var previous = "";

function showTooltip(id, event, alignment) {
    if (previous != "") {
        hideTooltip(previous);
    }
    var iX = event.clientX + document.body.scrollLeft;
    var iY = event.clientY + document.body.scrollTop + 10;
    var winWidth = window.innerWidth ? window.innerWidth : document.body.clientWidth;

    var tooltip = byId(id);
    if (tooltip) {
        previous = id;
        if (alignment == "right") iX -= tooltip.offsetWidth;
        else if (alignment == "center") iX -= tooltip.offsetWidth / 2;
        if (winWidth && winWidth > 0 && iX + tooltip.offsetWidth > winWidth) iX = winWidth - tooltip.offsetWidth;
        if (iX < 0) iX = 0;
        tooltip.style.left = iX + "px";
        tooltip.style.top = iY + "px";
        tooltip.style.visibility = "visible";
    }
}

function hideTooltip(id) {
    var tooltip = byId(id);
    if (tooltip) {
        tooltip.style.visibility = "hidden";
        previous = "";
    }
}