box-shadow on top of children

Question

How do I get an inset CSS3 box-shadow to render on top of its children elements?

Problem:

HTML:

<div id="chatroom">
    <div class="chatmessage"><b>User 1:</b>Test</div>
    <div class="chatmessage"><b>User 2:</b>Test</div>
    <div class="chatmessage"><b>User 1:</b>Test</div>
    <div class="chatmessage"><b>User 2:</b>Test</div>
</div>

CSS:

#chatroom{
    border: 1px solid #CCC;
    height: 135px;
    font-size: 0.75em;
    line-height: 1.2em;
    overflow: auto;
    -moz-box-shadow: inset 0 0px 4px rgba(0,0,0,.55);
    -webkit-box-shadow: inset 0 0px 4px rgba(0,0,0,.55);
}
.chatmessage{
    padding: 4px 2px;
}
.chatmessage b{
    margin-right: 2px;
}
.chatmessage:nth-child(2n) {
    background: #EEE;
}

Answer 1

cant be done directly from css.. (it is not shadow if it goes above overlapping elements)

you would need to rework your html a bit by adding a div (or use a pseudo element as suggested by miguelcobain's answer) to overlay the shadow and your CSS to make the new div have the shadow..

#chatroom {
  border: 1px solid #CCC;
  height: 135px;
  font-size: 0.75em;
  line-height: 1.2em;
  overflow: auto;
  position: relative;
}

.shadow {
  position: absolute;
  left: 0px;
  top: 0px;
  right: 0px;
  bottom: 0px;
  -moz-box-shadow: inset 0 0px 4px rgba(0, 0, 0, .55);
  -webkit-box-shadow: inset 0 0px 4px rgba(0, 0, 0, .55);
  box-shadow: inset 0 0px 4px rgba(0, 0, 0, .55);
}

.chatmessage {
  padding: 4px 2px;
}

.chatmessage b {
  margin-right: 2px;
}

.chatmessage:nth-child(2n) {
  background: #EEE;
}

<div id="chatroom">
  <div class="chatmessage"><b>User 1:</b>Test</div>
  <div class="chatmessage"><b>User 2:</b>Test</div>
  <div class="chatmessage"><b>User 1:</b>Test</div>
  <div class="chatmessage"><b>User 2:</b>Test</div>
  <div class="shadow"></div>
</div>

Answer 2

To avoid the use of an additional element, you can use css pseudo-elements. Try this demo.

#chatroom {
    position: relative;
}

#chatroom:before {
    content: "";

    /* Expand element */
    position: absolute;
    left: 0px;
    top: 0px;
    right: 0px;
    bottom: 0px;

    -moz-box-shadow: inset 0 0 8px rgba(0,0,0,.55);
    -webkit-box-shadow: inset 0 0 8px rgba(0,0,0,.55);
    box-shadow: inset 0 0 8px rgba(0,0,0,.55);

    /* Disable click events */
    pointer-events: none;
}

Basically this css creates that additional element for you. Notice the pointer-events:none to allow click events to pass through this element.

Keep in mind that pointer-events:none doesn't work well on some mobile devices regarding touch scrolling (clicking/taping works well). I ended up not using inset shadows at all because of this.

Answer 3

Change the background-color of any children to also be RGBA (this only gets set in browsers that understand it which, conveniently, is any browser that can handle the shadow):

.chatmessage:nth-child(2n) {
    background : #EEE;
    background : RGBA(0, 0, 0, .066);
}

Note that the two colors (#EEE, RGBA( 0, 0, 0, .066)) are identical as long as the background behind them is white.

Demo since people seem to be down voting this for no reason: http://jsfiddle.net/6NrkR/