wacom_stu_plugin

A Flutter Windows plugin for Wacom STU signature tablet communication.

Provides MethodChannel and EventChannel interfaces to connect, disconnect, control the display, and stream real-time pen input from Wacom STU USB devices.

Platform: Windows only. Requires the Wacom STU SDK installed at C:/Program Files (x86)/Wacom STU SDK/cpp.

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Used by

flutter_wacom_signature_pad — a higher-level package providing ready-made PDF signing widgets built on top of this plugin. Use that package if you want drag-to-place signature boxes, PDF embedding, and upload support without writing low-level channel code.

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Platform support

Android	iOS	macOS	Windows	Linux	Web
❌	❌	❌	✅	❌	❌

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Installation

dependencies:
  wacom_stu_plugin: ^1.0.1

flutter pub get

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Channels

MethodChannel — wacom_stu_channel

Method	Returns	Description
connect	Map	Connects to the first available Wacom STU USB device. Returns status, maxX, maxY, screenWidth, screenHeight
disconnect	String	Disconnects the device
clearScreen	void	Clears the tablet display
setSignatureScreen	void	Renders an RGB image onto the tablet display

EventChannel — wacom_stu_events

Streams real-time pen input events as Map<String, int>:

Field	Type	Description
x	int	Pen X coordinate in raw tablet units
y	int	Pen Y coordinate in raw tablet units
pressure	int	Pen pressure value
sw	int	Switch state — 1 when pen button is pressed

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Usage

Connect and disconnect

import 'package:flutter/services.dart';

const _channel = MethodChannel('wacom_stu_channel');

// Connect — returns tablet capabilities
final Map result = await _channel.invokeMethod('connect');
final double maxX         = (result['maxX'] as int).toDouble();
final double maxY         = (result['maxY'] as int).toDouble();
final double screenWidth  = (result['screenWidth'] as int).toDouble();
final double screenHeight = (result['screenHeight'] as int).toDouble();

// Disconnect
await _channel.invokeMethod('disconnect');

Stream pen events

import 'package:flutter/services.dart';

const _events = EventChannel('wacom_stu_events');

final subscription = _events.receiveBroadcastStream().listen((event) {
  final int x        = event['x'];
  final int y        = event['y'];
  final int pressure = event['pressure'];
  final int sw       = event['sw']; // 1 = pen button pressed

  // Convert raw tablet coords to canvas coords:
  // canvasX = (x / maxX) * canvasWidth
  // canvasY = (y / maxY) * canvasHeight
});

// Cancel when done
await subscription.cancel();

Display an image on the tablet screen

import 'dart:typed_data';
import 'package:flutter/services.dart';

const _channel = MethodChannel('wacom_stu_channel');

// rgbBytes — raw RGB bytes (width × height × 3)
// mode     — display mode integer (device-specific)
await _channel.invokeMethod('setSignatureScreen', {
  'data': rgbBytes,
  'mode': mode,
});

Clear the tablet screen

await _channel.invokeMethod('clearScreen');

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Full example — capture a signature

import 'dart:async';
import 'package:flutter/material.dart';
import 'package:flutter/services.dart';

class WacomSignatureCapture extends StatefulWidget {
  const WacomSignatureCapture({super.key});

  @override
  State<WacomSignatureCapture> createState() => _WacomSignatureCaptureState();
}

class _WacomSignatureCaptureState extends State<WacomSignatureCapture> {
  static const _channel = MethodChannel('wacom_stu_channel');
  static const _events  = EventChannel('wacom_stu_events');

  StreamSubscription? _sub;
  final List<Offset> _points = [];
  double _maxX = 1.0, _maxY = 1.0;
  bool _connected = false;

  @override
  void initState() {
    super.initState();
    _connect();
  }

  Future<void> _connect() async {
    final result = await _channel.invokeMethod('connect');
    setState(() {
      _maxX = (result['maxX'] as int).toDouble();
      _maxY = (result['maxY'] as int).toDouble();
      _connected = true;
    });

    _sub = _events.receiveBroadcastStream().listen((event) {
      final double px = (event['x'] as int) / _maxX;
      final double py = (event['y'] as int) / _maxY;
      setState(() => _points.add(Offset(px, py)));
    });
  }

  @override
  void dispose() {
    _sub?.cancel();
    _channel.invokeMethod('disconnect');
    super.dispose();
  }

  @override
  Widget build(BuildContext context) {
    return Scaffold(
      appBar: AppBar(
        title: Text(_connected ? 'Tablet connected' : 'Connecting...'),
        actions: [
          IconButton(
            icon: const Icon(Icons.clear),
            onPressed: () => setState(() => _points.clear()),
          ),
        ],
      ),
      body: CustomPaint(
        painter: _SignaturePainter(_points),
        child: const SizedBox.expand(),
      ),
    );
  }
}

class _SignaturePainter extends CustomPainter {
  final List<Offset> points;
  _SignaturePainter(this.points);

  @override
  void paint(Canvas canvas, Size size) {
    final paint = Paint()
      ..color = Colors.black
      ..strokeWidth = 2.0
      ..strokeCap = StrokeCap.round;

    for (int i = 0; i < points.length - 1; i++) {
      canvas.drawLine(
        Offset(points[i].dx * size.width, points[i].dy * size.height),
        Offset(points[i + 1].dx * size.width, points[i + 1].dy * size.height),
        paint,
      );
    }
  }

  @override
  bool shouldRepaint(_SignaturePainter old) => old.points != points;
}

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Requirements

• Wacom STU SDK installed at C:/Program Files (x86)/Wacom STU SDK/cpp
• Windows 10 or later
• Wacom STU device connected via USB

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Changelog

See CHANGELOG.md.

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License

MIT — see LICENSE.