[playground] ViewTransition on config expand (#34595)

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## Summary

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Explain the **motivation** for making this change. What existing problem
does the pull request solve?
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Introduced `<ViewTransition>` to the React Compiler Playground. Added an
initial animation on the config panel opening/closing to allow for a
smoother visual experience. Previously, the panel would flash in and out
of the screen upon open/close.

## How did you test this change?

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https://github.com/user-attachments/assets/9dc77a6b-d4a5-4a7a-9d81-007ebb55e8d2

compiler/apps/playground/__tests__/e2e/page.spec.ts

@@ -23,7 +23,8 @@ function formatPrint(data: Array<string>): Promise<string> {
 
 async function expandConfigs(page: Page): Promise<void> {
   const expandButton = page.locator('[title="Expand config editor"]');
-  expandButton.click();
+  await expandButton.click();
+  await page.waitForSelector('.monaco-editor-config', {state: 'visible'});
 }
 
 const TEST_SOURCE = `export default function TestComponent({ x }) {

compiler/apps/playground/components/AccordionWindow.tsx

@@ -18,6 +18,7 @@ export default function AccordionWindow(props: {
   changedPasses: Set<string>;
 }): React.ReactElement {
   return (
+    <div className="flex-1 min-w-[550px] sm:min-w-0">
       <div className="flex flex-row h-full">
         {Array.from(props.tabs.keys()).map(name => {
           return (
@@ -32,6 +33,7 @@ export default function AccordionWindow(props: {
           );
         })}
       </div>
+    </div>
   );
 }
 

compiler/apps/playground/components/Editor/ConfigEditor.tsx

@@ -9,12 +9,19 @@ import MonacoEditor, {loader, type Monaco} from '@monaco-editor/react';
 import {PluginOptions} from 'babel-plugin-react-compiler';
 import type {editor} from 'monaco-editor';
 import * as monaco from 'monaco-editor';
-import React, {useState, useRef} from 'react';
+import React, {
+  useState,
+  useRef,
+  unstable_ViewTransition as ViewTransition,
+  unstable_addTransitionType as addTransitionType,
+  startTransition,
+} from 'react';
 import {Resizable} from 're-resizable';
 import {useStore, useStoreDispatch} from '../StoreContext';
 import {monacoOptions} from './monacoOptions';
 import {IconChevron} from '../Icons/IconChevron';
 import prettyFormat from 'pretty-format';
+import {CONFIG_PANEL_TRANSITION} from '../../lib/transitionTypes';
 
 // @ts-expect-error - webpack asset/source loader handles .d.ts files as strings
 import compilerTypeDefs from 'babel-plugin-react-compiler/dist/index.d.ts';
@@ -36,7 +43,12 @@ export default function ConfigEditor({
           display: isExpanded ? 'block' : 'none',
         }}>
         <ExpandedEditor
-          onToggle={setIsExpanded}
+          onToggle={() => {
+            startTransition(() => {
+              addTransitionType(CONFIG_PANEL_TRANSITION);
+              setIsExpanded(false);
+            });
+          }}
           appliedOptions={appliedOptions}
         />
       </div>
@@ -44,7 +56,14 @@ export default function ConfigEditor({
         style={{
           display: !isExpanded ? 'block' : 'none',
         }}>
-        <CollapsedEditor onToggle={setIsExpanded} />
+        <CollapsedEditor
+          onToggle={() => {
+            startTransition(() => {
+              addTransitionType(CONFIG_PANEL_TRANSITION);
+              setIsExpanded(true);
+            });
+          }}
+        />
       </div>
     </>
   );
@@ -54,7 +73,7 @@ function ExpandedEditor({
   onToggle,
   appliedOptions,
 }: {
-  onToggle: (expanded: boolean) => void;
+  onToggle: () => void;
   appliedOptions: PluginOptions | null;
 }): React.ReactElement {
   const store = useStore();
@@ -111,6 +130,8 @@ function ExpandedEditor({
     : 'Invalid configs';
 
