much size to take up
+ * @param child the child to layout
+ * @return a configured ASRelativeLayoutSpec
+ */
++ (instancetype)relativePositionLayoutSpecWithHorizontalPosition:(ASRelativeLayoutSpecPosition)horizontalPosition
+                                                verticalPosition:(ASRelativeLayoutSpecPosition)verticalPosition
+                                                    sizingOption:(ASRelativeLayoutSpecSizingOption)sizingOption
+                                                           child:(id<ASLayoutable>)child;
+
+/*!
+ * @discussion convenience initializer for a ASRelativeLayoutSpec
+ * @param horizontalPosition how to position the item on the horizontal (x) axis
+ * @param verticalPosition how to position the item on the vertical (y) axis
+ * @param sizingOption how much size to take up
+ * @param child the child to layout
+ * @return a configured ASRelativeLayoutSpec
+ */
+- (instancetype)initWithHorizontalPosition:(ASRelativeLayoutSpecPosition)horizontalPosition
+                          verticalPosition:(ASRelativeLayoutSpecPosition)verticalPosition
+                              sizingOption:(ASRelativeLayoutSpecSizingOption)sizingOption
+                                     child:(id<ASLayoutable>)child;
+
+@end
+
+NS_ASSUME_NONNULL_END
+

AsyncDisplayKit/Layout/ASRelativeLayoutSpec.mm

@@ -0,0 +1,117 @@
+//
+//  ASRelativeLayoutSpec.mm
+//  AsyncDisplayKit
+//
+//  Created by Samuel Stow on 12/31/15.
+//
+
+#import "ASRelativeLayoutSpec.h"
+
+#import "ASInternalHelpers.h"
+#import "ASLayout.h"
+
+@implementation ASRelativeLayoutSpec
+
+- (instancetype)initWithHorizontalPosition:(ASRelativeLayoutSpecPosition)horizontalPosition verticalPosition:(ASRelativeLayoutSpecPosition)verticalPosition sizingOption:(ASRelativeLayoutSpecSizingOption)sizingOption child:(id<ASLayoutable>)child
+{
+  if (!(self = [super init])) {
+    return nil;
+  }
+  ASDisplayNodeAssertNotNil(child, @"Child cannot be nil");
+  _horizontalPosition = horizontalPosition;
+  _verticalPosition = verticalPosition;
+  _sizingOption = sizingOption;
+  [self setChild:child];
+  return self;
+}
+
++ (instancetype)relativePositionLayoutSpecWithHorizontalPosition:(ASRelativeLayoutSpecPosition)horizontalPosition verticalPosition:(ASRelativeLayoutSpecPosition)verticalPosition sizingOption:(ASRelativeLayoutSpecSizingOption)sizingOption child:(id<ASLayoutable>)child
+{
+  return [[self alloc] initWithHorizontalPosition:horizontalPosition verticalPosition:verticalPosition sizingOption:sizingOption child:child];
+}
+
+- (void)setHorizontalPosition:(ASRelativeLayoutSpecPosition)horizontalPosition
+{
+  ASDisplayNodeAssert(self.isMutable, @"Cannot set properties when layout spec is not mutable");
+  _horizontalPosition = horizontalPosition;
+}
+
+- (void)setVerticalPosition:(ASRelativeLayoutSpecPosition)verticalPosition {
+  ASDisplayNodeAssert(self.isMutable, @"Cannot set properties when layout spec is not mutable");
+  _verticalPosition = verticalPosition;
+}
+
+- (void)setSizingOption:(ASRelativeLayoutSpecSizingOption)sizingOption
+{
+  ASDisplayNodeAssert(self.isMutable, @"Cannot set properties when layout spec is not mutable");
+  _sizingOption = sizingOption;
+}
+
+- (ASLayout *)measureWithSizeRange:(ASSizeRange)constrainedSize
+{
+  CGSize size = {
+    constrainedSize.max.width,
+    constrainedSize.max.height
+  };
+  
+  BOOL reduceWidth = (_horizontalPosition & ASRelativeLayoutSpecPositionCenter) != 0 ||
+  (_horizontalPosition & ASRelativeLayoutSpecPositionEnd) != 0;
+  
+  BOOL reduceHeight = (_verticalPosition & ASRelativeLayoutSpecPositionCenter) != 0 ||
+  (_verticalPosition & ASRelativeLayoutSpecPositionEnd) != 0;
+  
+  // Layout the child
+  const CGSize minChildSize = {
+    reduceWidth ? 0 : constrainedSize.min.width,
+    reduceHeight ? 0 : constrainedSize.min.height,
+  };
+  ASLayout *sublayout = [self.child measureWithSizeRange:ASSizeRangeMake(minChildSize, constrainedSize.max)];
+  
+  // If we have an undetermined height or width, use the child size to define the layout
+  // size
+  size = ASSizeRangeClamp(constrainedSize, {
+    isfinite(size.width) == NO ? sublayout.size.width : size.width,
+    isfinite(size.height) == NO ? sublayout.size.height : size.height
+  });
+  
+  // If minimum size options are set, attempt to shrink the size to the size of the child
+  size = ASSizeRangeClamp(constrainedSize, {
+    MIN(size.width, (_sizingOption & ASRelativeLayoutSpecSizingOptionMinimumWidth) != 0 ? sublayout.size.width : size.width),
+    MIN(size.height, (_sizingOption & ASRelativeLayoutSpecSizingOptionMinimumHeight) != 0 ? sublayout.size.height : size.height)
+  });
+  
+  // Compute the position for the child on each axis according to layout parameters
+  CGFloat xPosition = [self proportionOfAxisForAxisPosition:_horizontalPosition];
+  CGFloat yPosition = [self proportionOfAxisForAxisPosition:_verticalPosition];
+  
+  sublayout.position = {
+    ASRoundPixelValue((size.width - sublayout.size.width) * xPosition),
+    ASRoundPixelValue((size.height - sublayout.size.height) * yPosition)
+  };
+  
+  return [ASLayout layoutWithLayoutableObject:self size:size sublayouts:@[sublayout]];
+}
+
+- (void)setChildren:(NSArray *)children
+{
+  ASDisplayNodeAssert(NO, @"not supported by this layout spec");
+}
+
+- (NSArray *)children
+{
+  ASDisplayNodeAssert(NO, @"not supported by this layout spec");
+  return nil;
+}
+
+- (CGFloat)proportionOfAxisForAxisPosition:(ASRelativeLayoutSpecPosition)position
+{
+  if ((position & ASRelativeLayoutSpecPositionCenter) != 0) {
+    return 0.5f;
+  } else if ((position & ASRelativeLayoutSpecPositionEnd) != 0) {
+    return 1.0f;
+  } else {
+    return 0.0f;
+  }
+}
+
+@end

