browser_test_background_tab_scroll.js

Enable keyboard shortcuts

add_task(async function test_main() {

  // Load page in the background. This will cause the first-paint of the

  // tab (which has ScrollPositionUpdate instances) to get sent to the

  // compositor, but the parent process RefLayer won't be pointing to this

  // tab so APZ never sees the ScrollPositionUpdate instances.

  let url =

    "http://mochi.test:8888/browser/gfx/layers/apz/test/mochitest/helper_background_tab_scroll.html#scrolltarget";

  let backgroundTab = BrowserTestUtils.addTab(gBrowser, url);

  let browser = backgroundTab.linkedBrowser;

  await BrowserTestUtils.browserLoaded(browser, false, url);

  dump("Done loading background tab\n");

  // Switch to the foreground, to let the APZ tree get built.

  await BrowserTestUtils.switchTab(gBrowser, backgroundTab);

  dump("Switched background tab to foreground\n");

  // Verify main-thread scroll position is where we expect

  let scrollPos = await ContentTask.spawn(browser, null, function () {

    return content.window.scrollY;

});

  is(scrollPos, 5000, "Expected background tab to be at scroll pos 5000");

  // Trigger an APZ-side scroll via native wheel event, followed by some code

  // to ensure APZ's repaint requests to arrive at the main-thread. If

  // things are working properly, the main thread will accept the repaint

  // requests and update the main-thread scroll position. If the APZ side

  // is sending incorrect scroll generations in the repaint request, then

  // the main thread will fail to clear the main-thread scroll origin (which

  // was set by the scroll to the #scrolltarget anchor), and so will not

  // accept APZ's scroll position updates.

  let contentScrollFunction = async function () {

    await content.window.wrappedJSObject.promiseNativeWheelAndWaitForWheelEvent(

      content.window,

      100,

      100,

0,

);

    // Advance some/all frames of the APZ wheel animation

    let utils = content.window.SpecialPowers.getDOMWindowUtils(content.window);

    for (var i = 0; i < 10; i++) {

      utils.advanceTimeAndRefresh(16);

    utils.restoreNormalRefresh();

    // Flush pending APZ repaints, then read the main-thread scroll

    // position

    await content.window.wrappedJSObject.promiseOnlyApzControllerFlushed(

      content.window

);

    return content.window.scrollY;

};

  scrollPos = await ContentTask.spawn(browser, null, contentScrollFunction);

  // Verify main-thread scroll position has changed

ok(

    scrollPos < 5000,

    `Expected background tab to have scrolled up, is at ${scrollPos}`

);

  // Cleanup

  let tabClosed = BrowserTestUtils.waitForTabClosing(backgroundTab);

  BrowserTestUtils.removeTab(backgroundTab);

  await tabClosed;

});