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let counter = 0;
const loadImage = size => {
return event => {
let zoom;
if (location.search.includes("replace")) {
zoom = document.getElementById("image");
} else {
zoom = new Image();
}
zoom.src=`/images/lcp-${size}.png`;
++counter;
zoom.elementTiming = "zoom" + counter;
document.body.appendChild(zoom);
}
};
const loadBackgroundImage = size => {
return event => {
const div = document.createElement("div");
const [width, height] = size.split("x");
++counter;
div.style = `background-image:
url(/images/lcp-${size}.png?${counter}); width: ${width}px; height: ${height}px`;
div.elementTiming = "zoom" + counter;
document.body.appendChild(div);
}
};
const registerMouseover = background => {
const image = document.getElementById("image");
const span = document.getElementById("span");
const func = background ? loadBackgroundImage : loadImage;
image.addEventListener("mouseover", func("100x50"));
span.addEventListener("mouseover", func("256x256"));
}
const dispatch_mouseover = () => {
span.dispatchEvent(new Event("mouseover"))
};
const wait_for_lcp_entries = async entries_expected => {
await new Promise(resolve => {
let entries_seen = 0;
const PO = new PerformanceObserver(list => {
const entries = list.getEntries();
for (let entry of entries) {
if (entry.url) {
entries_seen++;
}
}
if (entries_seen == entries_expected) {
PO.disconnect();
resolve()
} else if (entries_seen > entries_expected) {
PO.disconnect();
reject();
}
});
PO.observe({type: "largest-contentful-paint", buffered: true});
});
};
const wait_for_element_timing_entry = async identifier => {
await new Promise(resolve => {
const PO = new PerformanceObserver(list => {
const entries = list.getEntries();
for (let entry of entries) {
if (entry.identifier == identifier) {
PO.disconnect();
resolve()
}
}
});
PO.observe({type: "element", buffered: true});
});
};
const wait_for_resource_timing_entry = async name => {
await new Promise(resolve => {
const PO = new PerformanceObserver(list => {
const entries = list.getEntries();
for (let entry of entries) {
if (entry.name.includes(name)) {
PO.disconnect();
resolve()
}
}
});
PO.observe({type: "resource", buffered: true});
});
};
const run_mouseover_test = background => {
promise_test(async t => {
// await the first LCP entry
await wait_for_lcp_entries(1);
// Hover over the image
registerMouseover(background);
if (test_driver) {
await new test_driver.Actions().pointerMove(0, 0, {origin: image}).send();
}
if (!background) {
await wait_for_element_timing_entry("zoom1");
} else {
await wait_for_resource_timing_entry("png?1");
await new Promise(r => requestAnimationFrame(r));
}
// There's only a single LCP entry, because the zoom was skipped.
await wait_for_lcp_entries(1);
// Wait 600 ms as the heuristic is 500 ms.
// This will no longer be necessary once the heuristic relies on Task
// Attribution.
await new Promise(r => step_timeout(r, 600));
// Hover over the span.
if (test_driver) {
await new test_driver.Actions().pointerMove(0, 0, {origin: span}).send();
}
if (!background) {
await wait_for_element_timing_entry("zoom2");
} else {
await wait_for_resource_timing_entry("png?2");
await new Promise(r => requestAnimationFrame(r));
}
// There are 2 LCP entries, as the image loaded due to span hover is a
// valid LCP candidate.
await wait_for_lcp_entries(2);
}, `LCP mouseover heuristics ignore ${background ?
"background" : "element"}-based zoom widgets`);
}