Tusker/Packages/ComposeUI/Sources/ComposeUI/Views/ZoomableScrollView.swift

112 lines
4.3 KiB
Swift

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