feat(input): add pressedPosition and target/currentTarget to pointer event data

[cptbtptpbcptdtptp]

Summary

• Pointer.pressedPosition: captures screen position at pointer-down, useful for drag threshold and gesture recognition
• PointerEventData.target: the deepest hit-tested entity (stays constant during bubble)
• PointerEventData.currentTarget: the entity currently handling the event (changes during bubble traversal)

Aligns the event model with the DOM convention (event.target vs event.currentTarget).

Test plan

• Existing tests pass (pnpm run test)
• Verify target stays as the deepest entity during bubble; currentTarget changes per handler
• Verify pressedPosition is captured at pointer-down and does not change during drag

🤖 Generated with Claude Code

Summary by CodeRabbit

• New Features
  • Added pressed-position tracking to pointer interactions so the original press coordinates remain stable during subsequent moves.
  • Pointer and UI event payloads now report both the deepest hit target and the current handling target during bubbling.
  • Improved click dispatch across UI elements to bubble consistently through the event path.
• Bug Fixes
  • More accurate enter/exit and click behavior when transitioning between entities in pointer and UI flows.
• Tests
  • Added coverage for pressed-position behavior, event target/currentTarget propagation, and pointer event data pool garbage collection.

[coderabbitai]

No actionable comments were generated in the recent review. 🎉

ℹ️ Recent review info

⚙️ Run configuration

Configuration used: Repository UI

Review profile: CHILL

Plan: Pro

Run ID: 4c6fc68f-30f9-4ff6-87cb-be2d9d8c5587

📥 Commits

Reviewing files that changed from the base of the PR and between f24b5e3 and 7b2a4d4.

📒 Files selected for processing (8)

• packages/core/src/Engine.ts
• packages/core/src/input/InputManager.ts
• packages/core/src/input/pointer/Pointer.ts
• packages/core/src/input/pointer/PointerManager.ts
• packages/core/src/input/pointer/emitter/PhysicsPointerEventEmitter.ts
• packages/ui/src/input/UIPointerEventEmitter.ts
• tests/src/core/input/InputManager.test.ts
• tests/src/ui/UIEvent.test.ts

💤 Files with no reviewable changes (1)

• packages/core/src/input/pointer/Pointer.ts

🚧 Files skipped from review as they are similar to previous changes (2)

• packages/core/src/input/pointer/emitter/PhysicsPointerEventEmitter.ts
• packages/ui/src/input/UIPointerEventEmitter.ts

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Walkthrough

This PR enriches pointer events with entity context information throughout the event pipeline. Pointer gains pressedPosition to track press location; PointerEventData adds target and currentTarget properties; event emitters refactor to thread entity references through event creation and bubbling workflows; and garbage collection infrastructure is added to reclaim event data pools.

Changes

Pointer Event Entity Context Tracking

Layer / File(s)	Summary
Pointer Event Data Contracts packages/core/src/input/pointer/Pointer.ts, packages/core/src/input/pointer/PointerEventData.ts	Pointer adds pressedPosition: Vector2 field and removes _addEmitters() method; PointerEventData adds target and currentTarget entity properties with disposal cleanup.
Core Event Data Factory with Entity Context packages/core/src/input/pointer/emitter/PointerEventEmitter.ts	_createEventData() signature changes from (pointer) to (pointer, target, currentTarget = target), populating event entity references and world position from hit result.
Pointer Down Position Capture packages/core/src/input/pointer/PointerManager.ts	On "pointerdown", pointer.pressedPosition is set from the event coordinates after phase transition.
Emitter Registration Refactoring packages/core/src/input/pointer/PointerManager.ts	Pointer emitter instantiation extracted into private _addEmitters() helper that conditionally adds PhysicsPointerEventEmitter and appends registered emitters.
Physics Emitter Event Creation with Entities packages/core/src/input/pointer/emitter/PhysicsPointerEventEmitter.ts	All event data creation calls now pass entity context to _createEventData() for drag, down, up, leave, and raycast enter/exit events.
UI Event Bubbling and Raycast State Management packages/ui/src/input/UIPointerEventEmitter.ts	_updateRaycast() accepts nullable renderer and creates per-entity event data for enter/exit handlers; click dispatch uses _bubble() which updates currentTarget per entity; _composedPath() accepts nullable element.
Garbage Collection Infrastructure packages/core/src/input/pointer/PointerManager.ts, packages/core/src/input/InputManager.ts, packages/core/src/Engine.ts	New _gc() methods added to enable garbage collection of pointer event data pools during engine cycles.
Tests: Pressed Position and GC Pool Behavior tests/src/core/input/InputManager.test.ts, tests/src/ui/UIEvent.test.ts	Tests verify pressedPosition remains fixed after pointerdown, engine._pendingGC() reclaims pool entries, and target/currentTarget track through bubbling hierarchy.

Estimated code review effort

🎯 3 (Moderate) | ⏱️ ~28 minutes

Poem

🐰 A pointer pressed, its position now keeps trace,
While events flow through targets, bubbling with grace,
Each entity marked on the path that they take,
Hit-tested, pooled, and collected—no event's opaque!

🚥 Pre-merge checks | ✅ 4 | ❌ 1

❌ Failed checks (1 warning)

Check name	Status	Explanation	Resolution
Docstring Coverage	⚠️ Warning	Docstring coverage is 0.00% which is insufficient. The required threshold is 80.00%.	Write docstrings for the functions missing them to satisfy the coverage threshold.

