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fix(admin): prevent dark-mode flash on light-preference systems #983

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fix(admin): prevent dark-mode flash on light-preference systems #983

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17 changes: 16 additions & 1 deletion assets/js/litespeed-cache-admin.js
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Original file line number Diff line number Diff line change
Expand Up @@ -302,6 +302,18 @@ function litespeed_init_dark_mode() {
// Only add toggle on LiteSpeed pages
if (window.location.search.indexOf('page=litespeed') === -1) return;

// Mirror the saved preference into a cookie so PHP can stamp the body class
// on first paint (prevents the dark flash when localStorage says "light").
function litespeed_set_dark_cookie(value) {
var base = 'litespeed-dark-preference=' + (value || '') + '; path=/; SameSite=Lax';
document.cookie = base + '; max-age=' + (value ? 31536000 : 0);
}
// Back-fill the cookie for existing users whose preference is still localStorage-only.
var _savedPref = localStorage.getItem('litespeed-dark-preference');
if (_savedPref && document.cookie.indexOf('litespeed-dark-preference=') === -1) {
litespeed_set_dark_cookie(_savedPref);
}

// Create toggle button
var toggleBtn = document.createElement('button');
toggleBtn.className = 'litespeed-dark-mode-toggle';
Expand Down Expand Up @@ -351,8 +363,11 @@ function litespeed_init_dark_mode() {
// Toggle and store only if different from browser preference
if (!currentlyDark === prefersDark) {
localStorage.removeItem('litespeed-dark-preference');
litespeed_set_dark_cookie('');
} else {
localStorage.setItem('litespeed-dark-preference', currentlyDark ? 'light' : 'dark');
var newPref = currentlyDark ? 'light' : 'dark';
localStorage.setItem('litespeed-dark-preference', newPref);
litespeed_set_dark_cookie(newPref);
}

applyDarkMode();
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8 changes: 8 additions & 0 deletions src/admin-display.cls.php
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Original file line number Diff line number Diff line change
Expand Up @@ -337,6 +337,14 @@ function ( $footer_text ) {
if ( $screen && in_array( $screen->id, [ 'settings_page_litespeed-cache-options', 'toplevel_page_litespeed' ], true ) ) {
$classes .= ' litespeed-cache_page_litespeed';
}
// Stamp the dark/light override server-side from the cookie set by admin JS,
// so the stylesheet picks the right mode on first paint (no FOUC).
if ( ! empty( $_COOKIE['litespeed-dark-preference'] ) ) {
$pref = sanitize_key( wp_unslash( $_COOKIE['litespeed-dark-preference'] ) );
if ( 'dark' === $pref || 'light' === $pref ) {
$classes .= ' litespeed-' . $pref . 'mode';
}
}
return $classes;
} );
} );
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