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HTML

            
              <h1>Flex line behaviour</h1>

<p>If you have tried to apply padding to a flex container with an horizontal overflow behaviour of scroll, you might notice that the padding is not applied to the flex end side of your container.</p>

<div class="flex problem">
  <div class="flex__item card">
    <img src="http://placekitten.com/150/150">
    <div class="card__txt">
      <h3>Cards are popular</h3>
    </div>
  </div>
  <div class="flex__item card">
    <img src="http://placekitten.com/150/150">
    <div class="card__txt">
      <h3>Cards are popular</h3>
    </div>
  </div>
  <div class="flex__item card">
    <img src="http://placekitten.com/150/150">
    <div class="card__txt">
      <h3>Cards are popular</h3>
    </div>
  </div>
  <div class="flex__item card">
    <img src="http://placekitten.com/150/150">
    <div class="card__txt">
      <h3>Cards are popular</h3>
    </div>
  </div>
  <div class="flex__item card">
    <img src="http://placekitten.com/150/150">
    <div class="card__txt">
      <h3>Cards are popular</h3>
    </div>
  </div>
  <div class="flex__item card">
    <img src="http://placekitten.com/150/150">
    <div class="card__txt">
      <h3>Cards are popular</h3>
    </div>
  </div>
  <div class="flex__item card">
    <img src="http://placekitten.com/150/150">
    <div class="card__txt">
      <h3>Cards are popular</h3>
    </div>
  </div>
  <div class="flex__item card">
    <img src="http://placekitten.com/150/150">
    <div class="card__txt">
      <h3>Cards are popular</h3>
    </div>
  </div>
  <div class="flex__item card">
    <img src="http://placekitten.com/150/150">
    <div class="card__txt">
      <h3>Cards are popular</h3>
    </div>
  </div>
  <div class="flex__item card">
    <img src="http://placekitten.com/150/150">
    <div class="card__txt">
      <h3>Cards are popular</h3>
    </div>
  </div>
  <div class="flex__item card">
    <img src="http://placekitten.com/150/150">
    <div class="card__txt">
      <h3>Cards are popular</h3>
    </div>
  </div>
  <div class="flex__item card">
    <img src="http://placekitten.com/150/150">
    <div class="card__txt">
      <h3>Cards are popular</h3>
    </div>
  </div>
</div>

<p>This is because the available space allocated to flex items by the browser under such circumstances is: the width of flex container's containing block minus its margin, border and padding in the horizontal direction.</p>

<p>Reference: <a href="https://www.w3.org/TR/css-flexbox-1/#line-sizing">CSS Flexible Box Layout Module Level 1: 9.2 Line Sizing</a></p>

<p>However, this is a relatively common use-case and there are a couple of workarounds to achieve the desired effect.</p>

<hr>

<h2>Using border</h2>
<div class="flex border">
  <div class="flex__item card">
    <img src="http://placekitten.com/150/150">
    <div class="card__txt">
      <h3>Cards are popular</h3>
    </div>
  </div>
  <div class="flex__item card">
    <img src="http://placekitten.com/150/150">
    <div class="card__txt">
      <h3>Cards are popular</h3>
    </div>
  </div>
  <div class="flex__item card">
    <img src="http://placekitten.com/150/150">
    <div class="card__txt">
      <h3>Cards are popular</h3>
    </div>
  </div>
  <div class="flex__item card">
    <img src="http://placekitten.com/150/150">
    <div class="card__txt">
      <h3>Cards are popular</h3>
    </div>
  </div>
  <div class="flex__item card">
    <img src="http://placekitten.com/150/150">
    <div class="card__txt">
      <h3>Cards are popular</h3>
    </div>
  </div>
  <div class="flex__item card">
    <img src="http://placekitten.com/150/150">
    <div class="card__txt">
      <h3>Cards are popular</h3>
    </div>
  </div>
  <div class="flex__item card">
    <img src="http://placekitten.com/150/150">
    <div class="card__txt">
      <h3>Cards are popular</h3>
    </div>
  </div>
  <div class="flex__item card">
    <img src="http://placekitten.com/150/150">
    <div class="card__txt">
      <h3>Cards are popular</h3>
    </div>
  </div>
  <div class="flex__item card">
    <img src="http://placekitten.com/150/150">
    <div class="card__txt">
      <h3>Cards are popular</h3>
    </div>
  </div>
  <div class="flex__item card">
    <img src="http://placekitten.com/150/150">
    <div class="card__txt">
      <h3>Cards are popular</h3>
    </div>
  </div>
  <div class="flex__item card">
    <img src="http://placekitten.com/150/150">
    <div class="card__txt">
      <h3>Cards are popular</h3>
    </div>
  </div>
  <div class="flex__item card">
    <img src="http://placekitten.com/150/150">
    <div class="card__txt">
      <h3>Cards are popular</h3>
    </div>
  </div>
</div>

