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Fix jumpy cursor bug

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This fixes jumpy cursor bug by clamping cursor restoration and consuming tag diff only once.

Closes: https://github.com/damus-io/damus/issues/747
Changelog-Fixed: Fixed incorrect behaviour on the post editor that would cause the text cursor to occasionally jump beyond the correct location in some editing operations.
Signed-off-by: alltheseas <64376233+alltheseas@users.noreply.github.com>
Co-authored-by: Daniel D’Aquino <daniel@daquino.me>
Signed-off-by: Daniel D’Aquino <daniel@daquino.me>
This commit is contained in:
alltheseas
2025-12-08 18:32:38 -06:00
committed by GitHub
parent f1b81a3e5c
commit 5066a39ffb
1 changed files with 27 additions and 14 deletions
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41
damus/Shared/Components/Text/TextViewWrapper.swift
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@@ -49,21 +49,41 @@ struct TextViewWrapper: UIViewRepresentable {
}
func updateUIView(_ uiView: UITextView, context: Context) {
// Save the current selection BEFORE making any changes
// This is critical because setting attributedText causes UITextView to reset the cursor position
let savedRange = uiView.selectedRange
uiView.attributedText = attributedText
TextViewWrapper.setTextProperties(uiView)
setCursorPosition(textView: uiView)
let range = uiView.selectedRange
// Set the text height that will fit all the text
// This is needed because the UIKit auto-layout prefers to overflow the text to the right than to expand the text box vertically, even with low horizontal compression resistance
self.setIdealHeight(uiView: uiView)
// Restore cursor position with priority:
// 1. If cursorIndex is explicitly set (e.g., from mention insertion), use it
// 2. Otherwise, restore the saved range with tag diff adjustment
// Clamp saved selection to current text bounds to avoid out-of-range resets after text mutations
let adjustedLocation = max(0, min(savedRange.location + tagModel.diff, attributedText.length))
let adjustedLength = max(0, min(savedRange.length, attributedText.length - adjustedLocation))
let selectionRange = NSRange(location: adjustedLocation, length: adjustedLength)
uiView.selectedRange = NSRange(location: range.location + tagModel.diff, length: range.length)
if let index = cursorIndex,
let newPosition = uiView.position(from: uiView.beginningOfDocument, offset: index),
let textRange = uiView.textRange(from: newPosition, to: newPosition) {
uiView.selectedTextRange = textRange
tagModel.diff = 0
self.setIdealHeight(uiView: uiView)
return
} // If the explicit cursor target is invalid, fall back to the saved range
// Restore the saved range, adjusted for any tag model changes
uiView.selectedRange = selectionRange
tagModel.diff = 0
self.setIdealHeight(uiView: uiView)
}
/// Based on our desired layout, calculate the ideal size of the text box, then set the height to the ideal size
/// Based on our desired layout, calculate the ideal size of the text box, then set the height to the ideal size.
///
/// Sets the text height that will fit all the text.
/// This is needed because the UIKit auto-layout prefers to overflow the text to the right than to expand the text box vertically, even with low horizontal compression resistance.
private func setIdealHeight(uiView: UITextView) {
DispatchQueue.main.async { // Queue on main thread, because modifying view state directly during re-render causes undefined behavior
let idealSize = uiView.sizeThatFits(CGSize(
@@ -76,13 +96,6 @@ struct TextViewWrapper: UIViewRepresentable {
}
}
private func setCursorPosition(textView: UITextView) {
guard let index = cursorIndex, let newPosition = textView.position(from: textView.beginningOfDocument, offset: index) else {
return
}
textView.selectedTextRange = textView.textRange(from: newPosition, to: newPosition)
}
func makeCoordinator() -> Coordinator {
Coordinator(attributedText: $attributedText, getFocusWordForMention: getFocusWordForMention, updateCursorPosition: updateCursorPosition, initialTextSuffix: initialTextSuffix)
}