Only require node sizes once per run loop, and only if a node's size has changed

AsyncDisplayKit/ASCellNode.h

@@ -15,12 +15,13 @@ typedef NSUInteger ASCellNodeAnimation;
 @protocol ASCellNodeLayoutDelegate <NSObject>
 
 /**
- * Notifies the delegate that the specified cell node has done a relayout.
+ * Notifies the delegate that the specified cell node has done a relayout
+ * that resulted in a change of `calculatedSize`.
  * The notification is done on main thread.
  *
  * @param node A node informing the delegate about the relayout.
  */
-- (void)nodeDidRelayout:(ASCellNode *)node;
+- (void)nodeDidRelayoutWithSizeChange:(ASCellNode *)node;
 @end
 
 /**

AsyncDisplayKit/ASCellNode.m

@@ -53,11 +53,12 @@
 - (void)setNeedsLayout
 {
   ASDisplayNodeAssertThreadAffinity(self);  
+  CGSize oldSize = self.calculatedSize;
   [super setNeedsLayout];
   
-  if (_layoutDelegate != nil) {
+  if (_layoutDelegate != nil && !CGSizeEqualToSize(oldSize, self.calculatedSize)) {
     ASPerformBlockOnMainThread(^{
-      [_layoutDelegate nodeDidRelayout:self];
+      [_layoutDelegate nodeDidRelayoutWithSizeChange:self];
     });
   }
 }

AsyncDisplayKit/ASCollectionView.mm

@@ -155,6 +155,7 @@ static BOOL _isInterceptedSelector(SEL sel)
   BOOL _asyncDelegateImplementsInsetSection;
   BOOL _collectionViewLayoutImplementsInsetSection;
   BOOL _asyncDataSourceImplementsConstrainedSizeForNode;
+  BOOL _queuedNodeSizeUpdate;
 
   ASBatchContext *_batchContext;
   
@@ -912,10 +913,26 @@ static BOOL _isInterceptedSelector(SEL sel)
 
 #pragma mark - ASCellNodeDelegate
 
-- (void)nodeDidRelayout:(ASCellNode *)node
+- (void)nodeDidRelayoutWithSizeChange:(ASCellNode *)node
 {
   ASDisplayNodeAssertMainThread();
-  // Cause UICollectionView to requery for the new height of this node
+
+  if (_queuedNodeSizeUpdate) {
+    return;
+  }
+
+  _queuedNodeSizeUpdate = YES;
+  [self performSelector:@selector(requeryNodeSizes)
+             withObject:nil
+             afterDelay:0
+                inModes:@[ NSRunLoopCommonModes ]];
+}
+
+// Cause UICollectionView to requery for the new size of all nodes
+- (void)requeryNodeSizes
+{
+  _queuedNodeSizeUpdate = NO;
+
   [super performBatchUpdates:^{} completion:nil];
 }
 

AsyncDisplayKit/ASTableView.mm

@@ -179,6 +179,7 @@ static BOOL _isInterceptedSelector(SEL sel)
 
   CGFloat _nodesConstrainedWidth;
   BOOL _ignoreNodesConstrainedWidthChange;
+  BOOL _queuedNodeHeightUpdate;
 }
 
 @property (atomic, assign) BOOL asyncDataSourceLocked;
@@ -909,10 +910,26 @@ static BOOL _isInterceptedSelector(SEL sel)
 
 #pragma mark - ASCellNodeLayoutDelegate
 
-- (void)nodeDidRelayout:(ASCellNode *)node
+- (void)nodeDidRelayoutWithSizeChange:(ASCellNode *)node
 {
   ASDisplayNodeAssertMainThread();
-  // Cause UITableView to requery for the new height of this node
+
+  if (_queuedNodeHeightUpdate) {
+    return;
+  }
+
+  _queuedNodeHeightUpdate = YES;
+  [self performSelector:@selector(requeryNodeHeights)
+             withObject:nil
+             afterDelay:0
+                inModes:@[ NSRunLoopCommonModes ]];
+}
+
+// Cause UITableView to requery for the new height of this node
+- (void)requeryNodeHeights
+{
+  _queuedNodeHeightUpdate = NO;
+
   [super beginUpdates];
   [super endUpdates];
 }