function getCanvas() 
{
	// bepaal scherm-breedte
	if (document.width) this.w = document.width;
	else if (document.documentElement && document.documentElement.clientWidth) this.w = document.documentElement.clientWidth;
	else if (document.body && document.body.clientWidth) this.w = document.body.clientWidth;
	else if (window.innerWidth) this.w = window.innerWidth;
	else this.w = 0;
	
	// bepaal scherm-hoogte
	if (document.height) this.h = document.height;
	else if (document.documentElement && document.documentElement.clientHeight) this.h = document.documentElement.clientHeight;
	else if (document.body && document.body.clientHeight) this.h = document.body.clientHeight;
	else if (window.innerHeight) this.h = window.innerHeight;
	else this.h = 0;
	return this;
}
			
function posDiv( id ) 
{
	var docSize;
	docSize = getCanvas();

	// het te centreren element
	elem = document.getElementById(id);
	
	// bepaal hoogte scherm en element
	y1 = docSize.h;
	y2 = elem.offsetHeight;

	// bepaal gecentreerde hoogte
	y = ( (y1/2)  - (y2/2) );
	
	// bepaal breedte scherm en element
	x1 = docSize.w;
	x2 = elem.offsetWidth;
	
	// bepaal gecentreerde left-positie
	x = ( (x1/2) - (x2/2) )
	
	// zet de positie
	elem.style.top  = y;
	elem.style.left = x;
}

function openWindowScrollable(Url, WinName) 
{
	w = 800;
	h = 500;

	var docSize;
	docSize = getCanvas();

	// bepaal hoogte scherm en element
	y1 = docSize.h;
	y2 = h;
	
	// bepaal gecentreerde hoogte
	y = ( (y1/2) - (y2/2) );

	// bepaal breedte scherm en element
	x1 = docSize.w;
	x2 = w;

	// bepaal gecentreerde left-positie
	x = ( (x1/2) - (x2/2) )
	
	var features='height=' + h + 'px, width=' + w + 'px, menubar=no,resizable=yes,scrollbars=yes,status=no,titlebar=no,left=' + x + ';top=' + y;
	window.open(Url, WinName, features);
}

function openWindowScrollableHelp(Url, WinName) 
{
	w = 600;
	h = 500;

	var features='height=' + h + 'px, width=' + w + 'px, menubar=no,resizable=no,scrollbars=yes,status=no,titlebar=no';
	window.open(Url, WinName, features);
}

function openWindowScrollableHTML(sHTML, WinName) 
{
	w = 800;
	h = 500;

	var docSize;
	docSize = getCanvas();

	// bepaal hoogte scherm en element
	y1 = docSize.h;
	y2 = h;
	
	// bepaal gecentreerde hoogte
	y = ( (y1/2) - (y2/2) );

	// bepaal breedte scherm en element
	x1 = docSize.w;
	x2 = w;

	// bepaal gecentreerde left-positie
	x = ( (x1/2) - (x2/2) )
	
	var features='height=' + h + 'px, width=' + w + 'px, menubar=no,resizable=yes,scrollbars=yes,status=no,titlebar=no,left=' + x + ';top=' + y;
	var newWin = window.open("", WinName, features);
	newWin.document.write(sHTML)
}

//Shows or hides a control
function showHide(what, show)
{
	var varC = document.getElementById(what);
	if (varC) 
	{
		if (show)
		{
			varC.style.visibility = 'hidden';
			varC.style.display = 'none';
		}
		else
		{
			varC.style.visibility = 'visible';
			varC.style.display = 'block';
		}
	}
}