Improve measurement code for cell nodes (#3119)

Source/ASCellNode.mm

@@ -125,47 +125,10 @@
   }
 }
 
-- (void)transitionLayoutWithAnimation:(BOOL)animated
-                   shouldMeasureAsync:(BOOL)shouldMeasureAsync
-                measurementCompletion:(void(^)())completion
-{
-  CGSize oldSize = self.calculatedSize;
-  [super transitionLayoutWithAnimation:animated
-                    shouldMeasureAsync:shouldMeasureAsync
-                 measurementCompletion:^{
-                   [self didRelayoutFromOldSize:oldSize toNewSize:self.calculatedSize];
-                   if (completion) {
-                     completion();
-                   }
-                 }
-   ];
-}
-
-- (void)transitionLayoutWithSizeRange:(ASSizeRange)constrainedSize
-                             animated:(BOOL)animated
-                   shouldMeasureAsync:(BOOL)shouldMeasureAsync
-                measurementCompletion:(void(^)())completion
-{
-  CGSize oldSize = self.calculatedSize;
-  [super transitionLayoutWithSizeRange:constrainedSize
-                              animated:animated
-                    shouldMeasureAsync:shouldMeasureAsync
-                 measurementCompletion:^{
-                   [self didRelayoutFromOldSize:oldSize toNewSize:self.calculatedSize];
-                   if (completion) {
-                     completion();
-                   }
-                 }
-   ];
-}
-
-- (void)didRelayoutFromOldSize:(CGSize)oldSize toNewSize:(CGSize)newSize
+- (void)_layoutTransitionMeasurementDidFinish
 {
   if (_interactionDelegate != nil) {
-    ASPerformBlockOnMainThread(^{
-      BOOL sizeChanged = !CGSizeEqualToSize(oldSize, newSize);
-      [_interactionDelegate nodeDidRelayout:self sizeChanged:sizeChanged];
-    });
+    [_interactionDelegate nodeDidInvalidateSize:self];
   }
 }
 

Source/ASCollectionView.mm

@@ -32,6 +32,7 @@
 #import <AsyncDisplayKit/ASSectionContext.h>
 #import <AsyncDisplayKit/ASCollectionView+Undeprecated.h>
 #import <AsyncDisplayKit/_ASHierarchyChangeSet.h>
+#import <AsyncDisplayKit/CoreGraphics+ASConvenience.h>
 
 /**
  * A macro to get self.collectionNode and assign it to a local variable, or return
@@ -1563,6 +1564,15 @@ static NSString * const kReuseIdentifier = @"_ASCollectionReuseIdentifier";
   }
 }
 
+- (BOOL)dataController:(ASDataController *)dataController presentedSizeForElement:(ASCollectionElement *)element matchesSize:(CGSize)size
+{
+  NSIndexPath *indexPath = [self indexPathForNode:element.node];
+  UICollectionViewLayoutAttributes *attributes = [self layoutAttributesForItemAtIndexPath:indexPath];
+  CGRect rect = attributes.frame;
+  return CGSizeEqualToSizeWithIn(rect.size, size, FLT_EPSILON);
+  
+}
+
 - (id<ASTraitEnvironment>)dataControllerEnvironment
 {
   return self.collectionNode;

Source/ASDisplayNode.mm

@@ -1266,6 +1266,12 @@ ASLayoutElementFinalLayoutElementDefault
   return _calculatedDisplayNodeLayout->constrainedSize;
 }
 
+/**
+ * @abstract Informs the root node that the intrinsic size of the receiver is no longer valid.
+ *
+ * @discussion The size of a root node is determined by each subnode. Calling invalidateSize will let the root node know
+ * that the intrinsic size of the receiver node is no longer valid and a resizing of the root node needs to happen.
+ */
 - (void)setNeedsLayoutFromAbove
 {
   ASDisplayNodeAssertThreadAffinity(self);
@@ -1487,6 +1493,8 @@ ASLayoutElementFinalLayoutElementDefault
       });
       
       // Measurement pass completion
+      // Give the subclass a change to hook into before calling the completion block
+      [self _layoutTransitionMeasurementDidFinish];
       if (completion) {
         completion();
       }
@@ -1560,6 +1568,11 @@ ASLayoutElementFinalLayoutElementDefault
   return _transitionID;
 }
 
