feat(base): propagate theme and language changes across runtimes

packages/base/cypress/specs/ConfigurationSync.cy.tsx

@@ -0,0 +1,73 @@
+import { fireConfigChange, attachConfigChange, getSharedValue } from "../../src/config/ConfigurationSync.js";
+import { setTheme, getTheme } from "../../src/config/Theme.js";
+import { setLanguage, getLanguage } from "../../src/config/Language.js";
+import EventProvider from "../../src/EventProvider.js";
+import getSharedResource from "../../src/getSharedResource.js";
+
+describe("ConfigurationSync", () => {
+	describe("Shared value storage", () => {
+		it("fireConfigChange stores values readable via getSharedValue", () => {
+			fireConfigChange("testSetting", "testValue");
+
+			cy.wrap({ getSharedValue })
+				.invoke("getSharedValue", "testSetting")
+				.should("equal", "testValue");
+		});
+
+		it("getSharedValue returns undefined for unknown settings", () => {
+			cy.wrap({ getSharedValue })
+				.invoke("getSharedValue", "nonExistent")
+				.should("equal", undefined);
+		});
+	});
+
+	describe("Skip-guard", () => {
+		it("handler is NOT called when the same runtime fires", () => {
+			const handler = cy.stub().as("handler");
+			attachConfigChange("skipTest", handler);
+
+			fireConfigChange("skipTest", "value");
+
+			cy.get("@handler").should("not.have.been.called");
+		});
+	});
+
+	describe("Cross-runtime handler", () => {
+		it("handler is called only for its own setting name", () => {
+			const handlerA = cy.stub().as("handlerA");
+			const handlerB = cy.stub().as("handlerB");
+			attachConfigChange("settingA", handlerA);
+			attachConfigChange("settingB", handlerB);
+
+			// Simulate a cross-runtime fire by calling the shared EventProvider directly,
+			// bypassing the skip-guard that fireConfigChange sets for the current runtime.
+			const ep = getSharedResource("ConfigChange.eventProvider", new EventProvider());
+			ep.fireEvent("configChange", { name: "settingA", value: "cross-value" });
+
+			cy.get("@handlerA").should("have.been.calledOnce").and("have.been.calledWith", "cross-value");
+			cy.get("@handlerB").should("not.have.been.called");
+		});
+	});
+
+	describe("Theme integration", () => {
+		it("setTheme stores value in shared map", () => {
+			cy.wrap({ setTheme })
+				.invoke("setTheme", "sap_horizon_hcb");
+
+			cy.wrap({ getSharedValue })
+				.invoke("getSharedValue", "theme")
+				.should("equal", "sap_horizon_hcb");
+		});
+	});
+
+	describe("Language integration", () => {
+		it("setLanguage stores value in shared map", () => {
+			cy.wrap({ setLanguage })
+				.invoke("setLanguage", "de");
+
+			cy.wrap({ getSharedValue })
+				.invoke("getSharedValue", "language")
+				.should("equal", "de");
+		});
+	});
+});

packages/base/src/config/ConfigurationSync.ts

@@ -0,0 +1,50 @@
+import getSharedResource from "../getSharedResource.js";
+import EventProvider from "../EventProvider.js";
+
+type ConfigChangeDetail = { name: string; value: unknown };
+
+const getEventProvider = () => getSharedResource("ConfigChange.eventProvider", new EventProvider<ConfigChangeDetail, void>());
+const getSharedValues = () => getSharedResource<Record<string, unknown>>("ConfigChange.values", {});
+
+const CONFIG_CHANGE = "configChange";
+
+// Module-level skip flags — each runtime copy has its own Set,
+// so a runtime's own handler correctly skips when it fires.
+const skipFlags = new Set<string>();
+
+/**
+ * Stores value in shared map and fires a cross-runtime config change event.
+ * The firing runtime's own handler is skipped via the skip-guard pattern.
+ */
+const fireConfigChange = (name: string, value: unknown): void => {
+	getSharedValues()[name] = value;
+
+	skipFlags.add(name);
+	try {
+		getEventProvider().fireEvent(CONFIG_CHANGE, { name, value });
+	} finally {
+		skipFlags.delete(name);
+	}
+};
+
+/**
+ * Registers a per-setting cross-runtime listener.
+ * The handler is only called when another runtime fires the change.
+ */
+const attachConfigChange = (name: string, handler: (value: any) => void): void => { // eslint-disable-line
+	getEventProvider().attachEvent(CONFIG_CHANGE, (detail: ConfigChangeDetail) => {
+		if (detail.name === name && !skipFlags.has(name)) {
+			handler(detail.value);
+		}
+	});
+};
+
+/**
+ * Reads the last-set value from the shared values map.
+ * Used by late-booting runtimes to pick up values already set by others.
+ */
+const getSharedValue = <T>(name: string): T | undefined => {
+	return getSharedValues()[name] as T | undefined;
+};
+
+export { fireConfigChange, attachConfigChange, getSharedValue };

