103 lines
3.3 KiB
Swift
103 lines
3.3 KiB
Swift
// -=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-
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// Created by Sam Deane on 27/07/22.
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// All code (c) 2022 - present day, Elegant Chaos Limited.
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// -=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-
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import SwiftUI
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public enum VisibilityChange {
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case hidden
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case shown
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}
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public class VisibilityTracker<ID: Hashable>: ObservableObject {
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/// The global bounds of the container view.
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public var containerBounds: CGRect
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/// Dictionary containing the offset of every visible view.
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public var visibleViews: [ID:CGFloat]
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/// Ids of the visible views, sorted by offset.
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/// The first item is the top view, the last one, the bottom view.
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public var sortedViewIDs: [ID]
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/// Action to perform when a view becomes visible or is hidden.
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public var action: Action
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/// The id of the top visible view.
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public var topVisibleView: ID? { sortedViewIDs.first }
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/// The id of the bottom visible view.
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public var bottomVisibleView: ID? { sortedViewIDs.last }
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/// Action callback signature.
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public typealias Action = (ID, VisibilityChange, VisibilityTracker<ID>) -> ()
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public init(action: @escaping Action) {
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self.containerBounds = .zero
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self.visibleViews = [:]
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self.sortedViewIDs = []
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self.action = action
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}
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public func reportContainerBounds(_ bounds: CGRect) {
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containerBounds = bounds
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}
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public func reportContentBounds(_ bounds: CGRect, id: ID) {
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let topLeft = bounds.origin
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let size = bounds.size
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let bottomRight = CGPoint(x: topLeft.x + size.width, y: topLeft.y + size.height)
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let isVisible = containerBounds.contains(topLeft) || containerBounds.contains(bottomRight)
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let wasVisible = visibleViews[id] != nil
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// print("report content bounds start")
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// print(id)
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// print(bounds.width)
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// print(bounds.height)
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// print(bounds.origin)
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// print(containerBounds)
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// print("report content bounds end")
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visibleViews[id] = -1 * (bounds.origin.y - containerBounds.origin.y)
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// if (abs(visibleViews[id]! ) > 500 || visibleViews[id]! < 0) {
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if (((id.hashValue) != "1".hashValue && visibleViews[id]! < 0) ||
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bounds.width == 0 || bounds.height == 0
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|| bounds.origin.x == 0 || bounds.origin.y == 0
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|| abs(visibleViews[id]! ) > 500 )
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{
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visibleViews.removeValue(forKey: id)
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}
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// if (visibleViews[id]! > 0) {
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// visibleViews.removeValue(forKey: id)
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// }
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sortViews()
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action(id, .shown, self)
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// if isVisible {
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// visibleViews[id] = bounds.origin.y - containerBounds.origin.y
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// sortViews()
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// if !wasVisible {
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// action(id, .shown, self)
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// }
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// } else {
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// if wasVisible {
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// visibleViews.removeValue(forKey: id)
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// sortViews()
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// action(id, .hidden, self)
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// }
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// }
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}
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func sortViews() {
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let sortedPairs = visibleViews.sorted(by: { Int($0.1) < Int($1.1) })
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// let sortedPairs = visibleViews.sorted(by: { $0 < $1 })
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sortedViewIDs = sortedPairs.map { $0.0 }
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}
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}
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