Flexbox - Children expand to fill height

Question

I have a dynamic footer on my page and I expect the content above it to scale to reach the top of the footer, that's fine and all, but I'm having a problem:

#snippet-container {    height: 300px;    width: 200px;  }    #page {    display: flex;    flex-flow: column;    height: 100%;  }    #content {    flex: 1 1 auto;    background: blue;  }    #content .test {    width: 100%;    height: 100%;    background: yellow;    border: 2px solid red;  }    #footer {    flex: 0 1 10vh;    background: black;  }

<div id="snippet-container">    <div id="page">      <div id="content">        <div class="test"></div>      </div>      <div id="footer"></div>    </div>  </div>

I would expect the .test element to fill the #content element, hence the 100%/100% width/height however it does not.

You can see this reflected as I gave the .test element a red border in the snippet.

Answer 1

PROBLEM:

The problem is that your #page flex container is not reaching the .test element since .test is not a child, it is a descendant of the flex item.

The contents of a flex container consists of zero or more flex items: each child of a flex container becomes a flex item.

Each flex item is affected by the flex container, but the flex item's descendants are not.

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SOLUTION:

You need to add display: flex to your #content as well.

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JSFiddle

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CODE SNIPPET:

#snippet-container {    height: 300px;    width: 200px;  }  #page {    display: flex;    flex-flow: column;    height: 100%;  }  #content {    display: flex;    height: 100%;    background: blue;  }  #content .test {    width: 100%;    background: yellow;    border: 2px solid red;  }  #footer {    flex: 0 1 10vh;    background: black;  }

<div id="snippet-container">    <div id="page">      <div id="content">        <div class="test"></div>      </div>      <div id="footer"></div>    </div>  </div>