From 9e76d7b603f0b82612344ca96e6e051ebcf75836 Mon Sep 17 00:00:00 2001
From: Huy Nguyen <huy@pinterest.com>
Date: Sun, 20 Mar 2016 23:14:53 -0700
Subject: [PATCH] Add method to cancel layout transitions in progress

- Also make sure a transition isn't invalidated right after it passed the validation test and before it proceeds
---
 AsyncDisplayKit/ASDisplayNode+Beta.h |  5 +++++
 AsyncDisplayKit/ASDisplayNode.mm     | 28 ++++++++++++++++++----------
 2 files changed, 23 insertions(+), 10 deletions(-)

diff --git a/AsyncDisplayKit/ASDisplayNode+Beta.h b/AsyncDisplayKit/ASDisplayNode+Beta.h
index 11cd6d0e70..4bb108b66a 100644
--- a/AsyncDisplayKit/ASDisplayNode+Beta.h
+++ b/AsyncDisplayKit/ASDisplayNode+Beta.h
@@ -98,4 +98,9 @@ ASDISPLAYNODE_EXTERN_C_END
  */
 - (BOOL)placeholderShouldPersist;
 
+/**
+ * @abstract Cancels all performing layout transitions. Can be called on any thread.
+ */
+- (void)cancelLayoutTransitionsInProgress;
+
 @end
diff --git a/AsyncDisplayKit/ASDisplayNode.mm b/AsyncDisplayKit/ASDisplayNode.mm
index 0596eaf510..f1b6aa26f2 100644
--- a/AsyncDisplayKit/ASDisplayNode.mm
+++ b/AsyncDisplayKit/ASDisplayNode.mm
@@ -593,14 +593,7 @@ static ASDisplayNodeMethodOverrides GetASDisplayNodeMethodOverrides(Class c)
     return _layout;
   }
 
-  if ([self _hasTransitionsInProgress]) {
-    // Invalidate transition sentinel to cancel transitions in progress
-    [self _invalidateTransitionSentinel];
-    // Tell subnodes to exit layout pending state and clear related properties
-    ASDisplayNodePerformBlockOnEverySubnode(self, ^(ASDisplayNode * _Nonnull node) {
-      node.hierarchyState &= (~ASHierarchyStateLayoutPending);
-    });
-  }
+  [self cancelLayoutTransitionsInProgress];
 
   ASLayout *previousLayout = _layout;
   ASSizeRange previousConstrainedSize = _constrainedSize;
@@ -698,12 +691,14 @@ static ASDisplayNodeMethodOverrides GetASDisplayNodeMethodOverrides(Class c)
     }
     
     ASPerformBlockOnMainThread(^{
+      // Grab _propertyLock here to make sure this transition isn't invalidated
+      // right after it passed the validation test and before it proceeds
+      ASDN::MutexLocker l(_propertyLock);
+
       if ([self _shouldAbortTransitionWithID:transitionID]) {
         return;
       }
       
-      ASDN::MutexLocker l(_propertyLock);
-
       ASLayout *previousLayout = _layout;
       ASSizeRange previousConstrainedSize = _constrainedSize;
       [self applyLayout:newLayout constrainedSize:constrainedSize layoutContext:nil];
@@ -769,6 +764,19 @@ static ASDisplayNodeMethodOverrides GetASDisplayNodeMethodOverrides(Class c)
   // subclass override
 }
 
+- (void)cancelLayoutTransitionsInProgress
+{
+  ASDN::MutexLocker l(_propertyLock);
+  if ([self _hasTransitionsInProgress]) {
+    // Invalidate transition sentinel to cancel transitions in progress
+    [self _invalidateTransitionSentinel];
+    // Tell subnodes to exit layout pending state and clear related properties
+    ASDisplayNodePerformBlockOnEverySubnode(self, ^(ASDisplayNode * _Nonnull node) {
+      node.hierarchyState &= (~ASHierarchyStateLayoutPending);
+    });
+  }
+}
+
 #pragma mark - Layout Transition
 
 - (BOOL)usesImplicitHierarchyManagement