PencilKit Handwriting Recognition & Stroke Slicing

import SwiftUI
import PencilKit

struct HandwritingCheckerView: View {
    @State private var canvasView = PKCanvasView()
    @State private var recognizedText: String = "Draw something above, then tap Recognize"
    @State private var isRecognizing = false

    var body: some View {
        VStack(spacing: 16) {
            Text("PencilKit Handwriting Recognition")
                .font(.headline)

            CanvasRepresentable(canvasView: $canvasView)
                .frame(height: 260)
                .border(Color.secondary, width: 1)
                .cornerRadius(8)

            HStack(spacing: 12) {
                Button("Recognize") {
                    Task { await recognizeHandwriting() }
                }
                .buttonStyle(.borderedProminent)
                .disabled(isRecognizing)

                Button("Clear") {
                    canvasView.drawing = PKDrawing()
                    recognizedText = "Draw something above, then tap Recognize"
                }
                .buttonStyle(.bordered)
            }

            Text(recognizedText)
                .font(.title2)
                .multilineTextAlignment(.center)
                .padding()
                .frame(maxWidth: .infinity)
                .background(Color(.secondarySystemBackground))
                .cornerRadius(8)

            Spacer()
        }
        .padding()
    }

    private func recognizeHandwriting() async {
        guard !canvasView.drawing.strokes.isEmpty else {
            recognizedText = "Please draw something first."
            return
        }
        isRecognizing = true
        defer { isRecognizing = false }

        let recognizer = PKStrokeRecognizer()
        // Optionally pin to a specific language:
        // recognizer.preferredLanguages = [Locale.Language(identifier: "zh-Hans")]

        let drawing = canvasView.drawing
        let strokeIDs = drawing.strokes.map(\.id)

        do {
            let result = try await recognizer.recognizedText(
                in: drawing,
                strokeIDs: strokeIDs
            )
            recognizedText = result.isEmpty ? "(nothing recognized)" : result
        } catch {
            recognizedText = "Recognition failed: \(error.localizedDescription)"
        }
    }
}

struct CanvasRepresentable: UIViewRepresentable {
    @Binding var canvasView: PKCanvasView

    func makeUIView(context: Context) -> PKCanvasView {
        canvasView.tool = PKInkingTool(.pen, color: .label, width: 5)
        canvasView.backgroundColor = .systemBackground
        canvasView.drawingPolicy = .anyInput
        return canvasView
    }

    func updateUIView(_ uiView: PKCanvasView, context: Context) {}
}

#Preview {
    HandwritingCheckerView()
}