source: companies/celepar/jabberit_messenger/js/dragdrop.js @ 763

(function()
{
        var _element = null;

        function _config(pObj, pEvent, pHandler)
        {
                if ( typeof pObj == 'object' )
                {
                        if ( pEvent.substring(0, 2) == 'on' )
                                pEvent = pEvent.substring(2, pEvent.length);

                        if ( arguments.length == 3 )
                        {
                                if ( pObj.addEventListener )
                                        pObj.addEventListener(pEvent, pHandler, false);
                                else if ( pObj.attachEvent )
                                        pObj.attachEvent('on' + pEvent, pHandler);
                        }
                        else if ( arguments.length == 4 )
                        {
                                if ( pObj.removeEventListener )
                                        pObj.removeEventListener(pEvent, pHandler, false);
                                else if ( pObj.detachEvent )
                                        pObj.detachEvent('on' + pEvent, pHandler);
                        }
                }
        }

        function _getMouseOffset(e, el)
        {
                var docPos = _getPosition(el);
                var mousePos = _mouseCoords(e);
                return {
                        'x' : mousePos.x - docPos.x,
                        'y' : mousePos.y - docPos.y
                };
        }

        function _getPosition(_pObject)
        {
                var left = 0;
                var top  = 0;

                while ( _pObject.offsetParent )
                {
                        left += _pObject.offsetLeft;
                        top  += _pObject.offsetTop;
                        _pObject = _pObject.offsetParent;
                }

                left += _pObject.offsetLeft;
                top  += _pObject.offsetTop;

                return {
                        'x' : left,
                        'y' : top
                };
        }

        function _mouseCoords(ev)
        {
                var CoordX = "";
                var CoordY = "";

                if ( ev.pageX || ev.pageY )
                        return {
                                'x' : ev.pageX,
                                'y' : ev.pageY
                        };

                CoordX = ev.clientX + document.body.scrollLeft - document.body.clientLeft;
                CoordY = ev.clientY + document.body.scrollTop  - document.body.clientTop;
                return {
                        'x' : CoordX,
                        'y' : CoordY
                };
        }

        function _mouseMove(e)
        {
                if ( _element )
                {
                        if ( _element.mouseOffset == null )
                                _element.mouseOffset = _getMouseOffset(e, _element);

                        var mousePos = _mouseCoords(e);

                        var x = mousePos.x - _element.mouseOffset.x;
                        var y = mousePos.y - _element.mouseOffset.y;
                        _element.style.left = (( x < 0 ) ? 0 : x) + 'px';
                        _element.style.top  = (( y < 0 ) ? 0 : y) + 'px';
                }
        }

        function _mouseUp()
        {
                if ( _element )
                {
                        _config(_element, 'onmousemove', _mouseMove, 'remove');
                        _config(top.document, 'onmousemove', _mouseMove, 'remove');

                        _config(_element, 'onmouseup', _mouseUp, 'remove');
                        _config(top.document, 'onmouseup', _mouseUp, 'remove');

                        _element.mouseOffset = null;
                        _element = null;
                }
        }

        function _toDrag(el)
        {
                if ( el.getAttribute('dragdrop_parent') == null )
                {
                        if ( el.getAttribute('dragdrop_child') != null )
                        {
                                var children = 0;
                                while ( (++children < 5) && (el.getAttribute('dragdrop_parent') == null) )
                                        el = el.parentNode;
                        }
                        if ( el.getAttribute('dragdrop_parent') == null )
                                el = false;
                }
                return el;
        }

        function _drag(e)
        {
                if (typeof e.preventDefault != 'undefined')
                        e.preventDefault();
                else
                        e.onselectstart = new Function("return false;");

                var el = ( e.target ) ? e.target : e.srcElement;

                el = _toDrag(el);

                if ( el )
                {
                        _element = el;

                        _config(el, 'onmousemove', _mouseMove);
                        _config(top.document, 'onmousemove', _mouseMove);

                        _config(el, 'onmouseup', _mouseUp);
                        _config(top.document, 'onmouseup', _mouseUp);
                }
        }

        function _set(_pObject)
        {
                if ( typeof _pObject != 'object' )
                        return false;

                _pObject.setAttribute('dragdrop_parent', 'true');

                _config(_pObject, 'onmousedown', _drag);
        }

        function DragDrop()
        {
        }

        DragDrop.prototype.drag = _set;
        window.JITDragDrop = DragDrop;
}
)();