var contextString = "";
var mousex = 0;
var mousey = 0;
var grabx = 0;
var graby = 0;
var orix = 0;
var oriy = 0;
var elex = 0;
var eley = 0;
var algor = 0;

var dragobj = null;

function falsefunc() { return false; } // used to block cascading events

function init()
{
    document.onmousemove = update; // update(event) implied on NS, update(null) implied on IE
    update();
}

function getMouseXY(e) // works on IE6,FF,Moz,Opera7
{
    if (!e) e = window.event; // works on IE, but not NS (we rely on NS passing us the event)

    if (e)
    {
        if (e.pageX || e.pageY)
        { // this doesn't work on IE6!! (works on FF,Moz,Opera7)
            mousex = e.pageX;
            mousey = e.pageY;
            algor = '[e.pageX]';
            if (e.clientX || e.clientY) algor += ' [e.clientX] '
        }
        else if (e.clientX || e.clientY)
        { // works on IE6,FF,Moz,Opera7
            mousex = e.clientX + document.body.scrollLeft;
            mousey = e.clientY + document.body.scrollTop;
            algor = '[e.clientX]';
            if (e.pageX || e.pageY) algor += ' [e.pageX] '
        }
    }
}

function update(e)
{
    getMouseXY(e); // NS is passing (event), while IE is passing (null)
}

function grab(contextStr)
{
    contextString = contextStr;
    var context = document.getElementById("div" + contextStr);
    document.onmousedown = falsefunc; // in NS this prevents cascading of events, thus disabling text selection
    dragobj = context;
    document.onmousemove = drag;
    document.onmouseup = drop;
    grabx = mousex;
    graby = mousey;
    elex = orix = dragobj.offsetLeft;
    eley = oriy = dragobj.offsetTop;
    update();
}

function drag(e) // parameter passing is important for NS family
{
    if (dragobj)
    {
        elex = orix + (mousex-grabx);
        eley = oriy + (mousey-graby);
        dragobj.style.position = "absolute";
        dragobj.style.left = (elex).toString(10) + 'px';
        dragobj.style.top  = (eley).toString(10) + 'px';

        var frameObj = document.getElementById("frm" + contextString);
        frameObj.style.position = dragobj.style.position;
        frameObj.style.left = dragobj.style.left;
        frameObj.style.top = dragobj.style.top;
    }
    update(e);
    return false; // in IE this prevents cascading of events, thus text selection is disabled
}

function drop()
{
    if (dragobj)
    {
        dragobj = null;
    }
    update();
    document.onmousemove = update;
    document.onmouseup = null;
    document.onmousedown = null;   // re-enables text selection on NS
}

init();