React Native Signature Canvas

A React Native component for capturing signatures or drawing on a canvas with a smooth, native feel. Works on iOS, Android, and Expo.

Features

✅ Cross-platform support (iOS, Android, Expo)
✅ Smooth, responsive drawing experience with optimized performance
✅ Customizable pen color, size, and background
✅ Support for background and overlay images
✅ Export signatures as PNG, JPEG, or SVG
✅ Undo/redo functionality
✅ Drawing and erasing modes
✅ Full TypeScript support with enhanced type definitions
🆕 Advanced error handling with automatic recovery
🆕 Performance monitoring and optimization
🆕 Flexible WebView customization via webviewProps
🆕 Enhanced security with configurable restrictions
🆕 Memory management and leak prevention

Installation

For React Native ≥ 0.60.0 or Expo SDK ≥ 35.0.0

yarn add react-native-signature-canvas

npm install --save react-native-signature-canvas

This package depends on react-native-webview. If you're using React Native CLI (not Expo), you'll need to install react-native-webview separately:
yarn add react-native-webview
cd ios && pod install

For React Native < 0.60.0 or Expo SDK < 33.0.0

npm install --save react-native-signature-canvas@1.4.2

Basic Usage

import React, { useRef, useState } from 'react';
import { StyleSheet, View, Image } from 'react-native';
import SignatureCanvas from 'react-native-signature-canvas';

const SignatureScreen = () => {
  const [signature, setSignature] = useState(null);
  const [isLoading, setIsLoading] = useState(false);
  const ref = useRef();

  const handleSignature = (signature) => {
    console.log('Signature captured:', signature);
    setSignature(signature);
    setIsLoading(false);
  };

  const handleEmpty = () => {
    console.log('Signature is empty');
    setIsLoading(false);
  };

  const handleClear = () => {
    console.log('Signature cleared');
    setSignature(null);
  };

  const handleError = (error) => {
    console.error('Signature pad error:', error);
    setIsLoading(false);
  };

  const handleEnd = () => {
    setIsLoading(true);
    ref.current?.readSignature();
  };

  return (
    <View style={styles.container}>
      <View style={styles.preview}>
        {signature && (
          <Image
            resizeMode="contain"
            style={{ width: 335, height: 114 }}
            source={{ uri: signature }}
          />
        )}
      </View>
      <SignatureCanvas
        ref={ref}
        onEnd={handleEnd}
        onOK={handleSignature}
        onEmpty={handleEmpty}
        onClear={handleClear}
        onError={handleError}
        autoClear={true}
        descriptionText="Sign here"
        clearText="Clear"
        confirmText={isLoading ? "Processing..." : "Save"}
        penColor="#000000"
        backgroundColor="rgba(255,255,255,0)"
        webviewProps={{
          // Custom WebView optimization
          cacheEnabled: true,
          androidLayerType: "hardware",
        }}
      />
    </View>
  );
};

const styles = StyleSheet.create({
  container: {
    flex: 1,
  },
  preview: {
    width: 335,
    height: 114,
    backgroundColor: '#F8F8F8',
    justifyContent: 'center',
    alignItems: 'center',
    marginTop: 15,
  },
});

export default SignatureScreen;

Props

Prop	Type	Default	Description
`androidHardwareAccelerationDisabled`	`boolean`	`false`	Disable hardware acceleration on Android
`autoClear`	`boolean`	`false`	Auto clear signature after clicking the Confirm button
`backgroundColor`	`string`	`rgba(255,255,255,0)`	Background color of the canvas
`bgHeight`	`number`	`0`	Height of the background image
`bgWidth`	`number`	`0`	Width of the background image
`bgSrc`	`string`	`null`	Background image source URI
`clearText`	`string`	`Clear`	Clear button text
`confirmText`	`string`	`Confirm`	Save button text
`customHtml`	`(injectedJavaScript: string) => string`	`null`	Custom HTML template for the canvas
`dataURL`	`string`	`""`	Base64 string to draw saved signature
`descriptionText`	`string`	`Sign above`	Description text for signature
`dotSize`	`number`	`null`	Radius of a single dot
`imageType`	`string`	`image/png`	Image type for export (`image/png`, `image/jpeg`, `image/svg+xml`)
`minWidth`	`number`	`0.5`	Minimum width of a line
`maxWidth`	`number`	`2.5`	Maximum width of a line
`nestedScrollEnabled`	`boolean`	`false`	Enable nested scrolling for use inside a ScrollView
`showsVerticalScrollIndicator`	`boolean`	`true`	Show vertical scroll indicator in WebView
`onOK`	`function`	-	Callback after saving non-empty signature
`onEmpty`	`function`	-	Callback after trying to save an empty signature
`onClear`	`function`	-	Callback after clearing the signature
`onGetData`	`function`	-	Callback when getData() is called
`onBegin`	`function`	-	Callback when a new stroke is started
`onEnd`	`function`	-	Callback when the stroke has ended
`onLoadEnd`	`function`	-	Callback when the WebView canvas load ended
`onUndo`	`function`	-	Callback when undo() is called
`onRedo`	`function`	-	Callback when redo() is called
`onDraw`	`function`	-	Callback when drawing is enabled
`onErase`	`function`	-	Callback when erasing is enabled
`onChangePenColor`	`function`	-	Callback after changing the pen color
`onChangePenSize`	`function`	-	Callback after changing the pen size
`overlayHeight`	`number`	`0`	Height of the overlay image
`overlayWidth`	`number`	`0`	Width of the overlay image
`overlaySrc`	`string`	`null`	Overlay image source URI (must be PNG with transparent background)
`penColor`	`string`	`black`	Color of the pen
`rotated`	`boolean`	`false`	Rotate signature pad 90 degrees
`style`	`object`	-	Style of the wrapper view
`scrollable`	`boolean`	`false`	Enable scrolling in the signature pad
`trimWhitespace`	`boolean`	`false`	Trim image whitespace
`webStyle`	`string`	-	WebView style to override default style
`webviewContainerStyle`	`object`	-	Style for the WebView container
`androidLayerType`	`none\|software\|hardware`	`hardware`	Sets the Android WebView layer type
`onError`	`function`	-	Callback when an error occurs
`webviewProps`	`object`	`{}`	Additional props to pass to the underlying WebView

