437 lines
21 KiB
Swift
437 lines
21 KiB
Swift
//
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// Copyright 2025 New Vector Ltd.
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//
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// SPDX-License-Identifier: AGPL-3.0-only OR LicenseRef-Element-Commercial
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// Please see LICENSE files in the repository root for full details.
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//
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import Compound
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import LRUCache
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import MatrixRustSDK
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import SwiftSoup
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import UIKit
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struct AttributedStringBuilderV2: AttributedStringBuilderProtocol {
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private let cacheKey: String
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private let mentionBuilder: MentionBuilderProtocol
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private static let attributeMSC4286 = "data-msc4286-external-payment-details"
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private static let cacheDispatchQueue = DispatchQueue(label: "io.element.elementx.attributed_string_builder_v2_cache")
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private static var caches: [String: LRUCache<String, AttributedString>] = [:]
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static func invalidateCaches() {
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caches.removeAll()
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}
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init(cacheKey: String, mentionBuilder: MentionBuilderProtocol) {
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self.cacheKey = cacheKey
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self.mentionBuilder = mentionBuilder
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}
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func fromPlain(_ string: String?) -> AttributedString? {
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guard let string else {
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return nil
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}
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if let cached = Self.cachedValue(forKey: string, cacheKey: cacheKey) {
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return cached
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}
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let mutableAttributedString = NSMutableAttributedString(string: string)
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addLinksAndMentions(mutableAttributedString)
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addMatrixEntityPermalinkAttributesTo(mutableAttributedString)
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let result = try? AttributedString(mutableAttributedString, including: \.elementX)
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Self.cacheValue(result, forKey: string, cacheKey: cacheKey)
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return result
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}
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// Do not use the default HTML renderer of NSAttributedString because this method
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// runs on the UI thread which we want to avoid because renderHTMLString is called
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// most of the time from a background thread.
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// Use DTCoreText HTML renderer instead.
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// Using DTCoreText, which renders static string, helps to avoid code injection attacks
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// that could happen with the default HTML renderer of NSAttributedString which is a
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// webview.
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func fromHTML(_ htmlString: String?) -> AttributedString? {
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guard let originalHTMLString = htmlString else {
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return nil
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}
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if let cached = Self.cachedValue(forKey: originalHTMLString, cacheKey: cacheKey) {
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return cached
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}
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let htmlString = originalHTMLString.replacingHtmlBreaksOccurrences()
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let doc = try? SwiftSoup.parseBodyFragment(htmlString)
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guard let body = doc?.body() else {
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return nil
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}
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var listIndex = 1
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let mutableAttributedString = attributedString(from: body, preserveFormatting: false, listTag: nil, listIndex: &listIndex, indentLevel: 0)
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detectPhishingAttempts(mutableAttributedString)
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addLinksAndMentions(mutableAttributedString)
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addMatrixEntityPermalinkAttributesTo(mutableAttributedString)
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let result = try? AttributedString(mutableAttributedString, including: \.elementX)
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Self.cacheValue(result, forKey: originalHTMLString, cacheKey: cacheKey)
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return result
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}
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// MARK: - Private
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func attributedString(from element: Element, preserveFormatting: Bool,
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listTag: String?,
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listIndex: inout Int,
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indentLevel: Int) -> NSMutableAttributedString {
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let result = NSMutableAttributedString()
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for node in element.getChildNodes() {
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if let textNode = node as? TextNode {
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var text = preserveFormatting ? textNode.getWholeText() : textNode.text()
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// There seem to be sibling TextNodes following every </br> tag that
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// contain one single space character which we don't want as it
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// breaks line head indents.
