//global variables that can be used by ALL the function son this page.
var inputs;
var imgFalse = '/img/layout/check-false.png';
var imgTrue = '/img/layout/check-true.png';

//this function runs when the page is loaded, put all your other onload stuff in here too.
function initCheck() {
	replaceChecks();
}

function replaceChecks() {	
	//get all the input fields on the page
	inputs = document.getElementsByTagName('input');

	//cycle trough the input fields
	for(var i=0; i < inputs.length; i++) {

		//check if the input is a checkbox
		if(inputs[i].getAttribute('type') == 'checkbox') {
			
			//create a new image
			if(document.getElementById('checkImage'+i) == null){
		    	var img = document.createElement('img');
		    	img.alt = '';
		    	img.style.cursor='pointer';
			
		    	//check if the checkbox is checked
		    	if(inputs[i].checked) {
			    	img.src = imgTrue;
			    } else {
			    	img.src = imgFalse;
			    }

			    //set image ID and onclick action
			    img.id = 'checkImage'+i;
			    //set image 
			    img.onclick = new Function('checkChange('+i+')');
			    //place image in front of the checkbox
			    inputs[i].parentNode.insertBefore(img, inputs[i]);
			
			    //hide the checkbox
			    inputs[i].style.display='none';
			    inputs[i].style.visible='false';
			}
		}
	}
}

//change the checkbox status and the replacement image
function checkChange(i) {
	if(inputs[i].checked) {
		inputs[i].checked = '';
		document.getElementById('checkImage'+i).src=imgFalse;
	} else {
		inputs[i].checked = 'checked';
		document.getElementById('checkImage'+i).src=imgTrue;
	}
}

//esegue la funzione js initCheck ad ogni PostBack scatenato all'interno di un UpdatePanel //
function initPageRequestManager() {
    Sys.WebForms.PageRequestManager.getInstance().add_endRequest(initCheck);
}

initPageRequestManager();
initCheck();