Merge pull request #898 from Adlai-Holler/OptimizeNodeDidRelayout

Reduce Frequency of beginUpdates/endUpdates Due to Node Relayout

AsyncDisplayKit/ASCellNode.h

@@ -19,8 +19,9 @@ typedef NSUInteger ASCellNodeAnimation;
  * The notification is done on main thread.
  *
  * @param node A node informing the delegate about the relayout.
+ * @param sizeChanged `YES` if the node's `calculatedSize` changed during the relayout, `NO` otherwise.
  */
-- (void)nodeDidRelayout:(ASCellNode *)node;
+- (void)nodeDidRelayout:(ASCellNode *)node sizeChanged:(BOOL)sizeChanged;
 @end
 
 /**

AsyncDisplayKit/ASCellNode.m

@@ -53,11 +53,13 @@
 - (void)setNeedsLayout
 {
   ASDisplayNodeAssertThreadAffinity(self);  
+  CGSize oldSize = self.calculatedSize;
   [super setNeedsLayout];
 
   if (_layoutDelegate != nil) {
+    BOOL sizeChanged = !CGSizeEqualToSize(oldSize, self.calculatedSize);
     ASPerformBlockOnMainThread(^{
-      [_layoutDelegate nodeDidRelayout:self];
+      [_layoutDelegate nodeDidRelayout:self sizeChanged:sizeChanged];
     });
   }
 }

AsyncDisplayKit/ASCollectionView.mm

@@ -156,6 +156,7 @@ static BOOL _isInterceptedSelector(SEL sel)
   BOOL _asyncDelegateImplementsInsetSection;
   BOOL _collectionViewLayoutImplementsInsetSection;
   BOOL _asyncDataSourceImplementsConstrainedSizeForNode;
+  BOOL _queuedNodeSizeUpdate;
 
   ASBatchContext *_batchContext;
   
@@ -911,10 +912,26 @@ static BOOL _isInterceptedSelector(SEL sel)
 
 #pragma mark - ASCellNodeDelegate
 
-- (void)nodeDidRelayout:(ASCellNode *)node
+- (void)nodeDidRelayout:(ASCellNode *)node sizeChanged:(BOOL)sizeChanged
 {
   ASDisplayNodeAssertMainThread();
-  // Cause UICollectionView to requery for the new height of this node
+
+  if (!sizeChanged || _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

@@ -181,6 +181,7 @@ static BOOL _isInterceptedSelector(SEL sel)
 
   CGFloat _nodesConstrainedWidth;
   BOOL _ignoreNodesConstrainedWidthChange;
+  BOOL _queuedNodeHeightUpdate;
 }
 
 @property (atomic, assign) BOOL asyncDataSourceLocked;
@@ -908,10 +909,26 @@ static BOOL _isInterceptedSelector(SEL sel)
 
 #pragma mark - ASCellNodeLayoutDelegate
 
-- (void)nodeDidRelayout:(ASCellNode *)node
+- (void)nodeDidRelayout:(ASCellNode *)node sizeChanged:(BOOL)sizeChanged
 {
   ASDisplayNodeAssertMainThread();
+
+  if (!sizeChanged || _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];
 }