From efdd8acd99f4442265f57b1c0907aea8a03813b0 Mon Sep 17 00:00:00 2001
From: Ben Dolman <ben.dolman@gmail.com>
Date: Tue, 6 Oct 2020 10:36:43 -0600
Subject: [PATCH] Fix hit point when ASCollectionNode inverted set to true
 (#1781)

* Account for possible inverted transform during hit test

When ASCollectionNode has the `inverted` flag set, a transform gets
set on the cell node. We need to make sure that we account for that
when dealing in the view coordinates.

* Store self.node and self.node.view in local variables for better readability.

* Add a test for hit testing in an inverted ASCollectionNode
---
 Source/Details/_ASCollectionViewCell.mm | 10 +++++++---
 Tests/ASCollectionViewTests.mm          | 25 +++++++++++++++++++++++++
 2 files changed, 32 insertions(+), 3 deletions(-)

diff --git a/Source/Details/_ASCollectionViewCell.mm b/Source/Details/_ASCollectionViewCell.mm
index 28d8cec2a..93f4626a4 100644
--- a/Source/Details/_ASCollectionViewCell.mm
+++ b/Source/Details/_ASCollectionViewCell.mm
@@ -97,6 +97,9 @@ - (void)layoutSubviews
 
 - (UIView *)hitTest:(CGPoint)point withEvent:(UIEvent *)event
 {
+  ASCellNode *node = self.node;
+  UIView *nodeView = node.view;
+  
   /**
    * The documentation for hitTest:withEvent: on an UIView explicitly states the fact that:
    * it ignores view objects that are hidden, that have disabled user interactions, or have an
@@ -106,12 +109,13 @@ - (UIView *)hitTest:(CGPoint)point withEvent:(UIEvent *)event
    * superclass hitTest:withEvent: implementation. If this returns a valid value we can go on with
    * checking the node as it's expected to not be in one of these states.
    */
-  if (![super hitTest:self.bounds.origin withEvent:event]) {
+  CGPoint originPointOnView = [self convertPoint:nodeView.bounds.origin fromView:nodeView];
+  if (![super hitTest:originPointOnView withEvent:event]) {
     return nil;
   }
 
-  CGPoint pointOnNode = [self.node.view convertPoint:point fromView:self];
-  return [self.node hitTest:pointOnNode withEvent:event];
+  CGPoint pointOnNode = [node.view convertPoint:point fromView:self];
+  return [node hitTest:pointOnNode withEvent:event];
 }
 
 - (BOOL)pointInside:(CGPoint)point withEvent:(nullable UIEvent *)event
diff --git a/Tests/ASCollectionViewTests.mm b/Tests/ASCollectionViewTests.mm
index 496c1feba..ab4779ea9 100644
--- a/Tests/ASCollectionViewTests.mm
+++ b/Tests/ASCollectionViewTests.mm
@@ -387,6 +387,31 @@ - (void)testThatCollectionNodeConformsToExpectedProtocols
   XCTAssert([node conformsToProtocol:@protocol(ASRangeControllerUpdateRangeProtocol)]);
 }
 
+/**
+ * Test that hit tests are correct when the collection node is inverted.
+ */
+- (void)testInvertedCollectionViewHitTest
+{
+  ASCollectionViewTestController *testController = [[ASCollectionViewTestController alloc] initWithNibName:nil bundle:nil];
+  UIWindow *window = [[UIWindow alloc] initWithFrame:[[UIScreen mainScreen] bounds]];
+  [window setRootViewController:testController];
+  [window makeKeyAndVisible];
+  
+  testController.collectionNode.inverted = true;
+  [testController.collectionNode reloadData];
+  [testController.collectionNode waitUntilAllUpdatesAreProcessed];
+  [testController.collectionView layoutIfNeeded];
+  
+  NSIndexPath *indexPath = [NSIndexPath indexPathForItem:0 inSection:0];
+  UICollectionViewCell *cell = [testController.collectionView cellForItemAtIndexPath:indexPath];
+  ASDisplayNode *node = [testController.collectionNode nodeForItemAtIndexPath:indexPath];
+  
+  CGPoint testPointInCollectionView = CGPointMake(CGRectGetMidX(cell.frame), CGRectGetMidY(cell.frame));
+  UIView *hitTestView = [testController.collectionView hitTest:testPointInCollectionView withEvent:nil];
+  
+  XCTAssertEqualObjects(hitTestView, node.view, @"Expected node's view to be the result of the hit test.");
+}
+
 #pragma mark - Update Validations
 
 #define updateValidationTestPrologue \