function CheckboxMenu(id, data, persistkeys, globals)
{
	this.id = id;
	this.menuCheckboxIds = new Array();
	this.data = data;
	this.count = 0;

	var element = document.getElementById(id);
	var checkboxNodes = element.getElementsByTagName("input");

	for(var checkboxCount=0; checkboxCount < checkboxNodes.length; checkboxCount++)
	{
		var checkboxId = checkboxNodes[checkboxCount].getAttribute('id');
		var checkboxData = checkboxNodes[checkboxCount].getAttribute('data');
		var dataSplits = checkboxData.split(',');
		var defaultValue = checkboxNodes[checkboxCount].getAttribute('value');
		if (checkboxData != null && checkboxData.indexOf("persist") != -1)
			persistkeys.push(checkboxId);
	
		this.menuCheckboxIds[dataSplits[0]] = checkboxId;
	
		// try to get the value for this checkbox id from globals
		var persistedValue = (globals == null) ? null : globals.VariableExists(checkboxId) ? globals.VariableValue(checkboxId) : null;
		var currentValue = (persistedValue != null) ? persistedValue : (defaultValue == null) ? "on" : defaultValue;
	
		// set the checkbox's check state
		this.SetCheckState(checkboxId, currentValue);
	
		this.count++;
}
}

CheckboxMenu.prototype.SetCheckState=function(id, value)
{
	var checkbox = document.getElementById(id);
	if(checkbox != null)
	{
		checkbox.checked = (value == "on") ? true : false;
}

	// set the value for the checkbox id in the data array
	this.data[id] = value;
}

CheckboxMenu.prototype.GetCheckState=function(id)
{
	var checkbox = document.getElementById(id);
	if(checkbox != null)
		return checkbox.checked;
	return false;
}

CheckboxMenu.prototype.ToggleCheckState=function(id)
{
	// at least one checkbox must always be checked
	var checkedCount = this.GetCheckedCount();
	
	if(this.data[id] == "on" && checkedCount > 1)
		this.SetCheckState(id, "off");
	else
		this.SetCheckState(id, "on");
}

// returns the checkbox id associated with a key
CheckboxMenu.prototype.GetCheckboxId=function(key)
{
	return this.menuCheckboxIds[key];
}

// returns the array of checkbox ids
CheckboxMenu.prototype.GetCheckboxIds=function()
{
	return this.menuCheckboxIds;
}

// returns the @data attribute of the checkbox element
CheckboxMenu.prototype.GetCheckboxData=function(checkboxId)
{
	var checkbox = document.getElementById(checkboxId);
	if (checkbox == null) return "";
	return checkbox.getAttribute('data');
}

CheckboxMenu.prototype.GetDropdownLabelId=function()
{
	var checkboxCount = this.count;
	var checkedCount = this.GetCheckedCount();
	var idPrefix = this.id;

	// if all boxes checked, use showall label
	if (checkedCount == checkboxCount)
		return idPrefix.concat("AllLabel");

	// if only one is checked, use label appropriate for that one checkbox
	if (checkedCount == 1)
	{
		for(var key in this.menuCheckboxIds)
		{
			if (this.data[this.menuCheckboxIds[key]] == "on")
			{
				return idPrefix.concat(key,'Label');
		}
	}
}

	// if multiple or zero checked, use multiple label
	return idPrefix.concat("MultipleLabel");
}

CheckboxMenu.prototype.GetCheckedCount=function()
{
	var count = 0;
	for(var key in this.menuCheckboxIds)
	{
		if (this.data[this.menuCheckboxIds[key]] == "on")
			count++;
}
	return (count);
}

// returns an array containing the ids of the checkboxes that are checked
CheckboxMenu.prototype.GetCheckedIds=function()
{
	var idArray = new Array();
	for(var key in this.menuCheckboxIds)
	{
		if (this.data[this.menuCheckboxIds[key]] == "on")
			idArray.push(this.menuCheckboxIds[key]);
}
	return idArray;
}

CheckboxMenu.prototype.GetGroupCheckedCount=function(checkboxGroup)
{
	var count = 0;
	for(var i = 0; i < checkboxGroup.length; i++)
	{
		if (this.data[checkboxGroup[i]] == "on")
			count++;
}
	return (count);
}

CheckboxMenu.prototype.ToggleGroupCheckState=function(id, checkboxGroup)
{
	// at least one checkbox must always be checked
	var checkedCount = this.GetGroupCheckedCount(checkboxGroup);

	// if the group has multiple checkboxes, one must always be checked; so toggle to "off" only if more than one currently checked
	// if the group has only one checkbox, it's okay to toggle it on/off
	if(this.data[id] == "on" && (checkedCount > 1 || checkboxGroup.length == 1))
		this.SetCheckState(id, "off");
	else
		this.SetCheckState(id, "on");
}