function buttonDown(event) {
	if( isCheckable(event) 
		|| (event.type == "mouseup" && event.button == 0) 
		|| (event.type == "mousedown" && event.button == 0) 
		|| (event.type == "mouseout" && event.button == 0)) {
		event.target.setAttributeNS("http://www.w3.org/2005/07/aaa", "selected", "true");
		return false;  // Don't continue propagating event
	}
	return true;  // Browser can still use event
}

function buttonUp(event) {
	if( isCheckable(event) 
		|| (event.type == "mouseup" && event.button == 0) 
		|| (event.type == "mousedown" && event.button == 0) 
		|| (event.type == "mouseout" && event.button == 0)) {
		event.target.setAttributeNS("http://www.w3.org/2005/07/aaa", "selected", "false");
		return false;  // Don't continue propagating event
	}
	return true;  // Browser can still use event
}

function checkboxCheck(node) {
	node.setAttributeNS("http://www.w3.org/2005/07/aaa", "checked", "true");
}

// Mouse and keyboard event handlers for controls, copied from Mozilla's Page
function checkboxEvent(event) {
	if( isCheckable(event) ) {
		checkboxToggle(event.target);
		return false;  // Don't continue propagating event
	}
	return true;  // Browser can still use event
}

function checkboxMixedCheck(node) {
	node.setAttributeNS("http://www.w3.org/2005/07/aaa", "checked", "mixed");
}

// Removes the "checked" attribute from a node
function checkboxNoCheck(node) {
	node.removeAttributeNS("http://www.w3.org/2005/07/aaa", "checked");
}

function checkboxToggle(node) {
	if (node.getAttributeNS("http://www.w3.org/2005/07/aaa", "checked") == "true") {
		checkboxUnCheck(node);
	} else {
		checkboxCheck(node);
	}
}

function checkboxTriStateCycle(node) {
	if (node.getAttributeNS("http://www.w3.org/2005/07/aaa", "checked") == "true") {
		checkboxMixedCheck(node);
	} else if (node.getAttributeNS("http://www.w3.org/2005/07/aaa", "checked") == "mixed") {
		checkboxUnCheck(node);
	} else {
		checkboxCheck(node);
	}
}

// Mouse and keyboard event handlers for controls, copied from Mozilla's Page
function checkboxTriStateEvent(event) {
	if( isCheckable(event) ) {
		checkboxTriStateCycle(event.target);
		return false;  // Don't continue propagating event
	}
	return true;  // Browser can still use event
}
// Sets the "checked" attribute to false
function checkboxUnCheck(node) {
	node.setAttributeNS("http://www.w3.org/2005/07/aaa", "checked", "false");
}

// Returns an a array of radio controls in a group given a DOM radio group node
// radioArray is used in the recursion, the root call should pass in "new Array()"
function getRadioGroupArray(radioGroupNode, radioArray) {
	// Recursively search the tree below this node unless they are a radio group node
	for(var i=0; i<radioGroupNode.childNodes.length; i++) {
		childNode = radioGroupNode.childNodes[i];
		if(childNode.nodeType != childNode.ELEMENT_NODE) {
			continue;
		}

		if(isRadioGroup(childNode)) {
			return radioArray; // Don't descend
		} else if(isRadio(childNode)) {
			radioArray.push(childNode);
		}
		getRadioGroupArray(childNode, radioArray); // Descend
	}
	return radioArray;
}

// Returns the encapsulating radio group for a given node or null if none found
function getRadioParentGroup(node) {
	if( node.parentNode == null ) {
		return null;
	} 
	node = node.parentNode;	

	if( isRadioGroup(node) ) {
		return(node);
	}

	return getRadioParentGroup(node);
}

// Returns true if checkable event 
function isCheckable(event) {
	if ((event.type == "click" && event.button == 0) 
		|| (event.type == "keypress" && event.charCode == 32)
		|| ( (event.type == "keydown" || event.type == "keyup") && event.keyCode == 32 ) ) {
		
		if( event.target == event.currentTarget ) { 
			return true;
		}
	}
	return false;
}

// Returns true if a node has the aaa state "checked" set
function isChecked(node) {
	if (node.getAttributeNS("http://www.w3.org/2005/07/aaa", "checked") == "true") {
		return true;
	}
	return false;
}

// returns true if node has role=radiogroup
function isRadioGroup(node) {
	// Attempt to match last part of string because of unrecognized-namespace-in-value issues
	if( node.getAttributeNS("http://www.w3.org/TR/xhtml2", "role").search(/radiogroup$/) > -1 ) {
		return true;
	}
	return false;
}

// returns true if node has role=radio
function isRadio(node) {
	// Attempt to match last part of string because of unrecognized-namespace-in-value issues
	if( node.getAttributeNS("http://www.w3.org/TR/xhtml2", "role").search(/radio$/) > -1 ) {
		return true;
	}
	return false;
}

// If radio node is previously unchecked, unchecks the previous 
// ... radio control in the same group and checks this one.
// If radio node was checked, no changes are made.
function radioCheck(node) {
	if(isChecked(node)) {
		return; // no changes necessary.
	}
	
	radios = getRadioGroupArray(getRadioParentGroup(node), new Array());

	for(var i=0; i<radios.length; i++) {
		if(isChecked(radios[i])) {
			checkboxUnCheck(radios[i]);
		}
	}
	checkboxCheck(node);
}


// Mouse and keyboard event handlers for controls, copied from Mozilla's Page
function radioEvent(event) {
	if( isCheckable(event) ) {
		radioCheck(event.target);
		return false;  // Don't continue propagating event
	}
	return true;  // Browser can still use event
}