Methods

Access these methods using a ref to the SignatureCanvas component.

Method	Description
`clearSignature()`	Clear the current signature
`changePenColor(color)`	Change pen color
`changePenSize(minW, maxW)`	Change pen size
`draw()`	Enable drawing mode
`erase()`	Enable erasing mode
`getData()`	Triggers the `onGetData` callback with signature data
`readSignature()`	Read the current signature and trigger callbacks
`undo()`	Undo last stroke
`redo()`	Redo last stroke

WebView Customization (New!)

The webviewProps parameter allows you to customize the underlying WebView behavior while maintaining signature functionality:

<SignatureCanvas
  // ... other props
  webviewProps={{
    // Performance optimization
    cacheEnabled: true,
    androidLayerType: "hardware",
    androidHardwareAccelerationDisabled: false,
    
    // Security settings
    allowFileAccess: false,
    allowFileAccessFromFileURLs: false,
    mixedContentMode: "never",
    
    // UI customization
    decelerationRate: 'fast',
    bounces: false,
    
    // Any other WebView props...
  }}
/>

Performance Optimization Examples

// High-performance mode
<SignatureCanvas
  webviewProps={{
    cacheEnabled: true,
    androidLayerType: "hardware",
    androidHardwareAccelerationDisabled: false,
  }}
/>

// Low-memory mode
<SignatureCanvas
  webviewProps={{
    cacheEnabled: false,
    androidLayerType: "software",
    androidHardwareAccelerationDisabled: true,
  }}
/>

Error Handling (Enhanced!)

const [error, setError] = useState(null);

const handleError = (error) => {
  console.error('Signature error:', error);
  setError(error.message);
  // Error recovery is automatic, but you can handle it here
};

<SignatureCanvas
  onError={handleError}
  // Component automatically retries on recoverable errors
/>

{error && (
  <Text style={{ color: 'red' }}>Error: {error}</Text>
)}

Advanced Usage

Using a Background Image

const imgWidth = 300;
const imgHeight = 200;
const style = `.m-signature-pad {box-shadow: none; border: none; } 
              .m-signature-pad--body {border: none;}
              .m-signature-pad--footer {display: none; margin: 0px;}
              body,html {
              width: ${imgWidth}px; height: ${imgHeight}px;}`;

<View style={{ width: imgWidth, height: imgHeight }}>
  <SignatureCanvas
    ref={ref}
    bgSrc="https://example.com/background.jpg"
    bgWidth={imgWidth}
    bgHeight={imgHeight}
    webStyle={style}
    onOK={handleSignature}
  />
</View>

Using an Overlay Image

const imgWidth = 256;
const imgHeight = 256;
const style = `.m-signature-pad {box-shadow: none; border: none; } 
              .m-signature-pad--body {border: none;}
              .m-signature-pad--footer {display: none; margin: 0px;}
              body,html {
              width: ${imgWidth}px; height: ${imgHeight}px;}`;

<View style={{ width: imgWidth, height: imgHeight }}>
  <SignatureCanvas
    ref={ref}
    overlaySrc="https://example.com/overlay.png" // Must be PNG with transparent background
    overlayWidth={imgWidth}
    overlayHeight={imgHeight}
    webStyle={style}
    onOK={handleSignature}
  />
</View>

