Added missing files

Author: kvdesa

Package.swift

@@ -0,0 +1,28 @@
+// swift-tools-version:5.3
+// The swift-tools-version declares the minimum version of Swift required to build this package.
+
+import PackageDescription
+
+let package = Package(
+    name: "SnappingLayout",
+    products: [
+        // Products define the executables and libraries a package produces, and make them visible to other packages.
+        .library(
+            name: "SnappingLayout",
+            targets: ["SnappingLayout"]),
+    ],
+    dependencies: [
+        // Dependencies declare other packages that this package depends on.
+        // .package(url: /* package url */, from: "1.0.0"),
+    ],
+    targets: [
+        // Targets are the basic building blocks of a package. A target can define a module or a test suite.
+        // Targets can depend on other targets in this package, and on products in packages this package depends on.
+        .target(
+            name: "SnappingLayout",
+            dependencies: []),
+        .testTarget(
+            name: "SnappingLayoutTests",
+            dependencies: ["SnappingLayout"]),
+    ]
+)

Sources/SnappingLayout/Assets/.gitkeep

@@ -0,0 +1,78 @@
+//
+//  HorizontalSnappingLayout.swift
+//
+
+/// This works best when setting `collectionView.decelerationRate = .fast`.
+public class SnappingLayout: UICollectionViewFlowLayout {
+
+    // MARK: - Enums
+
+    public enum SnapPositionType: Int {
+        case left
+        case center
+        case right
+    }
+
+    // MARK: - Properties
+
+    /// Position to snap the cells.
+    public var snapPosition = SnapPositionType.center
+
+    /// Minimum horizontal velocity to trigger the snap effect.
+    private let minimumSnapVelocity: CGFloat = 0.3
+
+    // MARK: - UICollectionViewFlowLayout
+
+    public override func targetContentOffset(forProposedContentOffset proposedContentOffset: CGPoint, withScrollingVelocity velocity: CGPoint) -> CGPoint {
+        guard let collectionView = collectionView else {
+            return super.targetContentOffset(forProposedContentOffset: proposedContentOffset, withScrollingVelocity: velocity)
+        }
+
+        var offsetAdjusment = CGFloat.greatestFiniteMagnitude
+        let horizontalPosition: CGFloat
+
+        switch snapPosition {
+        case .left:
+            horizontalPosition = proposedContentOffset.x + collectionView.contentInset.left + sectionInset.left
+        case .center:
+            horizontalPosition = proposedContentOffset.x + (collectionView.bounds.width * 0.5)
+        case .right:
+            horizontalPosition = proposedContentOffset.x + collectionView.bounds.width - sectionInset.right
+        }
+
+        let targetRect = CGRect(x: proposedContentOffset.x, y: 0, width: collectionView.bounds.size.width, height: collectionView.bounds.size.height)
+        let layoutAttributesArray = super.layoutAttributesForElements(in: targetRect)
+        layoutAttributesArray?.forEach { layoutAttributes in
+            let itemHorizontalPosition: CGFloat
+
+            switch snapPosition {
+            case .left:
+                itemHorizontalPosition = layoutAttributes.frame.minX - collectionView.contentInset.left
+            case .center:
+                itemHorizontalPosition = layoutAttributes.center.x
+            case .right:
+                itemHorizontalPosition = layoutAttributes.frame.maxX + collectionView.contentInset.right
+            }
+
+            if abs(itemHorizontalPosition - horizontalPosition) < abs(offsetAdjusment) {
+                // If the drag velocity is lower than the minimum velocity (no matter the direction):
+                // snap the current cell to it's original position.
+                if abs(velocity.x) < self.minimumSnapVelocity {
+                    offsetAdjusment = itemHorizontalPosition - horizontalPosition
+                }
+                // If the velocity is higher than the snap threshold and drag is right->left:
+                // move to the next cell on the right.
+                else if velocity.x > 0 {
+                    offsetAdjusment = itemHorizontalPosition - horizontalPosition + (layoutAttributes.bounds.width + self.minimumLineSpacing)
+                }
+                // If the velocity is higher than the snap threshold and drag is left->right:
+                // move to the next cell on the left.
+                else { // velocity.x < 0
+                    offsetAdjusment = itemHorizontalPosition - horizontalPosition - (layoutAttributes.bounds.width + self.minimumLineSpacing)
+                }
+            }
+        }
+
+        return CGPoint(x: proposedContentOffset.x + offsetAdjusment, y: proposedContentOffset.y)
+    }
+}