refactor(web-components): use adopted style sheets to set theme tokens

change/@fluentui-web-components-22e3e36e-c30c-4866-85ad-9e28421977d6.json

@@ -0,0 +1,7 @@
+{
+  "type": "prerelease",
+  "comment": "refactor setTheme() to use adoptedStyleSheets",
+  "packageName": "@fluentui/web-components",
+  "email": "[email protected]",
+  "dependentChangeType": "patch"
+}

packages/web-components/.eslintrc.json

@@ -15,6 +15,12 @@
     }
   },
   "rules": {
+    "no-empty": [
+      "error",
+      {
+        "allowEmptyCatch": true
+      }
+    ],
     "no-extra-boolean-cast": "off",
     "no-prototype-builtins": "off",
     "no-fallthrough": "off",

packages/web-components/docs/api-report.md

@@ -4,6 +4,8 @@
 
 ```ts
 
+/// <reference types="web" />
+
 import type { Constructable } from '@microsoft/fast-element';
 import { CSSDirective } from '@microsoft/fast-element';
 import { Direction } from '@microsoft/fast-web-utilities';
@@ -3152,6 +3154,8 @@ class Text_2 extends FASTElement {
     block: boolean;
     // (undocumented)
     connectedCallback(): void;
+    // (undocumented)
+    disconnectedCallback(): void;
     // @internal
     elementInternals: ElementInternals;
     font?: TextFont;

packages/web-components/package.json

@@ -230,9 +230,9 @@
   },
   "devDependencies": {
     "@microsoft/fast-element": "2.0.0-beta.26",
+    "@tensile-perf/web-components": "~0.2.0",
     "@types/web": "^0.0.142",
     "@storybook/html": "6.5.15",
-    "@tensile-perf/web-components": "~0.1.15",
     "chromedriver": "^125.0.0"
   },
   "dependencies": {

packages/web-components/src/theme/set-theme.bench.ts

@@ -0,0 +1,30 @@
+import { measurePerformance, type TestRenderFunction } from '@tensile-perf/web-components';
+import { teamsDarkTheme, teamsLightTheme, webDarkTheme, webLightTheme } from '@fluentui/tokens';
+
+import { setTheme } from './set-theme.js';
+
+const tests: Record<string, TestRenderFunction> = {
+  mount: ({ onComplete }) => {
+    const { startMeasure, endMeasure } = measurePerformance();
+
+    startMeasure();
+
+    // Newly set themes
+    setTheme(webLightTheme);
+    setTheme(webDarkTheme);
+    setTheme(teamsDarkTheme);
+    setTheme(teamsLightTheme);
+
+    // Cached themes
+    setTheme(webLightTheme);
+    setTheme(webDarkTheme);
+    setTheme(teamsDarkTheme);
+    setTheme(teamsLightTheme);
+
+    endMeasure();
+
+    onComplete();
+  },
+};
+
+export { tests };

packages/web-components/src/theme/set-theme.stories.ts

@@ -0,0 +1,16 @@
+import { html } from '@microsoft/fast-element';
+import { teamsDarkTheme, teamsLightTheme, webDarkTheme, webLightTheme } from '@fluentui/tokens';
+
+import { renderComponent } from '../helpers.stories.js';
+import { setTheme } from './set-theme.js';
+
+export default {
+  title: 'Theme/SetTheme',
+};
+
+export const SetTheme = renderComponent(html`
+  <fluent-button @click="${() => setTheme(webLightTheme)}">webLightTheme</fluent-button>
+  <fluent-button @click="${() => setTheme(webDarkTheme)}">webDarkTheme</fluent-button>
+  <fluent-button @click="${() => setTheme(teamsLightTheme)}">teamsLightTheme</fluent-button>
+  <fluent-button @click="${() => setTheme(teamsDarkTheme)}">teamsDarkTheme</fluent-button>
+`);

