Fixes to make ExpoPixi.Signature work on web

lib/components/Signature.js

@@ -1,7 +1,7 @@
 //@flow
 import React from 'react';
 import { GLView } from 'expo-gl';
-import { PanResponder, PixelRatio } from 'react-native';
+import { Platform, PanResponder, PixelRatio } from 'react-native';
 import { vec2 } from 'gl-matrix';
 
 import PIXI from '../Pixi';
@@ -41,7 +41,7 @@ export default class Signature extends React.Component<Props> {
     this._setupPanResponder();
   }
 
-  componentWillMount() {
+  UNSAFE_componentWillMount() {
     global.__ExpoSignatureId++;
   }
 
@@ -127,8 +127,12 @@ export default class Signature extends React.Component<Props> {
     return null;
   };
 
-  takeSnapshotAsync = (...args) => {
-    return takeSnapshotAsync(this.glView, ...args);
+  takeSnapshotAsync = async (...args) => {
+    if (Platform.OS === "web") {
+      this.renderer._update();
+      return await GLView.takeSnapshotAsync(this.context, ...args);
+    }
+    return await takeSnapshotAsync(this.glView, ...args);
   };
 
   onContextCreate = async (context: WebGLRenderingContext) => {
@@ -138,7 +142,10 @@ export default class Signature extends React.Component<Props> {
     this.stage = new PIXI.Container();
     this.stage.addChild(this.graphicsTmp);
 
-    const getAttributes = context.getContextAttributes || (() => ({}));
+    const getAttributes = (Platform.OS === 'web') ?
+      (() => ({})) :
+      context.getContextAttributes || (() => ({}));
+
     context.getContextAttributes = () => {
       const contextAttributes = getAttributes();
       return {
@@ -182,15 +189,28 @@ export default class Signature extends React.Component<Props> {
   };
 
   render() {
+    if (Platform.OS === 'web') {
+      const glView = (
+        <GLView
+          {...this.panResponder.panHandlers}
+          onLayout={this.onLayout}
+          key={'Expo.Signature-' + global.__ExpoSignatureId}
+          {...this.props}
+          onContextCreate={this.onContextCreate}
+        />
+      );
+      this.setRef(glView);
+      return glView;
+    }
     return (
-      <GLView
-        {...this.panResponder.panHandlers}
-        onLayout={this.onLayout}
-        key={'Expo.Signature-' + global.__ExpoSignatureId}
-        ref={this.setRef}
-        {...this.props}
-        onContextCreate={this.onContextCreate}
-      />
-    );
+        <GLView
+          {...this.panResponder.panHandlers}
+          onLayout={this.onLayout}
+          ref={this.setRef}
+          key={'Expo.Signature-' + global.__ExpoSignatureId}
+          {...this.props}
+          onContextCreate={this.onContextCreate}
+        />
+    )
   }
 }