From a3892a338d5ea12f809671d40eb79ab8bc8eccd5 Mon Sep 17 00:00:00 2001
From: Stamen Stoychev <SStoychev@infragistics.com>
Date: Wed, 5 Aug 2026 15:17:42 +0300
Subject: [PATCH] feat(*): add theming widget handling

---
 browser/src/index.tsx       |   4 +
 browser/src/sample-theme.ts | 187 ++++++++++++++++++++++++++++++++++++
 2 files changed, 191 insertions(+)
 create mode 100644 browser/src/sample-theme.ts

diff --git a/browser/src/index.tsx b/browser/src/index.tsx
index 8448fe8ebb..31ffb41769 100644
--- a/browser/src/index.tsx
+++ b/browser/src/index.tsx
@@ -5,6 +5,7 @@ import { BrowserRouter } from "react-router-dom";
 import SamplesBrowser from "./navigation/SamplesBrowser";
 import RegisterServiceWorker from './serviceWorker';
 import { createRoot } from 'react-dom/client';
+import { initSampleThemeListener } from './sample-theme';
 
 import './index.css'; // styles shared between all samples
 
@@ -21,6 +22,9 @@ import './index.css'; // styles shared between all samples
    // );
 //  });
 
+// Lets the docs ThemingWidget re-theme this browser while embedded.
+initSampleThemeListener();
+
 const container = document.getElementById('root');
 const root = createRoot(container);
 root.render(
diff --git a/browser/src/sample-theme.ts b/browser/src/sample-theme.ts
new file mode 100644
index 0000000000..1c202a346a
--- /dev/null
+++ b/browser/src/sample-theme.ts
@@ -0,0 +1,187 @@
+/**
+ * sample-theme.ts
+ *
+ * Lets the docs site re-theme this samples browser while it is embedded in a
+ * docs `<Sample>` iframe.
+ *
+ * The docs ThemingWidget dispatches `igd-theme-change`; the Sample widget
+ * bridges that to `postMessage({ type: 'igd-sample-theme', theme, mode })` on
+ * the frame, and re-posts the current selection on every iframe `load`. Here we
+ * validate the sender and swap the Ignite UI theme stylesheets to match.
+ *
+ * Dormant unless a trusted docs host asks for a theme.
+ */
+
+type ThemeName = 'material' | 'fluent' | 'bootstrap' | 'indigo';
+type ThemeMode = 'light' | 'dark' | 'system';
+type ResolvedMode = 'light' | 'dark';
+
+interface ThemeMessage {
+    type?: string;
+    event?: string;
+    theme?: string;
+    themeName?: string;
+    mode?: string;
+}
+
+type CssLoader = () => Promise<{ default: string }>;
+
+const MESSAGE_TYPE = 'igd-sample-theme';
+const STYLE_ATTR = 'data-igd-sample-theme';
+const DARK_QUERY = '(prefers-color-scheme: dark)';
+
+// Vite only bundles dynamic imports with literal specifiers, so every
+// mode/theme pair is spelled out. `?inline` yields the CSS as a string instead
+// of injecting a sheet, which lets selections replace each other in owned
+// <style> elements rather than stacking sheets that can never be removed.
+const THEME_CSS: Record<string, CssLoader[]> = {
+    'light:material': [
+        () => import('igniteui-react-grids/grids/themes/light/material.css?inline'),
+        () => import('igniteui-webcomponents/themes/light/material.css?inline'),
+    ],
+    'light:fluent': [
+        () => import('igniteui-react-grids/grids/themes/light/fluent.css?inline'),
+        () => import('igniteui-webcomponents/themes/light/fluent.css?inline'),
+    ],
+    'light:bootstrap': [
+        () => import('igniteui-react-grids/grids/themes/light/bootstrap.css?inline'),
+        () => import('igniteui-webcomponents/themes/light/bootstrap.css?inline'),
+    ],
+    'light:indigo': [
+        () => import('igniteui-react-grids/grids/themes/light/indigo.css?inline'),
+        () => import('igniteui-webcomponents/themes/light/indigo.css?inline'),
+    ],
+    'dark:material': [
+        () => import('igniteui-react-grids/grids/themes/dark/material.css?inline'),
+        () => import('igniteui-webcomponents/themes/dark/material.css?inline'),
+    ],
+    'dark:fluent': [
+        () => import('igniteui-react-grids/grids/themes/dark/fluent.css?inline'),
+        () => import('igniteui-webcomponents/themes/dark/fluent.css?inline'),
+    ],
+    'dark:bootstrap': [
+        () => import('igniteui-react-grids/grids/themes/dark/bootstrap.css?inline'),
+        () => import('igniteui-webcomponents/themes/dark/bootstrap.css?inline'),
+    ],
+    'dark:indigo': [
+        () => import('igniteui-react-grids/grids/themes/dark/indigo.css?inline'),
+        () => import('igniteui-webcomponents/themes/dark/indigo.css?inline'),
