refactor[devtools]: highlight an array of elements for native (#27734)

We are currently just pass the first element, which diverges from the
implementation for web. This is especially bad if you are inspecting
something like a list, where host fiber can represent multiple elements.

This part runs on the backend of React DevTools, so it should not affect
cases for React Native when frontend version can be more up-to-date than
backend's. I will double-check it before merging.

Once version of `react-devtools-core` is updated in React Native, this
should be supported, I will work on that later.

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

@@ -283,3 +283,9 @@ export function gt(a: string = '', b: string = ''): boolean {
 export function gte(a: string = '', b: string = ''): boolean {
   return compareVersions(a, b) > -1;
 }
+
+export const isReactNativeEnvironment = (): boolean => {
+  // We've been relying on this for such a long time
+  // We should probably define the client for DevTools on the backend side and share it with the frontend
+  return window.document == null;
+};

packages/react-devtools-shared/src/backend/views/Highlighter/Highlighter.js

@@ -9,6 +9,8 @@
 
 import type Agent from 'react-devtools-shared/src/backend/agent';
 
+import {isReactNativeEnvironment} from 'react-devtools-shared/src/backend/utils';
+
 import Overlay from './Overlay';
 
 const SHOW_DURATION = 2000;
@@ -16,11 +18,11 @@ const SHOW_DURATION = 2000;
 let timeoutID: TimeoutID | null = null;
 let overlay: Overlay | null = null;
 
-export function hideOverlay(agent: Agent) {
-  if (window.document == null) {
-    agent.emit('hideNativeHighlight');
-    return;
-  }
+function hideOverlayNative(agent: Agent): void {
+  agent.emit('hideNativeHighlight');
+}
+
+function hideOverlayWeb(): void {
   timeoutID = null;
 
   if (overlay !== null) {
@@ -29,27 +31,26 @@ export function hideOverlay(agent: Agent) {
   }
 }
 
-export function showOverlay(
-  elements: Array<HTMLElement> | null,
+export function hideOverlay(agent: Agent): void {
+  return isReactNativeEnvironment()
+    ? hideOverlayNative(agent)
+    : hideOverlayWeb();
+}
+
+function showOverlayNative(elements: Array<HTMLElement>, agent: Agent): void {
+  agent.emit('showNativeHighlight', elements);
+}
+
+function showOverlayWeb(
+  elements: Array<HTMLElement>,
   componentName: string | null,
   agent: Agent,
   hideAfterTimeout: boolean,
-) {
-  if (window.document == null) {
-    if (elements != null && elements[0] != null) {
-      agent.emit('showNativeHighlight', elements[0]);
-    }
-    return;
-  }
-
+): void {
   if (timeoutID !== null) {
     clearTimeout(timeoutID);
   }
 
-  if (elements == null) {
-    return;
-  }
-
   if (overlay === null) {
     overlay = new Overlay(agent);
   }
@@ -60,3 +61,14 @@ export function showOverlay(
     timeoutID = setTimeout(() => hideOverlay(agent), SHOW_DURATION);
   }
 }
+
+export function showOverlay(
+  elements: Array<HTMLElement>,
+  componentName: string | null,
+  agent: Agent,
+  hideAfterTimeout: boolean,
+): void {
+  return isReactNativeEnvironment()
+    ? showOverlayNative(elements, agent)
+    : showOverlayWeb(elements, componentName, agent, hideAfterTimeout);
+}

packages/react-devtools-shared/src/backend/views/TraceUpdates/canvas.js

@@ -12,6 +12,8 @@ import type {Rect} from '../utils';
 import type {NativeType} from '../../types';
 import type Agent from '../../agent';
 
+import {isReactNativeEnvironment} from 'react-devtools-shared/src/backend/utils';
+
 const OUTLINE_COLOR = '#f0f0f0';
 
 // Note these colors are in sync with DevTools Profiler chart colors.
@@ -30,17 +32,16 @@ const COLORS = [
 
 let canvas: HTMLCanvasElement | null = null;
 
-export function draw(nodeToData: Map<NativeType, Data>, agent: Agent): void {
-  if (window.document == null) {
-    const nodesToDraw = [];
-    iterateNodes(nodeToData, (_, color, node) => {
-      nodesToDraw.push({node, color});
-    });
+function drawNative(nodeToData: Map<NativeType, Data>, agent: Agent) {
+  const nodesToDraw = [];
+  iterateNodes(nodeToData, (_, color, node) => {
+    nodesToDraw.push({node, color});
+  });
 
-    agent.emit('drawTraceUpdates', nodesToDraw);
-    return;
-  }
+  agent.emit('drawTraceUpdates', nodesToDraw);
+}
 
+function drawWeb(nodeToData: Map<NativeType, Data>) {
   if (canvas === null) {
     initialize();
   }
@@ -58,6 +59,12 @@ export function draw(nodeToData: Map<NativeType, Data>, agent: Agent): void {
   });
 }
 
+export function draw(nodeToData: Map<NativeType, Data>, agent: Agent): void {
+  return isReactNativeEnvironment()
+    ? drawNative(nodeToData, agent)
+    : drawWeb(nodeToData);
+}
+
 function iterateNodes(
   nodeToData: Map<NativeType, Data>,
   execute: (rect: Rect | null, color: string, node: NativeType) => void,
@@ -97,12 +104,11 @@ function drawBorder(
   context.setLineDash([0]);
 }
 
-export function destroy(agent: Agent): void {
-  if (window.document == null) {
-    agent.emit('disableTraceUpdates');
-    return;
-  }
+function destroyNative(agent: Agent) {
+  agent.emit('disableTraceUpdates');
+}
 
+function destroyWeb() {
   if (canvas !== null) {
     if (canvas.parentNode != null) {
       canvas.parentNode.removeChild(canvas);
@@ -111,6 +117,10 @@ export function destroy(agent: Agent): void {
   }
 }
 
+export function destroy(agent: Agent): void {
+  return isReactNativeEnvironment() ? destroyNative(agent) : destroyWeb();
+}
+
 function initialize(): void {
   canvas = window.document.createElement('canvas');
   canvas.style.cssText = `