Initial attempt at implementing Display Traits

Initial attempt to get display traits working with ASEnvironment.

To get proper ASDisplayTraits support, you must use an ASViewController. The ASViewController implements UITraitCollection-related methods (`traitCollectionDidChange:`, `willTransitionToTraitCollection:withTransitionCoordinator:`, viewWillTransitionToSize:withTransitionCoordinator`) to update the internal ASDisplayTraits and propagate them to subnodes.

ASTableNode and ASCollectionNode don't actually have their cells as subnodes, so a little bit of trickery is involved (on `setEnvironment:` the table/collection node gets its data controllers completedNodes and propagates the new traits. see `ASDisplayTraitsCollectionTableSetEnvironmentState`). The data controller also passes the current display traits when creating new cells.

ASViewController also supports the ability to return a custom set of display traits. So if you have a modal dialog that should always be told it is in a compact size class, you can set the override block before displaying the VC.

A new example, called Display Traits, has been added. It shows how display traits can be used in a ASViewController with a normal ASDisplayNode as its root, as well as in ASViewControllers hosting table nodes and collection nodes. There is also an example of overriding the default display traits of a VC.

Please provide feedback!

Author: rcancro

AsyncDisplayKit.xcodeproj/project.pbxproj

@@ -10,6 +10,7 @@
 #import "ASCollectionInternal.h"
 #import "ASCollectionViewLayoutFacilitatorProtocol.h"
 #import "ASDisplayNode+Subclasses.h"
+#import "ASEnvironmentInternal.h"
 #import "ASRangeControllerUpdateRangeProtocol+Beta.h"
 #include <vector>
 
@@ -244,4 +245,6 @@ - (void)reloadDataImmediately
   [self.view reloadDataImmediately];
 }
 
+ASDisplayTraitsCollectionTableSetEnvironmentState
+
 @end

AsyncDisplayKit/ASCollectionNode.mm

@@ -91,7 +91,7 @@ - (instancetype)init
 #pragma mark -
 #pragma mark ASCollectionView.
 
-@interface ASCollectionView () <ASRangeControllerDataSource, ASRangeControllerDelegate, ASDataControllerSource, ASCellNodeLayoutDelegate, ASDelegateProxyInterceptor, ASBatchFetchingScrollView> {
+@interface ASCollectionView () <ASRangeControllerDataSource, ASRangeControllerDelegate, ASDataControllerSource, ASCellNodeLayoutDelegate, ASDelegateProxyInterceptor, ASBatchFetchingScrollView, ASDataControllerEnvironmentDelegate> {
   ASCollectionViewProxy *_proxyDataSource;
   ASCollectionViewProxy *_proxyDelegate;
 
@@ -225,6 +225,7 @@ - (instancetype)_initWithFrame:(CGRect)frame collectionViewLayout:(UICollectionV
   _dataController = [[ASCollectionDataController alloc] initWithAsyncDataFetching:NO];
   _dataController.delegate = _rangeController;
   _dataController.dataSource = self;
+  _dataController.environmentDelegate = self;
 
   _batchContext = [[ASBatchContext alloc] init];
 
@@ -917,6 +918,14 @@ - (void)dataControllerUnlockDataSource
   }
 }
 
+- (id<ASEnvironment>)dataControllerEnvironment
+{
+  if (self.collectionNode) {
+    return self.collectionNode;
+  }
+  return self.strongCollectionNode;
+}
+
 #pragma mark - ASCollectionViewDataControllerSource Supplementary view support
 
 - (ASCellNode *)dataController:(ASCollectionDataController *)dataController supplementaryNodeOfKind:(NSString *)kind atIndexPath:(NSIndexPath *)indexPath

AsyncDisplayKit/ASCollectionView.mm

@@ -2687,11 +2687,13 @@ - (void)setInHierarchy:(BOOL)inHierarchy
 
 - (ASEnvironmentState)environmentState
 {
+  ASDN::MutexLocker l(_propertyLock);
   return _environmentState;
 }
 
