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[UX] Prevent flash when in dark mode #2343

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Merged
chalin merged 2 commits into from
Oct 17, 2025
Merged

[UX] Prevent flash when in dark mode #2343

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93b6cba
[UX] Minimize dark-mode flash, an initial and simple no-JS solution
chalin Oct 17, 2025
14656c1
Set td theme color before CSS loads
chalin Oct 17, 2025
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2 changes: 2 additions & 0 deletions assets/js/dark-mode.js
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Original file line number Diff line number Diff line change
Expand Up @@ -34,6 +34,8 @@

setTheme(getPreferredTheme())

document.documentElement.removeAttribute('data-theme-init')

const showActiveTheme = (theme, focus = false) => {
const themeSwitcher = document.querySelector('#bd-theme')

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35 changes: 35 additions & 0 deletions layouts/_partials/head.html
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@@ -1,6 +1,41 @@
{{/* cSpell:ignore docsearch opengraph outputformat */ -}}
<meta charset="utf-8">
<meta name="viewport" content="width=device-width, initial-scale=1, shrink-to-fit=no">

{{ if .Site.Params.ui.showLightDarkModeMenu -}}
{{/* Browser hints before CSS loads */ -}}
<meta name="color-scheme" content="light dark">
<meta name="theme-color" media="(prefers-color-scheme: light)" content="#ffffff">
<meta name="theme-color" media="(prefers-color-scheme: dark)" content="#000000">

{{/* Styles to set canvas colors and avoid transitions */ -}}
<style>
{{/* Set system colors as default */ -}}
html { background: Canvas; color: CanvasText; }
{{/* Define reasonable dark defaults */ -}}
@media (prefers-color-scheme: dark) {
html { background: #0b0d12; color: #e6e6e6; }
}
{{/* Avoid transitions until theme CSS is loaded */ -}}
html[data-theme-init] * { transition: none !important; }
</style>

{{/* Set theme attribute before CSS loads to prevent flash */ -}}
<script>
(function() {
const themeKey = 'td-color-theme';
const storedTheme = localStorage.getItem(themeKey);
let theme = storedTheme || (window.matchMedia('(prefers-color-scheme: dark)').matches ? 'dark' : 'light');

if (theme === 'auto') {
theme = window.matchMedia('(prefers-color-scheme: dark)').matches ? 'dark' : 'light';
}

document.documentElement.setAttribute('data-bs-theme', theme);
})();
</script>
{{ end -}}

{{ range .AlternativeOutputFormats -}}
<link rel="{{ .Rel }}" type="{{ .MediaType.Type }}" href="{{ .Permalink | safeURL }}">
{{ end -}}
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3 changes: 2 additions & 1 deletion layouts/baseof.html
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Expand Up @@ -2,7 +2,8 @@
<html itemscope itemtype="http://schema.org/WebPage"
{{- with .Site.Language.LanguageDirection }} dir="{{ . }}" {{- end -}}
{{ with .Site.Language.Lang }} lang="{{ . }}" {{- end }} {{/**/ -}}
class="no-js">
class="no-js"
{{- if .Site.Params.ui.showLightDarkModeMenu }} data-theme-init{{ end }}>
<head>
{{ partial "head.html" . }}
</head>
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