[DevTools] Show component names while highlighting renders

[piotrski]

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

Before.mov

After.with.labels.mov

[vercel]

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Name	Status	Preview	Comments	Updated (UTC)
react-compiler-playground	✅ Ready (Inspect)	Visit Preview	💬 Add feedback	Nov 19, 2024 11:13am