AsyncDisplayKitTests/ASCenterLayoutSpecSnapshotTests.mm

@@ -38,10 +38,14 @@ static const ASSizeRange kSize = {{100, 120}, {320, 160}};
 
 - (void)testWithSizingOptions
 {
-  [self testWithCenteringOptions:ASCenterLayoutSpecCenteringNone sizingOptions:ASCenterLayoutSpecSizingOptionDefault];
-  [self testWithCenteringOptions:ASCenterLayoutSpecCenteringNone sizingOptions:ASCenterLayoutSpecSizingOptionMinimumX];
-  [self testWithCenteringOptions:ASCenterLayoutSpecCenteringNone sizingOptions:ASCenterLayoutSpecSizingOptionMinimumY];
-  [self testWithCenteringOptions:ASCenterLayoutSpecCenteringNone sizingOptions:ASCenterLayoutSpecSizingOptionMinimumXY];
+  [self testWithCenteringOptions:ASCenterLayoutSpecCenteringNone
+                   sizingOptions:ASCenterLayoutSpecSizingOptionDefault];
+  [self testWithCenteringOptions:ASCenterLayoutSpecCenteringNone
+                   sizingOptions:ASCenterLayoutSpecSizingOptionMinimumX];
+  [self testWithCenteringOptions:ASCenterLayoutSpecCenteringNone
+                   sizingOptions:ASCenterLayoutSpecSizingOptionMinimumY];
+  [self testWithCenteringOptions:ASCenterLayoutSpecCenteringNone
+                   sizingOptions:ASCenterLayoutSpecSizingOptionMinimumXY];
 }
 
 - (void)testWithCenteringOptions:(ASCenterLayoutSpecCenteringOptions)options
@@ -51,14 +55,7 @@ static const ASSizeRange kSize = {{100, 120}, {320, 160}};
   ASStaticSizeDisplayNode *foregroundNode = ASDisplayNodeWithBackgroundColor([UIColor greenColor]);
   foregroundNode.staticSize = {70, 100};
 
-  ASLayoutSpec *layoutSpec =
-  [ASBackgroundLayoutSpec
-   backgroundLayoutSpecWithChild:
-   [ASCenterLayoutSpec
-    centerLayoutSpecWithCenteringOptions:options
-    sizingOptions:sizingOptions
-    child:foregroundNode]
-   background:backgroundNode];
+  ASLayoutSpec *layoutSpec = [ASBackgroundLayoutSpec backgroundLayoutSpecWithChild:[ASCenterLayoutSpec centerLayoutSpecWithCenteringOptions:options sizingOptions:sizingOptions child:foregroundNode]background:backgroundNode];
 
