# UC-019: Mouse Enter/Leave Events

**As a** Vaadin application developer, **I want to** react to mouse hover on entries **so that** I can show tooltips or highlight related information.

**Status:** Implemented
**Date:** 2026-03-21

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## Scope

**Addon module:** addon
**Related Options:** —
**Related Events:** `EntryMouseEnterEvent`, `EntryMouseLeaveEvent`

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## User-Facing Behavior

- When the mouse enters an entry element, `EntryMouseEnterEvent` fires
- When the mouse leaves, `EntryMouseLeaveEvent` fires
- Useful for showing tooltips, detail panels, or highlighting

### Tooltip Pattern

The native HTML `title` attribute (set via `ENTRY_DID_MOUNT`) provides basic tooltips but is **not accessible** on touch or keyboard-only devices. For accessible tooltips, use a Vaadin `Tooltip` component or a custom overlay positioned relative to the entry element. See UC-016 for the `ENTRY_DID_MOUNT` callback pattern.

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## Java API Usage

```java
calendar.addEntryMouseEnterListener(event -> {
    Entry entry = event.getEntry();
    // show tooltip or detail panel
});

calendar.addEntryMouseLeaveListener(event -> {
    // hide tooltip
});
```

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## Business Rules

| ID | Rule |
|----|------|
| BR-01 | Events fire for all visible entries regardless of editable state |
| BR-02 | Events contain the entry reference |

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## Acceptance Criteria

- [ ] `EntryMouseEnterEvent` fires when hovering an entry
- [ ] `EntryMouseLeaveEvent` fires when leaving an entry
- [ ] Events contain correct entry data

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## Tests

### Unit Tests
- [ ] No dedicated unit tests — hover events are covered by E2E tests

### E2E Tests
- [ ] `calendar-entry.spec.js` — hover events

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## Related FullCalendar Docs

- [eventMouseEnter](https://fullcalendar.io/docs/eventMouseEnter)
- [eventMouseLeave](https://fullcalendar.io/docs/eventMouseLeave)