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Make the Help dropdown and Light/Dark Mode dropdown UI consistent #30575

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b42ca18
✨ Replace ThemeSelect with custom ThemeSelectDropdown component
ahaywood May 4, 2026
038b48c
✨ Replace ThemeSelect with flash-free Astro + lazy React dropdown
mvvmm May 4, 2026
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286 changes: 286 additions & 0 deletions src/components/ThemeSelectDropdown.astro
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Original file line number Diff line number Diff line change
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---
// The button is static HTML rendered by Astro — no hydration, no flash.
// An is:inline script reads localStorage synchronously before first paint
// to patch the icon and label in-place (same technique as Starlight's ThemeSelect).
//
// The dropdown menu is a React component (ThemeSelectMenu.tsx) that is lazily
// imported only when the user clicks the button. By that point React is already
// loaded and hydration is irrelevant — there is nothing to hydrate.
---

<starlight-theme-select>
{/* Hidden select keeps StarlightThemeProvider.updatePickers() working */}
<select aria-hidden="true" tabindex="-1" style="display:none">
<option value="light">Light</option>
<option value="dark">Dark</option>
<option value="auto" selected>Auto</option>
</select>

<button
id="theme-toggle"
aria-haspopup="listbox"
aria-expanded="false"
aria-label="Theme: Auto"
class="theme-toggle"
>
<span class="theme-toggle-inner">
<span class="theme-icon-slot" aria-hidden="true">
{/* Desktop/auto icon — patched synchronously by is:inline script */}
<svg
class="theme-icon"
stroke="currentColor"
fill="currentColor"
stroke-width="0"
viewBox="0 0 256 256"
xmlns="http://www.w3.org/2000/svg"
><path
d="M208,36H48A28,28,0,0,0,20,64V172a28,28,0,0,0,28,28h68v12H96a12,12,0,0,0,0,24h64a12,12,0,0,0,0-24H140V200h68a28,28,0,0,0,28-28V64A28,28,0,0,0,208,36ZM48,60H208a4,4,0,0,1,4,4v72H44V64A4,4,0,0,1,48,60ZM208,176H48a4,4,0,0,1-4-4V160H212v12A4,4,0,0,1,208,176Z"
></path></svg
>
</span>
<span class="theme-label">Auto</span>
</span>
<span class="theme-caret" aria-hidden="true">
<svg
class="caret-icon"
stroke="currentColor"
fill="currentColor"
stroke-width="0"
viewBox="0 0 256 256"
xmlns="http://www.w3.org/2000/svg"
><path
d="M216.49,104.49l-80,80a12,12,0,0,1-17,0l-80-80a12,12,0,0,1,17-17L128,159l71.51-71.52a12,12,0,0,1,17,17Z"
></path></svg
>
</span>
</button>
</starlight-theme-select>

{
/* Runs synchronously before paint — reads localStorage and patches the button DOM */
}
<script is:inline>
(function () {
const storageKey = "starlight-theme";
const stored = typeof localStorage !== "undefined" && localStorage.getItem(storageKey);
const theme = stored === "light" || stored === "dark" ? stored : "auto";

const labels = { light: "Light", dark: "Dark", auto: "Auto" };