 - (void)setEnvironmentState:(ASEnvironmentState)environmentState
 {
+  ASDN::MutexLocker l(_propertyLock);
   _environmentState = environmentState;
 }
 
@@ -2707,7 +2709,12 @@ - (ASDisplayNode *)parent
 
 - (BOOL)supportsUpwardPropagation
 {
-  return ASEnvironmentStatePropagationEnabled();
+  return ASEnvironmentStateUpwardPropagationEnabled();
+}
+
+- (BOOL)supportsDownwardPropagation
+{
+  return ASEnvironmentStateDownwardPropagationEnabled();
 }
 
 ASEnvironmentLayoutOptionsForwarding

AsyncDisplayKit/ASDisplayNode.mm

@@ -6,6 +6,7 @@
 //  Copyright © 2015 Facebook. All rights reserved.
 //
 
+#import "ASEnvironmentInternal.h"
 #import "ASFlowLayoutController.h"
 #import "ASTableViewInternal.h"
 #import "ASDisplayNode+Subclasses.h"
@@ -158,4 +159,6 @@ - (void)clearFetchedData
   [self.view clearFetchedData];
 }
 
+ASDisplayTraitsCollectionTableSetEnvironmentState
+
 @end

AsyncDisplayKit/ASTableNode.m AsyncDisplayKit/ASTableNode.mmAsyncDisplayKit/ASTableNode.m renamed to AsyncDisplayKit/ASTableNode.mm

@@ -16,6 +16,7 @@
 #import "ASDisplayNodeExtras.h"
 #import "ASDisplayNode+Beta.h"
 #import "ASDisplayNode+FrameworkPrivate.h"
+#import "ASEnvironmentInternal.h"
 #import "ASInternalHelpers.h"
 #import "ASLayout.h"
 #import "ASLayoutController.h"
@@ -88,7 +89,7 @@ @interface ASTableNode ()
 - (instancetype)_initWithTableView:(ASTableView *)tableView;
 @end
 
-@interface ASTableView () <ASRangeControllerDataSource, ASRangeControllerDelegate, ASDataControllerSource,     _ASTableViewCellDelegate, ASCellNodeLayoutDelegate, ASDelegateProxyInterceptor, ASBatchFetchingScrollView>
+@interface ASTableView () <ASRangeControllerDataSource, ASRangeControllerDelegate, ASDataControllerSource, _ASTableViewCellDelegate, ASCellNodeLayoutDelegate, ASDelegateProxyInterceptor, ASBatchFetchingScrollView, ASDataControllerEnvironmentDelegate>
 {
   ASTableViewProxy *_proxyDataSource;
   ASTableViewProxy *_proxyDelegate;
@@ -175,6 +176,7 @@ - (void)configureWithDataControllerClass:(Class)dataControllerClass
   _dataController = [[dataControllerClass alloc] initWithAsyncDataFetching:NO];
   _dataController.dataSource = self;
   _dataController.delegate = _rangeController;
+  _dataController.environmentDelegate = self;
 
   _layoutController.dataSource = _dataController;
 
@@ -1078,6 +1080,16 @@ - (NSUInteger)numberOfSectionsInDataController:(ASDataController *)dataControlle
   }
 }
 
+#pragma mark - ASDataControllerEnvironmentDelegate
+
+- (id<ASEnvironment>)dataControllerEnvironment
+{
+  if (self.tableNode) {
+    return self.tableNode;
+  }
+  return self.strongTableNode;
+}
+
 #pragma mark - _ASTableViewCellDelegate
 
 - (void)didLayoutSubviewsOfTableViewCell:(_ASTableViewCell *)tableViewCell

AsyncDisplayKit/ASTableView.mm

@@ -11,12 +11,27 @@
 
 NS_ASSUME_NONNULL_BEGIN
 
+typedef ASDisplayTraits (^ASDisplayTraitsForTraitCollectionBlock)(UITraitCollection *traitCollection);
+typedef ASDisplayTraits (^ASDisplayTraitsForTraitWindowSizeBlock)(CGSize windowSize);
+
 @interface ASViewController<__covariant DisplayNodeType : ASDisplayNode *> : UIViewController
 
