Daniel Schmidt Daniel Schmidt -4 years ago 74
CSS Question

How can I have a position: fixed; behaviour for a flexbox sized element?

I have a div called .side-el which I would like to have in a position: fixed; behavior, but as soon as I apply position fixed the width alternates from the right one. The right width would be the one set by flexbox. How can I achieve this goal?

.container {
-webkit-align-content: flex-start;
align-content: flex-start;
-webkit-align-items: flex-start;
align-items: flex-start;
display: -webkit-flex;
display: flex;
-webkit-flex-direction: row;
flex-direction: row;
-webkit-flex-wrap: wrap;
flex-wrap: wrap;
-webkit-justify-content: flex-start;
justify-content: flex-start;

* {
box-sizing: border-box;
-webkit-flex-grow: 1;
flex-grow: 1;
-webkit-flex-shrink: 0;
flex-shrink: 0;

.main-el {
box-sizing: border-box;
padding:0 2em;
width: 70%;

.side-el {
box-sizing: border-box;
width: 30%;

<div class="container" style="background-color: blue; height: 100px;">
<div class="main-el">
<div style="background-color: red; height: 1000px;">content</div>
<div class="side-el" >
<div style="background-color: red; height: 100px;">content</div>

Answer Source

You can't.

As explained by the CSS2.1 spec:

Absolutely positioned boxes are taken out of the normal flow.

And the Flexible Box Layout spec confirms that:

An absolutely-positioned child of a flex container does not participate in flex layout. However, it does participate in the reordering step (see order), which has an effect in their painting order.

(Emphasis mine)

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