<hr>

<h2>Using the <code>::after</code> pseudo-element</h2>
<div class="flex pseudo-elem">
  <div class="flex__item card">
    <img src="http://placekitten.com/150/150">
    <div class="card__txt">
      <h3>Cards are popular</h3>
    </div>
  </div>
  <div class="flex__item card">
    <img src="http://placekitten.com/150/150">
    <div class="card__txt">
      <h3>Cards are popular</h3>
    </div>
  </div>
  <div class="flex__item card">
    <img src="http://placekitten.com/150/150">
    <div class="card__txt">
      <h3>Cards are popular</h3>
    </div>
  </div>
  <div class="flex__item card">
    <img src="http://placekitten.com/150/150">
    <div class="card__txt">
      <h3>Cards are popular</h3>
    </div>
  </div>
  <div class="flex__item card">
    <img src="http://placekitten.com/150/150">
    <div class="card__txt">
      <h3>Cards are popular</h3>
    </div>
  </div>
  <div class="flex__item card">
    <img src="http://placekitten.com/150/150">
    <div class="card__txt">
      <h3>Cards are popular</h3>
    </div>
  </div>
  <div class="flex__item card">
    <img src="http://placekitten.com/150/150">
    <div class="card__txt">
      <h3>Cards are popular</h3>
    </div>
  </div>
  <div class="flex__item card">
    <img src="http://placekitten.com/150/150">
    <div class="card__txt">
      <h3>Cards are popular</h3>
    </div>
  </div>
  <div class="flex__item card">
    <img src="http://placekitten.com/150/150">
    <div class="card__txt">
      <h3>Cards are popular</h3>
    </div>
  </div>
  <div class="flex__item card">
    <img src="http://placekitten.com/150/150">
    <div class="card__txt">
      <h3>Cards are popular</h3>
    </div>
  </div>
  <div class="flex__item card">
    <img src="http://placekitten.com/150/150">
    <div class="card__txt">
      <h3>Cards are popular</h3>
    </div>
  </div>
  <div class="flex__item card">
    <img src="http://placekitten.com/150/150">
    <div class="card__txt">
      <h3>Cards are popular</h3>
    </div>
  </div>
</div>
!

CSS

            
              // Key styles
.problem {
  padding: 1em;  
}

.border {
  border: 1em indigo solid;
}

.pseudo-elem {
  padding: 1em;
  
  &::after {
    content: '';
    padding: 0.5em;
  }
}

// General styles
body {
  padding: 1em;
  background-color: gold;
}

img {
  max-width: 100%;
}

h1 {
  font-size: 199%;
  margin-bottom: 0.5rem;
}

h2 {
  font-size: 141.4%;
  margin-bottom: 0.5rem;
}

h3 {
  text-align: center;
}

hr {
  margin: 1.5em 0;
}

p {
  line-height: 1.3;
  margin-bottom: 0.5em;
}

.flex {
  box-sizing: border-box;
  width: 100%;
  height: 16em;
  display: flex;
  overflow-x: scroll;
  background-color: indigo;
  margin-bottom: 0.5em;
}

.flex__item {
  width: 9em;
  flex: none;
  margin-right: 1em;
  
  &:last-child {
    margin-right: 0;
  }
}

.card {
  background-color: white;
  
  img {
    object-fit: cover;
  }
}

.card__txt {
  padding: 0.5em;
}
!

JS
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