fix[DevTools/Tree]: only scroll to item when panel is visible

packages/react-devtools-extensions/src/main/index.js

@@ -206,8 +206,12 @@ function createComponentsPanel() {
         }
       });
 
-      // TODO: we should listen to createdPanel.onHidden to unmount some listeners
-      // and potentially stop highlighting
+      createdPanel.onShown.addListener(() => {
+        bridge.emit('extensionComponentsPanelShown');
+      });
+      createdPanel.onHidden.addListener(() => {
+        bridge.emit('extensionComponentsPanelHidden');
+      });
     },
   );
 }

packages/react-devtools-shared/src/bridge.js

@@ -217,6 +217,8 @@ type FrontendEvents = {
   clearWarningsForElementID: [ElementAndRendererID],
   copyElementPath: [CopyElementPathParams],
   deletePath: [DeletePath],
+  extensionComponentsPanelShown: [],
+  extensionComponentsPanelHidden: [],
   getBackendVersion: [],
   getBridgeProtocol: [],
   getIfHasUnsupportedRendererVersion: [],

packages/react-devtools-shared/src/devtools/views/Components/Tree.js

@@ -37,6 +37,7 @@ import styles from './Tree.css';
 import ButtonIcon from '../ButtonIcon';
 import Button from '../Button';
 import {logEvent} from 'react-devtools-shared/src/Logger';
+import {useExtensionComponentsPanelVisibility} from 'react-devtools-shared/src/frontend/hooks/useExtensionComponentsPanelVisibility';
 
 // Never indent more than this number of pixels (even if we have the room).
 const DEFAULT_INDENTATION_SIZE = 12;
@@ -76,36 +77,28 @@ export default function Tree(): React.Node {
   const bridge = useContext(BridgeContext);
   const store = useContext(StoreContext);
   const {hideSettings} = useContext(OptionsContext);
+  const {lineHeight} = useContext(SettingsContext);
+
   const [isNavigatingWithKeyboard, setIsNavigatingWithKeyboard] =
     useState(false);
   const {highlightHostInstance, clearHighlightHostInstance} =
     useHighlightHostInstance();
+  const [treeFocused, setTreeFocused] = useState<boolean>(false);
+  const componentsPanelVisible = useExtensionComponentsPanelVisibility(bridge);
+
   const treeRef = useRef<HTMLDivElement | null>(null);
   const focusTargetRef = useRef<HTMLDivElement | null>(null);
+  const listRef = useRef(null);
 
-  const [treeFocused, setTreeFocused] = useState<boolean>(false);
-
-  const {lineHeight} = useContext(SettingsContext);
+  useEffect(() => {
+    if (!componentsPanelVisible) {
+      return;
+    }
 
-  // Make sure a newly selected element is visible in the list.
-  // This is helpful for things like the owners list and search.
-  //
-  // TRICKY:
-  // It's important to use a callback ref for this, rather than a ref object and an effect.
-  // As an optimization, the AutoSizer component does not render children when their size would be 0.
-  // This means that in some cases (if the browser panel size is initially really small),
-  // the Tree component might render without rendering an inner List.
-  // In this case, the list ref would be null on mount (when the scroll effect runs),
-  // meaning the scroll action would be skipped (since ref updates don't re-run effects).
-  // Using a callback ref accounts for this case...
-  const listCallbackRef = useCallback(
-    (list: $FlowFixMe) => {
-      if (list != null && inspectedElementIndex !== null) {
-        list.scrollToItem(inspectedElementIndex, 'smart');
-      }
-    },
-    [inspectedElementIndex],
-  );
+    if (listRef.current != null && inspectedElementIndex !== null) {
+      listRef.current.scrollToItem(inspectedElementIndex, 'smart');
+    }
+  }, [inspectedElementIndex, componentsPanelVisible]);
 
   // Picking an element in the inspector should put focus into the tree.
   // If possible, navigation works right after picking a node.
@@ -426,7 +419,7 @@ export default function Tree(): React.Node {
                   itemData={itemData}
                   itemKey={itemKey}
                   itemSize={lineHeight}
-                  ref={listCallbackRef}
+                  ref={listRef}
                   width={width}>
                   {Element}
                 </FixedSizeList>

packages/react-devtools-shared/src/frontend/hooks/useExtensionComponentsPanelVisibility.js

@@ -0,0 +1,38 @@
+/**
+ * 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.
+ *
+ * @flow
+ */
+
+import {useState, useEffect} from 'react';
+import type {FrontendBridge} from 'react-devtools-shared/src/bridge';
+
+// Events that are prefixed with `extension` will only be emitted for the browser extension implementation.
+// For other implementations, this hook will just return constant `true` value.
+export function useExtensionComponentsPanelVisibility(
+  bridge: FrontendBridge,
+): boolean {
+  const [isVisible, setIsVisible] = useState(true);
+
+  useEffect(() => {
+    function onPanelShown() {
+      setIsVisible(true);
+    }
+    function onPanelHidden() {
+      setIsVisible(false);
+    }
+
+    bridge.addListener('extensionComponentsPanelShown', onPanelShown);
+    bridge.addListener('extensionComponentsPanelHidden', onPanelHidden);
+
+    return () => {
+      bridge.removeListener('extensionComponentsPanelShown', onPanelShown);
+      bridge.removeListener('extensionComponentsPanelHidden', onPanelHidden);
+    };
+  }, [bridge]);
+
+  return isVisible;
+}