var browser = new Browser(); // include browserControl.js before this js

// Global object to hold drag information.
var dragObj = new Object();
/*dragObj.zIndex = 0;*/

function dragStart(event, id)
{
    setTopest(id);
    
    var el;
    var x, y;

    // If an element id was given, find it. Otherwise use the element being
    // clicked on.
    if (id)
        dragObj.elNode = document.getElementById(id);
    else
    {
        if (browser.isIE || browser.isOpera)
            dragObj.elNode = window.event.srcElement;
        
        if (browser.isNS)
            dragObj.elNode = event.target;
            
        // If this is a text node, use its parent element.
        if (dragObj.elNode.nodeType == 3) //TEXT_NODE = 3
            dragObj.elNode = dragObj.elNode.parentNode;
    }

    // Get cursor position with respect to the page.
    if (browser.isIE || browser.isOpera)
    {
        x = window.event.clientX + document.documentElement.scrollLeft + document.body.scrollLeft;
        y = window.event.clientY + document.documentElement.scrollTop + document.body.scrollTop;
    }
  
    if (browser.isNS)
    {
        x = event.clientX + window.scrollX;
        y = event.clientY + window.scrollY;
    }
  
    // Save starting positions of cursor and element.

    dragObj.cursorStartX = x;
    dragObj.cursorStartY = y;
    dragObj.elStartLeft  = parseInt(dragObj.elNode.style.left, 10);
    dragObj.elStartTop   = parseInt(dragObj.elNode.style.top,  10);

    if (isNaN(dragObj.elStartLeft))
        dragObj.elStartLeft = 0;
    
    if (isNaN(dragObj.elStartTop))
        dragObj.elStartTop  = 0;

    /*
    // Update element's z-index.
    dragObj.elNode.style.zIndex = ++dragObj.zIndex;*/

    // Capture mousemove and mouseup events on the page.

    if (browser.isIE || browser.isOpera)
    {
        document.attachEvent("onmousemove", dragGo);
        document.attachEvent("onmouseup",   dragStop);
        window.event.cancelBubble = true;
        window.event.returnValue = false;
    }
  
    if (browser.isNS)
    {
        document.addEventListener("mousemove", dragGo,   true);
        document.addEventListener("mouseup",   dragStop, true);
        event.preventDefault();
    }
}

function dragGo(event)
{
    var x, y;
    
    // Get cursor position with respect to the page.
    if (browser.isIE || browser.isOpera)
    {
        x = window.event.clientX + document.documentElement.scrollLeft + document.body.scrollLeft;
        y = window.event.clientY + document.documentElement.scrollTop + document.body.scrollTop;
    }
    
    if (browser.isNS)
    {
        x = event.clientX + window.scrollX;
        y = event.clientY + window.scrollY;
    }

    // Move drag element by the same amount the cursor has moved.
    dragObj.elNode.style.left = (dragObj.elStartLeft + x - dragObj.cursorStartX) + "px";
    dragObj.elNode.style.top  = (dragObj.elStartTop  + y - dragObj.cursorStartY) + "px";

    if (browser.isIE || browser.isOpera)
    {
        window.event.cancelBubble = true;
        window.event.returnValue = false;
    }
    
    if (browser.isNS)
        event.preventDefault();
}

function dragStop(event)
{
    // Stop capturing mousemove and mouseup events.
    if (browser.isIE || browser.isOpera)
    {
        document.detachEvent("onmousemove", dragGo);
        document.detachEvent("onmouseup",   dragStop);
    }
    
    if (browser.isNS)
    {
        document.removeEventListener("mousemove", dragGo,   true);
        document.removeEventListener("mouseup",   dragStop, true);
    }
}