Working implementation of ASInterfaceState for Display and FetchData behaviors.

AsyncDisplayKit/ASDisplayNode.h

@@ -181,7 +181,10 @@ typedef NS_OPTIONS(NSUInteger, ASInterfaceState)
  */
 @property (nonatomic, readonly, retain) CALayer *layer;
 
-@property (nonatomic, readwrite) ASInterfaceState interfaceState;
+@property (nonatomic, readonly) ASInterfaceState interfaceState;
+
+- (void)enterInterfaceState:(ASInterfaceState)interfaceState;
+- (void)exitInterfaceState:(ASInterfaceState)interfaceState;
 
 /** @name Managing dimensions */
 

AsyncDisplayKit/ASDisplayNode.mm

@@ -1729,6 +1729,46 @@ void recursivelyEnsureDisplayForLayer(CALayer *layer)
   }
 }
 
+- (void)enterInterfaceState:(ASInterfaceState)interfaceState
+{
+  recursivelyPerformBlockOnEveryNode(nil, self, ^(ASDisplayNode *node) {
+    node.interfaceState |= interfaceState;
+  });
+}
+
+- (void)exitInterfaceState:(ASInterfaceState)interfaceState
+{
+  recursivelyPerformBlockOnEveryNode(nil, self, ^(ASDisplayNode *node) {
+    node.interfaceState &= (!interfaceState);
+  });
+}
+
+void recursivelyPerformBlockOnEveryNode(CALayer *layer, ASDisplayNode *node, void(^performOnNode)(ASDisplayNode *node))
+{
+  if (!node) {
+    ASDisplayNodeCAssertNotNil(layer, @"Cannot recursively perform with nil node and nil layer");
+    ASDisplayNodeCAssertMainThread();
+    node = [layer asyncdisplaykit_node];
+  }
+  
+  if (node) {
+    performOnNode(node);
+  }
+  if (!layer && [node isNodeLoaded]) {
+    layer = node.layer;
+  }
+  
+  if (layer) {
+    for (CALayer *sublayer in [layer sublayers]) {
+      recursivelyPerformBlockOnEveryNode(sublayer, nil, performOnNode);
+    }
+  } else if (node) {
+    for (ASDisplayNode *subnode in [node subnodes]) {
+      recursivelyPerformBlockOnEveryNode(nil, subnode, performOnNode);
+    }
+  }
+}
+
 - (void)layout
 {
   ASDisplayNodeAssertMainThread();

AsyncDisplayKit/Details/ASRangeHandlerPreload.mm

@@ -16,13 +16,13 @@
 - (void)node:(ASDisplayNode *)node enteredRangeOfType:(ASLayoutRangeType)rangeType
 {
   ASDisplayNodeAssert(rangeType == ASLayoutRangeTypePreload, @"Preload delegate should not handle other ranges");
-  [node recursivelyFetchData];
+  [node enterInterfaceState:ASInterfaceStateFetchData];
 }
 
 - (void)node:(ASDisplayNode *)node exitedRangeOfType:(ASLayoutRangeType)rangeType
 {
   ASDisplayNodeAssert(rangeType == ASLayoutRangeTypePreload, @"Preload delegate should not handle other ranges");
-  [node recursivelyClearFetchedData];
+  [node exitInterfaceState:ASInterfaceStateFetchData];
 }
 
 @end

AsyncDisplayKit/Details/ASRangeHandlerRender.mm

@@ -57,7 +57,8 @@
     [node.view removeFromSuperview];
   }
   
-  [node recursivelySetDisplaySuspended:NO];
+  // The node un-suspends display.
+  [node enterInterfaceState:ASInterfaceStateDisplay];
 
   // Add the node's layer to an off-screen window to trigger display and mark its contents as non-volatile.
   // Use the layer directly to avoid the substantial overhead of UIView heirarchy manipulations.
@@ -89,7 +90,8 @@
   // preservation of this content could result in the app being killed, which is not likely preferable over briefly seeing placeholders in the event the user scrolls backwards.
   // Nonetheless, future changes to the implementation will likely eliminate this behavior to simplify debugging and extensibility of working range functionality.
   
-  [node recursivelySetDisplaySuspended:YES];
+  // The node calls clearCurrentContents and suspends display
+  [node exitInterfaceState:ASInterfaceStateDisplay];
   
   if (node.layer.superlayer != [[self workingWindow] layer]) {
     // In this case, the node has previously passed through the working range (or it is zero), and it has now fallen outside the working range.
@@ -102,7 +104,6 @@
   
   // At this point, the node's layer may validly be present either in the workingWindow, or in the contentsView of a cell.
   [node.layer removeFromSuperlayer];
-  [node recursivelyClearContents];
 }
 
 @end