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gdkraus committed Dec 12, 2013
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149 changes: 149 additions & 0 deletions index.html
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<!doctype html>
<html lang="en-US">
<head>
<meta charset="utf-8">
<title>The Incredible Accessible Modal Window</title>
<script src="../../../jquery/jquery-1.6.4.min.js"></script>
<script src="modal-window.js"></script>
<style type="text/css">
#modalOverlay {
width:100%;
height:100%;
z-index:2; /* places the modal overlay between the main page and the modal dialog*/
background-color:#000;
opacity:0.5;
position:fixed;
top:0;
left:0;
display:none;
margin:0;
padding:0;
}

#modal {
width:50%;
margin-left:auto;
margin-right:auto;
padding: 5px;
border: thin #000 solid;
background-color:#fff;
z-index:3; /* places the modal dialog on top of everything else */
position:fixed;
top:25%;
left:25%;
display:none;
}
#modal h1 {
text-align:center;
}

.modalCloseButton {
float:right;
position:absolute;
top:10px;
left:95%;
}
.modalCloseButton img {
border:0;
}

.screen-reader-offscreen {
position:absolute;
left:-999px;
width:1px;
height:1px;
top:auto;
}

</style>
</head>

<body>
<script>
(function(i,s,o,g,r,a,m){i['GoogleAnalyticsObject']=r;i[r]=i[r]||function(){
(i[r].q=i[r].q||[]).push(arguments)},i[r].l=1*new Date();a=s.createElement(o),
m=s.getElementsByTagName(o)[0];a.async=1;a.src=g;m.parentNode.insertBefore(a,m)
})(window,document,'script','//www.google-analytics.com/analytics.js','ga');

ga('create', 'UA-40224544-1', 'ncsu.edu');
ga('send', 'pageview');

