Implement swipe to reply on timeline items (#1148)

2026-11-03 06:55:59 +00:00 · 2023-06-29 11:31:46 +03:00
parent 10e167732b
commit 93022dd7f2
6 changed files with 190 additions and 18 deletions
@@ -0,0 +1,149 @@
+//
+// Copyright 2023 New Vector Ltd
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+// http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+//
+
+import SwiftUI
+
+struct SwipeRightAction<Label: View>: ViewModifier {
+    private let actionThreshold = 50.0
+    private let xOffsetThreshold = 100.0
+    private let swipeThreshold = 1000.0
+    
+    private let feedbackGenerator = UIImpactFeedbackGenerator(style: .heavy)
+    
+    @State private var canStartAction = false
+    @GestureState private var dragGestureActive = false
+    
+    @State private var hasReachedActionThreshold = false
+    @State private var xOffset = 0.0
+    
+    /// The view to be shown on the left side of the content
+    let label: () -> Label
+    /// Defer computing whether an action is available until the gesture is started
+    let shouldStartAction: () -> Bool
+    /// Callback for when the dragged past the action threshold
+    let action: () -> Void
+    
+    func body(content: Content) -> some View {
+        content
+            .offset(x: xOffset, y: 0.0)
+            .animation(.interactiveSpring().speed(0.5), value: xOffset)
+            .gesture(DragGesture()
+                .updating($dragGestureActive) { _, state, _ in
+                    // Available actions should be computed on the fly so we use a gesture state change
+                    // to ask whether the move should be started or not.
+                    state = true
+                }
+                .onChanged { value in
+                    guard canStartAction else {
+                        return
+                    }
+                    
+                    // We want to add a spring like behavior to the drag in which the view
+                    // moves slower the more it's dragged. We use a circular easing function
+                    // to generate those values up to the `swipeThreshold`
+                    // The final translation will be between 0 and `swipeThreshold` with the action being enabled from
+                    // `actionThreshold` onwards
+                    let screenWidthNormalisedTranslation = max(0.0, min(value.translation.width, swipeThreshold)) / swipeThreshold
+                    let easedTranslation = circularEaseOut(screenWidthNormalisedTranslation)
+                    xOffset = easedTranslation * xOffsetThreshold
+                    
+                    if xOffset > actionThreshold {
+                        if !hasReachedActionThreshold {
+                            feedbackGenerator.impactOccurred()
+                            hasReachedActionThreshold = true
+                        }
+                    } else {
+                        hasReachedActionThreshold = false
+                    }
+                }
+                .onEnded { _ in
+                    if xOffset > actionThreshold {
+                        action()
+                    }
+                    
+                    xOffset = 0.0
+                }
+            )
+            .onChange(of: dragGestureActive, perform: { value in
+                if value == true {
+                    if shouldStartAction() {
+                        feedbackGenerator.prepare()
+                        canStartAction = true
+                    }
+                }
+            })
+            .overlay(alignment: .leading) {
+                // We want the action icon to follow the view translation and gradually fade in
+                label()
+                    .opacity(xOffset / 50)
+                    .animation(.interactiveSpring().speed(0.5), value: xOffset)
+                    .offset(x: -actionThreshold + min(xOffset, actionThreshold), y: 0.0)
+            }
+    }
+    
+    /// Used to compute the horizontal translation amount.
+    /// The more it's dragged the less it moves on a circular ease out curve
+    private func circularEaseOut(_ value: Double) -> Double {
+        sqrt((2 - value) * value)
+    }
+}
+
+extension View {
+    func swipeRightAction(label: @escaping () -> some View,
+                          shouldStartAction: @escaping () -> Bool,
+                          action: @escaping () -> Void) -> some View {
+        modifier(SwipeRightAction(label: label, shouldStartAction: shouldStartAction, action: action))
+    }
+}
+
+struct SwipeRightAction_Previews: PreviewProvider {
+    static var previews: some View { Preview() }
+    
+    struct Preview: View {
+        @State private var isPresentingSheet = false
+        
+        var body: some View {
+            NavigationStack {
+                ScrollView {
+                    VStack(alignment: .leading) {
+                        mockBubble("This is a message from somebody with a couple of lines of text.")
+                            .swipeRightAction {
+                                Image(systemName: "flame")
+                            } shouldStartAction: {
+                                true
+                            } action: {
+                                isPresentingSheet = true
+                            }
+                    }
+                    .padding()
+                }
+                .navigationTitle("Work chat")
+                .navigationBarTitleDisplayMode(.inline)
+            }
+            .sheet(isPresented: $isPresentingSheet) {
+                Text("Action triggered!")
+                    .presentationDetents([.medium])
+            }
+        }
+        
+        func mockBubble(_ body: String) -> some View {
+            Text(body)
+                .padding(.horizontal, 12)
+                .padding(.vertical, 4)
+                .background(Color.compound._bgBubbleOutgoing, in: RoundedRectangle(cornerRadius: 12))
+        }
+    }
+}