packages/web-components/src/theme/set-theme.ts

@@ -3,34 +3,52 @@ import * as tokens from './design-tokens.js';
 
 const tokenNames = Object.keys(tokens) as (keyof Theme)[];
 
+const SUPPORTS_REGISTER_PROPERTY = 'registerProperty' in CSS;
+const SUPPORTS_ADOPTED_STYLE_SHEETS = 'adoptedStyleSheets' in document;
+const themeStyleSheet = new CSSStyleSheet();
+const themeStyleTextMap = new Map<Theme, string>();
+
 /**
  * Sets the theme tokens on defaultNode.
  * @param theme - Flat object of theme token values.
  * @internal
  */
 export const setTheme = (theme: Theme) => {
-  for (const t of tokenNames) {
-    let registered = false;
-
-    if ('registerProperty' in CSS) {
-      try {
-        CSS.registerProperty({
-          name: `--${t}`,
-          inherits: true,
-          initialValue: theme[t] as string,
-        });
-        registered = true;
-      } catch {
-        // Do nothing.
+  // Fallback to setting token custom properties on `<html>` element’s `style`
+  // attribute, only checking the support of  `document.adoptedStyleSheets`
+  // here because it has broader support than `CSS.registerProperty()`, which
+  // is checked later.
+  if (!SUPPORTS_ADOPTED_STYLE_SHEETS) {
+    setThemeFor(document.documentElement, theme);
+    return;
+  }
+
+  if (!themeStyleTextMap.has(theme)) {
+    const tokenDeclarations: string[] = [];
+
+    for (const t of tokenNames) {
+      if (SUPPORTS_REGISTER_PROPERTY) {
+        try {
+          CSS.registerProperty({
+            name: `--${t}`,
+            inherits: true,
+            initialValue: theme[t] as string,
+          });
+        } catch {}
       }
+      tokenDeclarations.push(`--${t}: ${theme[t] as string};`);
     }
 
-    if (!registered) {
-      // TODO: Find a better way to update the values. Current approach adds
-      // lots of code to the `style` attribute on `<body>`. Maybe look into
-      // `document.adoptedStyleSheets`.
-      setThemeFor(document.body, theme);
-    }
+    themeStyleTextMap.set(theme, `html{${tokenDeclarations.join('')}}`);
+  }
+
+  if (!document.adoptedStyleSheets.includes(themeStyleSheet)) {
+    document.adoptedStyleSheets.push(themeStyleSheet);
+  } else {
+    // The very first call to `setTheme()` within a document doesn’t need to
+    // call `replaceSync()`, because `CSS.registerProperty()` above is
+    // sufficient to set the tokens.
+    themeStyleSheet.replaceSync(themeStyleTextMap.get(theme)!);
   }
 };
 

yarn.lock

@@ -4640,10 +4640,10 @@
   dependencies:
     "@tensile-perf/tools" "0.1.7"
 
-"@tensile-perf/web-components@~0.1.15":
-  version "0.1.15"
-  resolved "https://registry.yarnpkg.com/@tensile-perf/web-components/-/web-components-0.1.15.tgz#95587b220d0b09b79b339da4e4f8694772fab91a"
-  integrity sha512-gawc20t7uvZyWUZOqBCA6/2Z7wEGECy2ytxe2/FMplDOuUj/CLXKoDY9mtS1dlo+6HjERuL8iP4IjdqURXo2UA==
+"@tensile-perf/web-components@~0.2.0":
+  version "0.2.0"
+  resolved "https://registry.yarnpkg.com/@tensile-perf/web-components/-/web-components-0.2.0.tgz#355ac463a121656e68c0567f9c15accf19b61734"
+  integrity sha512-NEKH6d/2HrOJgW60E/oZ/O2D4vjzBv9xgSQmAz1cQnrEyQ/Odz/l3OWDwfEobcg8VHm6iODVoNAyvYAr4ESTKQ==
   dependencies:
     "@tensile-perf/runner" "0.4.0"
     "@tensile-perf/tools" "0.1.7"