+- (void)_layoutTransitionMeasurementDidFinish
+{
+  // No-Op in ASDisplayNode
+}
+
 - (void)_finishOrCancelTransition
 {
   ASDN::MutexLocker l(__instanceLock__);

Source/ASTableView.mm

@@ -1695,6 +1695,22 @@ static NSString * const kCellReuseIdentifier = @"_ASTableViewCell";
   }
 }
 
+- (BOOL)dataController:(ASDataController *)dataController presentedSizeForElement:(ASCollectionElement *)element matchesSize:(CGSize)size
+{
+  NSIndexPath *indexPath = [self indexPathForNode:element.node];
+  CGRect rect = [self rectForRowAtIndexPath:indexPath];
+  
+  /**
+   * Weirdly enough, Apple expects the return value in tableView:heightForRowAtIndexPath: to _include_ the height
+   * of the separator, if there is one! So if rectForRow would return 44.0 we need to use 43.5.
+   */
+  if (self.separatorStyle != UITableViewCellSeparatorStyleNone) {
+    rect.size.height -= 1.0 / ASScreenScale();
+  }
+
+  return (fabs(rect.size.height - size.height) < FLT_EPSILON);
+}
+
 #pragma mark - ASDataControllerEnvironmentDelegate
 
 - (id<ASTraitEnvironment>)dataControllerEnvironment

Source/Details/ASDataController.h

@@ -29,6 +29,7 @@ NS_ASSUME_NONNULL_BEGIN
 @class ASCellNode;
 @class ASDataController;
 @class ASElementMap;
+@class ASCollectionElement;
 @class _ASHierarchyChangeSet;
 @protocol ASTraitEnvironment;
 @protocol ASSectionContext;
@@ -65,6 +66,11 @@ extern NSString * const ASCollectionInvalidUpdateException;
  */
 - (NSUInteger)numberOfSectionsInDataController:(ASDataController *)dataController;
 
+/**
+ Returns if the collection element size matches a given size
+ */
+- (BOOL)dataController:(ASDataController *)dataController presentedSizeForElement:(ASCollectionElement *)element matchesSize:(CGSize)size;
+
 @optional
 
 - (NSArray<NSString *> *)dataController:(ASDataController *)dataController supplementaryNodeKindsInSections:(NSIndexSet *)sections;

Source/Details/ASDataController.mm

@@ -640,10 +640,9 @@ typedef void (^ASDataControllerCompletionBlock)(NSArray<ASCollectionElement *> *
     NSString *kind = node.collectionElement.supplementaryElementKind ?: ASDataControllerRowNodeKind;
     NSIndexPath *indexPath = [_pendingMap indexPathForElement:node.collectionElement];
     ASSizeRange constrainedSize = [self constrainedSizeForNodeOfKind:kind atIndexPath:indexPath];
-    
-    CGSize oldSize = node.bounds.size;
     [self _layoutNode:node withConstrainedSize:constrainedSize];
-    if (! CGSizeEqualToSize(node.frame.size, oldSize)) {
+    BOOL matchesSize = [_dataSource dataController:self presentedSizeForElement:node.collectionElement matchesSize:node.frame.size];
+    if (! matchesSize) {
       [nodesSizesChanged addObject:node];
     }
   }

Source/Private/ASDisplayNode+FrameworkPrivate.h

@@ -214,20 +214,18 @@ __unused static NSString * _Nonnull NSStringFromASHierarchyState(ASHierarchyStat
  */
 - (BOOL)shouldScheduleDisplayWithNewInterfaceState:(ASInterfaceState)newInterfaceState;
 
-/**
- * @abstract Informs the root node that the intrinsic size of the receiver is no longer valid.
- *
- * @discussion The size of a root node is determined by each subnode. Calling invalidateSize will let the root node know
- * that the intrinsic size of the receiver node is no longer valid and a resizing of the root node needs to happen.
- */
-- (void)setNeedsLayoutFromAbove;
-
 /**
  * @abstract Subclass hook for nodes that are acting as root nodes. This method is called if one of the subnodes
  * size is invalidated and may need to result in a different size as the current calculated size.
  */
 - (void)_locked_rootNodeDidInvalidateSize;
 
+/**
+ * @abstract Subclass hook for nodes that are acting as root nodes. This method is called after measurement
+ * finished in a layout transition but before the measurement completion handler is called
+ */
+- (void)_layoutTransitionMeasurementDidFinish;
+
 @end
 
 @interface UIView (ASDisplayNodeInternal)