</script>
<div id="mainPage" aria-hidden="false">
<h1>The Incredible Accessible Modal Window</h1>
<p><a href="http://accessibility.oit.ncsu.edu/blog/2013/09/13/the-incredible-accessible-modal-dialog/">Read the blog post about creating this demonstration.</a></p>
<p>This page demonstrates how to make a modal window as accessible as possible to assistive technology users. Modal windows are especially problematic for screen reader users. Often times the user is able to &quot;escape&quot; the window and interact with other parts of the page when they should not be able to. This is partially due to the way screen reader software interacts with the Web browser.</p>
<h2>The Accessible Modal Window in Action</h2>
<p>To see this in action, you just need to <button id="startModal">view the modal window</button>. If the modal window works as planned, once the modal window is visible you should not be able to interact with other links on the main page like <a href="http://accessibility.ncsu.edu">going to our main accessibility page</a>. If you can interact with the page behind the modal window, guidance is given for how to get back to the modal window.</p>
<h2>Features</h2>
<p>This example implements the following features:</p>
<ol>
<li>The page is divided into three sections:
<ol>
<li>&lt;div id=&quot;mainPage&gt;&lt;/div&gt;</li>
<li>&lt;div id=&quot;modal&quot; role=&quot;dialog&quot;&gt;&lt;/div&gt;</li>
<li>&lt;div id=&quot;modalOverlay&quot;&gt;&lt;/div&gt;</li>
</ol>
</li>
<li>When the modal dialog is displayed, an overlay is placed over top of the mainPage so it is
<ol>
<li>visually grayed out in order to indicate you cannot interact with what is behind the window</li>
<li>not clickable with the mouse</li>
</ol>
</li>
<li>When the modal dialog is displayed, the mainPage is marked with aria-hidden=&quot;true&quot; to prevent screen readers from interacting with it once the modal dialog is open</li>
<li>Keyboard access is limited to only interacting with the modal dialog once it is visible
<ol>
<li>The tab key loops through all of the keyboard focusable items within the modal window</li>
<li>This is determined programmatically through the DOM each time the tab key is pressed so you do not have to create an explicit list of focusable items within the modal window to keep track of</li>
<li>The escape key is mapped to the function to close the modal window</li>
<li>The enter key is mapped to the submit function of the modal window</li>
</ol>
</li>
<li>The beginning of the modal dialog is marked with an h1</li>
<li>There are offscreen instructions that describe the modal dialog and how to interact with it
<ol>
<li>The instructions are attached through the aria-labelledby attribute.</li>
<li>note, the maximum length of text in an aria-labelledby attribute for JAWS is around 240 characters. Other screen readers do not have this limitation.</li>
</ol>
</li>
<li>There is a shim in place for VoiceOver in Safari support since this combination does not announce the aria-labelledby attribute of an element with role=&quot;dialog&quot; when an item within the element receives focus. The shim makes the modal window itself programmatically focusable (tabindex=&quot;-1&quot;) and sets the focus to the modal window itself instead of the first focusable item within the modal window. This goes against the <a href="http://www.w3.org/TR/wai-aria-practices/#modal_dialog">ARIA Authoring Practices for modal dialog windows</a>.</li>
<li>Configurations Tested
<ul>
<li>JAWS 14.0.6005 in IE 10.0.9200.16635 in Windows 7, Service Pack 1: <strong>Passed</strong></li>
<li>NVDA 2013.1.1 in Firefox 23.0.1 in Windows 7, Service Pack 1: <strong>Passed</strong></li>
<li>VoiceOver in Safari 6.0.5 (8536.30.1) in OS X 10.8.4: <strong>Passed, with shim</strong></li>
<li>ChromeVox 1.29.1 in Chrome 29.0.1547.62 in OS X 10.8.4: <strong>Passed</strong></li>
<li>Orca 3.4.2 in Firefox 23.0 in Ubuntu 12.04: <strong>Partial Functionality - does not support aria-hidden</strong></li>
</ul>
</li>
</ol>
</div>
<div id="modal" aria-hidden="true" aria-labelledby="modalTitle modalDescription" role="dialog">
<div id="modalDescription" class="screen-reader-offscreen">Beginning of dialog window. It begins with a heading 1 called &quot;Registration Form&quot;. Escape will cancel and close the window. This form does not collect any actual information.</div>
<h1 id="modalTitle">Registration Form</h1>
<form name="form1" method="post" action="">
<p>
<label for="firstName">First Name</label>
<input type="text" name="firstName" id="firstName">
</p>
<p>
<label for="lastName">Last Name</label>
<input type="text" name="lastName" id="lastName">
</p>
<p>
<label for="email">Email Address</label>
<input type="text" name="email" id="email">
</p>
<p>
<input type="button" name="button" id="enter" value="Submit">
<input type="button" name="cancelButton" id="cancelButton" value="Cancel">
</p>
<a id="modalCloseButton" class="modalCloseButton" href="javascript:void(0)" title="Close registration form"><img id="cancel" src="x.png" alt="close the registration form"></a>

</form>
</div>
<div id="modalOverlay" tabindex="-1"></div>

</body>
</html>
194 changes: 194 additions & 0 deletions modal-window.js
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/*
============================================
License for Application
============================================
This license is governed by United States copyright law, and with respect to matters
of tort, contract, and other causes of action it is governed by North Carolina law,
without regard to North Carolina choice of law provisions. The forum for any dispute
resolution shall be in Wake County, North Carolina.
Redistribution and use in source and binary forms, with or without modification, are
permitted provided that the following conditions are met:
1. Redistributions of source code must retain the above copyright notice, this list
of conditions and the following disclaimer.
2. Redistributions in binary form must reproduce the above copyright notice, this
list of conditions and the following disclaimer in the documentation and/or other
materials provided with the distribution.
3. The name of the author may not be used to endorse or promote products derived from
this software without specific prior written permission.
THIS SOFTWARE IS PROVIDED BY THE AUTHOR "AS IS" AND ANY EXPRESS OR IMPLIED
WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY
AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHOR BE
LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING
NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF
ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
*/

// jQuery formatted selector to search for focusable items
var focusableElementsString ="a[href], area[href], input:not([disabled]), select:not([disabled]), textarea:not([disabled]), button:not([disabled]), iframe, object, embed, *[tabindex], *[contenteditable]";

// store the item that has focus before opening the modal window
var focusedElementBeforeModal;