 - (instancetype)initWithNode:(DisplayNodeType)node NS_DESIGNATED_INITIALIZER;
 
 @property (nonatomic, strong, readonly) DisplayNodeType node;
 
+@property (nonatomic, strong) id displayTraitsContext;
+
+/**
+ * Set this block to customize the ASDisplayTraits returned when the VC transitions to the given traitCollection.
+ */
+@property (nonatomic, copy) ASDisplayTraitsForTraitCollectionBlock overrideDisplayTraitsWithTraitCollection;
+
+/**
+ * Set this block to customize the ASDisplayTraits returned when the VC transitions to the given window size.
+ */
+@property (nonatomic, copy) ASDisplayTraitsForTraitWindowSizeBlock overrideDisplayTraitsWithWindowSize;
+
 /**
  * @abstract Passthrough property to the the .interfaceState of the node.
  * @return The current ASInterfaceState of the node, indicating whether it is visible and other situational properties.

AsyncDisplayKit/ASViewController.h

@@ -11,6 +11,7 @@
 #import "ASDimension.h"
 #import "ASDisplayNode+FrameworkPrivate.h"
 #import "ASDisplayNode+Beta.h"
+#import "ASEnvironmentInternal.h"
 #import "ASRangeControllerUpdateRangeProtocol+Beta.h"
 
 @implementation ASViewController
@@ -42,10 +43,18 @@ - (instancetype)initWithNode:(ASDisplayNode *)node
   _node = node;
 
   _automaticallyAdjustRangeModeBasedOnViewEvents = NO;
-  
+
   return self;
 }
 
+- (void)dealloc
+{
+  if (_displayTraitsContext != nil) {
+    ASDisplayTraitsClearDisplayContext(self.node);
+    _displayTraitsContext = nil;
+  }
+}
+
 - (void)loadView
 {
   ASDisplayNodeAssertTrue(!_node.layerBacked);
@@ -132,4 +141,66 @@ - (ASInterfaceState)interfaceState
   return _node.interfaceState;
 }
 
+#pragma mark - ASDisplayTraits
+
+- (ASDisplayTraits)displayTraitsForTraitCollection:(UITraitCollection *)traitCollection
+{
+  if (self.overrideDisplayTraitsWithTraitCollection) {
+    return self.overrideDisplayTraitsWithTraitCollection(traitCollection);
+  }
+  
+  ASDisplayTraits displayTraits = ASDisplayTraitsFromUITraitCollection(traitCollection);
+  displayTraits.displayContext = _displayTraitsContext;
+  return displayTraits;
+}
+
+- (ASDisplayTraits)displayTraitsForWindowSize:(CGSize)windowSize
+{
+  if (self.overrideDisplayTraitsWithWindowSize) {
+    return self.overrideDisplayTraitsWithWindowSize(windowSize);
+  }
+  return self.node.environmentState.displayTraits;
+}
+
+- (void)progagateNewDisplayTraits:(ASDisplayTraits)displayTraits
+{
+  ASEnvironmentState environmentState = self.node.environmentState;
+  ASDisplayTraits oldDisplayTraits = environmentState.displayTraits;
+  
+  if (ASDisplayTraitsIsEqualToASDisplayTraits(displayTraits, oldDisplayTraits) == NO) {
+    environmentState.displayTraits = displayTraits;
+    [self.node setEnvironmentState:environmentState];
+    [self.node setNeedsLayout];
+    
+    NSArray<id<ASEnvironment>> *children = [self.node children];
+    for (id<ASEnvironment> child in children) {
+      ASEnvironmentStatePropagateDown(child, environmentState.displayTraits);
+    }
+  }
+}
+
+- (void)traitCollectionDidChange:(UITraitCollection *)previousTraitCollection
+{
+  [super traitCollectionDidChange:previousTraitCollection];
+  
+  ASDisplayTraits displayTraits = [self displayTraitsForTraitCollection:self.traitCollection];
+  [self progagateNewDisplayTraits:displayTraits];
+}
+
+- (void)willTransitionToTraitCollection:(UITraitCollection *)newCollection withTransitionCoordinator:(id<UIViewControllerTransitionCoordinator>)coordinator
+{
+  [super willTransitionToTraitCollection:newCollection withTransitionCoordinator:coordinator];
+  
+  ASDisplayTraits displayTraits = [self displayTraitsForTraitCollection:self.traitCollection];
+  [self progagateNewDisplayTraits:displayTraits];
+}
+
+- (void)viewWillTransitionToSize:(CGSize)size withTransitionCoordinator:(id<UIViewControllerTransitionCoordinator>)coordinator
+{
+  [super viewWillTransitionToSize:size withTransitionCoordinator:coordinator];
+  
+  ASDisplayTraits displayTraits = [self displayTraitsForWindowSize:size];
+  [self progagateNewDisplayTraits:displayTraits];
+}
+
 @end

