blob: 1c35fe2aa234c96fce8798e6a1c35362f418e6f1 [file] [log] [blame]
<!DOCTYPE HTML>
<meta charset=utf-8>
<title>Layout Instability: observe layout shift value via PerformanceObserver</title>
<body>
<style>
#myDiv { position: relative; width: 300px; height: 100px; }
/* Disable the button's focus ring, which otherwise expands its visual rect by
* 1px on all sides, triggering a layout shift event.
*/
#button { outline: none; }
</style>
<div id='myDiv'></div>
<button id='button'>Generate a 'click' event</button>
<script src="/resources/testharness.js"></script>
<script src="/resources/testharnessreport.js"></script>
<script src=/resources/testdriver.js></script>
<script src=/resources/testdriver-vendor.js></script><script>
let timeAfterClick;
function mainThreadBusy(duration) {
const now = performance.now();
while (performance.now() < now + duration);
}
function clickOnElement(id, callback) {
const element = document.getElementById(id);
const rect = element.getBoundingClientRect();
const xCenter = rect.x + rect.width / 2;
const yCenter = rect.y + rect.height / 2;
const leftButton = 0;
const clickHandler = () => {
mainThreadBusy(120);
if (callback)
callback();
element.removeEventListener("mousedown", clickHandler);
};
element.addEventListener("mousedown", clickHandler);
test_driver.click(element);
}
function clickAndBlockMain(id) {
return new Promise((resolve, reject) => {
clickOnElement(id, resolve);
});
}
async_test(function (t) {
if (!window.LayoutShift)
assert_unreached('LayoutShift entries are not supported');
const startTime = performance.now();
const observer = new PerformanceObserver(
t.step_func_done(function(entryList) {
const endTime = performance.now();
assert_equals(entryList.getEntries().length, 1);
const entry = entryList.getEntries()[0];
assert_equals(entry.entryType, "layout-shift");
assert_equals(entry.name, "");
assert_greater_than_equal(entry.startTime, startTime)
assert_less_than_equal(entry.startTime, endTime)
assert_equals(entry.duration, 0.0);
const maxDimension = Math.max(document.documentElement.clientWidth,
document.documentElement.clientHeight);
// The layout shift value should be:
// 300 * (100 + 60) * (60 / maxDimension) / viewport size.
assert_equals(entry.value, 300 * (100 + 60) * (60 / maxDimension) /
(document.documentElement.clientWidth * document.documentElement.clientHeight));
})
);
observer.observe({entryTypes: ['layout-shift']});
window.onload = () => {
// Modify the position of the div.
document.getElementById('myDiv').style = "top: 60px";
};
}, 'Layout shift is observable via PerformanceObserver.');
async_test(function (t) {
const startTime = performance.now();
const observer = new PerformanceObserver(
t.step_func_done(function(entryList) {
const endTime = performance.now();
assert_equals(entryList.getEntries().length, 1);
const entry = entryList.getEntries()[0];
assert_equals(entry.entryType, "layout-shift");
assert_equals(entry.name, "");
assert_greater_than_equal(entry.startTime, startTime)
assert_less_than_equal(entry.startTime, endTime)
assert_equals(entry.duration, 0.0);
const maxDimension = Math.max(document.documentElement.clientWidth,
document.documentElement.clientHeight);
// The layout shift value should be:
// 300 * (100 + 60) * (60 / maxDimension) / viewport size.
assert_equals(entry.value, 300 * (100 + 60) * (60 / maxDimension) /
(document.documentElement.clientWidth * document.documentElement.clientHeight));
// We should see that there was a click input entry
assert_equals(entry.hadRecentInput, true);
assert_greater_than_equal(timeAfterClick, entry.lastInputTime);
})
);
observer.observe({entryTypes: ['layout-shift']});
window.onload = () => {
// User input event
clickAndBlockMain('button').then( () => {
timeAfterClick = performance.now();
// Modify the position of the div.
document.getElementById('myDiv').style = "top: 60px";
});
};
}, 'Layout shift within user input is observable via PerformanceObserver.');
</script>
</body>