diff --git a/src/components/App/context.js b/src/components/App/context.js
index e4dab10..0207df5 100644
--- a/src/components/App/context.js
+++ b/src/components/App/context.js
@@ -1,5 +1,149 @@
 import React from 'react';
+import PropTypes from 'prop-types';
+import URLSearchParams from '@ungap/url-search-params';
 
 const AppContext = React.createContext();
 
+const toUrl = params => new URLSearchParams(params).toString();
+
+const readURLHash = () => {
+  const query = document.location.hash.slice(1);
+  const params = new URLSearchParams(query);
+
+  if (params.get('syntax')) {
+    return {
+      syntax: params.get('syntax'),
+      expr: params.get('expr')
+    };
+  } else {
+    // Assuming old-style URL
+    return {
+      syntax: 'js',
+      expr: query || ''
+    };
+  }
+};
+
+const createSvgLink = async ({ svg }) => {
+  try {
+    const type = 'image/svg+xml';
+    const blob = new Blob([svg], { type });
+
+    return {
+      url: URL.createObjectURL(blob),
+      label: 'Download SVG',
+      filename: 'image.svg',
+      type
+    };
+  }
+  catch (e) {
+    console.error(e); // eslint-disable-line no-console
+  }
+};
+
+const createPngLink = async ({ svg, width, height }) => {
+  try {
+    const type = 'image/png';
+    const canvas = document.createElement('canvas');
+    const context = canvas.getContext('2d');
+    const loader = new Image();
+
+    loader.width = canvas.width = Number(width) * 2;
+    loader.height = canvas.height = Number(height) * 2;
+
+    await new Promise(resolve => {
+      loader.onload = resolve;
+      loader.src = 'data:image/svg+xml,' + encodeURIComponent(svg);
+    });
+
+    context.drawImage(loader, 0, 0, loader.width, loader.height);
+
+    const blob = await new Promise(resolve => canvas.toBlob(resolve, type));
+
+    return {
+      url: URL.createObjectURL(blob),
+      label: 'Download PNG',
+      filename: 'image.png',
+      type
+    };
+  }
+  catch (e) {
+    console.error(e); // eslint-disable-line no-console
+  }
+};
+
+class AppContextProvider extends React.PureComponent {
+  state = {}
+
+  mutations = {
+    svgData: async ({ svg, width, height }) => {
+      if (svg !== this.state.svg) {
+        this.setState({
+          svg,
+          svgLink: await createSvgLink({ svg }),
+          pngLink: await createPngLink({ svg, width, height })
+        });
+      }
+    },
+
+    renderExpr: ({ syntax, expr }) => {
+      if (expr) {
+        document.location.hash = toUrl({ syntax, expr });
+      }
+    }
+  }
+
+  componentDidMount() {
+    // Gatsby doesn't have document.location, so readURLHash can't be called
+    // until here
+    this.setState(readURLHash());
+
+    window.addEventListener('hashchange', this.handleHashChange);
+    this.handleHashChange();
+  }
+
+  componentWillUnmount() {
+    window.removeEventListener('hashchange', this.handleHashChange);
+  }
+
+  handleHashChange = () => {
+    const { expr, syntax } = readURLHash();
+
+    if (!expr) {
+      return;
+    }
+
+    this.setState({
+      syntax,
+      expr,
+      permalinkUrl: document.location.toString()
+    });
+
+    if (this.props.onExpressionChange) {
+      this.props.onExpressionChange({ syntax, expr });
+    }
+  }
+
+  render() {
+    const { children } = this.props;
+    const context = {
+      ...this.state,
+      ...this.mutations
+    };
+
+    return <AppContext.Provider value={ context }>
+      { children }
+    </AppContext.Provider>;
+  }
+}
+
+AppContextProvider.propTypes = {
+  onExpressionChange: PropTypes.func,
+  children: PropTypes.oneOfType([
+    PropTypes.arrayOf(PropTypes.node),
+    PropTypes.node
+  ]).isRequired
+};
+
+export { AppContextProvider };
 export default AppContext;
diff --git a/src/components/App/index.js b/src/components/App/index.js
index 009c171..724ce63 100644
--- a/src/components/App/index.js
+++ b/src/components/App/index.js
@@ -1,151 +1,26 @@
 import React from 'react';
-import URLSearchParams from '@ungap/url-search-params';
 
