为什么背景打破了盒阴影嵌入效应？

问题描述

我试图在一个简单的盒子上实现内部阴影效果，像：

其中绿色框是另一个框内的内容。

我的问题是，如果我给内容框任何种类的背景，外框框阴影效果消失！

（与markup和css），我已经设置内容高度更小，以证明问题 - atm我真的不关心IE *，这只是

$ b
$ b

框中的内容是一种幻灯片，：基本上，而不是使用 box-shadow 在包装器上，这将作为一个掩码，我使用 box-shadow 和 border-radius 直接对内容（ .step 元素）
然而，'mask'效果正是我想要完成的，所以这个is not解决方案。 / p>

UPDATE3

打开了，并得到了澄清问题的答案：

特别地，元素的 children 背景将会在
之上（事实上​​，它们在元素本身的边框和背景上绘制元素本身）。

所以渲染正是spec所要求的。

UPDATE4

Fabio A.指出了另一种解决方案，。
看起来不错，在IE8上也有效;）

解决方案

因为我也有这个问题，看到这种行为正常，我提交了一个错误报告

我可以在Google Chrome中重现这个问题，不过，我想知道这是否真的是一个错误。

确实，这不是一个错误，但只是它的工作方式。因此，根据这些信息，我示例，并提出了此解决方案：

标记现在看起来像这样：

 < div id = > 
< div id =wrapper> 
< div id =box_content> 
此处的内容
< / div> 
< div id =mask>< / div> 
< / div> 
< / div> 
  

掩码变成另一个div，它是通过绝对的方式叠加在#box_content的顶部定位。这是CSS：

  #wrapper {
 position：relative; 
 display：inline-block; 
 width：280px; 
 height：280px; 
 border-radius：5px; 
 margin：10px; 
} 
 #mask {
 position：absolute; 
 top：0px; left：0px; 
 width：100％; 
 height：100％; 
 
 pointer-events：none; / *让点击通过* / 
 
 box-shadow：0 0 10px＃000000 inset; 
} 
 #box_content {
 background-color：＃0ef83f; 
 height：100％; 
} 
  

Im trying to achieve an inner-shadow effect on a simple box, something like:alt text http://gotinsane.com/test.jpg

where the green box is the content inside another box.

My problem is that if i give the content box any kind of background, the outer box box-shadow effect vanish!

Here an example of my problem (with markup and css), i've set the content height smaller to evidence the problem - atm i really dont care about IE*, this is just a test.

Any idea?

UPDATE

The content inside the box is a somewhat kind of slide, here an example (original problem).thirtydot's answer does the trick, but it forces me to make a little hack, changing the wrapper background in function of the content: example here (thirtydot trick).

This can be a solution, but i dont like it too much and still dont understand why the outer box shadow get behind the inner box background (color, image)

UPDATE 2

Talking about this problem on another forum, i found another way: basically, instead of use box-shadow on the wrapper, that will act as a mask, I use box-shadow and border-radius directly on the content (.step elements)However, the 'mask' effect is exactly what i was trying to accomplish, so this isnt the solution neither.

UPDATE3

Someone opened a bug on mozilla, and got this answer that clearify the 'problem':

In particular, the backgrounds of children of the element would paint above the inset shadow (and in fact they paint above the borders and background of the element itself).

So the rendering is exactly what the spec calls for.

UPDATE4

Fabio A. pointed out another solution, with css3 pointer-events.Looks good and works on IE8 too ;)

解决方案

Since I am having this problem too and I too don't see this behaviour being normal, I filed a bug report over at mozilla

I can reproduce the problem in Google Chrome too, though, so I wonder whether this is really a bug. But it could be.

edit:

Indeed it's not a bug, but just the way it's meant to work. So, on the basis of this information, I forked your jfiddle example and came up with this solution:

The markup now looks like this:

<div id="box">
    <div id="wrapper">
        <div id="box_content">
            Content here
        </div>
        <div id="mask"></div>
    </div>
</div>

The mask becomes another div, which is layered on top of the #box_content one by means of being absolutely positioned. This is the CSS:

#wrapper{
    position: relative;
    display: inline-block;
    width: 280px;
    height: 280px;
    border-radius: 5px;
    margin: 10px;
}
#mask {
    position: absolute;
    top: 0px; left: 0px;
    width: 100%;
    height: 100%;

    pointer-events: none; /* to make clicks pass through */

    box-shadow: 0 0 10px #000000 inset;
}
#box_content{
    background-color: #0ef83f;
    height: 100%;
}

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