Add setNeedsDataFetch method to queue off screen fetchData calls

AsyncDisplayKit/ASDisplayNode.h

@@ -442,7 +442,6 @@ NS_ASSUME_NONNULL_BEGIN
  *
  * @see displaySuspended and setNeedsDisplay
  */
-
 - (void)recursivelyClearContents;
 
 /**
@@ -465,6 +464,13 @@ NS_ASSUME_NONNULL_BEGIN
  */
 - (void)recursivelyFetchData;
 
+/**
+ * @abstract Marks the node as needing to call fetchData
+ * @discussion If the node is outside of the preload range, it is queued to call fetchData the next time it enters the range.
+ * Otherwise, fetchData is called immediately if the node is currently within the preload range.
+ */
+- (void)setNeedsDataFetch;
+
 /**
  * @abstract Toggle displaying a placeholder over the node that covers content until the node and all subnodes are
  * displayed.

AsyncDisplayKit/ASDisplayNode.mm

@@ -1727,6 +1727,15 @@ static BOOL ShouldUseNewRenderingRange = YES;
   // subclass override
 }
 
+- (void)setNeedsDataFetch
+{
+  if (ASInterfaceStateIncludesFetchData(_interfaceState)) {
+    [self fetchData];
+  } else {
+    _needsDataFetch = YES;
+  }
+}
+
 // TODO: Replace this with ASDisplayNodePerformBlockOnEveryNode or enterInterfaceState:
 - (void)recursivelyFetchData
 {
@@ -1793,9 +1802,10 @@ static BOOL ShouldUseNewRenderingRange = YES;
   BOOL nowFetchData = ASInterfaceStateIncludesFetchData(newState);
   BOOL wasFetchData = ASInterfaceStateIncludesFetchData(oldState);
   
-  if (nowFetchData != wasFetchData) {
+  if (nowFetchData != wasFetchData || _needsDataFetch) {
-    if (nowFetchData) {
+    if (nowFetchData || _needsDataFetch) {
       [self fetchData];
+      _needsDataFetch = NO;
     } else {
       if ([self supportsRangeManagedInterfaceState]) {
         [self clearFetchedData];

AsyncDisplayKit/ASDisplayNodeExtras.h

@@ -29,6 +29,33 @@ inline BOOL ASInterfaceStateIncludesFetchData(ASInterfaceState interfaceState)
   return ((interfaceState & ASInterfaceStateFetchData) == ASInterfaceStateFetchData);
 }
 
+inline BOOL ASInterfaceStateIncludesMeasureLayout(ASInterfaceState interfaceState)
+{
+  return ((interfaceState & ASInterfaceStateMeasureLayout) == ASInterfaceStateMeasureLayout);
+}
+
+inline NSString * _Nonnull NSStringFromASInterfaceState(ASInterfaceState interfaceState)
+{
+  NSMutableString *result = [NSMutableString stringWithString:@"{ "];
+  if (interfaceState == ASInterfaceStateNone) {
+    [result appendString:@"No state"];
+  }
+  if (ASInterfaceStateIncludesMeasureLayout(interfaceState)) {
+    [result appendString:@"MeasureLayout"];
+  }
+  if (ASInterfaceStateIncludesFetchData(interfaceState)) {
+    [result appendString:@" - FetchData"];
+  }
+  if (ASInterfaceStateIncludesDisplay(interfaceState)) {
+    [result appendString:@" - Display"];
+  }
+  if (ASInterfaceStateIncludesVisible(interfaceState)) {
+    [result appendString:@" - Visible"];
+  }
+  [result appendString:@" }"];
+  return result;
+}
+
 NS_ASSUME_NONNULL_BEGIN
 
 ASDISPLAYNODE_EXTERN_C_BEGIN

AsyncDisplayKit/Private/ASDisplayNodeInternal.h

@@ -100,6 +100,8 @@ typedef NS_OPTIONS(NSUInteger, ASDisplayNodeMethodOverrides)
   } _flags;
 
   ASDisplayNodeExtraIvars _extra;
+  
+  BOOL _needsDataFetch;
 
 #if TIME_DISPLAYNODE_OPS
 @public