Implement horizontal and vertical alignments for stack layout

AsyncDisplayKit/Layout/ASStackLayoutDefines.h

@@ -67,3 +67,27 @@ typedef NS_ENUM(NSUInteger, ASStackLayoutAlignSelf) {
   /** Expand to fill cross axis */
   ASStackLayoutAlignSelfStretch,
 };
+
+/** Orientation of children along horizontal axis */
+typedef NS_ENUM(NSUInteger, ASHorizontalAlignment) {
+  /** No alignment specified. Default value */
+  ASHorizontalAlignmentNone,
+  /** Left aligned */
+  ASAlignmentLeft,
+  /** Center aligned */
+  ASAlignmentMiddle,
+  /** Right aligned */
+  ASAlignmentRight,
+};
+
+/** Orientation of children along vertical axis */
+typedef NS_ENUM(NSUInteger, ASVerticalAlignment) {
+  /** No alignment specified. Default value */
+  ASVerticalAlignmentNone,
+  /** Top aligned */
+  ASAlignmentTop,
+  /** Center aligned */
+  ASAlignmentCenter,
+  /** Bottom aligned */
+  ASAlignmentBottom,
+};

AsyncDisplayKit/Layout/ASStackLayoutSpec.h

@@ -35,10 +35,25 @@
  */
 @interface ASStackLayoutSpec : ASLayoutSpec
 
-/** Specifies the direction children are stacked in. */
+/** 
+ Specifies the direction children are stacked in. If horizontalAlignment and verticalAlignment were set, 
+ they will be resolved again, causing justifyContent and alignItems to be updated accordingly
+ */
 @property (nonatomic, assign) ASStackLayoutDirection direction;
 /** The amount of space between each child. */
 @property (nonatomic, assign) CGFloat spacing;
+/** 
+ Specifies how children are aligned horizontally. Depends on the stack direction, setting the alignment causes either
+ justifyContent or alignItems to be updated. The alignment will remain valid after future direction changes.
+ Thus, it is preferred to those properties
+ */
+@property (nonatomic, assign) ASHorizontalAlignment horizontalAlignment;
+/** 
+ Specifies how children are aligned vertically. Depends on the stack direction, setting the alignment causes either
+ justifyContent or alignItems to be updated. The alignment will remain valid after future direction changes.
+ Thus, it is preferred to those properties
+ */
+@property (nonatomic, assign) ASVerticalAlignment verticalAlignment;
 /** The amount of space between each child. */
 @property (nonatomic, assign) ASStackLayoutJustifyContent justifyContent;
 /** Orientation of children along cross axis */

AsyncDisplayKit/Layout/ASStackLayoutSpec.mm

@@ -25,7 +25,7 @@
 
 @implementation ASStackLayoutSpec
 {
- ASDN::RecursiveMutex _propertyLock;
+  ASDN::RecursiveMutex _propertyLock;
 }
 
 - (instancetype)init
@@ -58,8 +58,10 @@
     return nil;
   }
   _direction = direction;
-  _alignItems = alignItems;
   _spacing = spacing;
+  _horizontalAlignment = ASHorizontalAlignmentNone;
+  _verticalAlignment = ASVerticalAlignmentNone;
+  _alignItems = alignItems;
   _justifyContent = justifyContent;
   
   [self setChildren:children];
@@ -69,18 +71,44 @@
 - (void)setDirection:(ASStackLayoutDirection)direction
 {
   ASDisplayNodeAssert(self.isMutable, @"Cannot set properties when layout spec is not mutable");
-  _direction = direction;
+  if (_direction != direction) {
+    _direction = direction;
+    [self resolveHorizontalAlignment];
+    [self resolveVerticalAlignment];
+  }
+}
+
+- (void)setHorizontalAlignment:(ASHorizontalAlignment)horizontalAlignment
+{
+  ASDisplayNodeAssert(self.isMutable, @"Cannot set properties when layout spec is not mutable");
+  if (_horizontalAlignment != horizontalAlignment) {
+    _horizontalAlignment = horizontalAlignment;
+    [self resolveHorizontalAlignment];
+  }
+}
+
+- (void)setVerticalAlignment:(ASVerticalAlignment)verticalAlignment
+{
+  ASDisplayNodeAssert(self.isMutable, @"Cannot set properties when layout spec is not mutable");
+  if (_verticalAlignment != verticalAlignment) {
+    _verticalAlignment = verticalAlignment;
+    [self resolveVerticalAlignment];
+  }
 }
 
