Initial timeline HTML support.

2026-11-02 21:33:26 +00:00 · 2022-03-24 14:47:55 +02:00
parent d3588cf6f1
commit cf42d61d27
20 changed files with 683 additions and 51 deletions
@@ -0,0 +1,85 @@
+//
+//  AttributedStringBuilder.swift
+//  ElementX
+//
+//  Created by Stefan Ceriu on 22/03/2022.
+//  Copyright © 2022 Element. All rights reserved.
+//
+
+import Foundation
+import DTCoreText
+
+struct AttributedStringBuilder: AttributedStringBuilderProtocol {
+    
+    private var defaultCSS: String {
+        AttributedStringBuilderUtils.cssToMarkBlockquotes() +
+"""
+        pre,code {
+            background-color: #F5F7FA;
+            display: inline;
+            font-family: monospace;
+            white-space: pre;
+            -coretext-fontname: Menlo-Regular;
+        }
+        h1,h2,h3 {
+            font-size: 1.2em;
+        }
+"""
+    }
+    
+    // Do not use the default HTML renderer of NSAttributedString because this method
+    // runs on the UI thread which we want to avoid because renderHTMLString is called
+    // most of the time from a background thread.
+    // Use DTCoreText HTML renderer instead.
+    // Using DTCoreText, which renders static string, helps to avoid code injection attacks
+    // that could happen with the default HTML renderer of NSAttributedString which is a
+    // webview.
+    func fromHTML(_ htmlString: String?) -> AttributedString? {
+        guard let htmlString = htmlString,
+              let data = htmlString.data(using: .utf8) else {
+                  return nil
+              }
+        
+        let defaultFont = UIFont.preferredFont(forTextStyle: .body)
+        let defaultColor = UIColor.black
+        
+        let parsingOptions: [String: Any] = [
+            DTUseiOS6Attributes: true,
+            DTDefaultFontFamily: defaultFont.familyName,
+            DTDefaultFontName: defaultFont.fontName,
+            DTDefaultFontSize: defaultFont.pointSize,
+            DTDefaultTextColor: defaultColor,
+            DTDefaultLinkDecoration: false,
+            DTDefaultStyleSheet: DTCSSStylesheet(styleBlock: self.defaultCSS) as Any
+        ]
+        
+        guard let builder = DTHTMLAttributedStringBuilder(html: data, options: parsingOptions, documentAttributes: nil) else {
+            return nil
+        }
+        
+        builder.willFlushCallback = { element in
+            element?.sanitize(font: defaultFont)
+        }
+            
+        guard var nsAttributedString = builder.generatedAttributedString() else {
+            return nil
+        }
+        
+        nsAttributedString = AttributedStringBuilderUtils.removeDTCoreTextArtifacts(nsAttributedString)
+        
+        nsAttributedString = AttributedStringBuilderUtils.removeMarkedBlockquotesArtifacts(nsAttributedString)
+        
+        return try? AttributedString(nsAttributedString, including: \.elementX)
+    }
+    
+    func blockquoteCoalescedComponentsFrom(_ attributedString: AttributedString?) -> [AttributedStringBuilderComponent]? {
+        guard let attributedString = attributedString else {
+            return nil
+        }
+
+        return attributedString.runs[\.blockquote].map { (value, range) in
+            AttributedStringBuilderComponent(attributedString: AttributedString(attributedString[range]),
+                                             isBlockquote: value != nil)
+        }
+    }
+}