// Returns a Number for the font size in CSS pixels.
function elementFontSize(element) {
return parseFloat(getComputedStyle(element).getPropertyValue("font-size"));
}
// "look-and-feel-changed" may be dispatched twice: once for the pref
// change and once after receiving the new values from
// ContentChild::RecvThemeChanged().
// pushPrefEnv() resolves after the former. This resolves after the latter.
function promiseNewFontSizeOnThemeChange(element) {
return new Promise(resolve => {
const lastSize = elementFontSize(element);
function ThemeChanged() {
const size = elementFontSize(element);
if (size != lastSize) {
resolve(size);
}
}
// "look-and-feel-changed" is dispatched before the style system is flushed,
// https://searchfox.org/mozilla-central/rev/380fc5571b039fd453b45bbb64ed13146fe9b066/layout/base/nsPresContext.cpp#1684,1703-1705
// so use an async observer to get a notification after style changes.
SpecialPowers.addAsyncObserver(ThemeChanged, "look-and-feel-changed");
SimpleTest.registerCleanupFunction(function() {
SpecialPowers.removeAsyncObserver(ThemeChanged, "look-and-feel-changed");
});
});
}
add_task(async () => {
// MOZ_HEADLESS is set in content processes with GTK regardless of the
// headless state of the parent process. Check the parent state.
const headless = await SpecialPowers.spawnChrome([], function get_headless() {
return Services.env.get("MOZ_HEADLESS");
});
// LookAndFeel::TextScaleFactor::FloatID is implemented only for WINNT and
// GTK. ui.textScaleFactor happens to scale CSS pixels on other platforms
// but system font integration has not been implemented.
const expectSuccess = AppConstants.MOZ_WIDGET_TOOLKIT == "windows" ||
(AppConstants.MOZ_WIDGET_TOOLKIT == "gtk" &&
// Headless GTK doesn't get system font sizes from the system, but
// uses sizes fixed in CSS pixels.
!headless);
async function setScaleAndPromiseFontSize(scale, element) {
const prefPromise = SpecialPowers.pushPrefEnv({
set: [["ui.textScaleFactor", scale]],
});
if (!expectSuccess) {
// The size is not expected to change but get it afresh to check our
// assumption.
await prefPromise;
return elementFontSize(element);
}
const [size] = await Promise.all([
promiseNewFontSizeOnThemeChange(element),
prefPromise,
]);
return size;
}
const menu = document.getElementById("menu");
const def = document.getElementById("default");
// Choose a scaleFactor value different enough from possible default values
// that app unit rounding does not prevent a change in devicePixelRatio.
// A scaleFactor of 120 also has no rounding of app units per dev pixel.
const referenceScale = 120;
const menuSize1 = await setScaleAndPromiseFontSize(referenceScale, menu);
const menuRect1 = menu.getBoundingClientRect();
const defSize1 = elementFontSize(def);
const defRect1 = def.getBoundingClientRect();
const expectFn = expectSuccess ? ok : todo;
const menuSize2 = await setScaleAndPromiseFontSize(2*referenceScale, menu);
{
const singlePrecisionULP = Math.pow(2, -23);
// Precision seems to be lost in the conversion to decimal string for the
// property value.
const reltolerance = 30 * singlePrecisionULP;
fuzzyCompareLength(menuSize2, menuSize1/2, "size of menu font",
reltolerance*menuSize1/2, expectFn);
}
{
const menuRect2 = menu.getBoundingClientRect();
// The menufont text renders exactly the same and app-unit rects are
// equal, but the DOMRect conversion is rounded to 1/65536 CSS pixels.
// https://searchfox.org/mozilla-central/rev/380fc5571b039fd453b45bbb64ed13146fe9b066/dom/base/DOMRect.cpp#151-159
// See also https://bugzilla.mozilla.org/show_bug.cgi?id=1640441#c28
//
// Increased tolerance in https://bugzilla.mozilla.org/show_bug.cgi?id=1920733
// as the change to rendering mode seems to have perturbed results a bit, though
// it's still "basically the same".
const absTolerance = 0.05;
fuzzyCompareLength(menuRect2.width, menuRect1.width/2, "width of menu font
in px"
, absTolerance, expectFn);
fuzzyCompareLength(menuRect2.height, menuRect1.height/2, "height of menu font
in px"
, absTolerance, expectFn);
}
const defSize2 = elementFontSize(def);
is(defSize2, defSize1, "size of default font");
{
const defRect2 = def.getBoundingClientRect();
// Wider tolerance for hinting and snapping
const relTolerance = 1/12;
fuzzyCompareLength(defRect2.width, defRect1.width, "width of default font
in px"
,
relTolerance*defRect1.width, ok);
fuzzyCompareLength(defRect2.height, defRect1.height, "height of default font
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