fune/browser/base/content/test/performance/browser_tabclose_reflows.js

37 lines
1.3 KiB
JavaScript

"use strict";
/**
* WHOA THERE: We should never be adding new things to EXPECTED_REFLOWS. This
* is a whitelist that should slowly go away as we improve the performance of
* the front-end. Instead of adding more reflows to the whitelist, you should
* be modifying your code to avoid the reflow.
*
* See https://developer.mozilla.org/en-US/Firefox/Performance_best_practices_for_Firefox_fe_engineers
* for tips on how to do that.
*/
const EXPECTED_REFLOWS = [
/**
* Nothing here! Please don't add anything new!
*/
];
/*
* This test ensures that there are no unexpected
* uninterruptible reflows when closing new tabs.
*/
add_task(async function() {
await ensureNoPreloadedBrowser();
let tab = await BrowserTestUtils.openNewForegroundTab(gBrowser);
await BrowserTestUtils.waitForCondition(() => tab._fullyOpen);
// Add a reflow observer and open a new tab.
await withReflowObserver(async function() {
let switchDone = BrowserTestUtils.waitForEvent(window, "TabSwitchDone");
gBrowser.removeTab(tab, { animate: true });
await BrowserTestUtils.waitForEvent(tab, "transitionend",
false, e => e.propertyName === "max-width");
await switchDone;
}, EXPECTED_REFLOWS);
is(EXPECTED_REFLOWS.length, 0, "No reflows are expected when closing a tab");
});