103 lines
3.5 KiB
Markdown
103 lines
3.5 KiB
Markdown
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# ShowAsInputPin
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- **功能描述：** 使得UMaterialExpression里的一些基础类型属性变成材质节点上的引脚。
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- **使用位置：** UPROPERTY
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- **引擎模块：** Material
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- **元数据类型：** bool
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- **限制类型：** UMaterialExpression里的属性
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- **常用程度：** ★★★
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使得UMaterialExpression里的一些基础类型属性变成材质节点上的引脚。
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- 所谓基础类型，指的是float，FVector这种常用的类型。
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- 默认这些基础类型属性是不显示为引脚的。
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- ShowAsInputPin 值有两个选项，Primary可以直接显示出来，Advanced需要展开箭头后显示。
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## 测试代码：
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```cpp
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public:
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UPROPERTY(EditAnywhere, BlueprintReadWrite, Category = PinTest)
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float MyFloat;
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UPROPERTY(EditAnywhere, BlueprintReadWrite, Category = PinTest, meta = (ShowAsInputPin = "Primary"))
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float MyFloat_Primary;
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UPROPERTY(EditAnywhere, BlueprintReadWrite, Category = PinTest, meta = (ShowAsInputPin = "Advanced"))
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float MyFloat_Advanced;
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```
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## 测试结果：
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可见MyFloat没有显示在节点上。
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MyFloat_Primary显示在节点上。
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MyFloat_Advanced需要展开箭头后才显示出来。
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## 原理：
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遍历UMaterialExpression里的属性，根据含有ShowAsInputPin 的类型来生成引脚。
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```cpp
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TArray<FProperty*> UMaterialExpression::GetPropertyInputs() const
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{
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TArray<FProperty*> PropertyInputs;
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static FName OverridingInputPropertyMetaData(TEXT("OverridingInputProperty"));
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static FName ShowAsInputPinMetaData(TEXT("ShowAsInputPin"));
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for (TFieldIterator<FProperty> InputIt(GetClass(), EFieldIteratorFlags::IncludeSuper, EFieldIteratorFlags::ExcludeDeprecated); InputIt; ++InputIt)
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{
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bool bCreateInput = false;
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FProperty* Property = *InputIt;
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// Don't create an expression input if the property is already associated with one explicitly declared
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bool bOverridingInputProperty = Property->HasMetaData(OverridingInputPropertyMetaData);
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// It needs to have the 'EditAnywhere' specifier
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const bool bEditAnywhere = Property->HasAnyPropertyFlags(CPF_Edit);
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// It needs to be marked with a valid pin category meta data
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const FString ShowAsInputPin = Property->GetMetaData(ShowAsInputPinMetaData);
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const bool bShowAsInputPin = ShowAsInputPin == TEXT("Primary") || ShowAsInputPin == TEXT("Advanced");
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if (!bOverridingInputProperty && bEditAnywhere && bShowAsInputPin)
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{
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// Check if the property type fits within the allowed widget types
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FFieldClass* PropertyClass = Property->GetClass();
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if (PropertyClass == FFloatProperty::StaticClass()
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|| PropertyClass == FDoubleProperty::StaticClass()
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|| PropertyClass == FIntProperty::StaticClass()
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|| PropertyClass == FUInt32Property::StaticClass()
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|| PropertyClass == FByteProperty::StaticClass()
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|| PropertyClass == FBoolProperty::StaticClass()
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)
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{
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bCreateInput = true;
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}
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else if (PropertyClass == FStructProperty::StaticClass())
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{
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FStructProperty* StructProperty = CastField<FStructProperty>(Property);
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UScriptStruct* Struct = StructProperty->Struct;
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if (Struct == TBaseStructure<FLinearColor>::Get()
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|| Struct == TBaseStructure<FVector4>::Get()
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|| Struct == TVariantStructure<FVector4d>::Get()
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|| Struct == TBaseStructure<FVector>::Get()
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|| Struct == TVariantStructure<FVector3f>::Get()
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|| Struct == TBaseStructure<FVector2D>::Get()
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)
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{
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bCreateInput = true;
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}
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}
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}
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if (bCreateInput)
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{
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PropertyInputs.Add(Property);
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}
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}
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return PropertyInputs;
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}
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```
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