css/css-contain/contain-paint-ifc-011.html

<!DOCTYPE html>

  <meta charset="UTF-8">

  <title>CSS Containment Test: 'contain: paint' and margin collapsing</title>

  <link rel="author" title="Gérard Talbot" href="http://www.gtalbot.org/BrowserBugsSection/css21testsuite/">
  <link rel="help" href="https://www.w3.org/TR/css-contain-1/#containment-paint">
  <link rel="match" href="reference/contain-paint-ifc-011-ref.html">

  <meta content="This test checks that a block element with 'contain: paint' establishes a new block formatting context which is independent and separate from others. This causes margin collapsing to be ineffective among vertically-adjacent boxes. In this test, the top margin of parent boxes and top margin of their respective first in-flow child do not collapse. Also, in this test, the bottom margin of the last in-flow child of boxes and bottom margin of their respective parent boxes do not collapse." name="assert">

  <style>
  div
    {
      contain: paint;
      margin: 30px 0px;
    }

  div#grand-grand-parent-orange
    {
      background-color: orange;
    }

  div#grand-parent-blue
    {
      background-color: blue;
    }

  div#parent-lime
    {
      background-color: lime;
    }

  div#collapse-through-child  /* margin collapsing through element */
    {
      contain: none;
    }
  </style>

  <p>Test passes if there are 5 horizontal stripes across the page in this order (from top to bottom): an orange stripe, a blue stripe, a bright green stripe, a blue stripe and then an orange stripe.

  <div id="grand-grand-parent-orange">

    <div id="grand-parent-blue">

      <div id="parent-lime">

        <div id="collapse-through-child"></div>

      </div>

    </div>

  </div>