 - (void)setAlignItems:(ASStackLayoutAlignItems)alignItems
 {
   ASDisplayNodeAssert(self.isMutable, @"Cannot set properties when layout spec is not mutable");
+  ASDisplayNodeAssert(_horizontalAlignment == ASHorizontalAlignmentNone, @"Cannot set this property directly because horizontalAlignment is being used");
+  ASDisplayNodeAssert(_verticalAlignment == ASVerticalAlignmentNone, @"Cannot set this property directly because verticalAlignment is being used");
   _alignItems = alignItems;
 }
 
 - (void)setJustifyContent:(ASStackLayoutJustifyContent)justifyContent
 {
   ASDisplayNodeAssert(self.isMutable, @"Cannot set properties when layout spec is not mutable");
+  ASDisplayNodeAssert(_horizontalAlignment == ASHorizontalAlignmentNone, @"Cannot set this property directly because horizontalAlignment is being used");
+  ASDisplayNodeAssert(_verticalAlignment == ASVerticalAlignmentNone, @"Cannot set this property directly because verticalAlignment is being used");
   _justifyContent = justifyContent;
 }
 
@@ -149,6 +177,24 @@
                                    sublayouts:sublayouts];
 }
 
+- (void)resolveHorizontalAlignment
+{
+  if (_direction == ASStackLayoutDirectionHorizontal) {
+    _justifyContent = justifyContent(_horizontalAlignment, _justifyContent);
+  } else {
+    _alignItems = alignment(_horizontalAlignment, _alignItems);
+  }
+}
+
+- (void)resolveVerticalAlignment
+{
+  if (_direction == ASStackLayoutDirectionHorizontal) {
+    _alignItems = alignment(_verticalAlignment, _alignItems);
+  } else {
+    _justifyContent = justifyContent(_verticalAlignment, _justifyContent);
+  }
+}
+
 @end
 
 @implementation ASStackLayoutSpec (Debugging)

AsyncDisplayKit/Private/ASStackLayoutSpecUtilities.h

@@ -68,3 +68,63 @@ inline ASStackLayoutAlignItems alignment(ASStackLayoutAlignSelf childAlignment,
       return stackAlignment;
   }
 }
+
+inline ASStackLayoutAlignItems alignment(ASHorizontalAlignment alignment, ASStackLayoutAlignItems defaultAlignment)
+{
+  switch (alignment) {
+    case ASAlignmentLeft:
+      return ASStackLayoutAlignItemsStart;
+    case ASAlignmentMiddle:
+      return ASStackLayoutAlignItemsCenter;
+    case ASAlignmentRight:
+      return ASStackLayoutAlignItemsEnd;
+    case ASHorizontalAlignmentNone:
+    default:
+      return defaultAlignment;
+  }
+}
+
+inline ASStackLayoutAlignItems alignment(ASVerticalAlignment alignment, ASStackLayoutAlignItems defaultAlignment)
+{
+  switch (alignment) {
+    case ASAlignmentTop:
+      return ASStackLayoutAlignItemsStart;
+    case ASAlignmentCenter:
+      return ASStackLayoutAlignItemsCenter;
+    case ASAlignmentBottom:
+      return ASStackLayoutAlignItemsEnd;
+    case ASVerticalAlignmentNone:
+    default:
+      return defaultAlignment;
+  }
+}
+
+inline ASStackLayoutJustifyContent justifyContent(ASHorizontalAlignment alignment, ASStackLayoutJustifyContent defaultJustifyContent)
+{
+  switch (alignment) {
+    case ASAlignmentLeft:
+      return ASStackLayoutJustifyContentStart;
+    case ASAlignmentMiddle:
+      return ASStackLayoutJustifyContentCenter;
+    case ASAlignmentRight:
+      return ASStackLayoutJustifyContentEnd;
+    case ASHorizontalAlignmentNone:
+    default:
+      return defaultJustifyContent;
+  }
+}
+
+inline ASStackLayoutJustifyContent justifyContent(ASVerticalAlignment alignment, ASStackLayoutJustifyContent defaultJustifyContent)
+{
+  switch (alignment) {
+    case ASAlignmentTop:
+      return ASStackLayoutJustifyContentStart;
+    case ASAlignmentCenter:
+      return ASStackLayoutJustifyContentCenter;
+    case ASAlignmentBottom:
+      return ASStackLayoutJustifyContentEnd;
+    case ASVerticalAlignmentNone:
+    default:
+      return defaultJustifyContent;
+  }
+}

