From 39cd3afa0db5d1ca28d59e749fe7d44e627ac076 Mon Sep 17 00:00:00 2001
From: Samuel Hsiung <hsiung@gmail.com>
Date: Thu, 28 Jan 2016 15:35:16 -0800
Subject: [PATCH] [AS(Table|Collection)View] make scrollDirection transform
 aware

---
 AsyncDisplayKit/ASCollectionView.mm         |  4 ++-
 AsyncDisplayKit/ASTableView.mm              |  3 ++-
 AsyncDisplayKit/Details/ASScrollDirection.h |  3 +++
 AsyncDisplayKit/Details/ASScrollDirection.m | 27 +++++++++++++++++++++
 4 files changed, 35 insertions(+), 2 deletions(-)

diff --git a/AsyncDisplayKit/ASCollectionView.mm b/AsyncDisplayKit/ASCollectionView.mm
index cefb45df04..523d8f9f8f 100644
--- a/AsyncDisplayKit/ASCollectionView.mm
+++ b/AsyncDisplayKit/ASCollectionView.mm
@@ -524,7 +524,9 @@ static NSString * const kCellReuseIdentifier = @"_ASCollectionViewCell";
   } else {
     scrollVelocity = _deceleratingVelocity;
   }
-  return [self _scrollDirectionForVelocity:scrollVelocity];
+  
+  ASScrollDirection scrollDirection = [self _scrollDirectionForVelocity:scrollVelocity];
+  return ASScrollDirectionApplyTransform(scrollDirection, self.transform);
 }
 
 - (ASScrollDirection)_scrollDirectionForVelocity:(CGPoint)scrollVelocity
diff --git a/AsyncDisplayKit/ASTableView.mm b/AsyncDisplayKit/ASTableView.mm
index a28522a3a0..31cbab7a77 100644
--- a/AsyncDisplayKit/ASTableView.mm
+++ b/AsyncDisplayKit/ASTableView.mm
@@ -571,7 +571,8 @@ static NSString * const kCellReuseIdentifier = @"_ASTableViewCell";
   } else {
     scrollVelocity = _deceleratingVelocity;
   }
-  return [self _scrollDirectionForVelocity:scrollVelocity];
+  ASScrollDirection scrollDirection = [self _scrollDirectionForVelocity:scrollVelocity];
+  return ASScrollDirectionApplyTransform(scrollDirection, self.transform);
 }
 
 - (ASScrollDirection)_scrollDirectionForVelocity:(CGPoint)velocity
diff --git a/AsyncDisplayKit/Details/ASScrollDirection.h b/AsyncDisplayKit/Details/ASScrollDirection.h
index 2d75703d69..d0192e1408 100644
--- a/AsyncDisplayKit/Details/ASScrollDirection.h
+++ b/AsyncDisplayKit/Details/ASScrollDirection.h
@@ -10,6 +10,8 @@
 
 #import "ASBaseDefines.h"
 
+#include <CoreGraphics/CGAffineTransform.h>
+
 NS_ASSUME_NONNULL_BEGIN
 
 typedef NS_OPTIONS(NSInteger, ASScrollDirection) {
@@ -32,6 +34,7 @@ BOOL ASScrollDirectionContainsRight(ASScrollDirection scrollDirection);
 BOOL ASScrollDirectionContainsLeft(ASScrollDirection scrollDirection);
 BOOL ASScrollDirectionContainsUp(ASScrollDirection scrollDirection);
 BOOL ASScrollDirectionContainsDown(ASScrollDirection scrollDirection);
+ASScrollDirection ASScrollDirectionApplyTransform(ASScrollDirection scrollDirection, CGAffineTransform transform);
 
 ASDISPLAYNODE_EXTERN_C_END
 
diff --git a/AsyncDisplayKit/Details/ASScrollDirection.m b/AsyncDisplayKit/Details/ASScrollDirection.m
index 40698d4279..778eabffbb 100644
--- a/AsyncDisplayKit/Details/ASScrollDirection.m
+++ b/AsyncDisplayKit/Details/ASScrollDirection.m
@@ -34,3 +34,30 @@ BOOL ASScrollDirectionContainsUp(ASScrollDirection scrollDirection) {
 BOOL ASScrollDirectionContainsDown(ASScrollDirection scrollDirection) {
   return (scrollDirection & ASScrollDirectionDown) != 0;
 }
+
+ASScrollDirection ASScrollDirectionInvertHorizontally(ASScrollDirection scrollDirection) {
+  if (scrollDirection == ASScrollDirectionRight) {
+    return ASScrollDirectionLeft;
+  } else if (scrollDirection == ASScrollDirectionLeft) {
+    return ASScrollDirectionRight;
+  }
+  return scrollDirection;
+}
+
+ASScrollDirection ASScrollDirectionInvertVertically(ASScrollDirection scrollDirection) {
+  if (scrollDirection == ASScrollDirectionUp) {
+    return ASScrollDirectionDown;
+  } else if (scrollDirection == ASScrollDirectionDown) {
+    return ASScrollDirectionUp;
+  }
+  return scrollDirection;
+}
+
+ASScrollDirection ASScrollDirectionApplyTransform(ASScrollDirection scrollDirection, CGAffineTransform transform) {
+  if ((transform.a < 0) && ASScrollDirectionContainsHorizontalDirection(scrollDirection)) {
+    return ASScrollDirectionInvertHorizontally(scrollDirection);
+  } else if ((transform.d < 0) && ASScrollDirectionContainsVerticalDirection(scrollDirection)) {
+    return ASScrollDirectionInvertVertically(scrollDirection);
+  }
+  return scrollDirection;
+}