SmoothTextHighlight

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A SwiftUI/UIKit library for karaoke-style text highlighting with smooth rounded paragraph backgrounds and precise word tracking. Perfect for reading apps, language learning, text-to-speech interfaces, and text animation effects.

Keywords: iOS text highlight, karaoke text effect, reading progress indicator, smooth text animation, paragraph highlight, word tracking, SwiftUI text effects

Features

• Smooth Rounded Highlights - Seamless paragraph backgrounds with rounded corners across multiple lines
• Karaoke-Style Word Tracking - Precise word-level highlighting following reading progress
• Adaptive Layout - Automatic line wrap and text reflow handling
• Bezier Curve Smoothing - Natural-looking connections using quadratic curves
• Fully Configurable - Customize colors, corner radius, padding, and reading speed
• Performance Optimized - Efficient rendering with NSLayoutManager

Screenshots

Core Components

File	Role
SmoothHighlightLayoutManager	Custom NSLayoutManager for rendering smooth paragraph highlights
SmoothHighlightedTextView	SwiftUI wrapper for easy integration
ReadingHighlighter	Text parser and playback controller with automatic tokenization

Installation

Copy the Highlighting folder into your project:

Highlighting/
├── SmoothHighlightLayoutManager.swift
├── SmoothHighlightedTextView.swift
└── ReadingHighlighter.swift

Usage

struct ContentView: View {
    @StateObject private var highlighter: ReadingHighlighter

    init() {
        let text = "Your text content here..."
        let attributed = NSAttributedString(string: text)
        _highlighter = StateObject(wrappedValue: ReadingHighlighter(
            text: text, attributedText: attributed
        ))
    }

    var body: some View {
        VStack {
            SmoothHighlightedTextView(
                attributedText: highlighter.attributedText,
                paragraphRange: highlighter.currentParagraphRange,
                wordRange: highlighter.currentWordRange,
                cornerRadius: 6.0,
                horizontalPadding: 6.0,
                verticalPadding: 2.0
            )

            HStack {
                Button(highlighter.isRunning ? "Pause" : "Play") {
                    highlighter.isRunning ? highlighter.stop() : highlighter.start()
                }
                Button("Reset") { highlighter.reset() }
            }
        }
    }
}

Configuration

// Colors
layoutManager.paragraphColor = UIColor(red: 0.74, green: 0.89, blue: 0.76, alpha: 1.0)
layoutManager.wordColor = UIColor(red: 0.20, green: 0.74, blue: 0.42, alpha: 1.0)

// Layout
layoutManager.cornerRadius = 6.0
layoutManager.horizontalPadding = 6.0
layoutManager.verticalPadding = 2.0

// Reading speed (60-600 WPM)
highlighter.updateWordsPerMinute(180)

// Scale highlights with font size
let cornerRadius = fontSize * 0.21
let horizontalPadding = fontSize * 0.21
let verticalPadding = fontSize * 0.07

Requirements

• iOS 15.0+
• Swift 5.9+
• Xcode 15.0+

License

MIT License - see LICENSE for details.