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<!DOCTYPE HTML>
<html>
<head>
  <meta charset="utf-8">
  <meta name="viewport" content="width=device-width; initial-scale=1.0">
  <title>Test that repeated scrollbar button clicks do not cause checkerboarding</title>
  <script type="application/javascript" src="apz_test_native_event_utils.js"></script>
  <script type="application/javascript" src="apz_test_utils.js"></script>
  <script src="/tests/SimpleTest/paint_listener.js"></script>
  <script type="text/javascript">
async function test() {
  let utils = SpecialPowers.getDOMWindowUtils(window);
  let scrollId = utils.getViewId(document.documentElement);
  let w = {}, h = {};
  utils.getScrollbarSizes(document.documentElement, w, h);
  let verticalScrollbarWidth = w.value;
  if (verticalScrollbarWidth == 0) {
    ok(true, "No scrollbar, can't do this test");
  }
  let downArrowHeight = verticalScrollbarWidth; // assume square scrollbar buttons
  var mouseX = document.documentElement.clientWidth + verticalScrollbarWidth / 2;
  let mouseY = document.documentElement.clientHeight - (downArrowHeight / 2);
  // Hold the mouse down on the scrollbar button and
  // keep it down to trigger the "button repeat" codepath.
  await promiseNativeMouseEventWithAPZ({
    type: "mousedown",
    target: window,
    offsetX: mouseX,
    offsetY: mouseY,
  });
  const repetitions = 20;
  const repeat_delay = 50;  // milliseconds
  for (i = 0; i < repetitions; i++) {
    // Wait for the results of the click (or, on subsequent iterations
    // the repeat) to be painted.
    await promiseFrame();
    assertNotCheckerboarded(utils, scrollId, "after scrollbar button click-hold", true);
    // Wait enough time to trigger the repeat timer.
    await SpecialPowers.promiseTimeout(repeat_delay);
  }
  // Release mouse button to clean up.
  await promiseNativeMouseEventWithAPZ({
    type: "mouseup",
    target: window,
    offsetX: mouseX,
    offsetY: mouseY,
  });
  // Sanity-check: we should have scrolled.
  ok(window.scrollY > 0, "Should have scrolled by clicking the scrollbar button");
}
waitUntilApzStable()
.then(test)
.then(subtestDone, subtestFailed);
  </script>
  <style>
    .page-footer {
      background-color: #212121;
      color: #fff;
      height: 3000px;
    }
  </style>
</head>
<body>
  <footer class="page-footer"></footer>
</body>
</html>