$(document).ready(function() {
jQuery('#startModal').click(function(e) {showModal($('#modal'));});
jQuery('#cancel').click(function(e) {hideModal();});
jQuery('#cancelButton').click(function(e) {hideModal();});
jQuery('#enter').click(function(e) {enterButtonModal();});
jQuery('#modalCloseButton').click(function(e) {hideModal();});
jQuery('#modalCloseButton').keydown(function(event){trapSpaceKey($(this),event,hideModal);})
jQuery('#modal').keydown(function(event){trapTabKey($(this),event);})
jQuery('#modal').keydown(function(event){trapEscapeKey($(this),event);})

});


function usingSafari(){
var ua = navigator.userAgent.toLowerCase();
if (ua.indexOf('safari')!=-1){
if(ua.indexOf('chrome') > -1){
return false; // chrome
}else{
return true; // safari
}
} else {
return false;
}

}

function trapSpaceKey(obj,evt,f) {
// if space key pressed
if ( evt.which == 32 ) {
// fire the user passed event
f();
evt.preventDefault();
}
}

function trapEscapeKey(obj,evt) {

// if escape pressed
if ( evt.which == 27 ) {

// get list of all children elements in given object
var o = obj.find('*');

// get list of focusable items
var cancelElement;
cancelElement = o.filter("#cancel")

// close the modal window
cancelElement.click();
evt.preventDefault();
}

}

function trapTabKey(obj,evt) {

// if tab or shift-tab pressed
if ( evt.which == 9 ) {

// get list of all children elements in given object
var o = obj.find('*');

// get list of focusable items
var focusableItems;
focusableItems = o.filter(focusableElementsString).filter(':visible')

// get currently focused item
var focusedItem;
focusedItem = jQuery(':focus');

// get the number of focusable items
var numberOfFocusableItems;
numberOfFocusableItems = focusableItems.length

// get the index of the currently focused item
var focusedItemIndex;
focusedItemIndex = focusableItems.index(focusedItem);

if (evt.shiftKey) {
//back tab
// if focused on first item and user preses back-tab, go to the last focusable item
if(focusedItemIndex==0){
focusableItems.get(numberOfFocusableItems-1).focus();
evt.preventDefault();
}

} else {
//forward tab
// if focused on the last item and user preses tab, go to the first focusable item
if(focusedItemIndex==numberOfFocusableItems-1){
focusableItems.get(0).focus();
evt.preventDefault();
}
}
}

}

function setInitialFocusModal(obj){
// get list of all children elements in given object
var o = obj.find('*');

// set focus to first focusable item
var focusableItems;
focusableItems = o.filter(focusableElementsString).filter(':visible').first().focus();

}

function enterButtonModal(){
// BEGIN logic for executing the Enter button action for the modal window
alert('form submitted');
// END logic for executing the Enter button action for the modal window
hideModal();
}

function showModal(obj){
jQuery('#mainPage').attr('aria-hidden','true'); // mark the main page as hidden
jQuery('#modalOverlay').css('display','block'); // insert an overlay to prevent clicking and make a visual change to indicate the main apge is not available
jQuery('#modal').css('display','block'); // make the modal window visible
jQuery('#modal').attr('aria-hidden','false'); // mark the modal window as visible

// save current focus
focusedElementBeforeModal = jQuery(':focus');

// get list of all children elements in given object
var o = obj.find('*');

// Safari and VoiceOver shim
// if VoiceOver in Safari is used, set the initial focus to the modal window itself instead of the first keyboard focusable item. This causes VoiceOver to announce the aria-labelled attributes. Otherwise, Safari and VoiceOver will not announce the labels attached to the modal window.
if(usingSafari()){
// set a tabIndex of -1 to the modal window itself so we can set the focus on it
jQuery('#modal').attr('tabindex','-1');

// set the focus to the modal window itself
obj.focus();
} else {
// set the focus to the first keyboard focusable item
o.filter(focusableElementsString).filter(':visible').first().focus();
}

}

function hideModal(){
jQuery('#modalOverlay').css('display','none'); // remove the overlay in order to make the main screen available again
jQuery('#modal').css('display','none'); // hide the modal window
jQuery('#modal').attr('aria-hidden','true'); // mark the modal window as hidden
jQuery('#mainPage').attr('aria-hidden','false'); // mark the main page as visible

// set focus back to element that had it before the modal was opened
focusedElementBeforeModal.focus();
}
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