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/* This Source Code Form is subject to the terms of the Mozilla Public
* License, v. 2.0. If a copy of the MPL was not distributed with this
"use strict";
async function precacheAssets(tab, zoom) {
await SpecialPowers.spawn(tab.linkedBrowser, [zoom], async zoom => {
const { Layout } = ChromeUtils.importESModule(
);
Layout.zoomDocument(content.document, zoom);
const { promise, resolve } = Promise.withResolvers();
content.requestAnimationFrame(resolve);
await promise;
});
}
async function runForZoomLevel(tab, zoom) {
const [dpr, scale, cssScale] = await SpecialPowers.spawn(
tab.linkedBrowser,
[zoom],
async zoom => {
const img = content.document.getElementById("srcset");
const { Layout } = ChromeUtils.importESModule(
);
Layout.zoomDocument(content.document, zoom);
// The zoom change might trigger a new load. Be sure it is complete
// before checking the scale.
await new Promise(resolve => {
img.addEventListener("error", resolve, { once: true });
if (img.complete) {
resolve();
}
});
// Workaround: content.devicePixelRatio has the unspoofed value.
const dpr = content.wrappedJSObject.devicePixelRatio;
const current = img.currentSrc;
const scale = parseFloat(current.match(/.*\/([0-9\.]+)\.png$/)[1]);
const height = content.document
.getElementById("imgset")
.getBoundingClientRect().height;
// The images have been crafted so that it is possible to reverse their
// measured size (altered by the zoom) and find the scale.
const cssScale = Math.round((height * dpr - 50) / 10) / 10 + 0.3;
return [dpr, scale, cssScale];
}
);
is(
Math.abs(dpr - scale) < 0.1,
true,
`Image scale (${scale}) is within DPR (${dpr})`
);
is(
Math.abs(dpr - cssScale) < 0.1,
true,
`CSS scale (${cssScale}) is within DPR (${dpr})`
);
}
add_task(async () => {
await SpecialPowers.pushPrefEnv({
set: [["privacy.resistFingerprinting", true]],
});
const testPage =
getRootDirectory(gTestPath).replace(
) + "srcset.html";
const tab = await BrowserTestUtils.openNewForegroundTab(gBrowser, testPage);
for (let zoom = 0.3; zoom < 2.09; zoom += 0.1) {
await precacheAssets(tab, zoom);
}
for (let zoom = 0.3; zoom < 2.09; zoom += 0.1) {
await runForZoomLevel(tab, zoom);
}
BrowserTestUtils.removeTab(tab);
});