Google Chrome位置：固定border-radius overflow：隐藏问题

Question

I am having issues with Google Chrome while using border-radius on a position:fixed element with overflow:hidden . The overflow attribute does not seem to be working. When you hover over the navigation items the div with the red background, .bmopt , is supposed to be clipped to the shape of #mstrip , but instead it just shows as a standard rectangle.

HTML :

<div id='mstrip'>
    <div class='mlabel first'>
        <a href='#' class='mopt'>Item1</a>
        <div class='bmopt'></div>
    </div>
    <div class='mlabel'>
        <a href='#' class='mopt'>Item2</a>
        <div class='bmopt'></div>
    </div>
    <div class='mlabel'>
        <a href='#' class='mopt'>Item3</a>
        <div class='bmopt'></div>
    </div>
    <div class='mlabel'>
        <a href='#' class='mopt'>Item4</a>
        <div class='bmopt'></div>
    </div>
    <div class='mlabel'>
        <a href='#' class='mopt'>Item5</a>
        <div class='bmopt'></div>
    </div>
</div>

CSS:

#mstrip {
    width: 92px;
    height: 223px;
    position: fixed;
    top: 20px;
    border-radius: 40% 8px;
    z-index: 100;
    background: #000;
    overflow: hidden;
    box-shadow: 0 0 4px #000;
}
.mlabel {
    width: 92px;
    height: 35px;
}
.first {
    margin-top: 24px;
}
.mopt {
    display: block;
    width: 92px;
    height: 29px;
    padding-top: 6px;
    text-align: center;
    color: #FFF;
    text-decoration: none;
    font: menu;
    font-size: 0.9em;
    text-shadow: 0 0 1px #FFF;
}
.bmopt {
    position: relative;
    width: 92px;
    height: 35px;
    background: #F00;
    margin-top: -35px;
    z-index: -1;
}

Here is a working example of this bug: http://jsfiddle.net/UxLHR/7/

Is there a way around this?

Answer 1

I think that the problem arises from changing opacity in the element; that creates a separate stacking context and is probably the origin of the bug.

I have solved it making it simpler; just changing the color of the mlabel class on hover, and setting a transition on this. I don't think that the inner div is necesary.

.mlabel {
    width: 92px;
    height: 35px;
    background-color: black;
    -webkit-transition: background-color 1s;
}
.mlabel:hover {
    background-color: red;
}

updated fiddle

(transition only for webkit)