Litext

A lightweight, high-performance rich-text library for all Apple platforms — UIKit, AppKit, and SwiftUI (including watchOS).

Note: This fork is reimplemented in Swift 6.0 with strict concurrency. While API compatibility with the original has been maintained, 100% compatibility is not guaranteed.

Features

• ⚡️ High performance text layout and rendering via CoreText
• 📎 Native view embedding via attachments
• 🔗 Clickable links support
• ✏️ Text selection with copy/paste
• 🎨 Custom per-line drawing callbacks
• 📐 Auto layout integration (experimental)
• 🖥️ SwiftUI support on all platforms, including watchOS

Supported Platforms

Platform	Minimum Version	LTXLabel (UIKit/AppKit)	LitextLabel (SwiftUI)
iOS	13.0+	✅	✅
macOS	12.0+	✅	✅
tvOS	13.0+	✅	✅
visionOS	1.0+	✅	✅
Mac Catalyst	13.0+	✅	✅
watchOS	8.0+	—	✅

Installation

Add Litext as a dependency in your Package.swift file:

dependencies: [
    .package(url: "https://github.com/Helixform/Litext.git", branch: "main")
]

Or in Xcode: File → Add Package Dependencies and enter the repository URL.

Usage

UIKit / AppKit

import Litext

let label = LTXLabel()
view.addSubview(label)

let attributedString = NSMutableAttributedString(
    string: "Hello, Litext!",
    attributes: [
        .font: PlatformFont.systemFont(ofSize: 16),
        .foregroundColor: PlatformColor.label
    ]
)
label.attributedText = attributedString

SwiftUI

LitextLabel works on all platforms, including watchOS:

import Litext
import SwiftUI

struct ContentView: View {
    var body: some View {
        LitextLabel("Hello, Litext!")
            .selectable()
            .onTapLink { url in
                UIApplication.shared.open(url)
            }
    }
}

You can also initialise with an NSAttributedString or AttributedString:

LitextLabel(attributedString: myNSAttributedString)
LitextLabel(attributedString: myAttributedString) // AttributedString (iOS 15+, macOS 12+)

Link Handling

let mutable = NSMutableAttributedString(string: "Visit GitHub")
mutable.addAttribute(.link, value: URL(string: "https://github.com")!, range: NSRange(location: 6, length: 6))
label.attributedText = mutable

// UIKit/AppKit — implement LTXLabelDelegate
label.delegate = self

func ltxLabelDidTapOnHighlightContent(
    _ ltxLabel: LTXLabel,
    region: LTXHighlightRegion?,
    location: CGPoint
) {
    if let url = region?.attributes[.link] as? URL {
        UIApplication.shared.open(url)
    }
}

// SwiftUI — use the modifier
LitextLabel(attributedString: mutable)
    .onTapLink { url in
        UIApplication.shared.open(url)
    }

Text Selection

// Enable selection
label.isSelectable = true
label.selectionBackgroundColor = UIColor.systemBlue.withAlphaComponent(0.2)

// Access selected text
let text = label.selectedPlainText()
let attributed = label.selectedAttributedText()

// Programmatic selection
label.selectionRange = NSRange(location: 0, length: 5)
label.selectAllText()
label.clearSelection()

// SwiftUI
LitextLabel("Some selectable text")
    .selectable()

Embedding Native Views (Attachments)

Use LTXAttachment to embed any view inline in the text:

// UIKit / AppKit
let attachment = LTXAttachment()
attachment.view = myCustomView          // UIView or NSView
attachment.size = myCustomView.intrinsicContentSize

// watchOS (SwiftUI view instead)
let attachment = LTXAttachment()
attachment.swiftUIView = AnyView(MyCustomView())
attachment.size = CGSize(width: 100, height: 50)

// Insert attachment into attributed string
let attachmentString = NSAttributedString(
    string: LTXReplacementText,
    attributes: [
        .ltxAttachment: attachment,
        kCTRunDelegateAttributeName as NSAttributedString.Key: attachment.runDelegate
    ]
)

Custom Per-Line Drawing

let drawingAction = LTXLineDrawingAction { context, line, origin in
    // Custom drawing for each line
    context.setStrokeColor(UIColor.red.cgColor)
    context.move(to: CGPoint(x: origin.x, y: origin.y - 2))
    context.addLine(to: CGPoint(x: origin.x + 100, y: origin.y - 2))
    context.strokePath()
}

attributedString.addAttribute(
    .ltxLineDrawingCallback,
    value: drawingAction,
    range: fullRange
)

watchOS

On watchOS, LTXLabel (the UIView/NSView subclass) is not available. Use LitextLabel instead — it renders via an off-screen CGContext and displays the result as a SwiftUI Image.

import Litext
import SwiftUI

struct WatchContentView: View {
    var body: some View {
        LitextLabel(attributedString: styledText)
    }

    var styledText: NSAttributedString {
        let s = NSMutableAttributedString(string: "Hello from Watch!")
        s.addAttribute(.font, value: UIFont.boldSystemFont(ofSize: 14), range: NSRange(location: 0, length: 17))
        return s
    }
}

For inline attachments on watchOS, provide a SwiftUI view via swiftUIView instead of view.

License

This project is licensed under the MIT License — see the LICENSE file for details.