# Plugin not compiling.  HComponentVisProxy unresolved external symbol

**URL:** <https://forums.unrealengine.com/t/plugin-not-compiling-hcomponentvisproxy-unresolved-external-symbol/345834>\
**Category:** Plugins\
**Tags:** unresolved-external-, unreal-engine, editor, Plugins, CPP, question\
**Created:** [January 30, 2016, 2:24am UTC](https://forums.unrealengine.com/t/plugin-not-compiling-hcomponentvisproxy-unresolved-external-symbol/345834 "2016-01-30T02:24:55Z")\
**Posts on this page:** 2\
**Page:** 1

<div class="post-metadata">

**Author:** ![anonymous\_user\_5b5c8515](https://d3kjluh73b9h9o.cloudfront.net/original/4X/2/8/5/28502927f1d97ba1051b3b47ccfe17233bf41ef0.png) [@anonymous\_user\_5b5c8515](https://forums.unrealengine.com/u/anonymous_user_5b5c8515)\
**Post date:** [January 30, 2016, 2:24am UTC](https://forums.unrealengine.com/t/plugin-not-compiling-hcomponentvisproxy-unresolved-external-symbol/345834/1 "2016-01-30T02:24:55Z")

</div>

**EDIT:** Typically I figured this out right after posting.  
I was missing 2 lines at the top of my cpp.

**IMPLEMENT\_HIT\_PROXY(HControlPointVisProxy, HComponentVisProxy)  
IMPLEMENT\_HIT\_PROXY(HControlPointProxy, HControlPointVisProxy)**

This seems to get things compiling. I’ll check back in if the issue comes back.

* * *

Hi.  
I’m making a Editor Mode plugin with a custom subclass of ComponentVisualizer.h. The plugin creates shapes in editor with handles to control them, similar to the Spline component.

I need to subclass ‘HComponentVisProxy’ to manage clicking on handles in the editor but as soon as I try access the sub-classed structs it fails to compile with the linker error below. If I pass it the base struct ‘HComponentVisProxy’ then everything compiles fine.

The compile fails on this line:

**PDI-\>SetHitProxy(new HControlPointProxy(Component, i));**

I’ve included “ComponentVisualizers” module in my Build.cs file so I should have access to the module.  
I’m using this tutorial on the Wiki which suggests using a custom editor module,but I’d prefer to keep this in a plugin.

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>
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Any gems of wisdom would be very helpful. Am I hitting a limitation of plugins or am I just blind to something obvious?

Thanks in advance.

**Error log:**

```
1>GeometryControlComponentVisualizer.cpp.obj : error LNK2019: unresolved external symbol "public: static class HHitProxyType * __cdecl HControlPointVisProxy::StaticGetType(void)" (?StaticGetType@HControlPointVisProxy@@SAPEAVHHitProxyType@@XZ) referenced in function "public: virtual class HHitProxyType *__cdecl HControlPointVisProxy::GetType(void)const " (?GetType@HControlPointVisProxy@@UEBAPEAVHHitProxyType@@XZ)

1>GeometryControlComponentVisualizer.cpp.obj : error LNK2019: unresolved external symbol "public: static class HHitProxyType * __cdecl HControlPointProxy::StaticGetType(void)" (?StaticGetType@HControlPointProxy@@SAPEAVHHitProxyType@@XZ) referenced in function "public: virtual class HHitProxyType *__cdecl HControlPointProxy::GetType(void)const " (?GetType@HControlPointProxy@@UEBAPEAVHHitProxyType@@XZ)

1>C:\Projects\BuildingBuilder\Plugins\Builder\Binaries\Win64\UE4Editor-Builder-7084.dll : fatal error LNK1120: 2 unresolved externals

```

**Declaring structs in FGeometryControlComponentVisualizer.h**

```
#pragma once
#include "BuilderPrivatePCH.h"
#include "UnrealEd.h"
#include "ComponentVisualizer.h"
#include "Engine.h"

/** Base class for control point editing proxies */
struct HControlPointVisProxy : public HComponentVisProxy
{
	DECLARE_HIT_PROXY();

	HControlPointVisProxy(const UActorComponent* InComponent)
		: HComponentVisProxy(InComponent, HPP_Wireframe)
	{}
};

/** Proxy for a control point */
struct HControlPointProxy : public HControlPointVisProxy
{
	DECLARE_HIT_PROXY();

	HControlPointProxy(const UActorComponent* InComponent, int32 InCPIndex)
		: HControlPointVisProxy(InComponent)
		, SelectedCPIndex(InCPIndex)
	{}

	int32 SelectedCPIndex;
};

class FGeometryControlComponentVisualizer : public FComponentVisualizer
{
public:
virtual void OnRegister() override;
	virtual void DrawVisualization(const UActorComponent* Component, const FSceneView* View, FPrimitiveDrawInterface* PDI) override;
}

```

**Utilizing them in FGeometryControlComponentVisualizer.cpp**

```
void FGeometryControlComponentVisualizer::DrawVisualization(const UActorComponent* Component, const FSceneView* View, FPrimitiveDrawInterface* PDI)
{
	if (const UGeometryControlComponent* ControlComp = Cast<const UGeometryControlComponent>(Component))
	{
		const FLinearColor SelectedColor = ControlComp->EditorSelectedColor;
		const FLinearColor UnselectedColor = ControlComp->EditorUnselectedColor;
		
		const TArray<FVector> ControlPoints = ControlComp->ControlPoints;

		for (int32 i = 0; i < ControlPoints.Num(); i++)
		{
			FLinearColor Color = (i == SelectedCPIndex) ? SelectedColor : UnselectedColor;

			int32 NextIdx = i + 1 > ControlPoints.Num() - 1 ? 0 : i + 1;	//Draw from last index back to first

			PDI->SetHitProxy(new HControlPointProxy(Component, i)); //Compile fails here
			PDI->DrawLine(ControlPoints[i], ControlPoints[NextIdx], Color, SDPG_Foreground);
			PDI->DrawPoint(ControlPoints[i], Color, 20.f, SDPG_Foreground);
			PDI->SetHitProxy(NULL);

		}
	}
}

```

**Plugins Build.cs**

```
PrivateDependencyModuleNames.AddRange(
			new string[]
			{
				"Core",
				"CoreUObject",
				"Engine",
				"Slate",
				"SlateCore",
				"InputCore",
				"UnrealEd",
				"LevelEditor",
				"ComponentVisualizers",
            }

```

---

<div class="post-metadata">

**Author:** ![anonymous\_user\_5b5c8515](https://d3kjluh73b9h9o.cloudfront.net/original/4X/2/8/5/28502927f1d97ba1051b3b47ccfe17233bf41ef0.png) [@anonymous\_user\_5b5c8515](https://forums.unrealengine.com/u/anonymous_user_5b5c8515)\
**Post date:** [January 30, 2016, 3:07am UTC](https://forums.unrealengine.com/t/plugin-not-compiling-hcomponentvisproxy-unresolved-external-symbol/345834/2 "2016-01-30T03:07:41Z")

</div>

Typically I figured this out right after posting. I was missing 2 lines at the top of my cpp.

IMPLEMENT\_HIT\_PROXY(HControlPointVisProxy, HComponentVisProxy) IMPLEMENT\_HIT\_PROXY(HControlPointProxy, HControlPointVisProxy)