const iconPaths = {
light:
"M116,36V20a12,12,0,0,1,24,0V36a12,12,0,0,1-24,0Zm80,92a68,68,0,1,1-68-68A68.07,68.07,0,0,1,196,128Zm-24,0a44,44,0,1,0-44,44A44.05,44.05,0,0,0,172,128ZM51.51,68.49a12,12,0,1,0,17-17l-12-12a12,12,0,0,0-17,17Zm0,119-12,12a12,12,0,0,0,17,17l12-12a12,12,0,1,0-17-17ZM196,72a12,12,0,0,0,8.49-3.51l12-12a12,12,0,0,0-17-17l-12,12A12,12,0,0,0,196,72Zm8.49,115.51a12,12,0,0,0-17,17l12,12a12,12,0,0,0,17-17ZM48,128a12,12,0,0,0-12-12H20a12,12,0,0,0,0,24H36A12,12,0,0,0,48,128Zm80,80a12,12,0,0,0-12,12v16a12,12,0,0,0,24,0V220A12,12,0,0,0,128,208Zm108-92H220a12,12,0,0,0,0,24h16a12,12,0,0,0,0-24Z",
dark: "M236.37,139.4a12,12,0,0,0-12-3A84.07,84.07,0,0,1,119.6,31.59a12,12,0,0,0-15-15A108.86,108.86,0,0,0,49.69,55.07,108,108,0,0,0,136,228a107.09,107.09,0,0,0,64.93-21.69,108.86,108.86,0,0,0,38.44-54.94A12,12,0,0,0,236.37,139.4Zm-49.88,47.74A84,84,0,0,1,68.86,69.51,84.93,84.93,0,0,1,92.27,48.29Q92,52.13,92,56A108.12,108.12,0,0,0,200,164q3.87,0,7.71-.27A84.79,84.79,0,0,1,186.49,187.14Z",
auto: "M208,36H48A28,28,0,0,0,20,64V172a28,28,0,0,0,28,28h68v12H96a12,12,0,0,0,0,24h64a12,12,0,0,0,0-24H140V200h68a28,28,0,0,0,28-28V64A28,28,0,0,0,208,36ZM48,60H208a4,4,0,0,1,4,4v72H44V64A4,4,0,0,1,48,60ZM208,176H48a4,4,0,0,1-4-4V160H212v12A4,4,0,0,1,208,176Z",
};

document
.querySelectorAll("starlight-theme-select")
.forEach(function (picker) {
const select = picker.querySelector("select");
if (select) select.value = theme;

const iconPath = picker.querySelector(".theme-icon path");
if (iconPath) iconPath.setAttribute("d", iconPaths[theme]);

const label = picker.querySelector(".theme-label");
if (label) label.textContent = labels[theme];

const btn = picker.querySelector("#theme-toggle");
if (btn) btn.setAttribute("aria-label", "Theme: " + labels[theme]);
});
})();
</script>

<script>
import { createElement } from "react";
import { createRoot } from "react-dom/client";
import type { Theme } from "./ThemeSelectMenu";

const storageKey = "starlight-theme";

const labels: Record<Theme, string> = {
light: "Light",
dark: "Dark",
auto: "Auto",
};

const iconPaths: Record<Theme, string> = {
light:
"M116,36V20a12,12,0,0,1,24,0V36a12,12,0,0,1-24,0Zm80,92a68,68,0,1,1-68-68A68.07,68.07,0,0,1,196,128Zm-24,0a44,44,0,1,0-44,44A44.05,44.05,0,0,0,172,128ZM51.51,68.49a12,12,0,1,0,17-17l-12-12a12,12,0,0,0-17,17Zm0,119-12,12a12,12,0,0,0,17,17l12-12a12,12,0,1,0-17-17ZM196,72a12,12,0,0,0,8.49-3.51l12-12a12,12,0,0,0-17-17l-12,12A12,12,0,0,0,196,72Zm8.49,115.51a12,12,0,0,0-17,17l12,12a12,12,0,0,0,17-17ZM48,128a12,12,0,0,0-12-12H20a12,12,0,0,0,0,24H36A12,12,0,0,0,48,128Zm80,80a12,12,0,0,0-12,12v16a12,12,0,0,0,24,0V220A12,12,0,0,0,128,208Zm108-92H220a12,12,0,0,0,0,24h16a12,12,0,0,0,0-24Z",
dark: "M236.37,139.4a12,12,0,0,0-12-3A84.07,84.07,0,0,1,119.6,31.59a12,12,0,0,0-15-15A108.86,108.86,0,0,0,49.69,55.07,108,108,0,0,0,136,228a107.09,107.09,0,0,0,64.93-21.69,108.86,108.86,0,0,0,38.44-54.94A12,12,0,0,0,236.37,139.4Zm-49.88,47.74A84,84,0,0,1,68.86,69.51,84.93,84.93,0,0,1,92.27,48.29Q92,52.13,92,56A108.12,108.12,0,0,0,200,164q3.87,0,7.71-.27A84.79,84.79,0,0,1,186.49,187.14Z",
auto: "M208,36H48A28,28,0,0,0,20,64V172a28,28,0,0,0,28,28h68v12H96a12,12,0,0,0,0,24h64a12,12,0,0,0,0-24H140V200h68a28,28,0,0,0,28-28V64A28,28,0,0,0,208,36ZM48,60H208a4,4,0,0,1,4,4v72H44V64A4,4,0,0,1,48,60ZM208,176H48a4,4,0,0,1-4-4V160H212v12A4,4,0,0,1,208,176Z",
};