   return (
+    <ViewTransition
+      update={{[CONFIG_PANEL_TRANSITION]: 'slide-in', default: 'none'}}>
       <Resizable
         minWidth={300}
         maxWidth={600}
@@ -120,7 +141,7 @@ function ExpandedEditor({
           <div
             className="absolute w-8 h-16 bg-blue-10 rounded-r-full flex items-center justify-center z-[2] cursor-pointer border border-l-0 border-gray-300"
             title="Minimize config editor"
-          onClick={() => onToggle(false)}
+            onClick={onToggle}
             style={{
               top: '50%',
               marginTop: '-32px',
@@ -188,13 +209,14 @@ function ExpandedEditor({
           </div>
         </div>
       </Resizable>
+    </ViewTransition>
   );
 }
 
 function CollapsedEditor({
   onToggle,
 }: {
-  onToggle: (expanded: boolean) => void;
+  onToggle: () => void;
 }): React.ReactElement {
   return (
     <div
@@ -203,7 +225,7 @@ function CollapsedEditor({
       <div
         className="absolute w-10 h-16 bg-blue-10 hover:translate-x-2 transition-transform rounded-r-full flex items-center justify-center z-[2] cursor-pointer border border-gray-300"
         title="Expand config editor"
-        onClick={() => onToggle(true)}
+        onClick={onToggle}
         style={{
           top: '50%',
           marginTop: '-32px',

compiler/apps/playground/components/Editor/EditorImpl.tsx

@@ -343,14 +343,10 @@ export default function Editor(): JSX.Element {
           <ConfigEditor appliedOptions={appliedOptions} />
         </div>
         <div className="flex flex-1 min-w-0">
-          <div className="flex-1 min-w-[550px] sm:min-w-0">
           <Input language={language} errors={errors} />
-          </div>
-          <div className="flex-1 min-w-[550px] sm:min-w-0">
           <Output store={deferredStore} compilerOutput={mergedOutput} />
         </div>
       </div>
-      </div>
     </>
   );
 }

compiler/apps/playground/components/Editor/Input.tsx

@@ -13,11 +13,17 @@ import {
 import invariant from 'invariant';
 import type {editor} from 'monaco-editor';
 import * as monaco from 'monaco-editor';
-import {useEffect, useState} from 'react';
+import {
+  useEffect,
+  useState,
+  unstable_ViewTransition as ViewTransition,
+} from 'react';
 import {renderReactCompilerMarkers} from '../../lib/reactCompilerMonacoDiagnostics';
 import {useStore, useStoreDispatch} from '../StoreContext';
 import TabbedWindow from '../TabbedWindow';
 import {monacoOptions} from './monacoOptions';
+import {CONFIG_PANEL_TRANSITION} from '../../lib/transitionTypes';
+
 // @ts-expect-error TODO: Make TS recognize .d.ts files, in addition to loading them with webpack.
 import React$Types from '../../node_modules/@types/react/index.d.ts';
 
@@ -155,9 +161,13 @@ export default function Input({errors, language}: Props): JSX.Element {
   const [activeTab, setActiveTab] = useState('Input');
 
   return (
-    <div className="relative flex flex-col flex-none border-r border-gray-200">
-      <div className="!h-[calc(100vh_-_3.5rem)]">
-        <div className="flex flex-col h-full">
+    <ViewTransition
+      update={{
+        [CONFIG_PANEL_TRANSITION]: 'container',
+        default: 'none',
+      }}>
+      <div className="flex-1 min-w-[550px] sm:min-w-0">
+        <div className="flex flex-col h-full !h-[calc(100vh_-_3.5rem)] border-r border-gray-200">
           <TabbedWindow
             tabs={tabs}
             activeTab={activeTab}
@@ -165,6 +175,6 @@ export default function Input({errors, language}: Props): JSX.Element {
           />
         </div>
       </div>
-    </div>
+    </ViewTransition>
   );
 }

