SwiftExtension // Backport the TextEditor to macOS 10.15 Catalina.

- This TextEditorEX is much faster than Apple official TextEditor for SwiftUI.

Packages/vChewing_SwiftExtension/Sources/SwiftExtension/SwiftUIExtension.swift

@@ -80,3 +80,83 @@ public struct VisualEffectView: NSViewRepresentable {
     visualEffectView.blendingMode = blendingMode
   }
 }
+
+// MARK: - TextEditor for macOS 10.15 Catalina
+
+// Ref: https://stackoverflow.com/a/63761738/4162914
+
+@available(macOS 10.15, *)
+/// A much faster alternative than Apple official TextEditor.
+public struct TextEditorEX: NSViewRepresentable {
+  @Binding var text: String
+
+  public init(text: Binding<String>) {
+    _text = text
+  }
+
+  public func makeNSView(context: Context) -> NSScrollView {
+    context.coordinator.createTextViewStack()
+  }
+
+  public func updateNSView(_ nsView: NSScrollView, context _: Context) {
+    if let textArea = nsView.documentView as? NSTextView, textArea.string != self.text {
+      textArea.string = text
+    }
+  }
+
+  public func makeCoordinator() -> Coordinator {
+    Coordinator(text: $text)
+  }
+
+  public class Coordinator: NSObject, NSTextViewDelegate {
+    public var text: Binding<String>
+
+    public init(text: Binding<String>) {
+      self.text = text
+    }
+
+    public func textView(_ textView: NSTextView, shouldChangeTextIn range: NSRange, replacementString text: String?)
+      -> Bool
+    {
+      defer {
+        self.text.wrappedValue = (textView.string as NSString).replacingCharacters(in: range, with: text!)
+      }
+      return true
+    }
+
+    fileprivate lazy var textStorage = NSTextStorage()
+    fileprivate lazy var layoutManager = NSLayoutManager()
+    fileprivate lazy var textContainer = NSTextContainer()
+    fileprivate lazy var textView: NSTextView = {
+      let result = NSTextView(frame: CGRect(), textContainer: textContainer)
+      result.font = NSFont.systemFont(ofSize: 13, weight: .regular)
+      result.allowsUndo = true
+      return result
+    }()
+
+    fileprivate lazy var scrollview = NSScrollView()
+
+    public func createTextViewStack() -> NSScrollView {
+      let contentSize = scrollview.contentSize
+
+      textContainer.containerSize = CGSize(width: contentSize.width, height: CGFloat.greatestFiniteMagnitude)
+      textContainer.widthTracksTextView = true
+
+      textView.minSize = CGSize(width: 0, height: 0)
+      textView.maxSize = CGSize(width: CGFloat.greatestFiniteMagnitude, height: CGFloat.greatestFiniteMagnitude)
+      textView.isVerticallyResizable = true
+      textView.frame = CGRect(x: 0, y: 0, width: contentSize.width, height: contentSize.height)
+      textView.autoresizingMask = [.width]
+      textView.delegate = self
+
+      scrollview.borderType = .noBorder
+      scrollview.hasVerticalScroller = true
+      scrollview.documentView = textView
+
+      textStorage.addLayoutManager(layoutManager)
+      layoutManager.addTextContainer(textContainer)
+
+      return scrollview
+    }
+  }
+}