packages/base/src/config/Language.ts

@@ -7,6 +7,7 @@ import { reRenderAllUI5Elements } from "../Render.js";
 import { DEFAULT_LANGUAGE } from "../generated/AssetParameters.js";
 import { isBooted } from "../Boot.js";
 import { attachConfigurationReset } from "./ConfigurationReset.js";
+import { fireConfigChange, attachConfigChange, getSharedValue } from "./ConfigurationSync.js";
 
 let curLanguage: string | undefined;
 let fetchDefaultLanguage: boolean | undefined;
@@ -25,6 +26,17 @@ attachConfigurationReset(() => {
 // will trigger a re-render of all language-aware components.
 let languageChangePending = false;
 
+attachConfigChange("language", (language: string) => {
+	curLanguage = language;
+	languageChangePending = true;
+	fireLanguageChange(language).then(() => {
+		languageChangePending = false;
+		if (isBooted()) {
+			reRenderAllUI5Elements({ languageAware: true });
+		}
+	});
+});
+
 const getLanguageChangePending = () => languageChangePending;
 
 /**
@@ -34,7 +46,7 @@ const getLanguageChangePending = () => languageChangePending;
  */
 const getLanguage = (): string | undefined => {
 	if (curLanguage === undefined) {
-		curLanguage = getConfiguredLanguage();
+		curLanguage = getSharedValue<string>("language") ?? getConfiguredLanguage();
 	}
 	return curLanguage;
 };
@@ -55,6 +67,8 @@ const setLanguage = async (language: string): Promise<void> => {
 	languageChangePending = true;
 	curLanguage = language;
 
+	fireConfigChange("language", language);
+
 	await fireLanguageChange(language);
 
 	languageChangePending = false;

packages/base/src/config/Theme.ts

@@ -5,6 +5,7 @@ import getThemeDesignerTheme from "../theming/getThemeDesignerTheme.js";
 import { DEFAULT_THEME, SUPPORTED_THEMES } from "../generated/AssetParameters.js";
 import { boot, isBooted } from "../Boot.js";
 import { attachConfigurationReset } from "./ConfigurationReset.js";
+import { fireConfigChange, attachConfigChange, getSharedValue } from "./ConfigurationSync.js";
 
 let curTheme: string | undefined;
 let curBaseTheme: string | undefined;
@@ -13,14 +14,21 @@ attachConfigurationReset(() => {
 	curTheme = undefined;
 });
 
+attachConfigChange("theme", (theme: string) => {
+	curTheme = theme;
+	if (isBooted()) {
+		applyTheme(curTheme).then(() => reRenderAllUI5Elements({ themeAware: true }));
+	}
+});
+
 /**
  * Returns the current theme.
  * @public
  * @returns {string} the current theme name
  */
 const getTheme = (): string => {
 	if (curTheme === undefined) {
-		curTheme = getConfiguredTheme();
+		curTheme = getSharedValue<string>("theme") ?? getConfiguredTheme();
 	}
 
 	return curTheme;
@@ -39,6 +47,8 @@ const setTheme = async (theme: string): Promise<void> => {
 
 	curTheme = theme;
 
+	fireConfigChange("theme", theme);
+
 	if (isBooted()) {
 		// Update CSS Custom Properties
 		await applyTheme(curTheme);