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97 changes: 97 additions & 0 deletions
97
Sources/SwiftUISnapDraggingModifier/Gesture/ScrollController.swift
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| Original file line number | Diff line number | Diff line change |
|---|---|---|
| @@ -0,0 +1,97 @@ | ||
| import UIKit | ||
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| final class ScrollController { | ||
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| struct LockingDirection: OptionSet { | ||
| let rawValue: Int | ||
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| static let vertical = LockingDirection(rawValue: 1 << 0) | ||
| static let horizontal = LockingDirection(rawValue: 1 << 1) | ||
| } | ||
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| private var scrollObserver: NSKeyValueObservation! | ||
| private(set) var lockingDirection: LockingDirection = [] | ||
| private var previousValue: CGPoint? | ||
| let scrollView: UIScrollView | ||
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| init(scrollView: UIScrollView) { | ||
| self.scrollView = scrollView | ||
| scrollObserver = scrollView.observe(\.contentOffset, options: .old) { | ||
| [weak self, weak _scrollView = scrollView] scrollView, change in | ||
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| guard let scrollView = _scrollView else { return } | ||
| guard let self = self else { return } | ||
| self.handleScrollViewEvent(scrollView: scrollView, change: change) | ||
| } | ||
| } | ||
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| deinit { | ||
| endTracking() | ||
| } | ||
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| func lockScrolling(direction: LockingDirection) { | ||
| lockingDirection.insert(direction) | ||
| } | ||
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| func unlockScrolling(direction: LockingDirection) { | ||
| lockingDirection.remove(direction) | ||
| } | ||
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| func setShowsVerticalScrollIndicator(_ flag: Bool) { | ||
| scrollView.showsVerticalScrollIndicator = flag | ||
| } | ||
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| func endTracking() { | ||
| unlockScrolling(direction: [.vertical, .horizontal]) | ||
| scrollObserver.invalidate() | ||
| } | ||
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| func resetContentOffsetY() { | ||
| let contentInset = scrollView.adjustedContentInset | ||
| if scrollView.contentOffset.y < -contentInset.top { | ||
| setContentOffset(scrollView.contentOffsetToResetY) | ||
| } | ||
| } | ||
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| func setContentOffset(_ offset: CGPoint) { | ||
| let previous = lockingDirection | ||
| lockingDirection = [] | ||
| defer { | ||
| lockingDirection = previous | ||
| } | ||
| scrollView.contentOffset = offset | ||
| } | ||
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| private func handleScrollViewEvent( | ||
| scrollView: UIScrollView, | ||
| change: NSKeyValueObservedChange<CGPoint> | ||
| ) { | ||
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| // For debugging | ||
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| guard let oldValue = change.oldValue else { return } | ||
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| guard lockingDirection.isEmpty == false else { | ||
| return | ||
| } | ||
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| // guard scrollView.contentOffset != oldValue else { return } | ||
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| guard oldValue != previousValue else { return } | ||
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| previousValue = scrollView.contentOffset | ||
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| var fixedOffset = scrollView.contentOffset | ||
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| if lockingDirection.contains(.vertical) { | ||
| fixedOffset.y = oldValue.y | ||
| } | ||
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| if lockingDirection.contains(.horizontal) { | ||
| fixedOffset.x = oldValue.x | ||
| } | ||
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| scrollView.setContentOffset(fixedOffset, animated: false) | ||
| } | ||
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| } |
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