XCEngine/docs/plan/NewEditor_TreeResidualDuplicationClosurePlan_2026-04-22.md

# NewEditor Tree Residual Duplication Closure Plan

Date: `2026-04-22`
Status: `In Progress`

## Goal

- Close the true remaining duplication between `HierarchyPanel` and the project left tree after the `TreePanelHost` / `UIEditorTreePanelBehavior` cleanup.
- Keep the solution rooted in existing modules instead of creating new `Behavior` / `Host` / `Support` files.
- Reduce code only where the duplication is structurally real, not where product semantics differ.

## Why A New Plan Is Needed

- The previous plan completed the removal of the tree glue layer.
- That did not automatically mean the hierarchy tree and project tree were free of all true duplication.
- The remaining work is smaller in scope, but it is real and should be tracked separately instead of being hidden under the completed root plan.

## Confirmed Residual Duplication

### 1. Hosted panel command focus claiming is still duplicated

Current duplicated shape:

- `HierarchyPanel::ClaimCommandFocus(...)`
- `ProjectPanel::ClaimCommandFocus(...)`
- `InspectorPanel::ClaimCommandFocus(...)`

This is app-layer hosted panel behavior, not tree-business behavior.

### 2. Tree rename host skeleton is still partially duplicated

Current duplicated shape:

- `ClearRenameState(...)`
- `QueueRenameSession(...)`
- `TryStartQueuedRenameSession(...)`
- `UpdateRenameSession(...)`

Notes:

- `HierarchyPanel` has a single tree surface.
- `ProjectPanel` has both tree and grid rename surfaces.
- The commit side-effects must stay local, but the session host skeleton still contains real duplication.

### 3. Tree append/update skeleton must be re-audited carefully

- Some call order is shared: tree background, tree foreground, inline rename overlay, drop preview.
- But `ProjectPanel` also owns splitter, breadcrumb, grid, context menu, asset drag/drop, and dual-surface rename.
- This area must not be “abstracted for symmetry” unless the extracted part is truly stable and reduces code clearly.

## Explicit Non-Goals

- Do not merge panel refresh loops.
- Do not merge project tree and asset grid logic.
- Do not move project or scene runtime semantics into `XCEditor`.
- Do not create any new `Behavior`, `Host`, `Helper`, `Support`, or similar glue files.
- Do not refactor for visual symmetry when code ownership would become less clear.

## Execution Plan

### Phase A. Hosted Panel Command Focus Dedup

Status: `Completed`

Target:

- Consolidate hosted-panel command focus claiming into an existing app-level module.

Rules:

- No new file.
- Prefer extending an existing app-level focus module.
- Update `HierarchyPanel`, `ProjectPanel`, and `InspectorPanel` together if they share the same pattern.

Validation:

- Build `XCUIEditorApp`
- Smoke test `XCUIEditor.exe`

Completed result:

- Consolidated hosted panel command focus claiming into `EditorCommandFocusService.h`
- Removed duplicated `ClaimCommandFocus(...)` implementations from `HierarchyPanel`, `ProjectPanel`, and `InspectorPanel`
- Verified by build and smoke test

### Phase B. Tree Rename Host Skeleton Dedup

Status: `Pending`

Target:

- Reduce duplicated tree rename session host code while preserving local business commit behavior.

Rules:

- No new glue layer.
- Keep tree-generic session mechanics in existing tree/editor modules.
- Keep `ProjectPanel` grid rename semantics local.
- Keep `HierarchyPanel` scene rename commit local.

Validation:

- Build `XCUIEditorApp`
- Smoke test `XCUIEditor.exe`
- Confirm hierarchy rename and project tree/grid rename still start and shut down correctly

### Phase C. Final Re-Audit Of Tree Skeleton Duplication

Status: `Pending`

Target:

- Re-check whether any remaining shared tree call sequence should still be extracted.

Rules:

- Only extract if it removes clear structural duplication.
- If the remaining overlap is just normal orchestration around different business surfaces, record it as intentional and stop.

Validation:

- `rg` verification of targeted duplicate blocks
- Build `XCUIEditorApp`
- Smoke test `XCUIEditor.exe`

## Acceptance

- Previous root plan is archived.
- Remaining true duplication is tracked separately.
- Hosted panel command focus duplicate is removed from the duplicated panels.
- Tree rename host skeleton duplication is reduced without breaking project grid/tree split semantics.
- No new glue-layer file is introduced.
- `XCUIEditorApp` builds and smoke tests pass after each completed phase.