[DevTools] Show component names while highlighting renders (facebook#…

…31577)

## Summary
This PR improves the Trace Updates feature by letting developers see
component names directly on the update overlay. Before this change, the
overlay only highlighted updated regions, leaving it unclear which
components were involved. With this update, you can now match visual
updates to their corresponding components, making it much easier to
debug rendering performance.

### New Feature: Show component names while highlighting
When the new **"Show component names while highlighting"** setting is
enabled, the update overlay display the names of affected components
above the rectangles, along with the update count. This gives immediate
context about what’s rendering and why. The preference is stored in
local storage and synced with the backend, so it’s remembered across
sessions.

### Improvements to Drawing Logic
The drawing logic has been updated to make the overlay sharper and
easier to read. Overlay now respect device pixel ratios, so they look
great on high-DPI screens. Outlines have also been made crisper, which
makes it easier to spot exactly where updates are happening.

> [!NOTE]
> **Grouping Logic and Limitations**
> Updates are grouped by their screen position `(left, top coordinates)`
to combine overlapping or nearby regions into a single group. Groups are
sorted by the highest update count within each group, making the most
frequently updated components stand out.
> Overlapping labels may still occur when multiple updates involve
components that overlap but are not in the exact same position. This is
intentional, as the logic aims to maintain a straightforward mapping
between update regions and component names without introducing
unnecessary complexity.

### Testing
This PR also adds tests for the new `groupAndSortNodes` utility, which
handles the logic for grouping and sorting updates. The tests ensure the
behavior is reliable across different scenarios.

## Before & After


https://github.com/user-attachments/assets/6ea0fe3e-9354-44fa-95f3-9a867554f74c


https://github.com/user-attachments/assets/32af4d98-92a5-47dd-a732-f05c2293e41b

---------

Co-authored-by: Ruslan Lesiutin <[email protected]>

packages/react-devtools-shared/src/__tests__/traceUpdates-test.js

@@ -0,0 +1,269 @@
+import {groupAndSortNodes} from 'react-devtools-shared/src/backend/views/TraceUpdates/canvas';
+
+describe('Trace updates group and sort nodes', () => {
+  test('should group nodes by position without changing order within group', () => {
+    const nodeToData = new Map([
+      [
+        {id: 1},
+        {
+          rect: {left: 0, top: 0, width: 100, height: 100},
+          color: '#80b393',
+          displayName: 'Node1',
+          count: 3,
+        },
+      ],
+      [
+        {id: 2},
+        {
+          rect: {left: 0, top: 0, width: 100, height: 100},
+          color: '#63b19e',
+          displayName: 'Node2',
+          count: 2,
+        },
+      ],
+    ]);
+
+    const result = groupAndSortNodes(nodeToData);
+
+    expect(result).toEqual([
+      [
+        {
+          rect: {left: 0, top: 0, width: 100, height: 100},
+          color: '#80b393',
+          displayName: 'Node1',
+          count: 3,
+        },
+        {
+          rect: {left: 0, top: 0, width: 100, height: 100},
+          color: '#63b19e',
+          displayName: 'Node2',
+          count: 2,
+        },
+      ],
+    ]);
+  });
+
+  test('should sort groups by lowest count in each group', () => {
+    const nodeToData = new Map([
+      [
+        {id: 1},
+        {
+          rect: {left: 0, top: 0, width: 100, height: 100},
+          color: '#97b488',
+          displayName: 'Group1',
+          count: 4,
+        },
+      ],
+      [
+        {id: 2},
+        {
+          rect: {left: 100, top: 0, width: 100, height: 100},
+          color: '#37afa9',
+          displayName: 'Group2',
+          count: 1,
+        },
+      ],
+      [
+        {id: 3},
+        {
+          rect: {left: 200, top: 0, width: 100, height: 100},
+          color: '#63b19e',
+          displayName: 'Group3',
+          count: 2,
+        },
+      ],
+    ]);
+
+    const result = groupAndSortNodes(nodeToData);
+
+    expect(result).toEqual([
+      [
+        {
+          rect: {left: 100, top: 0, width: 100, height: 100},
+          color: '#37afa9',
+          displayName: 'Group2',
+          count: 1,
+        },
+      ],
+      [
+        {
+          rect: {left: 200, top: 0, width: 100, height: 100},
+          color: '#63b19e',
+          displayName: 'Group3',
+          count: 2,
+        },
+      ],
+      [
+        {
+          rect: {left: 0, top: 0, width: 100, height: 100},
+          color: '#97b488',
+          displayName: 'Group1',
+          count: 4,
+        },
+      ],
+    ]);
+  });
+
+  test('should maintain order within groups while sorting groups by lowest count', () => {
+    const nodeToData = new Map([
+      [
+        {id: 1},
+        {
+          rect: {left: 0, top: 0, width: 50, height: 50},
+          color: '#97b488',
+          displayName: 'Pos1Node1',
+          count: 4,
+        },
+      ],
+      [
+        {id: 2},
+        {
+          rect: {left: 0, top: 0, width: 60, height: 60},
+          color: '#63b19e',
+          displayName: 'Pos1Node2',
+          count: 2,
+        },
+      ],
+      [
+        {id: 3},
+        {
+          rect: {left: 100, top: 0, width: 70, height: 70},
+          color: '#80b393',
+          displayName: 'Pos2Node1',
+          count: 3,
+        },
+      ],
+      [
+        {id: 4},
+        {
+          rect: {left: 100, top: 0, width: 80, height: 80},
+          color: '#37afa9',
+          displayName: 'Pos2Node2',
+          count: 1,
+        },
+      ],
+    ]);
+
+    const result = groupAndSortNodes(nodeToData);
+
+    expect(result).toEqual([
+      [
+        {
+          rect: {left: 100, top: 0, width: 70, height: 70},
+          color: '#80b393',
+          displayName: 'Pos2Node1',
+          count: 3,
+        },
+        {
+          rect: {left: 100, top: 0, width: 80, height: 80},
+          color: '#37afa9',
+          displayName: 'Pos2Node2',
+          count: 1,
+        },
+      ],
+      [
+        {
+          rect: {left: 0, top: 0, width: 50, height: 50},
+          color: '#97b488',
+          displayName: 'Pos1Node1',
+          count: 4,
+        },
+        {
+          rect: {left: 0, top: 0, width: 60, height: 60},
+          color: '#63b19e',
+          displayName: 'Pos1Node2',
+          count: 2,
+        },
+      ],
+    ]);
+  });
+
+  test('should handle multiple groups with same minimum count', () => {
+    const nodeToData = new Map([
+      [
+        {id: 1},
+        {
+          rect: {left: 0, top: 0, width: 100, height: 100},
+          color: '#37afa9',
+          displayName: 'Group1Node1',
+          count: 1,
+        },
+      ],
+      [
+        {id: 2},
+        {
+          rect: {left: 100, top: 0, width: 100, height: 100},
+          color: '#37afa9',
+          displayName: 'Group2Node1',
+          count: 1,
+        },
+      ],
+    ]);
+
+    const result = groupAndSortNodes(nodeToData);
+
+    expect(result).toEqual([
+      [
+        {
+          rect: {left: 0, top: 0, width: 100, height: 100},
+          color: '#37afa9',
+          displayName: 'Group1Node1',
+          count: 1,
+        },
+      ],
+      [
+        {
+          rect: {left: 100, top: 0, width: 100, height: 100},
+          color: '#37afa9',
+          displayName: 'Group2Node1',
+          count: 1,
+        },
+      ],
+    ]);
+  });
+
+  test('should filter out nodes without rect property', () => {
+    const nodeToData = new Map([
+      [
+        {id: 1},
+        {
+          rect: null,
+          color: '#37afa9',
+          displayName: 'NoRectNode',
+          count: 1,
+        },
+      ],
+      [
+        {id: 2},
+        {
+          rect: undefined,
+          color: '#63b19e',
+          displayName: 'UndefinedRectNode',
+          count: 2,
+        },
+      ],
+      [
+        {id: 3},
+        {
+          rect: {left: 0, top: 0, width: 100, height: 100},
+          color: '#80b393',
+          displayName: 'ValidNode',
+          count: 3,
+        },
+      ],
+    ]);
+
+    const result = groupAndSortNodes(nodeToData);
+
+    expect(result).toEqual([
+      [
+        {
+          rect: {left: 0, top: 0, width: 100, height: 100},
+          color: '#80b393',
+          displayName: 'ValidNode',
+          count: 3,
+        },
+      ],
+    ]);
+  });
+});