-import AppContext from 'components/App/context';
+import { AppContextProvider } from 'components/App/context';
 import Form from 'components/Form';
 import Loader from 'components/Loader';
 import Message from 'components/Message';
 import SVG from 'components/SVG';
 
-const toUrl = params => new URLSearchParams(params).toString();
-
-const readURLHash = () => {
-  const query = document.location.hash.slice(1);
-  const params = new URLSearchParams(query);
-
-  if (params.get('syntax')) {
-    return {
-      syntax: params.get('syntax'),
-      expr: params.get('expr')
-    };
-  } else {
-    // Assuming old-style URL
-    return {
-      syntax: 'js',
-      expr: query || ''
-    };
-  }
-};
-
-const createSvgLink = async ({ svg }) => {
-  try {
-    const type = 'image/svg+xml';
-    const blob = new Blob([svg], { type });
-
-    return {
-      url: URL.createObjectURL(blob),
-      label: 'Download SVG',
-      filename: 'image.svg',
-      type
-    };
-  }
-  catch (e) {
-    console.error(e); // eslint-disable-line no-console
-  }
-};
-
-const createPngLink = async ({ svg, width, height }) => {
-  try {
-    const type = 'image/png';
-    const canvas = document.createElement('canvas');
-    const context = canvas.getContext('2d');
-    const loader = new Image();
-
-    loader.width = canvas.width = Number(width) * 2;
-    loader.height = canvas.height = Number(height) * 2;
-
-    await new Promise(resolve => {
-      loader.onload = resolve;
-      loader.src = 'data:image/svg+xml,' + encodeURIComponent(svg);
-    });
-
-    context.drawImage(loader, 0, 0, loader.width, loader.height);
-
-    const blob = await new Promise(resolve => canvas.toBlob(resolve, type));
-
-    return {
-      url: URL.createObjectURL(blob),
-      label: 'Download PNG',
-      filename: 'image.png',
-      type
-    };
-  }
-  catch (e) {
-    console.error(e); // eslint-disable-line no-console
-  }
-};
-
 class App extends React.PureComponent {
   state={}
 
-  componentDidMount() {
-    // Gatsby doesn't have document.location, so readURLHash can't be called
-    // until here
-    this.setState(readURLHash());
-
-    window.addEventListener('hashchange', this.handleHashChange);
-    this.handleHashChange();
-  }
-
-  componentWillUnmount() {
-    window.removeEventListener('hashchange', this.handleHashChange);
-  }
-
-  handleHashChange = () => {
-    const { expr, syntax } = readURLHash();
-
-    if (!expr) {
-      return;
-    }
-
-    this.setState({
-      syntax,
-      expr,
-      permalinkUrl: document.location.toString()
-    });
+  handleRender = ({ syntax, expr }) => {
     console.log('Render:', syntax, expr); // eslint-disable-line no-console
+    this.setState({ syntax, expr });
   }
 
   handleRetry = event => {
     event.preventDefault();
-    this.handleHashChange();
-  }
-
-  renderExpr = ({ expr, syntax }) => {
-    if (expr) {
-      document.location.hash = toUrl({ syntax, expr });
-    }
-  }
-
-  svgData = async ({ svg, width, height }) => {
-    if (svg !== this.state.svg) {
-      this.setState({
-        svg,
-        svgLink: await createSvgLink({ svg }),
-        pngLink: await createPngLink({ svg, width, height })
-      });
-    }
+    this.handleRender(this.state);
   }
 
   render() {
-    const {
-      svgLink,
-      pngLink,
-      permalinkUrl,
-      expr,
-      syntax
-    } = this.state;
-    const context = {
-      svgLink,
-      pngLink,
-      permalinkUrl,
-      expr,
-      syntax,
-      renderExpr: this.renderExpr,
-      svgData: this.svgData
-    };
-
-    return <AppContext.Provider value={ context }>
+    return <AppContextProvider onExpressionChange={ this.handleRender }>
       <Form />
 
       <Loader />
@@ -156,7 +31,7 @@ class App extends React.PureComponent {
       </Message>
 
       <SVG />
-    </AppContext.Provider>;
+    </AppContextProvider>;
   }
 }