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if (node.previousSibling() as? Element)?.tagName() == "br" {
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text.trimPrefix(" ")
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}
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result.append(NSAttributedString(string: text))
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continue
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}
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guard let childElement = node as? Element else {
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continue
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}
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let tag = childElement.tagName().lowercased()
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var content = NSMutableAttributedString()
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var childIndex = 1
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switch tag {
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case "h1", "h2", "h3", "h4", "h5", "h6":
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let level = Int(String(tag.dropFirst())) ?? 1
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let size: CGFloat = UIFont.systemFontSize + CGFloat(6 - level) * 2
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content = attributedString(from: childElement, preserveFormatting: preserveFormatting, listTag: listTag, listIndex: &childIndex, indentLevel: indentLevel)
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content.setFontPreservingSymbolicTraits(UIFont.boldSystemFont(ofSize: size))
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case "p", "div":
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content = attributedString(from: childElement, preserveFormatting: preserveFormatting, listTag: listTag, listIndex: &childIndex, indentLevel: indentLevel)
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content.append(NSAttributedString(string: "\n"))
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case "br":
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content = NSMutableAttributedString(string: "\n")
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case "b", "strong":
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content = attributedString(from: childElement, preserveFormatting: preserveFormatting, listTag: listTag, listIndex: &childIndex, indentLevel: indentLevel)
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content.setFontPreservingSymbolicTraits(UIFont.boldSystemFont(ofSize: UIFont.systemFontSize))
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case "i", "em":
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content = attributedString(from: childElement, preserveFormatting: preserveFormatting, listTag: listTag, listIndex: &childIndex, indentLevel: indentLevel)
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content.setFontPreservingSymbolicTraits(UIFont.italicSystemFont(ofSize: UIFont.systemFontSize))
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case "u":
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content = attributedString(from: childElement, preserveFormatting: preserveFormatting, listTag: listTag, listIndex: &childIndex, indentLevel: indentLevel)
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content.addAttribute(.underlineStyle, value: NSUnderlineStyle.single.rawValue, range: NSRange(location: 0, length: content.length))
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case "s", "del":
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content = attributedString(from: childElement, preserveFormatting: preserveFormatting, listTag: listTag, listIndex: &childIndex, indentLevel: indentLevel)
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content.addAttribute(.strikethroughStyle, value: NSUnderlineStyle.single.rawValue, range: NSRange(location: 0, length: content.length))
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case "sup":
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content = attributedString(from: childElement, preserveFormatting: preserveFormatting, listTag: listTag, listIndex: &childIndex, indentLevel: indentLevel)
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content.addAttribute(.baselineOffset, value: 6, range: NSRange(location: 0, length: content.length))
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content.setFontPreservingSymbolicTraits(UIFont.systemFont(ofSize: UIFont.systemFontSize * 0.7))
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case "sub":
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content = attributedString(from: childElement, preserveFormatting: preserveFormatting, listTag: listTag, listIndex: &childIndex, indentLevel: indentLevel)
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content.addAttribute(.baselineOffset, value: -4, range: NSRange(location: 0, length: content.length))
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content.setFontPreservingSymbolicTraits(UIFont.systemFont(ofSize: UIFont.systemFontSize * 0.7))
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case "blockquote":
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content = attributedString(from: childElement, preserveFormatting: preserveFormatting, listTag: listTag, listIndex: &childIndex, indentLevel: indentLevel)
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content.addAttribute(.MatrixBlockquote, value: true, range: NSRange(location: 0, length: content.length))
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case "code", "pre":
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let preserveFormatting = preserveFormatting || tag == "pre"
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content = attributedString(from: childElement, preserveFormatting: preserveFormatting, listTag: listTag, listIndex: &childIndex, indentLevel: indentLevel)
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content.setFontPreservingSymbolicTraits(UIFont.monospacedSystemFont(ofSize: UIFont.systemFontSize, weight: .regular))
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content.addAttribute(.backgroundColor, value: UIColor.compound._bgCodeBlock as Any, range: NSRange(location: 0, length: content.length))
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// Don't allow identifiers in code blocks
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content.removeAttribute(.MatrixRoomID, range: NSRange(location: 0, length: content.length))
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content.removeAttribute(.MatrixRoomAlias, range: NSRange(location: 0, length: content.length))
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content.removeAttribute(.MatrixUserID, range: NSRange(location: 0, length: content.length))
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content.removeAttribute(.MatrixEventOnRoomID, range: NSRange(location: 0, length: content.length))
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content.removeAttribute(.MatrixEventOnRoomAlias, range: NSRange(location: 0, length: content.length))
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content.removeAttribute(.MatrixAllUsersMention, range: NSRange(location: 0, length: content.length))
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case "hr":
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content = NSMutableAttributedString(string: "\n")
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case "a":
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content = attributedString(from: childElement, preserveFormatting: preserveFormatting, listTag: listTag, listIndex: &childIndex, indentLevel: indentLevel)
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if let href = try? childElement.attr("href") {
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content.addAttribute(.link, value: href, range: NSRange(location: 0, length: content.length))
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}
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case "span":
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if (try? childElement.attr(Self.attributeMSC4286)) ?? nil != nil {
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content = attributedString(from: childElement, preserveFormatting: preserveFormatting, listTag: listTag, listIndex: &childIndex, indentLevel: indentLevel)
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}
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case "ul", "ol":
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var listIndex = 1
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content = attributedString(from: childElement, preserveFormatting: preserveFormatting, listTag: tag, listIndex: &listIndex, indentLevel: indentLevel + 1)
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if listTag == nil { // If not within another list
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content.insert(NSAttributedString(string: "\n"), at: 0)
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}
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case "li":
