<!DOCTYPE html>

  <meta charset="UTF-8">

  <title>CSS Values and Units Test: computed value of 'background-position' when specified with calc() function</title>

  <link rel="author" title="Gérard Talbot" href="http://www.gtalbot.org/BrowserBugsSection/css21testsuite/">
  <link rel="help" href="https://www.w3.org/TR/css-values-3/#calc-computed-value">

  <meta content="This test verifies how 6 calc() functions are computed for 'background-position'." name="assert">

  <script src="/resources/testharness.js"></script>

  <script src="/resources/testharnessreport.js"></script>

  <div id="target"></div>

  <script>
  function startTesting()
  {

  var targetElement = document.getElementById("target");

    function verifyComputedStyle(property_name, initial_value, specified_value, expected_value, description)
    {

    test(function()
      {

      targetElement.style.setProperty(property_name, initial_value);

      /*
      The purpose of the initial_value is to act as a fallback
      value in case the calc() function in the specified value
      fails or in case it generates an invalid value. Since we
      are running 6 consecutive tests on the same element,
      then it is necessary to 'reset' its property to an
      initial value.
      */

      targetElement.style.setProperty(property_name, specified_value);

      assert_equals(getComputedStyle(targetElement)[property_name], expected_value);

      }, description);
    }

 /* verifyComputedStyle(property_name, initial_value, specified_value, expected_value, description) */

    verifyComputedStyle("background-position", "initial", "calc(2px + 3px) calc(4px + 5px)", "5px 9px", "testing background-position: calc(2px + 3px) calc(4px + 5px)");

    verifyComputedStyle("background-position", "initial", "calc(18px - 7px) calc(19px - 7px)", "11px 12px", "testing background-position: calc(18px - 7px) calc(19px - 7px)");

    verifyComputedStyle("background-position", "initial", "calc(4 * 5px) calc(6px * 4)", "20px 24px", "testing background-position: calc(4 * 5px) calc(6px * 4)");

    verifyComputedStyle("background-position", "initial", "calc(100px / 4) calc(119px / 7)", "25px 17px", "testing background-position: calc(100px / 4) calc(119px / 7)");

    verifyComputedStyle("background-position", "initial", "calc(6px + 21%) calc(7em + 22%)", "calc(21% + 6px) calc(22% + 112px)", "testing background-position: calc(6px + 21%) calc(7em + 22%)");

  /*
    "
    (...) background-position has layout-dependent behavior for
    percentage values, and thus does not resolve percentages
    until used-value time. Due to this, background-position
    computation preserves the percentage in a calc(). (...)
    "
    https://www.w3.org/TR/css-values-3/#calc-computed-value
  */

    verifyComputedStyle("background-position", "initial", "calc(-8px + 23%) calc(-9em + 24%)", "calc(23% - 8px) calc(24% - 144px)", "testing background-position: calc(-8px + 23%) calc(-9em + 24%)");

 /* verifyComputedStyle(property_name, initial_value, specified_value, expected_value, description) */
  }

  startTesting();

  </script>
