html - Why is 'position: sticky' not working with Core UI's Bootstrap CSS

Question

I am trying to build a react dashboard using Core UI's react template found here.

CSS

.top-stick {
    position: sticky !important;
    position: -webkit-sticky;
    top: 5rem;
    overflow-y: auto;
    height: calc(100vh - 5rem);
}

JSX

<div className="animated fadeIn">
  <Row className="app-scrollable-body">
    <Col xs="12" sm="4" md="3" className="top-stick">
      <Card className="toic">
        <CardBody>
          Lorem ipsum dolor sit amet
        </CardBody>
      </Card>
    </Col>
    <Col xs="12" sm="8" md="9">
      <Card>
        <CardHeader>Card title</CardHeader>
        <CardBody>
        Lorem ipsum dolor sit amet
        </CardBody>
      </Card>
    </Col>
  </Row>
  <div className="app-fixed-footer">
    <span>
      <a href="https://coreui.io">CoreUI</a> &copy; 2018
      creativeLabs.
    </span>
    <span className="ml-auto">
      Powered by{" "}
      <a href="https://coreui.io/react">CoreUI for React</a>
    </span>
  </div>
</div>

But on scroll the card does not seem to stick.

On inspecting the CSS is present. Also no overflow: hidden is there in the CSS Tree.

Answer 1

The issue is the use of overflow inside .app-body. It's a bit tricky but there should be no overflow property set to any element between the element that has the scroll and the sticky element.

Here is a basic example to illustrate. The scroll is on the viewport and we have a wrapper with overflow:hidden (or even auto) thus the sticky behavior won't work.

.container {
  display:flex;
  align-items:flex-start;
  border:2px solid green;
}
.content {
  flex:1;
  height:200vh;
  background:red;
  margin:10px;
}
.sticky {
  flex:1;
  height:100px;
  background:blue;
  margin:10px;
  position:sticky;
  top:0;
}

.wrapper {
  overflow:hidden;
  border:2px solid red;
}

<div class="wrapper">
  <div class="container">
    <div class="sticky"></div>
    <div class="content"></div>
  </div>
</div>