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var bullet = ""
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if listTag == "ol" {
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bullet = "\(listIndex). "
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listIndex += 1
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} else {
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bullet = "• "
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}
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content = attributedString(from: childElement, preserveFormatting: preserveFormatting, listTag: listTag, listIndex: &childIndex, indentLevel: indentLevel + 1)
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content.insert(NSAttributedString(string: bullet), at: 0)
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content.append(NSAttributedString(string: "\n"))
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let paragraphStyle = NSMutableParagraphStyle()
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paragraphStyle.headIndent = CGFloat(indentLevel) * 20
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paragraphStyle.firstLineHeadIndent = CGFloat(indentLevel) * 20
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content.addAttribute(.paragraphStyle, value: paragraphStyle, range: NSRange(location: 0, length: content.length))
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default:
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content = attributedString(from: childElement, preserveFormatting: preserveFormatting, listTag: listTag, listIndex: &childIndex, indentLevel: indentLevel)
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}
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result.append(content)
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}
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return result
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}
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private static func cacheValue(_ value: AttributedString?, forKey key: String, cacheKey: String) {
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cacheDispatchQueue.sync {
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if caches[cacheKey] == nil {
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caches[cacheKey] = LRUCache<String, AttributedString>(countLimit: 1000)
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}
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caches[cacheKey]?.setValue(value, forKey: key)
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}
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}
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private static func cachedValue(forKey key: String, cacheKey: String) -> AttributedString? {
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var result: AttributedString?
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cacheDispatchQueue.sync {
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result = caches[cacheKey]?.value(forKey: key)
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}
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return result
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}
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private func addLinksAndMentions(_ attributedString: NSMutableAttributedString) {
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let string = attributedString.string
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// Event identifiers and room aliases and identifiers detected in plain text are techincally incomplete
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// without via parameters and we won't bother detecting them
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var matches: [TextParsingMatch] = MatrixEntityRegex.userIdentifierRegex.matches(in: string).compactMap { match in
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guard let matchRange = Range(match.range, in: string) else {
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return nil
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}
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let identifier = String(string[matchRange])
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return TextParsingMatch(type: .userID(identifier: identifier), range: match.range)
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}
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matches.append(contentsOf: MatrixEntityRegex.roomAliasRegex.matches(in: string).compactMap { match in
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guard let matchRange = Range(match.range, in: string) else {
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return nil
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}
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let alias = String(string[matchRange])
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return TextParsingMatch(type: .roomAlias(alias: alias), range: match.range)
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})
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matches.append(contentsOf: MatrixEntityRegex.uriRegex.matches(in: string).compactMap { match in
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guard let matchRange = Range(match.range, in: string) else {
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return nil
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}
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let uri = String(string[matchRange])
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return TextParsingMatch(type: .matrixURI(uri: uri), range: match.range)
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})
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matches.append(contentsOf: MatrixEntityRegex.linkRegex.matches(in: string).compactMap { match in
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guard let matchRange = Range(match.range, in: string) else {
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return nil
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}
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let link = String(string[matchRange]).asSanitizedLink
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return TextParsingMatch(type: .link(urlString: link), range: match.range)
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})
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matches.append(contentsOf: MatrixEntityRegex.allUsersRegex.matches(in: attributedString.string).map { match in
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TextParsingMatch(type: .atRoom, range: match.range)
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})
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guard matches.count > 0 else {
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return
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}
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// Sort the links by length so the longest one always takes priority
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matches.sorted { $0.range.length > $1.range.length }.forEach { [attributedString] match in
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var hasLink = false
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attributedString.enumerateAttribute(.link, in: match.range, options: []) { value, _, stop in
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if value != nil {
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hasLink = true
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stop.pointee = true
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}
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}
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if hasLink {
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return
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}
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switch match.type {
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case .atRoom:
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attributedString.addAttribute(.MatrixAllUsersMention, value: true, range: match.range)
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case .roomAlias(let alias):
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if let urlString = try? matrixToRoomAliasPermalink(roomAlias: alias),
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let url = URL(string: urlString) {
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attributedString.addAttribute(.link, value: url, range: match.range)
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}
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case .matrixURI(let uri):
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if let url = URL(string: uri) {
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attributedString.addAttribute(.link, value: url, range: match.range)
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}
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case .userID, .link:
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if let url = match.link {
