/***********************************************************************
/** Zet de watermerk tekst op tekstbox
/**********************************************************************/
function Ess_Web_UI_WebControls_TextBox_SetOverlay (e, tekst )
{
    if(e != null )
    {        
        if ( e.value.length == 0 )
        { 
            var divOverlay = document.createElement('div');
            var position   = Ess_Web_UI_WebControls_TextBox_getElementPosition(e);
            
            divOverlay.innerHTML       = tekst;
            divOverlay.id              = e.id + '_overlay';
            divOverlay.className       = 'Ess_Web_UI_WebControls_TextBox_Watermark';
            divOverlay.style.position  = 'absolute'
            divOverlay.style.top       = position.y + 'px';
            divOverlay.style.left      = position.x + 'px';            
              
            divOverlay.onclick = function ( )
            {  
                Ess_Web_UI_WebControls_TextBox_HideOverlay( e );
                
                document.getElementById ( e.id ).focus();
            }
            
            var oldEvent = (window.onresize) ? window.onresize : function () {};

            window.onresize = function() {
                oldEvent();

                var divOverlay = document.getElementById(e.id + '_overlay');
                var position = Ess_Web_UI_WebControls_TextBox_getElementPosition(document.getElementById(e.id));

                if (divOverlay != null) {

                    divOverlay.style.top = position.y + 'px';
                    divOverlay.style.left = position.x + 'px';
                }

            }
           
            document.getElementsByTagName('form')[0].appendChild(divOverlay);
        }
    } 
} 

/***********************************************************************
/** Verberg watermerk tekst bij tekstbox
/**********************************************************************/
function Ess_Web_UI_WebControls_TextBox_HideOverlay(e) {
    
    var overlay = document.getElementById(e.id + '_overlay');

    if (overlay != null) 
    {        
        document.getElementsByTagName('form')[0].removeChild(overlay);
    }
}

/***********************************************************************
/** Bereken de positie van een element
/**********************************************************************/
function Ess_Web_UI_WebControls_TextBox_getElementPosition(theElement)
{  
    var posX = 0;  
    var posY = 0;                
    
    while(theElement != null)
    {    
        posX += theElement.offsetLeft;    
        posY += theElement.offsetTop;    
        theElement = theElement.offsetParent;  
    }                        		       

    return {x:posX,y:posY};
}