TextShape

TextShape.swift

import SwiftUI

struct ContentView: View {
    var body: some View {
        TextShape(sample)
            .fill(.orange)
            .stroke(.blue, lineWidth: 2)
    }

    var sample: AttributedString {
        var text = AttributedString("Hello, world!")
        text.font = UIFont(name: "HiraginoSans-W8", size: 50)
        text.foregroundColor = .label
        return text
    }
}

struct TextShape: Shape {
    var text: AttributedString

    init(_ text: AttributedString) {
        self.text = text
    }

    func path(in rect: CGRect) -> Path {
        let font: UIFont = text.font ?? .systemFont(ofSize: UIFont.systemFontSize)
        let ctFont = CTFontCreateWithName(font.fontName as CFString, font.pointSize, nil)
        let attr = [NSAttributedString.Key.font: ctFont]
        let line = CTLineCreateWithAttributedString(
            NSAttributedString(string: String(text.characters), attributes: attr)
        )
        let runs = CTLineGetGlyphRuns(line) as! [CTRun]
        let rawPath = CGMutablePath()
        for run in runs {
            let count = CTRunGetGlyphCount(run)
            var glyphs = [CGGlyph](repeating: 0, count: count)
            var positions = [CGPoint](repeating: .zero, count: count)
            CTRunGetGlyphs(run, CFRange(location: 0, length: 0), &glyphs)
            CTRunGetPositions(run, CFRange(location: 0, length: 0), &positions)
            for i in 0..<count {
                if let path = CTFontCreatePathForGlyph(ctFont, glyphs[i], nil) {
                    let t = CGAffineTransform(translationX: positions[i].x, y: positions[i].y)
                    rawPath.addPath(path, transform: t)
                }
            }
        }
        // CGPath を上下反転（ iOS の座標系を考慮 ）
        var flip = CGAffineTransform(scaleX: 1, y: -1)
        let flipped = rawPath.copy(using: &flip)!
        let b = flipped.boundingBox
        let dx = (rect.width - b.width) / 2 - b.minX
        let dy = (rect.height - b.height) / 2 - b.minY
        var center = CGAffineTransform(translationX: dx, y: dy)
        return flipped.copy(using: &center).map(Path.init) ?? Path()
    }
}

#Preview {
    ContentView()
}