AsyncDisplayKitTests/ASStackLayoutSpecSnapshotTests.mm

@@ -28,6 +28,8 @@
   self.recordMode = NO;
 }
 
+#pragma mark - Utility methods
+
 static NSArray *defaultSubnodes()
 {
   return defaultSubnodesWithSameSize(CGSizeZero, NO);
@@ -63,6 +65,24 @@ static NSArray *defaultSubnodesWithSameSize(CGSize subnodeSize, BOOL flex)
   [self testStackLayoutSpecWithStyle:style sizeRange:sizeRange subnodes:subnodes identifier:identifier];
 }
 
+- (void)testStackLayoutSpecWithDirection:(ASStackLayoutDirection)direction
+                itemsHorizontalAlignment:(ASHorizontalAlignment)horizontalAlignment
+                  itemsVerticalAlignment:(ASVerticalAlignment)verticalAlignment
+                              identifier:(NSString *)identifier
+{
+  NSArray *subnodes = defaultSubnodesWithSameSize({50, 50}, NO);
+  
+  ASStackLayoutSpec *stackLayoutSpec = [[ASStackLayoutSpec alloc] init];
+  stackLayoutSpec.direction = direction;
+  stackLayoutSpec.children = subnodes;
+  [stackLayoutSpec setHorizontalAlignment:horizontalAlignment];
+  [stackLayoutSpec setVerticalAlignment:verticalAlignment];
+  
+  CGSize exactSize = CGSizeMake(200, 200);
+  static ASSizeRange kSize = ASSizeRangeMake(exactSize, exactSize);
+  [self testStackLayoutSpec:stackLayoutSpec sizeRange:kSize subnodes:subnodes identifier:identifier];
+}
+
 - (void)testStackLayoutSpecWithStyle:(ASStackLayoutSpecStyle)style
                            sizeRange:(ASSizeRange)sizeRange
                             subnodes:(NSArray *)subnodes
@@ -76,13 +96,23 @@ static NSArray *defaultSubnodesWithSameSize(CGSize subnodeSize, BOOL flex)
                            sizeRange:(ASSizeRange)sizeRange
                             subnodes:(NSArray *)subnodes
                           identifier:(NSString *)identifier
+{
+  ASStackLayoutSpec *stackLayoutSpec = [ASStackLayoutSpec stackLayoutSpecWithDirection:style.direction
+                                                                               spacing:style.spacing
+                                                                        justifyContent:style.justifyContent
+                                                                            alignItems:style.alignItems
+                                                                              children:children];
+  [self testStackLayoutSpec:stackLayoutSpec sizeRange:sizeRange subnodes:subnodes identifier:identifier];
+}
+
+- (void)testStackLayoutSpec:(ASStackLayoutSpec *)stackLayoutSpec
+                  sizeRange:(ASSizeRange)sizeRange
+                   subnodes:(NSArray *)subnodes
+                 identifier:(NSString *)identifier
 {
   ASDisplayNode *backgroundNode = ASDisplayNodeWithBackgroundColor([UIColor whiteColor]);
   
-  ASLayoutSpec *layoutSpec =
+  ASLayoutSpec *layoutSpec = [ASBackgroundLayoutSpec backgroundLayoutSpecWithChild:stackLayoutSpec background:backgroundNode];
-  [ASBackgroundLayoutSpec
-   backgroundLayoutSpecWithChild:[ASStackLayoutSpec stackLayoutSpecWithDirection:style.direction spacing:style.spacing justifyContent:style.justifyContent alignItems:style.alignItems children:children]
-   background:backgroundNode];
   
   NSMutableArray *newSubnodes = [NSMutableArray arrayWithObject:backgroundNode];
   [newSubnodes addObjectsFromArray:subnodes];
@@ -90,6 +120,8 @@ static NSArray *defaultSubnodesWithSameSize(CGSize subnodeSize, BOOL flex)
   [self testLayoutSpec:layoutSpec sizeRange:sizeRange subnodes:newSubnodes identifier:identifier];
 }
 
+#pragma mark -
+
 - (void)testUnderflowBehaviors
 {
   // width 300px; height 0-300px
@@ -522,4 +554,54 @@ static NSArray *defaultSubnodesWithSameSize(CGSize subnodeSize, BOOL flex)
   [self testStackLayoutSpecWithStyle:style sizeRange:kSize subnodes:subnodes identifier:nil];
 }
 
