From 68e2e068c358fcf5dc3ec19005e4bf2d8c920218 Mon Sep 17 00:00:00 2001
From: Ethan Nagel <eanagel@gmail.com>
Date: Fri, 17 Apr 2015 16:09:44 -0700
Subject: [PATCH] Bug Fix - ASTableVie sometimes fails to render cell contents
 when scrolling programatically. Root cause is because we assume UITableView's
 indexPathsForVisibleRows return the new item to be displayed after
 tableView:willDisplayCell:forRowAtIndexPath: is called. This is not always
 true, especially when we are scrolling programmatically. Fix is to track this
 "pending" visible index path and return it along with the UITableView's
 indexPathsForVisibleRows in rangeControllerVisibleNodeIndexPaths:.

---
 AsyncDisplayKit/ASTableView.mm | 24 +++++++++++++++++++++++-
 1 file changed, 23 insertions(+), 1 deletion(-)

diff --git a/AsyncDisplayKit/ASTableView.mm b/AsyncDisplayKit/ASTableView.mm
index 4c2b79ca01..26f9f9601e 100644
--- a/AsyncDisplayKit/ASTableView.mm
+++ b/AsyncDisplayKit/ASTableView.mm
@@ -118,6 +118,8 @@ static BOOL _isInterceptedSelector(SEL sel)
   BOOL _asyncDataFetchingEnabled;
 
   ASBatchContext *_batchContext;
+
+  NSIndexPath *_pendingVisibleIndexPath;
 }
 
 @property (atomic, assign) BOOL asyncDataSourceLocked;
@@ -366,6 +368,8 @@ static BOOL _isInterceptedSelector(SEL sel)
 
 - (void)tableView:(UITableView *)tableView willDisplayCell:(UITableViewCell *)cell forRowAtIndexPath:(NSIndexPath *)indexPath
 {
+  _pendingVisibleIndexPath = indexPath;
+
   [_rangeController visibleNodeIndexPathsDidChangeWithScrollDirection:self.scrollDirection];
 
   if ([_asyncDelegate respondsToSelector:@selector(tableView:willDisplayNodeForRowAtIndexPath:)]) {
@@ -375,6 +379,10 @@ static BOOL _isInterceptedSelector(SEL sel)
 
 - (void)tableView:(UITableView *)tableView didEndDisplayingCell:(UITableViewCell *)cell forRowAtIndexPath:(NSIndexPath*)indexPath
 {
+  if ([_pendingVisibleIndexPath isEqual:indexPath]) {
+    _pendingVisibleIndexPath = nil;
+  }
+
   [_rangeController visibleNodeIndexPathsDidChangeWithScrollDirection:self.scrollDirection];
 
   if ([_asyncDelegate respondsToSelector:@selector(tableView:didEndDisplayingNodeForRowAtIndexPath:)]) {
@@ -445,7 +453,21 @@ static BOOL _isInterceptedSelector(SEL sel)
 - (NSArray *)rangeControllerVisibleNodeIndexPaths:(ASRangeController *)rangeController
 {
   ASDisplayNodeAssertMainThread();
-  return [self indexPathsForVisibleRows];
+
+  NSArray *visibleIndexPaths = self.indexPathsForVisibleRows;
+
+  if ( _pendingVisibleIndexPath ) {
+    NSMutableSet *indexPaths = [NSMutableSet setWithArray:self.indexPathsForVisibleRows];
+
+    if ( [indexPaths containsObject:_pendingVisibleIndexPath]) {
+      _pendingVisibleIndexPath = nil; // once it has shown up in visibleIndexPaths, we can stop tracking it
+    } else {
+      [indexPaths addObject:_pendingVisibleIndexPath];
+      visibleIndexPaths = indexPaths.allObjects;
+    }
+  }
+
+  return visibleIndexPaths;
 }
 
 - (NSArray *)rangeController:(ASRangeController *)rangeController nodesAtIndexPaths:(NSArray *)indexPaths