Limits paging app screenshots on FeaturedViewController to bottom of cell

Prioritizes paging featured apps over app screenshots.

AltStore/Browse/FeaturedViewController.swift

@@ -363,6 +363,7 @@ private extension FeaturedViewController
         dataSource.cellConfigurationHandler = { cell, storeApp, indexPath in
             let cell = cell as! AppCardCollectionViewCell
             cell.configure(for: storeApp)
+            cell.prefersPagingScreenshots = false
             
             cell.bannerView.button.addTarget(self, action: #selector(FeaturedViewController.performAppAction), for: .primaryActionTriggered)
             cell.bannerView.sourceIconImageView.isHidden = true

AltStore/Components/AppCardCollectionViewCell.swift

@@ -20,9 +20,13 @@ class AppCardCollectionViewCell: UICollectionViewCell
     let bannerView: AppBannerView
     let captionLabel: UILabel
     
+    var prefersPagingScreenshots = true
+    
     private let screenshotsCollectionView: UICollectionView
     private let stackView: UIStackView
     
+    private let topAreaPanGestureRecognizer: UIPanGestureRecognizer
+    
     private lazy var dataSource = self.makeDataSource()
     
     private var screenshots: [AppScreenshot] = [] {
@@ -81,6 +85,12 @@ class AppCardCollectionViewCell: UICollectionViewCell
         let spacing = (inset * 2) + (minimumItemSpacing * 2)
         self.collectionViewAspectRatioConstraint = self.screenshotsCollectionView.widthAnchor.constraint(equalTo: self.screenshotsCollectionView.heightAnchor, multiplier: multiplier, constant: spacing)
         
+        // Allows us to ignore swipes in top portion of screenshotsCollectionView.
+        self.topAreaPanGestureRecognizer = UIPanGestureRecognizer(target: nil, action: nil)
+        self.topAreaPanGestureRecognizer.cancelsTouchesInView = false
+        self.topAreaPanGestureRecognizer.delaysTouchesBegan = false
+        self.topAreaPanGestureRecognizer.delaysTouchesEnded = false
+        
         super.init(frame: frame)
         
         self.contentView.clipsToBounds = true
@@ -101,6 +111,10 @@ class AppCardCollectionViewCell: UICollectionViewCell
         tapGestureRecognizer.delaysTouchesEnded = false
         self.screenshotsCollectionView.addGestureRecognizer(tapGestureRecognizer)
         
+        self.topAreaPanGestureRecognizer.delegate = self
+        self.screenshotsCollectionView.panGestureRecognizer.require(toFail: self.topAreaPanGestureRecognizer)
+        self.screenshotsCollectionView.addGestureRecognizer(self.topAreaPanGestureRecognizer)
+        
         self.screenshotsCollectionView.register(AppScreenshotCollectionViewCell.self, forCellWithReuseIdentifier: RSTCellContentGenericCellIdentifier)
         
         self.stackView.isLayoutMarginsRelativeArrangement = true
@@ -324,3 +338,51 @@ extension AppCardCollectionViewCell
         }
     }
 }
+
+extension AppCardCollectionViewCell: UIGestureRecognizerDelegate
+{
+    override func gestureRecognizerShouldBegin(_ gestureRecognizer: UIGestureRecognizer) -> Bool
+    {
+        // Never recognize topAreaPanGestureRecognizer unless prefersPagingScreenshots is false.
+        guard !self.prefersPagingScreenshots else { return false }
+        
+        let point = gestureRecognizer.location(in: self.screenshotsCollectionView)
+        
+        // Top area = Top 3/4
+        let isTopArea = point.y < (self.screenshotsCollectionView.bounds.height / 4) * 3
+        return isTopArea
+    }
+    
+    func gestureRecognizer(_ gestureRecognizer: UIGestureRecognizer, shouldBeRequiredToFailBy otherGestureRecognizer: UIGestureRecognizer) -> Bool 
+    {
+        guard let panGestureRecognizer = otherGestureRecognizer as? UIPanGestureRecognizer, let view = panGestureRecognizer.view else { return false }
+        
+        if view.isDescendant(of: self.screenshotsCollectionView)
+        {
+            // Only allow nested gesture recognizers if topAreaPanGestureRecognizer fails.
+            return true
+        }
+        else 
+        {
+            // Always allow parent gesture recognizers.
+            return false
+        }
+    }
+    
+    func gestureRecognizer(_ gestureRecognizer: UIGestureRecognizer, shouldRecognizeSimultaneouslyWith otherGestureRecognizer: UIGestureRecognizer) -> Bool 
+    {
+        guard let panGestureRecognizer = otherGestureRecognizer as? UIPanGestureRecognizer, let view = panGestureRecognizer.view else { return true }
+        
+        if view.isDescendant(of: self.screenshotsCollectionView)
+        {
+            // Don't recognize topAreaPanGestureRecognizer alongside nested gesture recognizers.
+            return false
+        }
+        else 
+        {
+            // Allow recognizing simultaneously with parent gesture recognizers.
+            // This fixes accidentally breaking scrolling in parent.
+            return true
+        }
+    }
+}