SVGPathKit

A high-performance Swift library for parsing and rendering SVG path data into CoreGraphics paths. SVGPathKit provides a complete solution for processing SVG path strings and converting them into CGPath objects that can be used with UIKit, AppKit, and CoreGraphics.

Features

✅ Complete SVG 2.0 Support - All path commands including complex elliptical arcs

✅ High Performance - Optimized tokenizer and parser with minimal memory allocation

✅ Comprehensive Error Handling - Detailed error messages with localization support

✅ Type Safety - Strongly typed command system with full Swift error handling

✅ Cross-Platform - Works on iOS, macOS, tvOS, and watchOS

✅ Extensive Testing - 100% test coverage with comprehensive validation

✅ DocC Documentation - Complete API documentation with examples

Supported SVG Path Commands

Command	Description	Example
M, m	Move to	M 10 10 / m 5 5
L, l	Line to	L 20 20 / l 10 10
H, h	Horizontal line to	H 50 / h 20
V, v	Vertical line to	V 50 / v 20
C, c	Cubic Bézier curve	C 10 20 30 40 50 60
S, s	Smooth cubic Bézier	S 30 40 50 60
Q, q	Quadratic Bézier curve	Q 15 25 20 30
T, t	Smooth quadratic Bézier	T 30 40
A, a	Elliptical arc	A 25 25 0 1 0 50 25
Z, z	Close path	Z

Installation

Swift Package Manager

Add the following to your Package.swift file:

dependencies: [
    .package(url: "https://github.com/s-emp/SVGPathKit.git", from: "1.0.0")
]

Or add it through Xcode: File → Add Package Dependencies → Enter URL

Requirements

• iOS 13.0+ / macOS 10.15+ / tvOS 13.0+ / watchOS 6.0+
• Swift 6.1+
• Xcode 15.0+

Quick Start

import SVGPathKit

// Create an SVGPathKit instance
let pathKit = SVGPathKit(path: "M 10 10 L 50 10 L 30 50 Z")

// Convert to CGPath
do {
    let cgPath = try pathKit.createCGPath()

    // Use with UIKit/AppKit
    let shapeLayer = CAShapeLayer()
    shapeLayer.path = cgPath
} catch {
    print("Error: \(error.localizedDescription)")
}

Usage Examples

Basic Shapes

// Rectangle
let rect = SVGPathKit(path: "M 0 0 H 100 V 50 H 0 Z")

// Circle (approximated with Bézier curves)
let circle = SVGPathKit(path: "M 50 0 A 50 50 0 1 1 50 100 A 50 50 0 1 1 50 0")

// Triangle
let triangle = SVGPathKit(path: "M 50 0 L 100 100 L 0 100 Z")

Complex Paths

// Heart shape
let heart = SVGPathKit(path: """
    M 50,25
    C 50,15 40,5 25,5
    C 10,5 0,15 0,25
    C 0,35 10,45 25,55
    L 50,80
    L 75,55
    C 90,45 100,35 100,25
    C 100,15 90,5 75,5
    C 60,5 50,15 50,25 Z
""")

// 5-pointed star
let star = SVGPathKit(path: """
    M 50,0
    L 61,35
    L 98,35
    L 68,57
    L 79,91
    L 50,70
    L 21,91
    L 32,57
    L 2,35
    L 39,35 Z
""")

Error Handling

let pathKit = SVGPathKit(path: "invalid path data")

do {
    let cgPath = try pathKit.createCGPath()
} catch let error as TokenError {
    print("Tokenization error: \(error.localizedDescription)")
} catch let error as ParserError {
    print("Parsing error: \(error.localizedDescription)")
} catch let error as ValidatorError {
    print("Validation error: \(error.localizedDescription)")
} catch {
    print("Unknown error: \(error)")
}

Dynamic Path Updates

let pathKit = SVGPathKit(path: "M 0 0")

// Update the path dynamically
pathKit.pathString = "M 10 10 L 50 50 Q 75 25 100 50"

// Generate new CGPath
let updatedPath = try pathKit.createCGPath()

Architecture

SVGPathKit uses a clean 4-stage pipeline:

1. Tokenization - Converts the path string into tokens
2. Parsing - Transforms tokens into structured commands
3. Validation - Ensures commands follow SVG 2.0 specification
4. Rendering - Converts commands to CoreGraphics path operations

"M 10 10 L 20 20" → [Token] → [Command] → Validation → CGPath

Each stage is independently testable and can throw specific errors for precise debugging.

API Documentation

Core Classes

• SVGPathKit - Main class for processing SVG paths
• Command - Represents individual SVG path commands
• Token - Represents tokenized elements from the path string

Error Types

• TokenError - Tokenization failures (unknown tokens, invalid numbers)
• ParserError - Parsing failures (invalid syntax, insufficient arguments)
• ValidatorError - Validation failures (invalid command sequences)

All errors conform to LocalizedError for user-friendly error messages.

Performance

SVGPathKit is optimized for performance:

• Zero-copy tokenization where possible
• Minimal memory allocations during parsing
• Efficient arc-to-Bézier conversion using mathematical optimization
• Lookup tables for fast character classification

Contributing

We welcome contributions! Please see CONTRIBUTING.md for guidelines.

Development Setup

1. Clone the repository
2. Open Package.swift in Xcode
3. Run tests with ⌘+U
4. Build documentation with ⌘+Control+Shift+D

Testing

Run the full test suite:

swift test

For verbose output:

swift test --verbose

License

SVGPathKit is released under the MIT License. See LICENSE for details.

Credits

Created with ❤️ for the Swift community.

• Arc rendering algorithm based on research by Mortoray
• SVG 2.0 specification compliance
• Mathematical foundations from L. Maisonobe's elliptical arc papers

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