css/css-flexbox/gap-collapse.html

<!DOCTYPE html>
<meta charset="utf-8">
<title>CSS Flexbox: gaps adjacent to a collapsed (visibility:collapse) flex item are not counted</title>
<link rel="author" title="Emilio Cobos Álvarez" href="mailto:emilio@crisal.io">
<link rel="author" title="Mozilla" href="https://mozilla.com">
<link rel="help" href="https://drafts.csswg.org/css-flexbox-1/#algo-visibility">
<link rel="help" href="https://drafts.csswg.org/css-align-3/#gaps">
<link rel="match" href="gap-collapse-ref.html">
<style>
  .flex {
    display: flex;
    gap: 50px;
    outline: 1px solid purple;
  }
  .intrinsic {
    width: max-content;
  }
  .flex > div {
    width: 50px;
    height: 50px;
    background: blue;
  }
  .collapse {
    visibility: collapse;
  }
</style>

<!-- Collapsed item in the middle. -->
<div class="flex">
  <div></div>
  <div class="collapse"></div>
  <div></div>
  <div></div>
</div>

<!-- Collapsed item at the beginning. -->
<div class="flex">
  <div class="collapse"></div>
  <div></div>
  <div></div>
  <div></div>
</div>

<!-- Collapsed item at the end. -->
<div class="flex">
  <div></div>
  <div></div>
  <div></div>
  <div class="collapse"></div>
</div>

<!-- Collapsed item in the middle. -->
<div class="flex intrinsic">
  <div></div>
  <div class="collapse"></div>
  <div></div>
  <div></div>
</div>

<!-- Collapsed item at the beginning. -->
<div class="flex intrinsic">
  <div class="collapse"></div>
  <div></div>
  <div></div>
  <div></div>
</div>

<!-- Collapsed item at the end. -->
<div class="flex intrinsic">
  <div></div>
  <div></div>
  <div></div>
  <div class="collapse"></div>
</div>