+    ],
+};
+
+const styleEls: HTMLStyleElement[] = [];
+let selected: { theme: ThemeName; mode: ThemeMode } = null;
+let latestRequest = 0;
+let listening = false;
+
+function isTrustedOrigin(origin: string): boolean {
+    if (origin === window.location.origin) { return true; }
+    let hostname: string;
+    try {
+        hostname = new URL(origin).hostname;
+    } catch {
+        return false;
+    }
+    if (hostname === 'localhost' || hostname === '127.0.0.1') { return true; }
+    return hostname === 'infragistics.com' || hostname.endsWith('.infragistics.com');
+}
+
+function parseMessage(data: any): { theme: ThemeName; mode: ThemeMode } {
+    if (!data || typeof data !== 'object') { return null; }
+    const msg = data as ThemeMessage;
+    if (msg.type !== MESSAGE_TYPE && msg.event !== MESSAGE_TYPE) { return null; }
+
+    const theme = (msg.theme || msg.themeName || '').toLowerCase();
+    if (!theme || !THEME_CSS['light:' + theme]) { return null; }
+
+    const rawMode = (msg.mode || 'light').toLowerCase();
+    const mode: ThemeMode =
+        rawMode === 'dark' || rawMode === 'system' ? rawMode : 'light';
+
+    return { theme: theme as ThemeName, mode };
+}
+
+function resolveMode(mode: ThemeMode): ResolvedMode {
+    if (mode === 'light' || mode === 'dark') { return mode; }
+    return window.matchMedia && window.matchMedia(DARK_QUERY).matches ? 'dark' : 'light';
+}
+
+// One element per source sheet: a stylesheet's `@import` rules are only valid
+// at its top, so the sheets must not be concatenated into a single element.
+function writeSheets(css: string[]): void {
+    css.forEach((text, i) => {
+        let el = styleEls[i];
+        if (!el) {
+            el = document.createElement('style');
+            el.setAttribute(STYLE_ATTR, String(i));
+            styleEls[i] = el;
+        }
+        el.textContent = text;
+        // Re-append on every swap so the override stays last in the cascade,
+        // ahead of any theme sheet a lazily routed sample imports after us.
+        document.head.appendChild(el);
+    });
+}
+
+function applyTheme(theme: ThemeName, mode: ThemeMode): void {
+    const resolved = resolveMode(mode);
+    const loaders = THEME_CSS[resolved + ':' + theme];
+    if (!loaders) { return; }
+
+    const request = ++latestRequest;
+    Promise.all(loaders.map((load) => load()))
+        .then((sheets) => {
+            // Drop stale responses so rapid switching can't land out of order.
+            if (request !== latestRequest) { return; }
+            writeSheets(sheets.map((s) => s.default));
+
+            const root = document.documentElement;
+            root.setAttribute('data-igd-theme', theme);
+            root.setAttribute('data-igd-mode', resolved);
+            root.style.colorScheme = resolved;
+        })
+        .catch((err) => {
+            console.warn('[sample-theme] Could not load theme "' + theme + '":', err);
+        });
+}
+
+function onMessage(event: MessageEvent): void {
+    // Only the embedding docs page may drive the theme.
+    if (event.source !== window.parent || !isTrustedOrigin(event.origin)) { return; }
+
+    const next = parseMessage(event.data);
+    if (!next) { return; }
+    if (selected && selected.theme === next.theme && selected.mode === next.mode) { return; }
+
+    selected = next;
+    applyTheme(next.theme, next.mode);
+}
+
+function watchSystemMode(): void {
+    if (!window.matchMedia) { return; }
+    const query = window.matchMedia(DARK_QUERY);
+    const onChange = () => {
+        if (selected && selected.mode === 'system') {
+            applyTheme(selected.theme, selected.mode);
+        }
+    };
+    if (query.addEventListener) {
+        query.addEventListener('change', onChange);
+    } else {
+        query.addListener(onChange);
+    }
+}
+
+/**
+ * Starts listening for theme messages from the embedding docs page.
+ *
+ * Must run during module evaluation of the app entry: the host re-posts on the
+ * iframe `load` event, which fires after module scripts execute, so no
+ * handshake is needed.
+ */
+export function initSampleThemeListener(): void {
+    if (listening || window.parent === window) { return; }
+    listening = true;
+    window.addEventListener('message', onMessage);
+    watchSystemMode();
+}