Create withViewTransition wrapper function (#27918)

* Create withViewTransition wrapper function

* Add missing space

* Remove function, check for view transition, add param

* Document

src/common/util/view-transition.ts

@@ -0,0 +1,30 @@
+/**
+ * Executes a callback within a View Transition if supported, otherwise runs it directly.
+ *
+ * @param callback - Function to execute. Can be synchronous or return a Promise. The callback will be passed a boolean indicating whether the view transition is available.
+ * @returns Promise that resolves when the transition completes (or immediately if not supported)
+ *
+ * @example
+ * ```typescript
+ * // Synchronous callback
+ * withViewTransition(() => {
+ *   this.large = !this.large;
+ * });
+ *
+ * // Async callback
+ * await withViewTransition(async () => {
+ *   await this.updateData();
+ * });
+ * ```
+ */
+export const withViewTransition = (
+  callback: (viewTransitionAvailable: boolean) => void | Promise<void>
+): Promise<void> => {
+  if (document.startViewTransition) {
+    return document.startViewTransition(() => callback(true)).finished;
+  }
+
+  // Fallback: Execute callback directly without transition
+  const result = callback(false);
+  return result instanceof Promise ? result : Promise.resolve();
+};

src/resources/theme/core.globals.ts

@@ -55,6 +55,7 @@ export const coreStyles = css`
     --ha-shadow-spread-sm: 0;
     --ha-shadow-spread-md: 0;
     --ha-shadow-spread-lg: 0;
+
     --ha-animation-base-duration: 350ms;
   }
 

src/util/launch-screen.ts

@@ -1,12 +1,16 @@
 import type { TemplateResult } from "lit";
 import { render } from "lit";
 import { parseAnimationDuration } from "../common/util/parse-animation-duration";
+import { withViewTransition } from "../common/util/view-transition";
 
-const removeElement = (
+export const removeLaunchScreen = () => {
-  launchScreenElement: HTMLElement,
+  const launchScreenElement = document.getElementById("ha-launch-screen");
-  skipAnimation: boolean
+  if (!launchScreenElement?.parentElement) {
-) => {
+    return;
-  if (skipAnimation) {
+  }
+
+  withViewTransition((viewTransitionAvailable: boolean) => {
+    if (!viewTransitionAvailable) {
       launchScreenElement.parentElement?.removeChild(launchScreenElement);
       return;
     }
@@ -20,22 +24,7 @@ const removeElement = (
     setTimeout(() => {
       launchScreenElement.parentElement?.removeChild(launchScreenElement);
     }, parseAnimationDuration(durationFromCss));
-};
-
-export const removeLaunchScreen = () => {
-  const launchScreenElement = document.getElementById("ha-launch-screen");
-  if (!launchScreenElement?.parentElement) {
-    return;
-  }
-
-  if (document.startViewTransition) {
-    document.startViewTransition(() => {
-      removeElement(launchScreenElement, false);
   });
-  } else {
-    // Fallback: Direct removal without transition
-    removeElement(launchScreenElement, true);
-  }
 };
 
 export const renderLaunchScreenInfoBox = (content: TemplateResult) => {