⚡ Optimize FancyCursor by replacing elementFromPoint with event delegation #6

2026-01-22T08:23:05Z

google-labs-jules[bot] commented

2026-01-22 08:23:05 +00:00

(Migrated from github.com)

💡 What:
Replaced the expensive document.elementFromPoint(x, y) call inside the mousemove animation loop with a global mouseover listener that caches the current hovered element.

🎯 Why:
elementFromPoint forces a layout recalculation (reflow) which is very expensive to do on every mouse move / animation frame, causing jank. Event delegation via mouseover is much more efficient as it only fires when the target changes and provides the element directly.

📊 Measured Improvement:

Baseline: document.elementFromPoint causes layout thrashing on every frame.
Improvement: Accessing a cached variable is O(1) and instant.
Note: A synthetic benchmark was attempted but could not be run in the CI environment because JSDOM lacks document.elementFromPoint. However, this is a standard performance optimization pattern. The functionality was verified with new unit tests ensuring correct hover state detection.

PR created automatically by Jules for task 18391845640472037951 started by @ragusa-it

💡 **What:** Replaced the expensive `document.elementFromPoint(x, y)` call inside the `mousemove` animation loop with a global `mouseover` listener that caches the current hovered element. 🎯 **Why:** `elementFromPoint` forces a layout recalculation (reflow) which is very expensive to do on every mouse move / animation frame, causing jank. Event delegation via `mouseover` is much more efficient as it only fires when the target changes and provides the element directly. 📊 **Measured Improvement:** * **Baseline:** `document.elementFromPoint` causes layout thrashing on every frame. * **Improvement:** Accessing a cached variable is O(1) and instant. * **Note:** A synthetic benchmark was attempted but could not be run in the CI environment because JSDOM lacks `document.elementFromPoint`. However, this is a standard performance optimization pattern. The functionality was verified with new unit tests ensuring correct hover state detection. --- *PR created automatically by Jules for task [18391845640472037951](https://jules.google.com/task/18391845640472037951) started by @ragusa-it*

google-labs-jules[bot] commented

2026-01-22 08:23:06 +00:00

(Migrated from github.com)

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👋 Jules, reporting for duty! I'm here to lend a hand with this pull request. When you start a review, I'll add a 👀 emoji to each comment to let you know I've read it. I'll focus on feedback directed at me and will do my best to stay out of conversations between you and other bots or reviewers to keep the noise down. I'll push a commit with your requested changes shortly after. Please note there might be a delay between these steps, but rest assured I'm on the job! For more direct control, you can switch me to **Reactive Mode**. When this mode is on, I will only act on comments where you specifically mention me with `@jules`. You can find this option in the **Pull Request** section of your [global Jules UI settings](https://jules.google.com/settings). You can always switch back! New to Jules? Learn more at [jules.google/docs](https://jules.google/docs). --- *_For security, I will only act on instructions from the user who triggered this task._*

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Reference: ragusa-it/ragusaitweb#6