112 lines
4.3 KiB
Swift
112 lines
4.3 KiB
Swift
//
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// ZoomableScrollView.swift
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// ComposeUI
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//
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// Created by Shadowfacts on 4/29/23.
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//
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import SwiftUI
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@available(iOS 16.0, *)
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struct ZoomableScrollView<Content: View>: UIViewControllerRepresentable {
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let content: Content
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init(@ViewBuilder content: () -> Content) {
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self.content = content()
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}
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func makeUIViewController(context: Context) -> Controller {
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return Controller(content: content)
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}
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func updateUIViewController(_ uiViewController: Controller, context: Context) {
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uiViewController.host.rootView = content
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}
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class Controller: UIViewController, UIScrollViewDelegate {
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let scrollView = UIScrollView()
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let host: UIHostingController<Content>
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private var lastIntrinsicSize: CGSize?
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private var contentViewTopConstraint: NSLayoutConstraint!
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private var contentViewLeadingConstraint: NSLayoutConstraint!
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private var hostBoundsObservation: NSKeyValueObservation?
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init(content: Content) {
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self.host = UIHostingController(rootView: content)
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super.init(nibName: nil, bundle: nil)
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}
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required init?(coder: NSCoder) {
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fatalError("init(coder:) has not been implemented")
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}
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override func viewDidLoad() {
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super.viewDidLoad()
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scrollView.delegate = self
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scrollView.bouncesZoom = true
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scrollView.translatesAutoresizingMaskIntoConstraints = false
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view.addSubview(scrollView)
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host.sizingOptions = .intrinsicContentSize
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host.view.backgroundColor = .clear
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host.view.translatesAutoresizingMaskIntoConstraints = false
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addChild(host)
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scrollView.addSubview(host.view)
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host.didMove(toParent: self)
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contentViewLeadingConstraint = host.view.leadingAnchor.constraint(equalTo: scrollView.contentLayoutGuide.leadingAnchor)
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contentViewTopConstraint = host.view.topAnchor.constraint(equalTo: scrollView.contentLayoutGuide.topAnchor)
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NSLayoutConstraint.activate([
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scrollView.frameLayoutGuide.leadingAnchor.constraint(equalTo: view.leadingAnchor),
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scrollView.frameLayoutGuide.trailingAnchor.constraint(equalTo: view.trailingAnchor),
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scrollView.frameLayoutGuide.topAnchor.constraint(equalTo: view.topAnchor),
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scrollView.frameLayoutGuide.bottomAnchor.constraint(equalTo: view.bottomAnchor),
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contentViewLeadingConstraint,
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contentViewTopConstraint,
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])
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}
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override func viewDidLayoutSubviews() {
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super.viewDidLayoutSubviews()
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if !host.view.intrinsicContentSize.equalTo(.zero),
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host.view.intrinsicContentSize != lastIntrinsicSize {
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self.lastIntrinsicSize = host.view.intrinsicContentSize
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let maxHeight = view.bounds.height - view.safeAreaInsets.top - view.safeAreaInsets.bottom
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let maxWidth = view.bounds.width - view.safeAreaInsets.left - view.safeAreaInsets.right
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let heightScale = maxHeight / host.view.intrinsicContentSize.height
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let widthScale = maxWidth / host.view.intrinsicContentSize.width
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let minScale = min(widthScale, heightScale)
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let maxScale = minScale >= 1 ? minScale + 2 : 2
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scrollView.minimumZoomScale = minScale
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scrollView.maximumZoomScale = maxScale
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scrollView.zoomScale = minScale
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}
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centerImage()
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}
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func viewForZooming(in scrollView: UIScrollView) -> UIView? {
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return host.view
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}
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func scrollViewDidZoom(_ scrollView: UIScrollView) {
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centerImage()
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}
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func centerImage() {
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let yOffset = max(0, (view.bounds.size.height - host.view.bounds.height * scrollView.zoomScale) / 2)
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contentViewTopConstraint.constant = yOffset
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let xOffset = max(0, (view.bounds.size.width - host.view.bounds.width * scrollView.zoomScale) / 2)
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contentViewLeadingConstraint.constant = xOffset
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}
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}
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}
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