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Fix: Light Styles Flash in Dark Mode #1063

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Jun 5, 2025
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4 changes: 4 additions & 0 deletions _layouts/new-layouts/base.html
Original file line number Diff line number Diff line change
Expand Up @@ -169,6 +169,10 @@
</head>

<body>
<script>
// Set theme before body content to avoid flash of light styles in dark mode
setColorScheme(getStoredScheme())
</script>
<main>
{% include new-includes/header/header.html %} {{content}} {% include
new-includes/footer/footer.html %}
Expand Down
84 changes: 42 additions & 42 deletions assets/javascripts/new-javascripts/color-scheme-toggle.js
Original file line number Diff line number Diff line change
@@ -1,125 +1,125 @@
document.addEventListener('DOMContentLoaded', initColorScheme);
document.addEventListener('DOMContentLoaded', initColorScheme)

const ColorScheme = {
auto: 'auto',
light: 'light',
dark: 'dark',
};
}

const localStorageKey = 'developer.setting.preferredColorScheme';
const localStorageKey = 'developer.setting.preferredColorScheme'

const supportsAutoColorScheme = (() => {
return typeof window.matchMedia !== 'undefined' &&
return (
typeof window.matchMedia !== 'undefined' &&
['light', 'dark', 'no-preference'].some(
(scheme) => window.matchMedia(`(prefers-color-scheme: ${scheme})`).matches
);
})();
(scheme) =>
window.matchMedia(`(prefers-color-scheme: ${scheme})`).matches,
)
)
})()

if (!supportsAutoColorScheme) {
document.getElementById('scheme-auto-wrapper')?.remove();
document.getElementById('scheme-auto-wrapper')?.remove()
}

function initColorScheme() {
setColorScheme(getStoredScheme());

const toggle = getToggle();
const toggle = getToggle()
if (toggle && toggle.value !== getStoredScheme()) {
toggle.value = getStoredScheme();
toggle.value = getStoredScheme()
}

getToggleForm()?.addEventListener('change', (e) => {
setColorScheme(e.target.value);
});
setColorScheme(e.target.value)
})
}

function systemPrefersLight() {
return window.matchMedia('(prefers-color-scheme: light)');
return window.matchMedia('(prefers-color-scheme: light)')
}

function systemPrefersDark() {
return window.matchMedia('(prefers-color-scheme: dark)');
return window.matchMedia('(prefers-color-scheme: dark)')
}

function isSystemDark() {
return systemPrefersDark().matches;
return systemPrefersDark().matches
}

function setColorScheme(value) {
if (!Object.values(ColorScheme).includes(value)) {
value = supportsAutoColorScheme ? ColorScheme.auto : ColorScheme.light;
value = supportsAutoColorScheme ? ColorScheme.auto : ColorScheme.light
}

if (value === ColorScheme.auto) {
updateScheme(isSystemDark() ? ColorScheme.dark : ColorScheme.light, value);
updateScheme(isSystemDark() ? ColorScheme.dark : ColorScheme.light, value)
} else {
updateScheme(value);
updateScheme(value)
}
}

function updateScheme(scheme, storedValue = scheme) {
if (getStoredScheme() !== storedValue) {
saveScheme(storedValue);
saveScheme(storedValue)
}

if (getCurrentScheme() !== scheme) {
document.body.setAttribute('data-color-scheme', scheme);
document.body.setAttribute('data-color-scheme', scheme)
}

const toggle = getToggle();
const toggle = getToggle()
if (toggle && toggle.value !== storedValue) {
toggle.value = storedValue;
toggle.value = storedValue
}
}

systemPrefersLight().addEventListener('change', (e) => {
if (e.matches && getStoredScheme() === ColorScheme.auto) {
const current = getCurrentScheme();
const current = getCurrentScheme()
if (current !== ColorScheme.light) {
document.body.setAttribute('data-color-scheme', ColorScheme.light);
document.body.setAttribute('data-color-scheme', ColorScheme.light)
}
}
});
})

systemPrefersDark().addEventListener('change', (e) => {
if (e.matches && getStoredScheme() === ColorScheme.auto) {
const current = getCurrentScheme();
const current = getCurrentScheme()
if (current !== ColorScheme.dark) {
document.body.setAttribute('data-color-scheme', ColorScheme.dark);
document.body.setAttribute('data-color-scheme', ColorScheme.dark)
}
}
});
})

window.addEventListener('storage', () => {
setColorScheme(getStoredScheme());
});
setColorScheme(getStoredScheme())
})

window.addEventListener('pageshow', () => {
setColorScheme(getStoredScheme());
});
setColorScheme(getStoredScheme())
})

function getToggleForm() {
return document.getElementById('color-scheme-toggle');
return document.getElementById('color-scheme-toggle')
}

function getToggle() {
return getToggleForm()?.elements['color-scheme-preference'];
return getToggleForm()?.elements['color-scheme-preference']
}

function getCurrentScheme() {
return document.body.getAttribute('data-color-scheme');
return document.body.getAttribute('data-color-scheme')
}

function getStoredScheme() {
try {
return localStorage.getItem(localStorageKey);
return localStorage.getItem(localStorageKey)
} catch {
return null;
return null
}
}

function saveScheme(value) {
try {
localStorage.setItem(localStorageKey, value);
} catch {
}
localStorage.setItem(localStorageKey, value)
} catch {}
}