Using in a Modal

import React, { useState, useRef } from 'react';
import { StyleSheet, View, TouchableOpacity, Modal, Text } from 'react-native';
import SignatureCanvas from 'react-native-signature-canvas';

const SignatureModal = ({ onSignature }) => {
  const [show, setShow] = useState(false);
  const ref = useRef();
  
  const handleSignature = (signature) => {
    onSignature(signature);
    setShow(false);
  };

  return (
    <View>
      <TouchableOpacity onPress={() => setShow(true)}>
        <Text>Open Signature Pad</Text>
      </TouchableOpacity>
      
      {show && (
        <Modal>
          <SignatureCanvas
            ref={ref}
            onOK={handleSignature}
            onEmpty={() => console.log('Empty')}
            descriptionText="Sign here"
            penColor="rgba(255,117,2,1)"
          />
        </Modal>
      )}
    </View>
  );
};

Scrollable Signature Canvas

import React, { useRef, useState } from 'react';
import { View, StyleSheet, ScrollView } from 'react-native';
import SignatureCanvas from 'react-native-signature-canvas';

const ScrollableSignature = () => {
  const [scrollEnabled, setScrollEnabled] = useState(true);
  const signatureRef = useRef(null);

  return (
    <ScrollView scrollEnabled={scrollEnabled}>
      <View style={styles.container}>
        <SignatureCanvas
          ref={signatureRef}
          style={styles.canvas}
          onBegin={() => setScrollEnabled(false)}
          onEnd={() => setScrollEnabled(true)}
        />
      </View>
    </ScrollView>
  );
};

const styles = StyleSheet.create({
  container: {
    flex: 1,
    alignItems: 'center',
  },
  canvas: {
    width: '90%',
    height: 300,
    borderWidth: 1,
    borderColor: '#000',
  },
});

Performance & Reliability

Automatic Error Recovery

Smart retry logic with exponential backoff
Circuit breaker pattern to prevent cascading failures
Memory leak prevention with automatic cleanup
Performance monitoring with automatic optimization

Performance Features

Debounced resize handling for smooth interaction
Memory pressure detection with adaptive optimization
Optimized rendering with reduced re-renders
Device-specific optimization based on hardware capabilities

Security Enhancements

Configurable WebView security via webviewProps
Input validation for all methods and callbacks
XSS protection with content security policies
File access restrictions by default

Migration Guide

From v4.6.x to v4.7.x

This version is fully backward compatible. New features:

// NEW: Enhanced error handling
<SignatureCanvas
  onError={(error) => console.error(error)} // New callback
/>

// NEW: WebView customization
<SignatureCanvas
  webviewProps={{ // New prop
    cacheEnabled: false,
    androidLayerType: "software"
  }}
/>

Troubleshooting

Common Issues

Issue: Signature pad not loading

// Solution: Add error handling and check WebView props
<SignatureCanvas
  onError={(error) => console.log('Error:', error)}
  onLoadEnd={() => console.log('Loaded successfully')}
  webviewProps={{
    startInLoadingState: true,
    renderLoading: () => <ActivityIndicator />
  }}
/>

Issue: Poor performance on older devices

// Solution: Use low-performance mode
<SignatureCanvas
  webviewProps={{
    androidLayerType: "software",
    androidHardwareAccelerationDisabled: true,
    cacheEnabled: false
  }}
/>

Issue: Memory issues

// Solution: The component now handles this automatically
// But you can customize via webviewProps if needed
<SignatureCanvas
  webviewProps={{
    cacheEnabled: false, // Reduce memory usage
    androidLayerType: "software" // Use software rendering
  }}
/>

API Reference

For detailed API documentation, see:

WEBVIEW_PROPS.md - WebView customization guide
TypeScript definitions - Complete type definitions

Core Technology

This component is built on:

signature_pad.js for the core signature functionality
React Native WebView for cross-platform rendering
Enhanced with performance monitoring and error recovery systems

Contributing

Contributions are welcome! Please read our contributing guidelines and submit pull requests to help improve this component.

Development Setup

# Clone the repository
git clone https://github.com/YanYuanFE/react-native-signature-canvas.git

# Install dependencies
cd react-native-signature-canvas
npm install

# Run example apps
cd example/expo-app
npm install && npm start

Changelog

v4.7.x (Latest)

🆕 Added webviewProps for WebView customization
🆕 Enhanced error handling with automatic recovery
🆕 Performance monitoring and optimization
🆕 Memory leak prevention
🆕 Improved TypeScript definitions
🔧 Fixed global variable pollution in WebView JavaScript
🔧 Added input validation for all methods
⚡ Optimized rendering performance

View full changelog

License

MIT License - see LICENSE file for details.

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