[ASDisplayNode] Notify rasterized subnodes that render pass has completed (#532)

* Notify rasterized subsides that render pass has completed

* Traverse entire subnode tree notifying all subnodes

* Add entry in changelog

* Retrieve rasterizesSubtree flag while holding instance lock

* Balance display delegate calls for rasterized subnodes

CHANGELOG.md

@@ -16,6 +16,7 @@
 - Table and collection views to consider content inset when calculating (default) element size range [Huy Nguyen](https://github.com/nguyenhuy) [#525](https://github.com/TextureGroup/Texture/pull/525)
 - [ASEditableTextNode] added -editableTextNodeShouldBeginEditing to ASEditableTextNodeDelegate to mirror the corresponding method from UITextViewDelegate. [Yan S.](https://github.com/yans) [#535](https://github.com/TextureGroup/Texture/pull/535)
 - [Breaking] Remove APIs that have been deprecated since 2.0 and/or for at least 6 months [Huy Nguyen](https://github.com/nguyenhuy) [#529](https://github.com/TextureGroup/Texture/pull/529)
+- [ASDisplayNode] Ensure `-displayWillStartAsynchronously:` and `-displayDidFinish` are invoked on rasterized subnodes.  [Eric Scheers](https://github.com/smeis) [#532](https://github.com/TextureGroup/Texture/pull/532)
 
 ##2.4
 - Fix an issue where inserting/deleting sections could lead to inconsistent supplementary element behavior. [Adlai Holler](https://github.com/Adlai-Holler)

Source/Private/ASDisplayNode+AsyncDisplay.mm

@@ -23,6 +23,8 @@
 #import <AsyncDisplayKit/ASDisplayNode+FrameworkSubclasses.h>
 #import <AsyncDisplayKit/ASInternalHelpers.h>
 #import <AsyncDisplayKit/ASSignpost.h>
+#import <AsyncDisplayKit/ASDisplayNodeExtras.h>
+
 
 @interface ASDisplayNode () <_ASDisplayLayerDelegate>
 @end
@@ -302,6 +304,7 @@
   }
   
   CALayer *layer = _layer;
+  BOOL rasterizesSubtree = _flags.rasterizesSubtree;
   
   __instanceLock__.unlock();
 
@@ -347,11 +350,23 @@
         layer.contents = (id)image.CGImage;
       }
       [self didDisplayAsyncLayer:self.asyncLayer];
+      
+      if (rasterizesSubtree) {
+        ASDisplayNodePerformBlockOnEverySubnode(self, NO, ^(ASDisplayNode * _Nonnull node) {
+          [node didDisplayAsyncLayer:node.asyncLayer];
+        });
+      }
     }
   };
 
   // Call willDisplay immediately in either case
   [self willDisplayAsyncLayer:self.asyncLayer asynchronously:asynchronously];
+  
+  if (rasterizesSubtree) {
+    ASDisplayNodePerformBlockOnEverySubnode(self, NO, ^(ASDisplayNode * _Nonnull node) {
+      [node willDisplayAsyncLayer:node.asyncLayer asynchronously:asynchronously];
+    });
+  }
 
   if (asynchronously) {
     // Async rendering operations are contained by a transaction, which allows them to proceed and concurrently

Tests/ASDisplayNodeTests.mm

@@ -110,6 +110,10 @@ for (ASDisplayNode *n in @[ nodes ]) {\
 @property (nonatomic) BOOL hasPreloaded;
 @property (nonatomic) BOOL preloadStateChangedToYES;
 @property (nonatomic) BOOL preloadStateChangedToNO;
+
+@property (nonatomic, assign) NSUInteger displayWillStartCount;
+@property (nonatomic, assign) NSUInteger didDisplayCount;
+
 @end
 
 @interface ASTestResponderNode : ASTestDisplayNode
@@ -154,6 +158,18 @@ for (ASDisplayNode *n in @[ nodes ]) {\
   }
 }
 
+- (void)displayDidFinish
+{
+  [super displayDidFinish];
+  _didDisplayCount++;
+}
+
+- (void)displayWillStartAsynchronously:(BOOL)asynchronously
+{
+  [super displayWillStartAsynchronously:asynchronously];
+  _displayWillStartCount++;
+}
+
 @end
 
 @interface UIDisplayNodeTestView : UIView
@@ -2018,6 +2034,39 @@ static bool stringContainsPointer(NSString *description, id p) {
   XCTAssertThrows([rasterizedSupernode addSubnode:subnode]);
 }
 
+- (void)testThatSubnodesGetDisplayUpdatesIfRasterized
+{
+  ASTestDisplayNode *supernode = [[ASTestDisplayNode alloc] init];
+  supernode.frame = CGRectMake(0.0, 0.0, 100.0, 100.0);
+  [supernode enableSubtreeRasterization];
+  
+  ASTestDisplayNode *subnode = [[ASTestDisplayNode alloc] init];
+  ASTestDisplayNode *subSubnode = [[ASTestDisplayNode alloc] init];
+  
+  ASSetDebugNames(supernode, subnode);
+  UIWindow *window = [[UIWindow alloc] initWithFrame:[UIScreen mainScreen].bounds];
+  [subnode addSubnode:subSubnode];
+  [supernode addSubnode:subnode];
+  [window addSubnode:supernode];
+  [window makeKeyAndVisible];
+  
+  XCTAssertTrue(ASDisplayNodeRunRunLoopUntilBlockIsTrue(^BOOL{
+    return (subnode.didDisplayCount == 1);
+  }));
+  
+  XCTAssertTrue(ASDisplayNodeRunRunLoopUntilBlockIsTrue(^BOOL{
+    return (subSubnode.didDisplayCount == 1);
+  }));
+  
+  XCTAssertTrue(ASDisplayNodeRunRunLoopUntilBlockIsTrue(^BOOL{
+    return (subnode.displayWillStartCount == 1);
+  }));
+  
+  XCTAssertTrue(ASDisplayNodeRunRunLoopUntilBlockIsTrue(^BOOL{
+    return (subSubnode.displayWillStartCount == 1);
+  }));
+}
+
 // Underlying issue for: https://github.com/facebook/AsyncDisplayKit/issues/2011
 - (void)testThatLayerBackedSubnodesAreMarkedInvisibleBeforeDeallocWhenSupernodesViewIsRemovedFromHierarchyWhileBeingRetained
 {