compiler/apps/playground/components/Editor/Output.tsx

@@ -20,11 +20,19 @@ import parserBabel from 'prettier/plugins/babel';
 import * as prettierPluginEstree from 'prettier/plugins/estree';
 import * as prettier from 'prettier/standalone';
 import {type Store} from '../../lib/stores';
-import {memo, ReactNode, use, useState, Suspense} from 'react';
+import {
+  memo,
+  ReactNode,
+  use,
+  useState,
+  Suspense,
+  unstable_ViewTransition as ViewTransition,
+} from 'react';
 import AccordionWindow from '../AccordionWindow';
 import TabbedWindow from '../TabbedWindow';
 import {monacoOptions} from './monacoOptions';
 import {BabelFileResult} from '@babel/core';
+import {CONFIG_PANEL_TRANSITION} from '../../lib/transitionTypes';
 import {LRUCache} from 'lru-cache';
 
 const MemoizedOutput = memo(Output);
@@ -280,15 +288,26 @@ function OutputContent({store, compilerOutput}: Props): JSX.Element {
 
   if (!store.showInternals) {
     return (
+      <ViewTransition
+        update={{
+          [CONFIG_PANEL_TRANSITION]: 'container',
+          default: 'none',
+        }}>
         <TabbedWindow
           tabs={tabs}
           activeTab={activeTab}
           onTabChange={setActiveTab}
         />
+      </ViewTransition>
     );
   }
 
   return (
+    <ViewTransition
+      update={{
+        [CONFIG_PANEL_TRANSITION]: 'accordion-container',
+        default: 'none',
+      }}>
       <AccordionWindow
         defaultTab={store.showInternals ? 'HIR' : 'Output'}
         setTabsOpen={setTabsOpen}
@@ -296,6 +315,7 @@ function OutputContent({store, compilerOutput}: Props): JSX.Element {
         tabs={tabs}
         changedPasses={changedPasses}
       />
+    </ViewTransition>
   );
 }
 

compiler/apps/playground/components/TabbedWindow.tsx

@@ -17,6 +17,7 @@ export default function TabbedWindow({
   onTabChange: (tab: string) => void;
 }): React.ReactElement {
   return (
+    <div className="flex-1 min-w-[550px] sm:min-w-0">
       <div className="flex flex-col h-full max-w-full">
         <div className="flex p-2 flex-shrink-0">
           {Array.from(tabs.keys()).map(tab => {
@@ -39,5 +40,6 @@ export default function TabbedWindow({
           {tabs.get(activeTab)}
         </div>
       </div>
+    </div>
   );
 }

compiler/apps/playground/lib/transitionTypes.ts

@@ -0,0 +1,8 @@
+/**
+ * Copyright (c) Meta Platforms, Inc. and affiliates.
+ *
+ * This source code is licensed under the MIT license found in the
+ * LICENSE file in the root directory of this source tree.
+ */
+
+export const CONFIG_PANEL_TRANSITION = 'config-panel';

compiler/apps/playground/next.config.js

@@ -11,6 +11,7 @@ const path = require('path');
 const nextConfig = {
   experimental: {
     reactCompiler: true,
+    viewTransition: true,
   },
   reactStrictMode: true,
   webpack: (config, options) => {

compiler/apps/playground/styles/globals.css

@@ -69,3 +69,42 @@
     scrollbar-width: none; /* Firefox */
   }
 }
+
+::view-transition-old(.slide-in) {
+  animation-name: slideOutLeft;
+}
+::view-transition-new(.slide-in) {
+  animation-name: slideInLeft;
+}
+::view-transition-group(.slide-in) {
+  z-index: 1;
+}
+
+@keyframes slideOutLeft {
+  from {
+    transform: translateX(0);
+  }
+  to {
+    transform: translateX(-100%);
+  }
+}
+@keyframes slideInLeft {
+  from {
+    transform: translateX(-100%);
+  }
+  to {
+    transform: translateX(0);
+  }
+}
+
+::view-transition-old(.container),
+::view-transition-new(.container) {
+  height: 100%;
+}
+
+::view-transition-old(.accordion-container),
+::view-transition-new(.accordion-container) {
+  height: 100%;
+  object-fit: none;
+  object-position: left;
+}