✅ Passed checks (4 passed)

Check name	Status	Explanation
Description Check	✅ Passed	Check skipped - CodeRabbit’s high-level summary is enabled.
Title check	✅ Passed	The title accurately describes the main changes: introducing pressedPosition to Pointer and target/currentTarget to PointerEventData for enhanced event tracking.
Linked Issues check	✅ Passed	Check skipped because no linked issues were found for this pull request.
Out of Scope Changes check	✅ Passed	Check skipped because no linked issues were found for this pull request.

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✨ Finishing Touches

📝 Generate docstrings

• Create stacked PR
• Commit on current branch

🧪 Generate unit tests (beta)

• Create PR with unit tests
• Commit unit tests in branch feat/pointer-event-target

---

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[codecov]

Codecov Report

❌ Patch coverage is 96.61017% with 2 lines in your changes missing coverage. Please review.
✅ Project coverage is 79.18%. Comparing base (97d8d61) to head (7b2a4d4).
⚠️ Report is 6 commits behind head on dev/2.0.

Files with missing lines	Patch %	Lines
packages/ui/src/input/UIPointerEventEmitter.ts	77.77%	2 Missing ⚠️

Additional details and impacted files

@@             Coverage Diff             @@
##           dev/2.0    #3031      +/-   ##
===========================================
+ Coverage    77.31%   79.18%   +1.86%     
===========================================
  Files          914      914              
  Lines       101723   101688      -35     
  Branches     10437    11214     +777     
===========================================
+ Hits         78647    80520    +1873     
+ Misses       22892    20981    -1911     
- Partials       184      187       +3     

Flag	Coverage Δ
unittests	79.18% <96.61%> (+1.86%)	⬆️

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[coderabbitai]

Actionable comments posted: 1

🤖 Prompt for all review comments with AI agents

Verify each finding against current code. Fix only still-valid issues, skip the
rest with a brief reason, keep changes minimal, and validate.

Inline comments:
In `@packages/core/src/input/pointer/PointerManager.ts`:
- Line 248: The code in PointerManager sets pointer.pressedPosition from
pointer.position (which was updated to latestEvent before the event loop), so a
batched pointerdown can record wrong coordinates; update the pointerdown branch
to copy coordinates from the current event (use event.position / event.clientX/Y
or the per-event coordinate object) instead of pointer.position, i.e., in the
pointerdown handling logic inside PointerManager, assign pressedPosition from
the event's coordinates rather than from pointer.position to ensure the down
location reflects that specific event.

🪄 Autofix (Beta)

Fix all unresolved CodeRabbit comments on this PR:

• Push a commit to this branch (recommended)
• Create a new PR with the fixes

---

ℹ️ Review info

⚙️ Run configuration

Configuration used: Repository UI

Review profile: CHILL

Plan: Pro

Run ID: befad6e6-c8c8-4571-86f8-25f80a822e1f

📥 Commits

Reviewing files that changed from the base of the PR and between de75496 and f24b5e3.

📒 Files selected for processing (6)

• packages/core/src/input/pointer/Pointer.ts
• packages/core/src/input/pointer/PointerEventData.ts
• packages/core/src/input/pointer/PointerManager.ts
• packages/core/src/input/pointer/emitter/PhysicsPointerEventEmitter.ts
• packages/core/src/input/pointer/emitter/PointerEventEmitter.ts
• packages/ui/src/input/UIPointerEventEmitter.ts

[GuoLei1990]

总结

本轮 HEAD 7b2a4d4 自上次 LGTM 以来未变（HEAD commit 时间 02:48 早于上轮 review 03:14），无新增 commit。逐项复核确认全部问题已闭环，故本次正式 APPROVE 解除历史 CHANGES_REQUESTED 门控。

• 上轮 P0（pressedPosition 批处理帧捕获错误坐标）已在 4f2bbc9 真修复——采集挪进 _updatePointerInfo 的 per-event 循环、用 pointerdown 事件自身的 event.clientX/clientY 算（PointerManager 247-250），配套回归测试同帧批处理 pointerdown@(1,1)+pointermove@(3,3) 断言 pressedPosition==(2,2) 而 position==(6,6)，revert 即红，反向证伪成立。
• target/currentTarget 的 DOM 语义忠实度已独立核验：引擎确有冒泡模型——UIPointerEventEmitter._composedPath 从命中元素（path[0]，最深）沿 entity 父链构建到根 Canvas，_bubble 逐级触发同一事件并逐级改写 eventData.currentTarget = path[i]，target 恒为 path[0]。故 currentTarget 有意义（非摆设），与 DOM event.target（事件起源）/event.currentTarget（当前 handler 宿主）一致。物理拾取无冒泡，target === currentTarget 经默认参数正确成立。
• 事件数据池接入 engine gc 与既有 _renderElementPool 生命周期同构：garbageCollection() 仅清 _elements、不重置 _usedElementCount，但下一帧 _update 首句 eventPool.clear() 必在任何 get() 之前归零，不变量成立，非 bug。热路径无新增分配（池 get() 复用、Vector2.set 原地、整条冒泡路径复用同一 eventData）。

CI 全绿（build/lint/e2e/codecov-patch/codecov-project）。

问题

无阻塞问题（无 P0/P1/P2）。

[P3] PointerEventData.ts:16 — currentTarget 的 JSDoc 偏机制描述

当前注释描述的是实现机制而非对外契约。可选择更贴近 DOM 文档口径的写法，例如「冒泡过程中当前正在处理事件的实体」。纯文案、非阻塞，当前措辞准确且带句号，不影响合并。

简化建议

无。上轮 _createEventData(pointer, entity, entity) 双传简化已采纳。构造器注入 vs 字段注入池的反复是作者明确把字段注入 cleanup 推迟到 follow-up PR 的主动决策，当前构造器注入工作正常、无对外影响，无需处理。

LGTM，APPROVE。