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问题:

I have 3 levels of div:

(In green below) A top level div with overflow: hidden. This is because I want some content (not shown here) inside that box to cropped if it exceeds the size of the box.
(In red below) Inside this, I have div with position: relative. The only use for this is for the next level.
(In blue below) Finally a div I take out of the flow with position: absolute but that I want positioned relative to the red div (not to the page).

I'd like to have the blue box be taken out of the flow and expand beyond the green box, but be positioned relative to the red box as in:

However, with the code below, I get:

And removing the position: relative on the red box, now the blue box is allowed to get out of the green box, but is not positioned anymore relative to the red box:

Is there a way to:

Keep the overflow: hidden on the green box.
Have the blue box expand beyond the green box and be positioned relative to red box?

The full source, with inline CSS for the sake of testing:

<html xmlns="http://www.w3.org/1999/xhtml" xml:lang="en" lang="en">
    <body>
        <br/><br/><br/>
        <div id="1" style="overflow: hidden; background: #efe; padding: 5px; width: 125px">
            <div id="2" style="position: relative; background: #fee; padding: 2px; width: 100px; height: 100px">
                <div id="3" style="position: absolute; top: 10px; background: #eef; padding: 2px; width: 75px; height: 150px"/>
            </div>
        </div>
    </body>
</html>

回答1:

A trick that works is to position box #2 with position: absolute instead of position: relative. We usually put a position: relative on an outer box (here box #2) when we want an inner box (here box #3) with position: absolute to be positioned relative to the outer box. But remember: for box #3 to be positioned relative to box #2, box #2 just need to be positioned. With this change, we get:

And here is the full code with this change:

<html xmlns="http://www.w3.org/1999/xhtml" xml:lang="en" lang="en">
    <head>
        <style type="text/css">

            /* Positioning */
            #box1 { overflow: hidden }
            #box2 { position: absolute }
            #box3 { position: absolute; top: 10px }

            /* Styling */
            #box1 { background: #efe; padding: 5px; width: 125px }
            #box2 { background: #fee; padding: 2px; width: 100px; height: 100px }
            #box3 { background: #eef; padding: 2px; width: 75px; height: 150px }

        </style>
    </head>
    <body>
        <br/><br/><br/>
        <div id="box1">
            <div id="box2">
                <div id="box3"/>
            </div>
        </div>
    </body>
</html>

I added more details about this on Absolutely positioned box inside a box with overflow: auto or hidden.

回答2:

There's no magical solution of displaying something outside an overflow hidden container.

A similar effect can be achieved by having an absolute positioned div that matches the size of its parent by positioning it inside your current relative container (the div you don't wish to clip should be outside this div):

#1 .mask {
  width: 100%;
  height: 100%;
  position: absolute;
  z-index: 1;
  overflow: hidden;
}

Take in mind that if you only have to clip content on the x axis (which appears to be your case, as you only have set the div's width), you can use overflow-x: hidden.

回答3:

I don't really see a way to do this as-is. I think you might need to remove the overflow:hidden from div#1 and add another div within div#1 (ie as a sibling to div#2) to hold your unspecified 'content' and add the overflow:hidden to that instead. I don't think that overflow can be (or should be able to be) over-ridden.

回答4:

If there is other content not being shown inside the outer-div (the green box), why not have that content wrapped inside another div, let's call it "content". Have overflow hidden on this new inner-div, but keep overflow visible on the green box.

The only catch is that you will then have to mess around to make sure that the content div doesn't interfere with the positioning of the red box, but it sounds like you should be able to fix that with little headache.

<div id="1" background: #efe; padding: 5px; width: 125px">
    <div id="content" style="overflow: hidden;">
    </div>
    <div id="2" style="position: relative; background: #fee; padding: 2px; width: 100px; height: 100px">
        <div id="3" style="position: absolute; top: 10px; background: #eef; padding: 2px; width: 75px; height: 150px"/>
    </div>
</div>