224 lines
8.0 KiB
Swift
224 lines
8.0 KiB
Swift
//
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// Copyright 2022 New Vector Ltd
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//
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// Licensed under the Apache License, Version 2.0 (the "License");
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// you may not use this file except in compliance with the License.
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// You may obtain a copy of the License at
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//
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// http://www.apache.org/licenses/LICENSE-2.0
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//
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// Unless required by applicable law or agreed to in writing, software
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// distributed under the License is distributed on an "AS IS" BASIS,
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// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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// See the License for the specific language governing permissions and
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// limitations under the License.
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//
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import DesignKit
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import SwiftUI
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/// The splash screen shown at the beginning of the onboarding flow.
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struct SplashScreen: View {
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// MARK: - Properties
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// MARK: Private
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@Environment(\.colorScheme) private var colorScheme
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@Environment(\.layoutDirection) private var layoutDirection
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private var isLeftToRight: Bool { layoutDirection == .leftToRight }
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private var pageCount: Int { context.viewState.content.count }
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/// A timer to automatically animate the pages.
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@State private var pageTimer: Timer?
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/// The amount of offset to apply when a drag gesture is in progress.
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@State private var dragOffset: CGFloat = .zero
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// MARK: Public
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@ObservedObject var context: SplashScreenViewModel.Context
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var body: some View {
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GeometryReader { geometry in
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VStack(alignment: .leading) {
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Spacer()
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.frame(height: UIConstants.spacerHeight(in: geometry))
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// The main content of the carousel
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HStack(alignment: .top, spacing: 0) {
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// Add a hidden page at the start of the carousel duplicating the content of the last page
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SplashScreenPageView(content: context.viewState.content[pageCount - 1])
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.frame(width: geometry.size.width)
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.accessibilityIdentifier("hiddenPage")
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ForEach(0..<pageCount, id: \.self) { index in
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SplashScreenPageView(content: context.viewState.content[index])
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.frame(width: geometry.size.width)
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}
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}
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.offset(x: pageOffset(in: geometry))
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Spacer()
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SplashScreenPageIndicator(pageCount: pageCount, pageIndex: context.pageIndex)
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.frame(width: geometry.size.width)
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.padding(.bottom)
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Spacer()
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buttons
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.frame(width: geometry.size.width)
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.padding(.bottom, UIConstants.actionButtonBottomPadding)
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.padding(.bottom, geometry.safeAreaInsets.bottom > 0 ? 0 : 16)
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Spacer()
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.frame(height: UIConstants.spacerHeight(in: geometry))
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}
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.frame(maxHeight: .infinity)
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.background(background.ignoresSafeArea().offset(x: pageOffset(in: geometry)))
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.gesture(
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DragGesture()
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.onChanged(handleDragGestureChange)
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.onEnded { handleDragGestureEnded($0, viewSize: geometry.size) }
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)
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}
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.navigationBarHidden(true)
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.onAppear(perform: startTimer)
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.onDisappear(perform: stopTimer)
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}
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/// The main action buttons.
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var buttons: some View {
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VStack(spacing: 12) {
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Button { context.send(viewAction: .login) } label: {
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Text(ElementL10n.loginSplashSubmit)
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}
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.buttonStyle(.elementAction(.xLarge))
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.accessibilityIdentifier("getStartedButton")
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}
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.padding(.horizontal, 16)
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.readableFrame()
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}
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@ViewBuilder
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/// The view's background, showing a gradient in light mode and a solid colour in dark mode.
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var background: some View {
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if colorScheme == .light {
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LinearGradient(gradient: context.viewState.backgroundGradient,
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startPoint: .leading,
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endPoint: .trailing)
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.flipsForRightToLeftLayoutDirection(true)
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} else {
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Color.element.background
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}
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}
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// MARK: - Animation
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/// Starts the animation timer for an automatic carousel effect.
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private func startTimer() {
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guard pageTimer == nil else { return }
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pageTimer = Timer.scheduledTimer(withTimeInterval: 5, repeats: true) { _ in
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if context.pageIndex == pageCount - 1 {
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showHiddenPage()
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withElementAnimation(.easeInOut(duration: 0.7)) {
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showNextPage()
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}
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} else {
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withElementAnimation(.easeInOut(duration: 0.7)) {
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showNextPage()
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}
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}
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}
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}
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/// Stops the animation timer for manual interaction.
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private func stopTimer() {
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guard let pageTimer = pageTimer else { return }
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self.pageTimer = nil
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pageTimer.invalidate()
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}
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private func showNextPage() {
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// Wrap back round to the first page index when reaching the end.
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context.pageIndex = (context.pageIndex + 1) % context.viewState.content.count
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}
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private func showPreviousPage() {
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// Prevent the hidden page at index -1 from being shown.
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context.pageIndex = max(0, context.pageIndex - 1)
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}
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private func showHiddenPage() {
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// Hidden page for a nicer animation when looping back to the start.
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context.pageIndex = -1
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}
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/// The offset to apply to the `HStack` of pages.
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private func pageOffset(in geometry: GeometryProxy) -> CGFloat {
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(CGFloat(context.pageIndex + 1) * -geometry.size.width) + dragOffset
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}
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// MARK: - Gestures
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/// Whether or not a drag gesture is valid or not.
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/// - Parameter width: The gesture's translation width.
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/// - Returns: `true` if there is another page to drag to.
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private func shouldSwipeForTranslation(_ width: CGFloat) -> Bool {
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if context.pageIndex == 0 {
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return isLeftToRight ? width < 0 : width > 0
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} else if context.pageIndex == pageCount - 1 {
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return isLeftToRight ? width > 0 : width < 0
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}
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return true
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}
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/// Updates the `dragOffset` based on the gesture's value.
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/// - Parameter drag: The drag gesture value to handle.
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private func handleDragGestureChange(_ drag: DragGesture.Value) {
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guard shouldSwipeForTranslation(drag.translation.width) else { return }
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stopTimer()
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// Animate the change over a few frames to smooth out any stuttering.
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withElementAnimation(.linear(duration: 0.05)) {
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dragOffset = isLeftToRight ? drag.translation.width : -drag.translation.width
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}
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}
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/// Clears the drag offset and informs the view model to switch to another page if necessary.
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/// - Parameter viewSize: The size of the view in which the gesture took place.
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private func handleDragGestureEnded(_ drag: DragGesture.Value, viewSize: CGSize) {
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guard shouldSwipeForTranslation(drag.predictedEndTranslation.width) else {
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// Reset the offset just in case.
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withElementAnimation { dragOffset = 0 }
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return
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}
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withElementAnimation(.easeInOut(duration: 0.2)) {
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if drag.predictedEndTranslation.width < -viewSize.width / 2 {
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showNextPage()
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} else if drag.predictedEndTranslation.width > viewSize.width / 2 {
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showPreviousPage()
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}
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dragOffset = 0
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}
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}
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}
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// MARK: - Previews
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struct SplashScreen_Previews: PreviewProvider {
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static let viewModel = SplashScreenViewModel()
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static var previews: some View {
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SplashScreen(context: viewModel.context)
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.tint(.element.accent)
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}
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}
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