a11y.js

define([
	"dojo/_base/array", // array.forEach array.map
	"dojo/_base/declare", // declare
	"dojo/dom",			// dom.byId
	"dojo/dom-attr", // domAttr.attr domAttr.has
	"dojo/dom-style", // style.style
	"dojo/sniff", // has("ie")
	"./main"	// for exporting methods to dijit namespace
], function(array, declare, dom, domAttr, domStyle, has, dijit){

	// module:
	//		dijit/a11y

	var shown = (dijit._isElementShown = function(/*Element*/ elem){
		var s = domStyle.get(elem);
		return (s.visibility != "hidden")
			&& (s.visibility != "collapsed")
			&& (s.display != "none")
			&& (domAttr.get(elem, "type") != "hidden");
	});

	dijit.hasDefaultTabStop = function(/*Element*/ elem){
		// summary:
		//		Tests if element is tab-navigable even without an explicit tabIndex setting

		// No explicit tabIndex setting, need to investigate node type
		switch(elem.nodeName.toLowerCase()){
			case "a":
				// An <a> w/out a tabindex is only navigable if it has an href
				return domAttr.has(elem, "href");
			case "area":
			case "button":
			case "input":
			case "object":
			case "select":
			case "textarea":
				// These are navigable by default
				return true;
			case "iframe":
				// If it's an editor <iframe> then it's tab navigable.
				var body;
				try{
					// non-IE
					var contentDocument = elem.contentDocument;
					if("designMode" in contentDocument && contentDocument.designMode == "on"){
						return true;
					}
					body = contentDocument.body;
				}catch(e1){
					// contentWindow.document isn't accessible within IE7/8
					// if the iframe.src points to a foreign url and this
					// page contains an element, that could get focus
					try{
						body = elem.contentWindow.document.body;
					}catch(e2){
						return false;
					}
				}
				return body && (body.contentEditable == 'true' ||
					(body.firstChild && body.firstChild.contentEditable == 'true'));
			default:
				return elem.contentEditable == 'true';
		}
	};

	var isTabNavigable = (dijit.isTabNavigable = function(/*Element*/ elem){
		// summary:
		//		Tests if an element is tab-navigable

		// TODO: convert (and rename method) to return effective tabIndex; will save time in _getTabNavigable()
		if(domAttr.get(elem, "disabled")){
			return false;
		}else if(domAttr.has(elem, "tabIndex")){
			// Explicit tab index setting
			return domAttr.get(elem, "tabIndex") >= 0; // boolean
		}else{
			// No explicit tabIndex setting, so depends on node type
			return dijit.hasDefaultTabStop(elem);
		}
	});

	dijit._getTabNavigable = function(/*DOMNode*/ root){
		// summary:
		//		Finds descendants of the specified root node.
		// description:
		//		Finds the following descendants of the specified root node:
		//
		//		- the first tab-navigable element in document order
		//		  without a tabIndex or with tabIndex="0"
		//		- the last tab-navigable element in document order
		//		  without a tabIndex or with tabIndex="0"
		//		- the first element in document order with the lowest
		//		  positive tabIndex value
		//		- the last element in document order with the highest
		//		  positive tabIndex value
		var first, last, lowest, lowestTabindex, highest, highestTabindex, radioSelected = {};

		function radioName(node){
			// If this element is part of a radio button group, return the name for that group.
			return node && node.tagName.toLowerCase() == "input" &&
				node.type && node.type.toLowerCase() == "radio" &&
				node.name && node.name.toLowerCase();
		}

		var walkTree = function(/*DOMNode*/ parent){
			for(var child = parent.firstChild; child; child = child.nextSibling){
				// Skip text elements, hidden elements, and also non-HTML elements (those in custom namespaces) in IE,
				// since show() invokes getAttribute("type"), which crash on VML nodes in IE.
				if(child.nodeType != 1 || (has("ie") <= 9 && child.scopeName !== "HTML") || !shown(child)){
					continue;
				}

				if(isTabNavigable(child)){
					var tabindex = +domAttr.get(child, "tabIndex");	// + to convert string --> number
					if(!domAttr.has(child, "tabIndex") || tabindex == 0){
						if(!first){
							first = child;
						}
						last = child;
					}else if(tabindex > 0){
						if(!lowest || tabindex < lowestTabindex){
							lowestTabindex = tabindex;
							lowest = child;
						}
						if(!highest || tabindex >= highestTabindex){
							highestTabindex = tabindex;
							highest = child;
						}
					}
					var rn = radioName(child);
					if(domAttr.get(child, "checked") && rn){
						radioSelected[rn] = child;
					}
				}
				if(child.nodeName.toUpperCase() != 'SELECT'){
					walkTree(child);
				}
			}
		};
		if(shown(root)){
			walkTree(root);
		}
		function rs(node){
			// substitute checked radio button for unchecked one, if there is a checked one with the same name.
			return radioSelected[radioName(node)] || node;
		}

		return { first: rs(first), last: rs(last), lowest: rs(lowest), highest: rs(highest) };
	};
	dijit.getFirstInTabbingOrder = function(/*String|DOMNode*/ root, /*Document?*/ doc){
		// summary:
		//		Finds the descendant of the specified root node
		//		that is first in the tabbing order
		var elems = dijit._getTabNavigable(dom.byId(root, doc));
		return elems.lowest ? elems.lowest : elems.first; // DomNode
	};

	dijit.getLastInTabbingOrder = function(/*String|DOMNode*/ root, /*Document?*/ doc){
		// summary:
		//		Finds the descendant of the specified root node
		//		that is last in the tabbing order
		var elems = dijit._getTabNavigable(dom.byId(root, doc));
		return elems.last ? elems.last : elems.highest; // DomNode
	};

	return {
		// summary:
		//		Accessibility utility functions (keyboard, tab stops, etc.)

		hasDefaultTabStop: dijit.hasDefaultTabStop,
		isTabNavigable: dijit.isTabNavigable,
		_getTabNavigable: dijit._getTabNavigable,
		getFirstInTabbingOrder: dijit.getFirstInTabbingOrder,
		getLastInTabbingOrder: dijit.getLastInTabbingOrder
	};
});