overlay: does not change position when relative to node

[yiminghe]

KISSY Version :

1.2.0

Browsers :

all

What steps will reproduce the problem?

<button id="show">show</button>
<button id="hide">hide</button>
<div id="wrap" style="position: relative;z-index: 0;
overflow: scroll;
height: 500px;border: 1px solid red;">
    <div style="height: 1000px;">

    </div>

</div>

    KISSY.use("overlay", function (S, Overlay) {
        var o = new Overlay.Dialog({
            headerContent:"哈哈",
            bodyContent:"嘿嘿",
            render:'#wrap',
            width:300,
            height:300
        });

        S.one("#show").on("click",function(){
            o.center('#wrap');
            o.show();

        });

        S.one("#hide").on("click",function(){
            o.hide();
        });

    });

1. click show
2. click hide
3. scroll wrap to bottom
4. click show

   Expected

overlay shows in the middle of wrap

actual

overlay does not show

[yiminghe]

http://docs.kissyui.com/kissy/src/overlay/demo/relative_align/align.html