forked from mirrors/gecko-dev
809beee368
*** Bug 1682898 Migrate Performance Best Practices for Front-end Engineers MDN page to in-tree docs *** Bug 1682898 Migrate Performance Best Practices for Front-end Engineers MDN page to in-tree docs Differential Revision: https://phabricator.services.mozilla.com/D109970
93 lines
3.1 KiB
JavaScript
93 lines
3.1 KiB
JavaScript
"use strict";
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/**
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* WHOA THERE: We should never be adding new things to EXPECTED_REFLOWS.
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* Instead of adding reflows to the list, you should be modifying your code to
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* avoid the reflow.
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*
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* See https://firefox-source-docs.mozilla.org/performance/bestpractices.html
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* for tips on how to do that.
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*/
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const EXPECTED_REFLOWS = [
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/**
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* Nothing here! Please don't add anything new!
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*/
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];
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/*
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* This test ensures that there are no unexpected
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* uninterruptible reflows when closing a tab that will
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* cause the existing tabs to grow bigger.
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*/
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add_task(async function() {
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// Force-enable tab animations
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gReduceMotionOverride = false;
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await ensureNoPreloadedBrowser();
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await disableFxaBadge();
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// The test starts on about:blank and opens an about:blank
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// tab which triggers opening the toolbar since
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// ensureNoPreloadedBrowser sets AboutNewTab.newTabURL to about:blank.
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await SpecialPowers.pushPrefEnv({
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set: [["browser.toolbars.bookmarks.visibility", "never"]],
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});
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// At the time of writing, there are no reflows on tab closing with
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// tab growth. Mochitest will fail if we have no assertions, so we
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// add one here to make sure nobody adds any new ones.
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Assert.equal(
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EXPECTED_REFLOWS.length,
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0,
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"We shouldn't have added any new expected reflows."
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);
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// Compute the number of tabs we can put into the strip without
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// overflowing. If we remove one of the tabs, we know that the
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// remaining tabs will grow to fill the remaining space in the
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// tabstrip.
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const TAB_COUNT_FOR_GROWTH = computeMaxTabCount();
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await createTabs(TAB_COUNT_FOR_GROWTH);
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let lastTab = gBrowser.tabs[gBrowser.tabs.length - 1];
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await BrowserTestUtils.switchTab(gBrowser, lastTab);
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let tabStripRect = gBrowser.tabContainer.arrowScrollbox.getBoundingClientRect();
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await withPerfObserver(
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async function() {
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let switchDone = BrowserTestUtils.waitForEvent(window, "TabSwitchDone");
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let tab = gBrowser.tabs[gBrowser.tabs.length - 1];
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gBrowser.removeTab(tab, { animate: true, byMouse: true });
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await BrowserTestUtils.waitForEvent(tab, "TabAnimationEnd");
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await switchDone;
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},
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{
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expectedReflows: EXPECTED_REFLOWS,
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frames: {
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filter: rects =>
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rects.filter(
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r =>
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!(
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// We expect plenty of changed rects within the tab strip.
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(
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r.y1 >= tabStripRect.top &&
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r.y2 <= tabStripRect.bottom &&
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r.x1 >= tabStripRect.left &&
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r.x2 <= tabStripRect.right &&
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// It would make sense for each rect to have a width smaller than
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// a tab (ie. tabstrip.width / tabcount), but tabs are small enough
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// that they sometimes get reported in the same rect.
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// So we accept up to the width of n-1 tabs.
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r.w <=
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(gBrowser.tabs.length - 1) *
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Math.ceil(tabStripRect.width / gBrowser.tabs.length)
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)
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)
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),
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},
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}
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);
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await removeAllButFirstTab();
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});
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