zoom-iframe-os-zoom.html

Enable keyboard shortcuts

This WPT test may be referenced by the following Test IDs:
- /css/css-viewport/zoom/zoom-iframe-os-zoom.html - WPT Dashboard Interop Dashboard

<!doctype html>

<meta charset=utf-8>

<title>OS zoom doesn't stack on iframes</title>

<script src="/resources/testharness.js"></script>

<script src="/resources/testharnessreport.js"></script>

<iframe srcdoc="Child frame"></iframe>

<script>

async function setOSZoom(t, factor, expectResize = true) {

  let resize = expectResize && new Promise(r => addEventListener("resize", r, { once: true }));

  await SpecialPowers.pushPrefEnv({

    set: [

      ["ui.textScaleFactor", factor],

      ["browser.display.os-zoom-behavior", 1]

});

  await resize;

  t.add_cleanup(async () => {

    await SpecialPowers.popPrefEnv();

});

const iframe = document.querySelector("iframe");

promise_test(async function(t) {

  await setOSZoom(t, 100, /* expectResize = */ false);

  let originalDpi = window.devicePixelRatio;

  assert_equals(originalDpi, iframe.contentWindow.devicePixelRatio, "DPI should match between frame and parent");

  await setOSZoom(t, 200);

  let newDpi = window.devicePixelRatio;

  assert_equals(newDpi, originalDpi * 2, "OS zoom should've changed DPI");

  assert_equals(newDpi, iframe.contentWindow.devicePixelRatio, "DPI should match between frame and parent");

  let frameResized = new Promise(r => {

    iframe.contentWindow.addEventListener("resize", r, { once: true });

});

  iframe.style.zoom = 2;

  await frameResized;

  assert_equals(iframe.contentWindow.devicePixelRatio, 2 * newDpi, "DPI should have doubled on the frame");

  await setOSZoom(t, 100);

  assert_equals(window.devicePixelRatio, originalDpi, "DPI should have been restored");

  assert_equals(iframe.contentWindow.devicePixelRatio, 2 * originalDpi, "DPI should still be zoomed on the frame");

});

</script>