AsyncDisplayKit/ASViewController.m AsyncDisplayKit/ASViewController.mmAsyncDisplayKit/ASViewController.m renamed to AsyncDisplayKit/ASViewController.mm

@@ -17,6 +17,7 @@ NS_ASSUME_NONNULL_BEGIN
 
 @class ASCellNode;
 @class ASDataController;
+@protocol ASEnvironment;
 
 typedef NSUInteger ASDataControllerAnimationOptions;
 
@@ -64,6 +65,11 @@ FOUNDATION_EXPORT NSString * const ASDataControllerRowNodeKind;
  */
 - (void)dataControllerUnlockDataSource;
 
+
+@end
+
+@protocol ASDataControllerEnvironmentDelegate
+- (id<ASEnvironment>)dataControllerEnvironment;
 @end
 
 /**
@@ -122,6 +128,11 @@ FOUNDATION_EXPORT NSString * const ASDataControllerRowNodeKind;
  */
 @property (nonatomic, weak) id<ASDataControllerDelegate> delegate;
 
+/**
+ *
+ */
+@property (nonatomic, weak) id<ASDataControllerEnvironmentDelegate> environmentDelegate;
+
 /**
  *  Designated initializer.
  *

AsyncDisplayKit/Details/ASDataController.h

@@ -13,6 +13,7 @@
 #import "ASAssert.h"
 #import "ASCellNode.h"
 #import "ASDisplayNode.h"
+#import "ASEnvironmentInternal.h"
 #import "ASFlowLayoutController.h"
 #import "ASInternalHelpers.h"
 #import "ASLayout.h"
@@ -519,8 +520,17 @@ - (void)accessDataSourceSynchronously:(BOOL)synchronously withBlock:(dispatch_bl
     for (NSUInteger i = 0; i < rowNum; i++) {
       NSIndexPath *indexPath = [sectionIndex indexPathByAddingIndex:i];
       ASCellNodeBlock nodeBlock = [_dataSource dataController:self nodeBlockAtIndexPath:indexPath];
+      
+      // When creating a node, make sure to pass along the current display traits so it will be laid out properly
+      ASCellNodeBlock nodeBlockPropagatingDisplayTraits = ^{
+        ASCellNode *cellNode = nodeBlock();
+        id<ASEnvironment> environment = [self.environmentDelegate dataControllerEnvironment];
+        ASEnvironmentStatePropagateDown(cellNode, [environment environmentState].displayTraits);
+        return cellNode;
+      };
+      
       ASSizeRange constrainedSize = [self constrainedSizeForNodeOfKind:ASDataControllerRowNodeKind atIndexPath:indexPath];
-      [contexts addObject:[[ASIndexedNodeContext alloc] initWithNodeBlock:nodeBlock
+      [contexts addObject:[[ASIndexedNodeContext alloc] initWithNodeBlock:nodeBlockPropagatingDisplayTraits
                                                                 indexPath:indexPath
                                                           constrainedSize:constrainedSize]];
     }