feature(headless): Add GhostObjectManagerDummy for headless mode

[bobtista]

Summary

• Adds GhostObjectManagerDummy class that provides no-op implementations for headless mode
• Factory in W3DGameLogic returns dummy when m_headless is true
• Intentionally does NOT override crc/xfer/loadPostProcess to maintain save compatibility

Related

Split from #2139 per @xezon's suggestion to review each dummy class separately.

[greptile-apps]

Greptile Summary

This PR introduces GhostObjectManagerDummy, a no-op subclass of GhostObjectManager, and wires it into the W3DGameLogic factory so that headless-mode builds skip all W3D snapshot/scene management for fogged objects. The factory signature is widened to accept a bool headless parameter (defaulting to false for backward compatibility), and TheGlobalData->m_headless is forwarded from GameLogic::init(). The PR is mirrored identically across both Generals/ and GeneralsMD/.

Key points:

• GhostObjectManagerDummy deliberately does not override crc/xfer/loadPostProcess, inheriting the lightweight base-class serialisation path (only m_localPlayer is xferred), which correctly maintains save-game compatibility.
• The base GhostObjectManager itself already has no-op implementations of all the overridden methods, so the dummy is structurally equivalent to directly instantiating the base class; the explicit subclass is a reasonable choice for documenting intent and providing a named type for the headless branch.
• Both W3DGhostObject.cpp files remove the W3DDisplay::m_3DScene != nullptr guard in W3DRenderObjectSnapshot::addToScene(). While safe by design (the dummy prevents W3DGhostObject from being instantiated in headless mode), this is an unmentioned behavioural change that removes a defensive null check and deserves an explanatory comment or assertion.

Confidence Score: 4/5

• Safe to merge with minor follow-up recommended on the removed null guard in W3DGhostObject.cpp.
• The core headless dummy pattern is correct, well-scoped, and mirrored cleanly across both game directories. The only concern is the unexplained removal of the W3DDisplay::m_3DScene null check in addToScene(), which changes a graceful-fail into a potential crash if the invariant is ever violated in non-headless mode.
• Generals/Code/GameEngineDevice/Source/W3DDevice/GameLogic/W3DGhostObject.cpp and its GeneralsMD counterpart — specifically the removed null guard in W3DRenderObjectSnapshot::addToScene().

Important Files Changed

Filename	Overview
Generals/Code/GameEngine/Include/GameLogic/GhostObject.h	Adds GhostObjectManagerDummy as a clean no-op subclass of GhostObjectManager for headless mode; intentionally omits crc/xfer/loadPostProcess overrides to inherit the lightweight base-class serialisation path.
Generals/Code/GameEngineDevice/Include/W3DDevice/GameLogic/W3DGameLogic.h	Factory override correctly selects GhostObjectManagerDummy or W3DGhostObjectManager based on the headless flag; static_cast is retained for VC6 compatibility as confirmed by a prior reviewer thread.
Generals/Code/GameEngineDevice/Source/W3DDevice/GameLogic/W3DGhostObject.cpp	Removes the W3DDisplay::m_3DScene != nullptr null-guard in W3DRenderObjectSnapshot::addToScene() without explanation; while safe under the new dummy design, it eliminates a defensive check and silently changes failure mode from a graceful no-op to a null dereference crash.
Generals/Code/GameEngine/Source/GameLogic/System/GameLogic.cpp	Correctly threads TheGlobalData->m_headless into the factory call; base-class implementation ignores the parameter and always returns a plain GhostObjectManager, which is the correct non-W3D behaviour.
GeneralsMD/Code/GameEngine/Include/GameLogic/GhostObject.h	Mirror of the Generals change; identical GhostObjectManagerDummy class added with the correct "Zero Hour" header.
GeneralsMD/Code/GameEngineDevice/Source/W3DDevice/GameLogic/W3DGhostObject.cpp	Same null-guard removal as the Generals counterpart; same concern about removing defensive programming without explanation.

Sequence Diagram

sequenceDiagram
    participant GL as GameLogic::init()
    participant F as createGhostObjectManager(headless)
    participant D as GhostObjectManagerDummy
    participant W as W3DGhostObjectManager
    participant PM as PartitionManager

    GL->>F: createGhostObjectManager(m_headless)
    alt headless == true
        F->>D: NEW GhostObjectManagerDummy
        D-->>GL: TheGhostObjectManager (no-op)
        PM->>D: addGhostObject(obj, pd)
        D-->>PM: nullptr (no-op)
    else headless == false
        F->>W: NEW W3DGhostObjectManager
        W-->>GL: TheGhostObjectManager (full W3D)
        PM->>W: addGhostObject(obj, pd)
        W-->>PM: W3DGhostObject*
    end

Loading

Prompt To Fix All With AI

This is a comment left during a code review.
Path: Generals/Code/GameEngineDevice/Source/W3DDevice/GameLogic/W3DGhostObject.cpp
Line: 156-161

Comment:
**Defensive null guard removed without explanation**

The prior check `W3DDisplay::m_3DScene != nullptr &&` ensured `Add_Render_Object` would never be called on a null scene. Although headless mode now uses `GhostObjectManagerDummy` (preventing `W3DGhostObject` instances from being created there), this code path can still be exercised in non-headless mode. If `m_3DScene` is ever null under non-headless conditions (e.g. during teardown, an abnormal initialisation sequence, or future refactors) the dereference on line 159 will crash rather than return `false`.

Consider adding a `DEBUG_ASSERTCRASH` for the null case to preserve the crash-on-invalid invariant in debug builds while making the intent explicit:

```suggestion
	if (!m_robj->Is_In_Scene())
	{
		DEBUG_ASSERTCRASH(W3DDisplay::m_3DScene != nullptr, ("W3DRenderObjectSnapshot::addToScene - m_3DScene is null"));
		W3DDisplay::m_3DScene->Add_Render_Object(m_robj);
		return true;
	}
```

The same change applies to `GeneralsMD/Code/GameEngineDevice/Source/W3DDevice/GameLogic/W3DGhostObject.cpp:158`.

How can I resolve this? If you propose a fix, please make it concise.

_{Last reviewed commit: ecf1ecf}

[greptile-apps]

_{2 files reviewed, 2 comments}

_{Edit Code Review Agent Settings | Greptile}

[greptile-apps]

Unnecessary static_cast<GhostObjectManager*> since GhostObjectManagerDummy already inherits from GhostObjectManager

Suggested change

	virtual GhostObjectManager *createGhostObjectManager(void) { return TheGlobalData->m_headless ? static_cast<GhostObjectManager*>(NEW GhostObjectManagerDummy) : NEW W3DGhostObjectManager; }
	virtual GhostObjectManager *createGhostObjectManager(void) { return TheGlobalData->m_headless ? NEW GhostObjectManagerDummy : NEW W3DGhostObjectManager; }

Prompt To Fix With AI

This is a comment left during a code review.
Path: Generals/Code/GameEngineDevice/Include/W3DDevice/GameLogic/W3DGameLogic.h
Line: 64:64

Comment:
Unnecessary `static_cast<GhostObjectManager*>` since `GhostObjectManagerDummy` already inherits from `GhostObjectManager`

```suggestion
	virtual GhostObjectManager *createGhostObjectManager(void) { return TheGlobalData->m_headless ? NEW GhostObjectManagerDummy : NEW W3DGhostObjectManager; }
```

How can I resolve this? If you propose a fix, please make it concise.

[xezon]

I suggest make the variant a Bool argument. Then the GlobalData include can be removed again.

[xezon]

override

Several times.