   [self testLayoutSpec:layoutSpec
              sizeRange:kSize
@@ -97,14 +94,7 @@ static NSString *suffixForCenteringOptions(ASCenterLayoutSpecCenteringOptions ce
   foregroundNode.staticSize = {10, 10};
   foregroundNode.flexGrow = YES;
   
-  ASCenterLayoutSpec *layoutSpec =
-  [ASCenterLayoutSpec
-   centerLayoutSpecWithCenteringOptions:ASCenterLayoutSpecCenteringNone
-   sizingOptions:{}
-   child:
-   [ASBackgroundLayoutSpec
-    backgroundLayoutSpecWithChild:[ASStackLayoutSpec stackLayoutSpecWithDirection:ASStackLayoutDirectionVertical spacing:0 justifyContent:ASStackLayoutJustifyContentStart alignItems:ASStackLayoutAlignItemsStart children:@[foregroundNode]]
-    background:backgroundNode]];
+  ASCenterLayoutSpec *layoutSpec = [ASCenterLayoutSpec centerLayoutSpecWithCenteringOptions:ASCenterLayoutSpecCenteringNone sizingOptions:{} child:[ASBackgroundLayoutSpec backgroundLayoutSpecWithChild:[ASStackLayoutSpec stackLayoutSpecWithDirection:ASStackLayoutDirectionVertical spacing:0 justifyContent:ASStackLayoutJustifyContentStart alignItems:ASStackLayoutAlignItemsStart children:@[foregroundNode]] background:backgroundNode]];
 
   [self testLayoutSpec:layoutSpec sizeRange:kSize subnodes:@[backgroundNode, foregroundNode] identifier:nil];
 }

