61 lines
2.2 KiB
Swift
61 lines
2.2 KiB
Swift
//
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// TextViewCaretScrolling.swift
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// Tusker
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//
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// Created by Shadowfacts on 11/11/20.
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// Copyright © 2020 Shadowfacts. All rights reserved.
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//
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import UIKit
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protocol TextViewCaretScrolling: AnyObject {
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var caretScrollPositionAnimator: UIViewPropertyAnimator? { get set }
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}
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extension TextViewCaretScrolling {
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func ensureCursorVisible(textView: UITextView) {
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guard textView.isFirstResponder,
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let range = textView.selectedTextRange,
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let scrollView = findParentScrollView(of: textView) else {
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return
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}
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// We use a UIViewProperty animator to change the scroll view position so that we can store the currently
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// running one on the Coordinator. This allows us to cancel the running one, preventing multiple animations
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// from attempting to change the scroll view offset simultaneously, causing it to jitter around. This can
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// happen if the user is pressing return and quickly creating many new lines.
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if let existing = caretScrollPositionAnimator {
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existing.stopAnimation(true)
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}
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let cursorRect = textView.caretRect(for: range.start)
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var rectToMakeVisible = textView.convert(cursorRect, to: scrollView)
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// expand the rect to be three times the cursor height centered on the cursor so that there's
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// some space between the bottom of the line of text being edited and the top of the keyboard
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rectToMakeVisible.origin.y -= cursorRect.height
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rectToMakeVisible.size.height *= 3
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let animator = UIViewPropertyAnimator(duration: 0.2, curve: .easeInOut) {
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scrollView.scrollRectToVisible(rectToMakeVisible, animated: false)
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}
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self.caretScrollPositionAnimator = animator
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animator.startAnimation()
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}
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private func findParentScrollView(of view: UIView) -> UIScrollView? {
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var current: UIView = view
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while let superview = current.superview {
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if let scrollView = superview as? UIScrollView,
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scrollView.isScrollEnabled {
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return scrollView
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} else {
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current = superview
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}
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}
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return nil
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}
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}
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