forked from shadowfacts/Tusker
46 lines
1.5 KiB
Swift
46 lines
1.5 KiB
Swift
//
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// UIScrollView+Top.swift
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// Tusker
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//
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// Created by Shadowfacts on 11/1/22.
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// Copyright © 2022 Shadowfacts. All rights reserved.
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//
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import UIKit
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private let prevScrollOffsetBeforeScrollToTopKey = UnsafeMutableRawPointer.allocate(byteCount: 0, alignment: 0)
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extension UIScrollView {
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private var prevScrollOffsetBeforeScrollToTop: CGFloat? {
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get {
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if let v = (objc_getAssociatedObject(self, prevScrollOffsetBeforeScrollToTopKey) as? NSNumber)?.doubleValue {
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return CGFloat(v)
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} else {
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return nil
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}
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}
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set {
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if let newValue {
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objc_setAssociatedObject(self, prevScrollOffsetBeforeScrollToTopKey, NSNumber(value: newValue), .OBJC_ASSOCIATION_COPY_NONATOMIC)
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} else {
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objc_setAssociatedObject(self, prevScrollOffsetBeforeScrollToTopKey, nil, .OBJC_ASSOCIATION_COPY_NONATOMIC)
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}
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}
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}
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func scrollToTop() {
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let top = -adjustedContentInset.top
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// +5 to add a little bit of wiggle room
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let isScrolledToTop = contentOffset.y < top + 5
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if isScrolledToTop {
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if let prevScrollOffsetBeforeScrollToTop {
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self.prevScrollOffsetBeforeScrollToTop = nil
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setContentOffset(CGPoint(x: 0, y: prevScrollOffsetBeforeScrollToTop), animated: true)
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}
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} else {
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prevScrollOffsetBeforeScrollToTop = contentOffset.y
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setContentOffset(CGPoint(x: 0, y: top), animated: true)
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}
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}
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}
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