[changed] Maintain focus inside of tray

This adds a new prop `maintainFocus` which defaults to `true`.
This makes the tray "modal" in that it will not allow focus to escape
from within it until it is explicitly closed via close button, escape key, or
clicking in the overlay area.

Previous behavior can be achieved by setting the `maintainFocus` prop
to `false`.  This defaults to `true` so that it can achieve a greater level of
accessibility support which I felt was valuable to everyone so it is opt-out
rather than opt-in.

lib/components/Tray.js

@@ -10,14 +10,16 @@ export default React.createClass({
     isOpen: React.PropTypes.bool,
     onBlur: React.PropTypes.func,
     closeTimeoutMS: React.PropTypes.number,
-    closeOnBlur: React.PropTypes.bool
+    closeOnBlur: React.PropTypes.bool,
+    maintainFocus: React.PropTypes.bool
   },
 
   getDefaultProps() {
     return {
       isOpen: false,
       closeTimeoutMS: 0,
-      closeOnBlur: true
+      closeOnBlur: true,
+      maintainFocus: false
     };
   },
 

lib/components/TrayPortal.js

@@ -2,6 +2,7 @@ import React, { PropTypes } from 'react';
 import cx from 'classnames';
 import focusManager from '../helpers/focusManager';
 import isLeavingNode from '../helpers/isLeavingNode';
+import findTabbable from '../helpers/tabbable';
 
 const styles = {
   overlay: {
@@ -55,7 +56,8 @@ export default React.createClass({
     onBlur: PropTypes.func,
     closeOnBlur: PropTypes.bool,
     closeTimeoutMS: PropTypes.number,
-    children: PropTypes.any
+    children: PropTypes.any,
+    maintainFocus: PropTypes.bool
   },
 
   getInitialState() {
@@ -108,6 +110,15 @@ export default React.createClass({
       this.props.onBlur();
     }
 
+    // Keep focus inside the tray if maintainFocus is true
+    if (e.keyCode === 9 && this.props.maintainFocus && isLeavingNode(this.refs.content, e)) {
+      e.preventDefault();
+      const tabbable = findTabbable(this.refs.content);
+      const target = tabbable[e.shiftKey ? tabbable.length - 1 : 0];
+      target.focus();
+      return;
+    }
+
     // Treat tabbing away from content as blur/close if closeOnBlur
     if (e.keyCode === 9 && this.props.closeOnBlur && isLeavingNode(this.refs.content, e)) {
       e.preventDefault();

lib/components/__tests__/Tray-test.js

@@ -79,4 +79,35 @@ describe('react-tray', function() {
       equal(document.querySelectorAll('.ReactTray__Content').length, 1);
     }, 0);
   });
+
+  describe('maintainFocus prop', function() {
+    this.timeout(0);
+    beforeEach(function(done) {
+      const props = {isOpen: true, onBlur: function() {}, closeTimeoutMS: 0, maintainFocus: true};
+      const children = (
+        <div>
+          <a href="#" id="one">One</a>
+          <a href="#" id="two">Two</a>
+          <a href="#" id="three">Three</a>
+        </div>
+      );
+      renderTray(props, children, () => done());
+    });
+
+    it('sends focus to the first item if tabbing away from the last element', function() {
+      const firstItem = document.querySelector('#one');
+      const lastItem = document.querySelector('#three');
+      lastItem.focus();
+      TestUtils.Simulate.keyDown(document.querySelector('.ReactTray__Content'), {keyCode: 9});
+      equal(document.activeElement, firstItem);
+    });
+
+    it('sends focus to the last item if shift + tabbing from the first item', function() {
+      const firstItem = document.querySelector('#one');
+      const lastItem = document.querySelector('#three');
+      firstItem.focus();
+      TestUtils.Simulate.keyDown(document.querySelector('.ReactTray__Content'), {keyCode: 9, shiftKey: true});
+      equal(document.activeElement, lastItem);
+    });
+  });
 });