author James Teh <>
Wed, 01 Feb 2023 05:02:01 +0000
changeset 651150 dd0fdd1daa69783be36acd5c50544f3694eaa8f9
parent 596374 8945af7c5524dcc692e803f8c868c2bc527da7a0
permissions -rw-r--r--
Bug 1813980: Check IsDoc before Parent in RemoteAccessibleBase::ApplyCrossDocOffset. r=morgan We call this function on every ancestor when calculating bounds. RemoteParent() currently requires a hash lookup, so it's more efficient to early return for !IsDoc() first. This is a micro-optimisation, but it might have some impact given that we call this on every ancestor, especially when hit testing, where we call Bounds() a lot. As a bit of drive-by cleanup, use RemoteParent() rather than calling Parent() and IsRemote/AsRemote(). Differential Revision:

  <title>Scrolling over checkerboarded area respects overscroll-behavior</title>
  <script type="application/javascript" src="apz_test_utils.js"></script>
  <script type="application/javascript" src="apz_test_native_event_utils.js"></script>
  <script src="/tests/SimpleTest/paint_listener.js"></script>
  <meta name="viewport" content="width=device-width"/>
    #subframe {
      width: 100px;
      height: 100px;
      overflow: scroll;
      margin-top: 10px;
      margin-left: 10px;
      overscroll-behavior: contain;
    #contents {
      width: 100%;
      height: 1000px;
      background-image: linear-gradient(red, blue);
  <div id="subframe">
    <div id="contents"></div>
  <div id="make_root_scrollable" style="height: 5000px"></div>
<script type="application/javascript">

async function test() {
  var config = getHitTestConfig();
  var utils = config.utils;

  var subframe = document.getElementById("subframe");

  // Activate the scrollframe but keep the main-thread scroll position at 0.
  // Also apply an async scroll offset in the y-direction large enough
  // to make the scrollframe checkerboard.
  // Note: We have to be careful with the numbers here.
  //   promiseMoveMouseAndScrollWheelOver() relies on the main thread receiving
  //   the synthesized mouse-move and wheel events. However, the async
  //   transform created by setAsyncScrollOffset() will cause an untransform
  //   to be applied to the synthesized events' coordinates before they're
  //   passed to the main thread. We have to make sure the transform is
  //   large enough to cause the scroll frame to checkerboard, but not so
  //   large that the untransformed coordinates hit-test out of bounds for
  //   the browser's content area. This is why we make the scroll frame
  //   small (100x100), and give it a display port that's also just 100x100,
  //   so we can keep the async scroll offset small enough (300 in this case)
  //   that the untransformed coordinates are still in-bounds for the window.
  utils.setDisplayPortForElement(0, 0, 100, 100, subframe, 1);
  await promiseAllPaintsDone();
  var scrollY = 300;
  utils.setAsyncScrollOffset(subframe, 0, scrollY);
  // Tick the refresh driver once to make sure the compositor has applied the
  // async scroll offset (for WebRender hit-testing we need to make sure WR has
  // the latest info).

  // Scroll over the subframe, and make sure that the page does not scroll,
  // i.e. overscroll-behavior is respected.
  var waitForScroll = false; // don't wait for a scroll event, it will never come
  await promiseMoveMouseAndScrollWheelOver(subframe, 50, 50, waitForScroll);
  is(window.scrollY, 0, "overscroll-behavior was respected");

.then(subtestDone, subtestFailed);