function parseTheme(theme: unknown): Theme {
return theme === "auto" || theme === "dark" || theme === "light"
? theme
: "auto";
}

function loadTheme(): Theme {
return parseTheme(
typeof localStorage !== "undefined" && localStorage.getItem(storageKey),
);
}

function storeTheme(theme: Theme): void {
if (typeof localStorage !== "undefined") {
localStorage.setItem(
storageKey,
theme === "light" || theme === "dark" ? theme : "",
);
}
}

function getPreferredColorScheme(): "light" | "dark" {
return matchMedia("(prefers-color-scheme: light)").matches
? "light"
: "dark";
}

function applyTheme(theme: Theme): void {
document.documentElement.dataset.theme =
theme === "auto" ? getPreferredColorScheme() : theme;
storeTheme(theme);
if ((window as any).StarlightThemeProvider) {
(window as any).StarlightThemeProvider.updatePickers(theme);
}
}

function updateButton(picker: Element, theme: Theme) {
const select = picker.querySelector("select");
if (select) select.value = theme;

const iconPath = picker.querySelector(".theme-icon path");
if (iconPath) iconPath.setAttribute("d", iconPaths[theme]);

const label = picker.querySelector(".theme-label");
if (label) label.textContent = labels[theme];

const btn = picker.querySelector<HTMLElement>("#theme-toggle");
if (btn) btn.setAttribute("aria-label", `Theme: ${labels[theme]}`);
}

document.querySelectorAll("starlight-theme-select").forEach((picker) => {
const toggle = picker.querySelector<HTMLButtonElement>("#theme-toggle");
if (!toggle) return;

// React root for the dropdown — created once on first click, reused after.
let menuContainer: HTMLDivElement | null = null;
let root: ReturnType<typeof createRoot> | null = null;
let isOpen = false;

function renderMenu(open: boolean) {
isOpen = open;
toggle!.setAttribute("aria-expanded", String(open));

if (!open) {
if (root) root.render(null);
return;
}

if (!menuContainer) {
menuContainer = document.createElement("div");
document.body.appendChild(menuContainer);
root = createRoot(menuContainer);
}

// Lazy-import ThemeSelectMenu only on first open.
import("./ThemeSelectMenu").then(({ default: ThemeSelectMenu }) => {
root!.render(
createElement(ThemeSelectMenu, {
anchor: toggle!,
onSelect(theme: Theme) {
applyTheme(theme);
updateButton(picker, theme);
renderMenu(false);
},
}),
);
});
}

toggle.addEventListener("click", () => renderMenu(!isOpen));

document.addEventListener("mousedown", (e) => {
if (isOpen && !picker.contains(e.target as Node)) {
renderMenu(false);
}
});

document.addEventListener("keydown", (e) => {
if (isOpen && e.key === "Escape") renderMenu(false);
});

// React to system color scheme changes when set to auto.
matchMedia("(prefers-color-scheme: light)").addEventListener(
"change",
() => {
if (loadTheme() === "auto") {
document.documentElement.dataset.theme = getPreferredColorScheme();
}
},
);
});
</script>

<style>
.theme-toggle {
display: flex;
height: 2.25rem;
width: 100%;
cursor: pointer;
align-items: center;
justify-content: space-between;
gap: 0.375rem;
border-radius: 0.5rem;
background: transparent;
border: none;
padding: 0 0.75rem;
font-size: 0.875rem;
font-weight: 500;
color: var(--color-header-text);
transition:
color 150ms,
background-color 150ms;
}

.theme-toggle:hover {
background-color: var(--color-header-fill);
color: var(--color-header-hover-text);
}

.theme-toggle-inner {
display: flex;
flex: 1;
align-items: center;
gap: 0.375rem;
}

.theme-icon-slot {
display: flex;
align-items: center;
color: var(--color-header-text-subtle);
}

.theme-toggle:hover .theme-icon-slot,
.theme-toggle:hover .theme-caret {
color: var(--color-header-hover-text);
}

.theme-icon {
width: 0.875rem;
height: 0.875rem;
}

.theme-caret {
flex-shrink: 0;
color: var(--color-header-text-subtle);
}

.caret-icon {
width: 0.625rem;
height: 0.625rem;
}
</style>
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