131 lines
3.6 KiB
Markdown
131 lines
3.6 KiB
Markdown
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# MaxPropertyDepth
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- **功能描述：** 指定对象或结构在细节面板里展开的层数。
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- **使用位置：** UPROPERTY
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- **引擎模块：** DetailsPanel
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- **元数据类型：** int32
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- **限制类型：** 对象或结构属性
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- **常用程度：** ★
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指定对象或结构在细节面板里展开的层数。
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- 默认是没有限制的，可以一直递归展开到最深层次字段。
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- 如果对象的子对象再有子对象，这样递归很多层级，可能我们会想要限制不想展开太深，因此我们可以指定一个层级限制。
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- 取值-1表示没有限制，0表示完全不展开，>0表示限制的层数。
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- 源码里没有找到例子，但却是可以工作的。
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## 测试代码：
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```cpp
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USTRUCT(BlueprintType)
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struct INSIDER_API FMyStructDepth1
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{
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GENERATED_BODY()
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public:
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UPROPERTY(BlueprintReadWrite, EditAnywhere)
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int32 MyInt1 = 123;
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UPROPERTY(BlueprintReadWrite, EditAnywhere)
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FString MyString1;
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};
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USTRUCT(BlueprintType)
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struct INSIDER_API FMyStructDepth2
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{
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GENERATED_BODY()
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public:
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UPROPERTY(BlueprintReadWrite, EditAnywhere)
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FMyStructDepth1 MyStruct1;
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};
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USTRUCT(BlueprintType)
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struct INSIDER_API FMyStructDepth3
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{
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GENERATED_BODY()
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public:
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UPROPERTY(BlueprintReadWrite, EditAnywhere)
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FMyStructDepth2 MyStruct2;
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};
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USTRUCT(BlueprintType)
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struct INSIDER_API FMyStructDepth4
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{
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GENERATED_BODY()
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public:
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UPROPERTY(BlueprintReadWrite, EditAnywhere)
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FMyStructDepth3 MyStruct3;
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};
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UCLASS(BlueprintType)
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class INSIDER_API UMyProperty_MaxPropertyDepth :public UObject
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{
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GENERATED_BODY()
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public:
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UPROPERTY(EditAnywhere, BlueprintReadWrite)
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FMyStructDepth4 MyStruct;
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UPROPERTY(EditAnywhere, BlueprintReadWrite,meta=(MaxPropertyDepth=2))
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FMyStructDepth4 MyStruct_Depth;
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};
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```
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## 测试效果：
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## 原理：
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在每个FPropertyNode构建子节点的时候，检查一下当前的MaxChildDepthAllowed ，超过了就不继续往下构建。
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```cpp
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/** Safety Value representing Depth in the property tree used to stop diabolical topology cases
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* -1 = No limit on children
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* 0 = No more children are allowed. Do not process child nodes
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* >0 = A limit has been set by the property and will tick down for successive children
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*/
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int32 MaxChildDepthAllowed;
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void FPropertyNode::InitNode(const FPropertyNodeInitParams& InitParams)
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{
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//Get the property max child depth
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static const FName Name_MaxPropertyDepth("MaxPropertyDepth");
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if (Property->HasMetaData(Name_MaxPropertyDepth))
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{
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int32 NewMaxChildDepthAllowed = Property->GetIntMetaData(Name_MaxPropertyDepth);
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//Ensure new depth is valid. Otherwise just let the parent specified value stand
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if (NewMaxChildDepthAllowed > 0)
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{
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//if there is already a limit on the depth allowed, take the minimum of the allowable depths
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if (MaxChildDepthAllowed >= 0)
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{
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MaxChildDepthAllowed = FMath::Min(MaxChildDepthAllowed, NewMaxChildDepthAllowed);
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}
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else
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{
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//no current limit, go ahead and take the new limit
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MaxChildDepthAllowed = NewMaxChildDepthAllowed;
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}
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}
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}
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}
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void FPropertyNode::RebuildChildren()
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{
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if (MaxChildDepthAllowed != 0)
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{
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//the case where we don't want init child nodes is when an Item has children that we don't want to display
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//the other option would be to make each node "Read only" under that item.
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//The example is a material assigned to a static mesh.
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if (HasNodeFlags(EPropertyNodeFlags::CanBeExpanded) && (ChildNodes.Num() == 0))
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{
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InitChildNodes();
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if (ExpandedPropertyItemSet.Size() > 0)
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{
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FPropertyNodeUtils::SetExpandedItems(ThisAsSharedRef, ExpandedPropertyItemSet);
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}
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}
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}
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}
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```
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