From 5e49cc438259d1e7b4a4778deaf786f1e34ceffe Mon Sep 17 00:00:00 2001
From: Huy Nguyen <huy@pinterest.com>
Date: Wed, 2 Mar 2016 22:43:28 -0800
Subject: [PATCH] Layout transition can measure in background

---
 AsyncDisplayKit/ASDisplayNode.mm                | 14 +++++++++-----
 AsyncDisplayKit/Private/ASDisplayNodeInternal.h |  1 +
 2 files changed, 10 insertions(+), 5 deletions(-)

diff --git a/AsyncDisplayKit/ASDisplayNode.mm b/AsyncDisplayKit/ASDisplayNode.mm
index 7cafc438d5..78c23f2b14 100644
--- a/AsyncDisplayKit/ASDisplayNode.mm
+++ b/AsyncDisplayKit/ASDisplayNode.mm
@@ -658,12 +658,16 @@ static ASDisplayNodeMethodOverrides GetASDisplayNodeMethodOverrides(Class c)
 
 - (ASLayout *)transitionLayoutWithSizeRange:(ASSizeRange)constrainedSize animated:(BOOL)animated
 {
-  _usesImplicitHierarchyManagement = YES; // Temporary flag for 1.9.x
+  self.usesImplicitHierarchyManagement = YES; // Temporary flag for 1.9.x
+  
   return [self measureWithSizeRange:constrainedSize completion:^{
-    _usesImplicitHierarchyManagement = NO; // Temporary flag for 1.9.x
-    _transitionContext = [[_ASTransitionContext alloc] initWithAnimation:animated delegate:self];
-    [self __implicitlyInsertSubnodes];
-    [self animateLayoutTransition:_transitionContext];
+    self.usesImplicitHierarchyManagement = NO; // Temporary flag for 1.9.x
+
+    ASPerformBlockOnMainThread(^{
+      _transitionContext = [[_ASTransitionContext alloc] initWithAnimation:animated delegate:self];
+      [self __implicitlyInsertSubnodes];
+      [self animateLayoutTransition:_transitionContext];
+    });
   }];
 }
 
diff --git a/AsyncDisplayKit/Private/ASDisplayNodeInternal.h b/AsyncDisplayKit/Private/ASDisplayNodeInternal.h
index b10c6d7f8c..d3a10724a9 100644
--- a/AsyncDisplayKit/Private/ASDisplayNodeInternal.h
+++ b/AsyncDisplayKit/Private/ASDisplayNodeInternal.h
@@ -103,6 +103,7 @@ FOUNDATION_EXPORT NSString * const ASRenderingEngineDidDisplayNodesScheduledBefo
   UIEdgeInsets _hitTestSlop;
   NSMutableArray *_subnodes;
   
+  // Main thread only
   _ASTransitionContext *_transitionContext;
   BOOL _usesImplicitHierarchyManagement;