var $activeBlock = null;

function showShader($object) {
    if ($activeBlock != null) clearTrigger();
    var $position = findPos($object);
    var $shdr = document.getElementById('shader');
    var $ovrly = document.getElementById('overlay');

    $shdr.style.left = $position[0] + 'px';
    $shdr.style.top = $position[1] + 'px';
    $shdr.href = $object.href;

    $ovrly.style.left = $position[0] + 'px';
    $ovrly.style.top = $position[1] + 'px';

    var link_img = $shdr.getElementsByTagName('img')[0];
    link_img.left = $position[0] + 'px';
    link_img.top = $position[1] + 'px';

    link_img.style.display = '';
    $shdr.style.display = '';
    $ovrly.style.display = '';
}

function clearTrigger() {
    var $shdr = document.getElementById('shader');
    var $ovrly = document.getElementById('overlay');
    $shdr.style.display = 'none';
    $ovrly.style.display = 'none';
}

function findPos(obj) {
    var curtop;
    var curleft = curtop = 0;
    if (obj.offsetParent) {
        curleft = obj.offsetLeft;
        curtop = obj.offsetTop;
        while (obj = obj.offsetParent) {
            curleft += obj.offsetLeft;
            curtop += obj.offsetTop;
        }
    }
    return [curleft, curtop];
}