AsyncDisplayKitTests/ASRelativeLayoutSpecSnapshotTests.mm

@@ -0,0 +1,130 @@
+/*
+ *  Copyright (c) 2014-present, Facebook, Inc.
+ *  All rights reserved.
+ *
+ *  This source code is licensed under the BSD-style license found in the
+ *  LICENSE file in the root directory of this source tree. An additional grant
+ *  of patent rights can be found in the PATENTS file in the same directory.
+ *
+ */
+
+#import "ASLayoutSpecSnapshotTestsHelper.h"
+
+#import "ASBackgroundLayoutSpec.h"
+#import "ASRelativeLayoutSpec.h"
+#import "ASStackLayoutSpec.h"
+#import "ASLayoutOptions.h"
+
+static const ASSizeRange kSize = {{100, 120}, {320, 160}};
+
+@interface ASRelativeLayoutSpecSnapshotTests : ASLayoutSpecSnapshotTestCase
+@end
+
+@implementation ASRelativeLayoutSpecSnapshotTests
+
+- (void)setUp
+{
+  [super setUp];
+  self.recordMode = NO;
+}
+
+- (void)testWithOptions
+{
+
+  [self testAllVerticalPositionsForHorizontalPosition:ASRelativeLayoutSpecPositionStart];
+  [self testAllVerticalPositionsForHorizontalPosition:ASRelativeLayoutSpecPositionCenter];
+  [self testAllVerticalPositionsForHorizontalPosition:ASRelativeLayoutSpecPositionEnd];
+
+}
+
+- (void)testAllVerticalPositionsForHorizontalPosition:(ASRelativeLayoutSpecPosition)horizontalPosition {
+  [self testWithHorizontalPosition:horizontalPosition verticalPosition:ASRelativeLayoutSpecPositionStart sizingOptions:{}];
+  [self testWithHorizontalPosition:horizontalPosition verticalPosition:ASRelativeLayoutSpecPositionCenter sizingOptions:{}];
+  [self testWithHorizontalPosition:horizontalPosition verticalPosition:ASRelativeLayoutSpecPositionEnd sizingOptions:{}];
+}
+
+- (void)testWithSizingOptions
+{
+  [self testWithHorizontalPosition:ASRelativeLayoutSpecPositionStart
+                  verticalPosition:ASRelativeLayoutSpecPositionStart
+                     sizingOptions:ASRelativeLayoutSpecSizingOptionDefault];
+  [self testWithHorizontalPosition:ASRelativeLayoutSpecPositionStart
+                  verticalPosition:ASRelativeLayoutSpecPositionStart
+                     sizingOptions:ASRelativeLayoutSpecSizingOptionMinimumWidth];
+  [self testWithHorizontalPosition:ASRelativeLayoutSpecPositionStart
+                  verticalPosition:ASRelativeLayoutSpecPositionStart
+                     sizingOptions:ASRelativeLayoutSpecSizingOptionMinimumHeight];
+  [self testWithHorizontalPosition:ASRelativeLayoutSpecPositionStart
+                  verticalPosition:ASRelativeLayoutSpecPositionStart
+                     sizingOptions:ASRelativeLayoutSpecSizingOptionMinimumSize];
+}
+
+- (void)testWithHorizontalPosition:(ASRelativeLayoutSpecPosition)horizontalPosition
+                  verticalPosition:(ASRelativeLayoutSpecPosition)verticalPosition
+                   sizingOptions:(ASRelativeLayoutSpecSizingOption)sizingOptions
+{
+  ASDisplayNode *backgroundNode = ASDisplayNodeWithBackgroundColor([UIColor redColor]);
+  ASStaticSizeDisplayNode *foregroundNode = ASDisplayNodeWithBackgroundColor([UIColor greenColor]);
+  foregroundNode.staticSize = {70, 100};
+
+  ASLayoutSpec *layoutSpec =
+  [ASBackgroundLayoutSpec
+   backgroundLayoutSpecWithChild:
+   [ASRelativeLayoutSpec
+    relativePositionLayoutSpecWithHorizontalPosition:horizontalPosition verticalPosition:verticalPosition sizingOption:sizingOptions child:foregroundNode]
+   background:backgroundNode];
+
+  [self testLayoutSpec:layoutSpec
+             sizeRange:kSize
+              subnodes:@[backgroundNode, foregroundNode]
+            identifier:suffixForPositionOptions(horizontalPosition, verticalPosition, sizingOptions)];
+}
+
+static NSString *suffixForPositionOptions(ASRelativeLayoutSpecPosition horizontalPosition,
+                                          ASRelativeLayoutSpecPosition verticalPosition,
+                                           ASRelativeLayoutSpecSizingOption sizingOptions)
+{
+  NSMutableString *suffix = [NSMutableString string];
+
+  if ((horizontalPosition & ASRelativeLayoutSpecPositionCenter) != 0) {
+    [suffix appendString:@"CenterX"];
+  } else if ((horizontalPosition & ASRelativeLayoutSpecPositionEnd) != 0) {
+    [suffix appendString:@"EndX"];
+  }
+
+  if ((verticalPosition & ASRelativeLayoutSpecPositionCenter) != 0) {
+    [suffix appendString:@"CenterY"];
+  } else if ((verticalPosition & ASRelativeLayoutSpecPositionEnd) != 0) {
+    [suffix appendString:@"EndY"];
+  }
+
+  if ((sizingOptions & ASRelativeLayoutSpecSizingOptionMinimumWidth) != 0) {
+    [suffix appendString:@"SizingMinimumWidth"];
+  }
+
+  if ((sizingOptions & ASRelativeLayoutSpecSizingOptionMinimumHeight) != 0) {
+    [suffix appendString:@"SizingMinimumHeight"];
+  }
+
+  return suffix;
+}
+
+- (void)testMinimumSizeRangeIsGivenToChildWhenNotPositioning
+{
+  ASDisplayNode *backgroundNode = ASDisplayNodeWithBackgroundColor([UIColor redColor]);
+  ASStaticSizeDisplayNode *foregroundNode = ASDisplayNodeWithBackgroundColor([UIColor redColor]);
+  foregroundNode.staticSize = {10, 10};
+  foregroundNode.flexGrow = YES;
+  
+  ASLayoutSpec *childSpec = [ASBackgroundLayoutSpec
+                             backgroundLayoutSpecWithChild:[ASStackLayoutSpec stackLayoutSpecWithDirection:ASStackLayoutDirectionVertical spacing:0 justifyContent:ASStackLayoutJustifyContentStart alignItems:ASStackLayoutAlignItemsStart children:@[foregroundNode]]
+                             background:backgroundNode];
+  
+  ASRelativeLayoutSpec *layoutSpec =  [ASRelativeLayoutSpec
+                                       relativePositionLayoutSpecWithHorizontalPosition:ASRelativeLayoutSpecPositionStart verticalPosition:ASRelativeLayoutSpecPositionStart sizingOption:{} child:childSpec];
+
+
+  [self testLayoutSpec:layoutSpec sizeRange:kSize subnodes:@[backgroundNode, foregroundNode] identifier:nil];
+}
+
+@end