// Navigation menu options array.
var buttons = new Array();

// Selected button index
var button_selected = '';
	
/* -----------------------------------------------------------------------------
 * This function declares Button object.
 * Parameters:
 *		image		  - image for menu option that represent normal state
 *		overImage	  - image for menu option that represent mouse over state
 *		selectedImage - image for menu option that represent mouse selected state
 */
function Button (image, overImage, selectedImage) {
	this.image = new Image();
	this.image.src = image;
	this.overImage = new Image();
	this.overImage.src = overImage;
	this.selectedImage = new Image();
	if (selectedImage != undefined) {
		this.selectedImage.src = selectedImage;
	}
}

/* -----------------------------------------------------------------------------
 * This function adds new Button object.
 * Parameters:
 *		name          - symbolic name of this option
 *		image         - image for menu option that represent normal state
 *		overImage     - image for menu option that represent mouse over state
 *		selectedImage - image for menu option that represent mouse selected state
 */
function button_addButton (name, image, overImage, selectedImage) {
	buttons[name] =
			new Button(image, overImage, selectedImage);
}

/* -----------------------------------------------------------------------------
 * This function sets selected image for specified button.
 * Parameters:
 *		name - symbolic name of this button
 */
function button_setSelectedImage (name) {
	var oldSelected = button_selected;

	document.images[name].src = buttons[name].selectedImage.src;
	button_selected = name;

	if (oldSelected != '') {
		button_setImage(oldSelected);
	}

}

/* -----------------------------------------------------------------------------
 * This function sets mouse over image for specified button.
 * Parameters:
 *		name - symbolic name of this button
 */
function button_setOverImage (name) {
	if (button_selected == name) {
		document.images[name].src = buttons[name].selectedImage.src;
	} else {
		document.images[name].src = buttons[name].overImage.src;
	}
}

/* -----------------------------------------------------------------------------
 * This function sets normal image for specified button.
 * Parameters:
 *		name - symbolic name of this button
 */
function button_setImage (name) {
	if (button_selected == name) {
		document.images[name].src = buttons[name].selectedImage.src;
	} else {
		document.images[name].src = buttons[name].image.src;
	}
}


			
/*
 * Initializes Navigation buttons
 */
 	button_addButton('btnAbout',
			'images/btn_about_off.gif',
			'images/btn_about_on.gif'); 
		
	button_addButton('btnServices',
			'images/btn_services_off.gif',
			'images/btn_services_on.gif');
	
	button_addButton('btnPeople',
			'images/btn_people_off.gif',
			'images/btn_people_on.gif');
			
	button_addButton('btnProjects',
			'images/btn_projects_off.gif',
			'images/btn_projects_on.gif');
			
	button_addButton('btnNews',
			'images/btn_news_off.gif',
			'images/btn_news_on.gif');
			
	button_addButton('btnContact',
			'images/btn_contact_off.gif',
			'images/btn_contact_on.gif');