After pseudo element hidden when using Flexbox

Question

I need two divs taking up 100% width, ideally 50% each (but I am flexible). With an arrow displaying below on the active tab.

The flex-grow feature of flexbox doesn't seem to be affecting the placement of the after pseudo-element arrow. In full screen, you can see the arrow, but when flex-grow kicks in the arrow stays put and is hidden by the background color.

https://codepen.io/sherrylking/pen/MWWXEBv

.qo-tab-section {
    display: flex;
}

.qo-tab-section div {
    padding: 20px 20px 20px 20px;
    flex-basis: 50%;
}

.qo-active-tab:after {
    content:'';
    position: relative;
    border-style: solid;
    border-width: 20px 20px 0;
    border-color: #027777 transparent;
    display: block;
    width: 0;
    z-index: 1;
    top: 43px;
}

Answer 1

The problem is your use of top: 43px which, as a fixed position, prevents the arrow from adjusting its location relative to the flex item when it re-sizes.

Instead, use absolute positioning on the arrow and relative positioning to set the containing block.

Add this to your code:

.qo-tab-section div {
    padding: 20px 20px 20px 20px;
    flex-basis: 50%;

    /*new */
    position: relative;
}

.qo-active-tab:after {
    content:'';
    /* position: relative; */
    border-style: solid;
    border-width: 20px 20px 0;
    border-color: #027777 transparent;
    /* display: block; */ /* not necessary */
    width: 0;
    z-index: 1;
    /* top: 43px; */

    /* new */
    position: absolute;
    top: 100%;
    left: 0;
}

.qo-tab-section {
  display: flex;
}

.qo-tab-section div {
  padding: 20px 20px 20px 20px;
  flex-basis: 50%;
  /*new */
  position: relative;
}

.qo-active-tab {
  color: white;
  background-color: #027777;
}

.qo-active-tab:after {
  content: '';
  /* position: relative; */
  border-style: solid;
  border-width: 20px 20px 0;
  border-color: #027777 transparent;
  /* display: block; */ /* not necessary */
  width: 0;
  z-index: 1;
  /* top: 43px; */
  /* new */
  position: absolute;
  top: 100%;
  left: 0;
}

.qo-purchase-area {
  background-color: #E4F6F9;
  overflow: auto;
  padding: 25px 15px 15px 15px;
  margin-top: -15px;
}

.qo-purchase-amount {
  font-weight: bold;
  font-size: 2em;
}

.float-l {
  float: left;
}

.float-r {
  float: right;
}

.qo-container {
  border: solid 3px #027777;
  padding: 15px;
}

.h1-small {
  font-size: .6em;
}

.main-button-not-selected {
  background-color: #EDEDED;
  color: #999999;
  border: solid 1px #999999;
}

.margin-r-15 {
  margin-right: 15px;
}

.qo-helptip {
  width: 20px;
  margin-bottom: 5px;
}

.qo-coverage-amount {
  background-color: #F7F6F6;
  padding-top: 15px;
  padding-bottom: 15px;
}

.qo-coverage-amount input {
  font-size: 2.35em;
  width: 6em;
  text-align: center;
}

.qo-coverage-alignment {
  float: left;
}

.qo-coverage-clear {
  padding: 5px;
  line-height: 45px;
}

.cov-a-warning:before {
  content: url("exclamation-triangle.svg");
  width: 20px;
  position: absolute;
  left: 13px;
}

.cov-a-warning {
  margin-left: 26px;
}

.qo-coverage-title {
  font-size: 1.4em;
  font-weight: bold;
}

.qo-section-body {
  font-size: 1.7em;
  padding-bottom: 120px;
  text-align: center;
}

<div class="qo-tab-section">


  <div><span class="qo-coverage-title">Title Here</span>
    <br> This content is longer than the other box. This content is longer than the other box. This content is longer than the other box. This content is longer than the other box. This content is longer than the other box. </div>


  <div class="qo-active-tab"><span class="qo-coverage-title">Title Here </span><br> small discription goes here.</div>

</div>

<div class="qo-container">

  <div class="row form-group qo-purchase-area">
    <div class="float-l qo-purchase-amount margin-r-15">$134.67 / month
    </div>

    <div class="float-l margin-r-15">please note that the arrows shows under the active tab in full screen but when the flexgrow kicks into effect the possitioning of the after not longer works well. The extra growth is not considered.
    </div>

    <div class="float-r">
      <button class="main-button" type="button">Purchase</button>
    </div>


  </div>
</div>

jsFiddle demo