vault backup: 2024-10-12 17:19:45

03-UnrealEngine/Gameplay/UObject/UnrealSpecifiers/Meta/Numeric/AllowPreserveRatio/AllowPreserveRatio.md

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+# AllowPreserveRatio
+
+- **功能描述：** 在细节面板上为FVector属性添加一个比率锁。
+- **使用位置：** UPROPERTY
+- **引擎模块：** Numeric Property
+- **元数据类型：** bool
+- **限制类型：** FVector
+- **常用程度：** ★★★
+
+在细节面板上为FVector属性添加一个比率锁。
+
+## 测试代码：
+
+```cpp
+public:
+	UPROPERTY(EditAnywhere, Category = VectorTest)
+	FVector MyVector_Default;
+
+	UPROPERTY(EditAnywhere, Category = VectorTest, meta = (AllowPreserveRatio))
+	FVector MyVector_AllowPreserveRatio;
+
+	UPROPERTY(EditAnywhere, Category = VectorTest, meta = (ShowNormalize))
+	FVector MyVector_ShowNormalize;
+```
+
+## 测试结果：
+
+可见MyVector_AllowPreserveRatio的值在锁上之后可以形成固定的比率。
+
+![AllowPreserveRatio](AllowPreserveRatio.gif)
+
+## 原理：
+
+其实就是UI定制化的时候检测出AllowPreserveRatio就创建单独的UI。
+
+```cpp
+void FMathStructCustomization::MakeHeaderRow(TSharedRef<class IPropertyHandle>& StructPropertyHandle, FDetailWidgetRow& Row)
+{
+		if (StructPropertyHandle->HasMetaData("AllowPreserveRatio"))
+		{
+			if (!GConfig->GetBool(TEXT("SelectionDetails"), *(StructPropertyHandle->GetProperty()->GetName() + TEXT("_PreserveScaleRatio")), bPreserveScaleRatio, GEditorPerProjectIni))
+			{
+				bPreserveScaleRatio = true;
+			}
+		
+			HorizontalBox->AddSlot()
+			.AutoWidth()
+			.MaxWidth(18.0f)
+			.VAlign(VAlign_Center)
+			[
+				// Add a checkbox to toggle between preserving the ratio of x,y,z components of scale when a value is entered
+				SNew(SCheckBox)
+				.IsChecked(this, &FMathStructCustomization::IsPreserveScaleRatioChecked)
+				.OnCheckStateChanged(this, &FMathStructCustomization::OnPreserveScaleRatioToggled, StructWeakHandlePtr)
+				.Style(FAppStyle::Get(), "TransparentCheckBox")
+				.ToolTipText(LOCTEXT("PreserveScaleToolTip", "When locked, scales uniformly based on the current xyz scale values so the object maintains its shape in each direction when scaled"))
+				[
+					SNew(SImage)
+					.Image(this, &FMathStructCustomization::GetPreserveScaleRatioImage)
+					.ColorAndOpacity(FSlateColor::UseForeground())
+				]
+			];
+		}
+
+}
+```