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attributedString.addAttribute(.link, value: url, range: match.range)
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}
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}
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}
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}
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func addMatrixEntityPermalinkAttributesTo(_ attributedString: NSMutableAttributedString) {
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attributedString.enumerateAttribute(.link, in: .init(location: 0, length: attributedString.length), options: []) { value, range, _ in
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if value != nil {
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if let url = value as? URL,
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let matrixEntity = parseMatrixEntityFrom(uri: url.absoluteString) {
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switch matrixEntity.id {
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case .user(let userID):
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mentionBuilder.handleUserMention(for: attributedString, in: range, url: url, userID: userID, userDisplayName: nil)
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case .room(let roomID):
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mentionBuilder.handleRoomIDMention(for: attributedString, in: range, url: url, roomID: roomID)
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case .roomAlias(let alias):
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mentionBuilder.handleRoomAliasMention(for: attributedString, in: range, url: url, roomAlias: alias, roomDisplayName: nil)
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case .eventOnRoomId(let roomID, let eventID):
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mentionBuilder.handleEventOnRoomIDMention(for: attributedString, in: range, url: url, eventID: eventID, roomID: roomID)
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case .eventOnRoomAlias(let alias, let eventID):
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mentionBuilder.handleEventOnRoomAliasMention(for: attributedString, in: range, url: url, eventID: eventID, roomAlias: alias)
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}
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}
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}
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}
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attributedString.enumerateAttribute(.MatrixAllUsersMention, in: .init(location: 0, length: attributedString.length), options: []) { value, range, _ in
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if let value = value as? Bool,
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value {
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mentionBuilder.handleAllUsersMention(for: attributedString, in: range)
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}
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}
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}
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private func detectPhishingAttempts(_ attributedString: NSMutableAttributedString) {
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attributedString.enumerateAttribute(.link, in: .init(location: 0, length: attributedString.length), options: []) { value, range, _ in
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guard value != nil, let internalURL = value as? URL else {
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return
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}
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let displayString = attributedString.attributedSubstring(from: range).string
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guard PhishingDetector.isPhishingAttempt(displayString: displayString, internalURL: internalURL) else {
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return
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}
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handlePhishingAttempt(for: attributedString, in: range, internalURL: internalURL, displayString: displayString)
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}
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}
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private func handlePhishingAttempt(for attributedString: NSMutableAttributedString,
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in range: NSRange,
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internalURL: URL,
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displayString: String) {
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// Let's remove the existing link attribute
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attributedString.removeAttribute(.link, range: range)
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var urlComponents = URLComponents()
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urlComponents.scheme = URL.confirmationScheme
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urlComponents.host = ""
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let parameters = ConfirmURLParameters(internalURL: internalURL, displayString: displayString)
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urlComponents.queryItems = parameters.urlQueryItems
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guard let finalURL = urlComponents.url else {
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return
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}
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attributedString.addAttribute(.link, value: finalURL, range: range)
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}
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}
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private struct TextParsingMatch {
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enum MatchType {
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case userID(identifier: String)
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case roomAlias(alias: String)
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case matrixURI(uri: String)
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case link(urlString: String)
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case atRoom
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}
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let type: MatchType
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let range: NSRange
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var link: URL? {
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switch type {
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case .userID(let identifier):
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return try? URL(string: matrixToUserPermalink(userId: identifier))
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case .link(let urlString):
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return URL(string: urlString)
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default:
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return nil
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}
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}
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}
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private extension NSMutableAttributedString {
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func setFontPreservingSymbolicTraits(_ newFont: UIFont) {
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enumerateAttribute(.font, in: NSRange(location: 0, length: length)) { value, range, _ in
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if let oldFont = value as? UIFont {
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// keep the traits (bold, italic, etc.)
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let traits = oldFont.fontDescriptor.symbolicTraits
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if let descriptor = newFont.fontDescriptor.withSymbolicTraits(traits) {
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let updatedFont = UIFont(descriptor: descriptor, size: newFont.pointSize)
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addAttribute(.font, value: updatedFont, range: range)
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} else {
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// fallback if traits can't be applied
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addAttribute(.font, value: newFont, range: range)
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}
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} else {
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addAttribute(.font, value: newFont, range: range)
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}
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}
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}
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}
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