var previewBox = document.getElementById('PreviewBox');
var previewImage = document.getElementById('PreviewImage');
var previewUrl = document.getElementById('previewUrl');
var previewFrom = null;
var previewTimeoutId = null;
var loadingImg = 'images/list/loading.gif';
var maxWidth = 300;
var maxHeight = 300;

/**
 * 获取页面元素的坐标
 */
function getPosXY(a, offset) {
	var p=offset?offset.slice(0):[0,0],tn;
	while(a) {
		tn=a.tagName.toUpperCase();
		if (tn == 'IMG') {
			a = a.offsetParent;
			continue;
		}
		p[0]+=a.offsetLeft-(tn=="DIV"&&a.scrollLeft?a.scrollLeft:0);
		p[1]+=a.offsetTop-(tn=="DIV"&&a.scrollTop?a.scrollTop:0);
		if (tn=="BODY") break;
		a=a.offsetParent;
	}
	return p;
}

function checkComplete() {
	if (checkComplete.__img && checkComplete.__img.complete)
		checkComplete.__onload();
}

checkComplete.__onload = function() {
	clearInterval(checkComplete.__timeId);
	var w = checkComplete.__img.width;
	var h = checkComplete.__img.height;
	if (w >= h && w > maxWidth) {
		previewImage.style.width = maxWidth + 'px';
	} 
	else if (h >= w && h > maxHeight) {
		previewImage.style.height = maxHeight + 'px';
	}
	else {
		previewImage.style.width = previewImage.style.height = '';
	}
	previewImage.src = checkComplete.__img.src;
	previewUrl.href = checkComplete.href;
	checkComplete.__img = null;
	//previewImage.style.display = '';
}

/**
 * 500毫秒后激发预览操作
 */
function showPreview(e) {
	hidePreview();
	previewFrom = e.target || e.srcElement;
	previewImage.src = loadingImg;
	previewImage.style.width = previewImage.style.height = '';
	previewTimeoutId = setTimeout('_showPreview()', 500);
	checkComplete.__img = null;	
}

/**
 * 取消预览
 */
function hidePreview(e) {
	if (e) {
		var toElement = e.relatedTarget || e.toElement;
		//alert(toElement.innerHTML);
		while (toElement) {
			if (toElement.id == 'PreviewBox')
				return;
			toElement = toElement.parentNode;
		}
	}
	try{
		clearInterval(checkComplete.__timeId);
		checkComplete.__img = null;
		previewImage.src = null;
	}
	catch (e){
	}
	clearTimeout(previewTimeoutId);
	previewBox.style.display = 'none';
}

/**
 *  预览操作
 */
function _showPreview() {
	//previewImage.style.display = 'none';
	checkComplete.__img = new Image();
	if (previewFrom.tagName.toUpperCase() == 'A')
		previewFrom = previewFrom.getElementsByTagName('img')[0];
	//获取大图的URL
	var largeSrc = previewFrom.getAttribute("large-src");
	var picLink = previewFrom.getAttribute("pic-link");
	if (!largeSrc) return;
	else {
		checkComplete.__img.src = largeSrc;
		checkComplete.href = picLink;
		checkComplete.__timeId = setInterval("checkComplete()", 20);
		var pos = getPosXY(previewFrom, [75, -2]);
		previewBox.style.left = pos[0] + 'px';
		previewBox.style.top = pos[1] + 'px';
		previewBox.style.display = 'block';
	}
}