Fix: Improvements to card swipe animations and gesture handling

Sources/CardStack/CardStack.swift

@@ -28,19 +28,25 @@ where Data.Index: Hashable {
     self._currentIndex = State<Data.Index>(initialValue: data.startIndex)
   }
 
+  @ViewBuilder private func cardViewOrEmpty(index: Data.Index) -> some View {
+    let relativeIndex = self.data.distance(from: self.currentIndex, to: index)
+    if relativeIndex >= 0 && relativeIndex < self.configuration.maxVisibleCards {
+       self.card(index: index, relativeIndex: relativeIndex)
+    } else {
+       EmptyView()
+    }
+  }
+
   public var body: some View {
     ZStack {
-      ForEach(data.indices.reversed(), id: \.self) { index -> AnyView in
-        let relativeIndex = self.data.distance(from: self.currentIndex, to: index)
-        if relativeIndex >= 0 && relativeIndex < self.configuration.maxVisibleCards {
-          return AnyView(self.card(index: index, relativeIndex: relativeIndex))
-        } else {
-          return AnyView(EmptyView())
-        }
+      ForEach(data.indices.reversed(), id: \.self) { index in
+        cardViewOrEmpty(index: index)
+          .zIndex(Double(self.data.distance(from: index, to: self.data.startIndex)))
       }
     }
   }
 
+
   private func card(index: Data.Index, relativeIndex: Int) -> some View {
     CardView(
       direction: direction,

Sources/CardStack/CardView.swift

@@ -1,14 +1,23 @@
 import SwiftUI
+import Combine
 
 struct CardView<Direction, Content: View>: View {
   @Environment(\.cardStackConfiguration) private var configuration: CardStackConfiguration
   @State private var translation: CGSize = .zero
+  @State private var draggingState: CardDraggingState = .idle
+  @GestureState private var isDragging: Bool = false
 
   private let direction: (Double) -> Direction?
   private let isOnTop: Bool
   private let onSwipe: (Direction) -> Void
   private let content: (Direction?) -> Content
 
+  private enum CardDraggingState {
+    case dragging
+    case ended
+    case idle
+  }
+
   init(
     direction: @escaping (Double) -> Direction?,
     isOnTop: Bool,
@@ -21,27 +30,59 @@ struct CardView<Direction, Content: View>: View {
     self.content = content
   }
 
-  var body: some View {
+  @ViewBuilder var cardView: some View {
     GeometryReader { geometry in
       self.content(self.swipeDirection(geometry))
+        .disabled(self.translation != .zero)
         .offset(self.translation)
         .rotationEffect(self.rotation(geometry))
         .simultaneousGesture(self.isOnTop ? self.dragGesture(geometry) : nil)
+        .animation(draggingState == .dragging ? .easeInOut(duration: 0.05) : self.configuration.animation, value: translation)
     }
     .transition(transition)
   }
 
+  private func cancelDragging() {
+    draggingState = .idle
+    translation = .zero
+  }
+
+  var body: some View {
+    if #available(iOS 14.0, *) {
+      cardView
+      .onChange(of: isDragging) { newValue in
+        if !newValue && draggingState == .dragging {
+          cancelDragging()
+        }
+      }
+    } else { // iOS 13.0, *
+      cardView
+        .onReceive(Just(isDragging)) { newValue in
+          if !newValue && draggingState == .dragging {
+            cancelDragging()
+          }
+        }
+    }
+  }
+
   private func dragGesture(_ geometry: GeometryProxy) -> some Gesture {
     DragGesture()
+      .updating($isDragging) { value, state, transaction in
+        state = true
+      }
       .onChanged { value in
+        self.draggingState = .dragging
         self.translation = value.translation
       }
       .onEnded { value in
-        self.translation = value.translation
+        draggingState = .ended
         if let direction = self.swipeDirection(geometry) {
-          withAnimation(self.configuration.animation) { self.onSwipe(direction) }
+          self.translation = value.translation
+          withAnimation(self.configuration.animation) {
+            self.onSwipe(direction)
+          }
         } else {
-          withAnimation { self.translation = .zero }
+          cancelDragging()
         }
       }
   }