+- (void)testHorizontalAndVerticalAlignments
+{
+  [self testStackLayoutSpecWithDirection:ASStackLayoutDirectionHorizontal itemsHorizontalAlignment:ASAlignmentLeft itemsVerticalAlignment:ASAlignmentTop identifier:@"horizontalTopLeft"];
+  [self testStackLayoutSpecWithDirection:ASStackLayoutDirectionHorizontal itemsHorizontalAlignment:ASAlignmentMiddle itemsVerticalAlignment:ASAlignmentCenter identifier:@"horizontalCenter"];
+  [self testStackLayoutSpecWithDirection:ASStackLayoutDirectionHorizontal itemsHorizontalAlignment:ASAlignmentRight itemsVerticalAlignment:ASAlignmentBottom identifier:@"horizontalBottomRight"];
+  [self testStackLayoutSpecWithDirection:ASStackLayoutDirectionVertical itemsHorizontalAlignment:ASAlignmentLeft itemsVerticalAlignment:ASAlignmentTop identifier:@"verticalTopLeft"];
+  [self testStackLayoutSpecWithDirection:ASStackLayoutDirectionVertical itemsHorizontalAlignment:ASAlignmentMiddle itemsVerticalAlignment:ASAlignmentCenter identifier:@"verticalCenter"];
+  [self testStackLayoutSpecWithDirection:ASStackLayoutDirectionVertical itemsHorizontalAlignment:ASAlignmentRight itemsVerticalAlignment:ASAlignmentBottom identifier:@"verticalBottomRight"];
+}
+
+- (void)testDirectionChangeAfterSettingHorizontalAndVerticalAlignments
+{
+  ASStackLayoutSpec *stackLayoutSpec = [[ASStackLayoutSpec alloc] init]; // Default direction is horizontal
+  stackLayoutSpec.horizontalAlignment = ASAlignmentRight;
+  stackLayoutSpec.verticalAlignment = ASAlignmentCenter;
+  XCTAssertEqual(stackLayoutSpec.alignItems, ASStackLayoutAlignItemsCenter);
+  XCTAssertEqual(stackLayoutSpec.justifyContent, ASStackLayoutJustifyContentEnd);
+  
+  stackLayoutSpec.direction = ASStackLayoutDirectionVertical;
+  XCTAssertEqual(stackLayoutSpec.alignItems, ASStackLayoutAlignItemsEnd);
+  XCTAssertEqual(stackLayoutSpec.justifyContent, ASStackLayoutJustifyContentCenter);
+}
+
+- (void)testAlignItemsAndJustifyContentRestrictionsIfHorizontalAndVerticalAlignmentsAreUsed
+{
+  ASStackLayoutSpec *stackLayoutSpec = [[ASStackLayoutSpec alloc] init];
+
+  // No assertions should be thrown here because alignments are not used
+  stackLayoutSpec.alignItems = ASStackLayoutAlignItemsEnd;
+  stackLayoutSpec.justifyContent = ASStackLayoutJustifyContentEnd;
+
+  // Set alignments and assert that assertions are thrown
+  stackLayoutSpec.horizontalAlignment = ASAlignmentMiddle;
+  stackLayoutSpec.verticalAlignment = ASAlignmentCenter;
+  XCTAssertThrows(stackLayoutSpec.alignItems = ASStackLayoutAlignItemsEnd);
+  XCTAssertThrows(stackLayoutSpec.justifyContent = ASStackLayoutJustifyContentEnd);
+
+  // Unset alignments. alignItems and justifyContent should not be changed
+  stackLayoutSpec.horizontalAlignment = ASHorizontalAlignmentNone;
+  stackLayoutSpec.verticalAlignment = ASVerticalAlignmentNone;
+  XCTAssertEqual(stackLayoutSpec.alignItems, ASStackLayoutAlignItemsCenter);
+  XCTAssertEqual(stackLayoutSpec.justifyContent, ASStackLayoutJustifyContentCenter);
+
+  // Now that alignments are none, setting alignItems and justifyContent should be allowed again
+  stackLayoutSpec.alignItems = ASStackLayoutAlignItemsEnd;
+  stackLayoutSpec.justifyContent = ASStackLayoutJustifyContentEnd;
+  XCTAssertEqual(stackLayoutSpec.alignItems, ASStackLayoutAlignItemsEnd);
+  XCTAssertEqual(stackLayoutSpec.justifyContent, ASStackLayoutJustifyContentEnd);
+}
+
 @end