packages/react-devtools-shared/src/backend/agent.js

@@ -28,6 +28,7 @@ import type {
   DevToolsHookSettings,
 } from './types';
 import type {ComponentFilter} from 'react-devtools-shared/src/frontend/types';
+import type {GroupItem} from './views/TraceUpdates/canvas';
 import {isReactNativeEnvironment} from './utils';
 import {
   sessionStorageGetItem,
@@ -142,10 +143,12 @@ export default class Agent extends EventEmitter<{
   shutdown: [],
   traceUpdates: [Set<HostInstance>],
   drawTraceUpdates: [Array<HostInstance>],
+  drawGroupedTraceUpdatesWithNames: [Array<Array<GroupItem>>],
   disableTraceUpdates: [],
   getIfHasUnsupportedRendererVersion: [],
   updateHookSettings: [$ReadOnly<DevToolsHookSettings>],
   getHookSettings: [],
+  showNamesWhenTracing: [boolean],
 }> {
   _bridge: BackendBridge;
   _isProfiling: boolean = false;
@@ -156,6 +159,7 @@ export default class Agent extends EventEmitter<{
   _onReloadAndProfile:
     | ((recordChangeDescriptions: boolean, recordTimeline: boolean) => void)
     | void;
+  _showNamesWhenTracing: boolean = true;
 
   constructor(
     bridge: BackendBridge,
@@ -200,6 +204,7 @@ export default class Agent extends EventEmitter<{
     bridge.addListener('reloadAndProfile', this.reloadAndProfile);
     bridge.addListener('renamePath', this.renamePath);
     bridge.addListener('setTraceUpdatesEnabled', this.setTraceUpdatesEnabled);
+    bridge.addListener('setShowNamesWhenTracing', this.setShowNamesWhenTracing);
     bridge.addListener('startProfiling', this.startProfiling);
     bridge.addListener('stopProfiling', this.stopProfiling);
     bridge.addListener('storeAsGlobal', this.storeAsGlobal);
@@ -722,6 +727,7 @@ export default class Agent extends EventEmitter<{
       this._traceUpdatesEnabled = traceUpdatesEnabled;
 
       setTraceUpdatesEnabled(traceUpdatesEnabled);
+      this.emit('showNamesWhenTracing', this._showNamesWhenTracing);
 
       for (const rendererID in this._rendererInterfaces) {
         const renderer = ((this._rendererInterfaces[
@@ -731,6 +737,14 @@ export default class Agent extends EventEmitter<{
       }
     };
 
+  setShowNamesWhenTracing: (show: boolean) => void = show => {
+    if (this._showNamesWhenTracing === show) {
+      return;
+    }
+    this._showNamesWhenTracing = show;
+    this.emit('showNamesWhenTracing', show);
+  };
+
   syncSelectionFromBuiltinElementsPanel: () => void = () => {
     const target = window.__REACT_DEVTOOLS_GLOBAL_HOOK__.$0;
     if (target == null) {