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

03-UnrealEngine/Gameplay/UObject/UnrealSpecifiers/Meta/Scene/ValidateWidgetUsing/ValidateWidgetUsing.md

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+# ValidateWidgetUsing
+
+- **功能描述：** 提供一个函数来验证当前属性值是否合法。
+- **使用位置：** UPROPERTY
+- **引擎模块：** Scene
+- **元数据类型：** bool
+- **限制类型：** 带有MakeEditWidget的FVector，FTransform
+- **关联项：** [MakeEditWidget](../MakeEditWidget/MakeEditWidget.md)
+- **常用程度：** ★★★
+
+ValidateWidgetUsing提供一个函数来验证当前属性值是否合法。
+
+- 当前属性要有MakeEditWidget的标记
+- 函数的原型是FString MyFunc()，返回非空表示错误信息。
+
+## 测试代码：
+
+```cpp
+	UFUNCTION()
+	FString ValidateMyVector()
+	{
+		if (MyVector_MakeEditWidget_Validate.Length()>100.f)
+		{
+			return TEXT("Exceed max length:100");
+		}
+		return TEXT("");
+	}
+
+	UPROPERTY(EditAnywhere, BlueprintReadWrite, Category = "EditWidget", meta = (MakeEditWidget, ValidateWidgetUsing = "ValidateMyVector"))
+	FVector MyVector_MakeEditWidget_Validate;
+```
+
+## 测试结果：
+
+可见MyVector_MakeEditWidget_Validate长度超过100之后，控件颜色变成红色，并且显示出错误的信息在控件上。
+
+![Untitled](Untitled.png)
+
+## 原理：
+
+逻辑比较简单。发现有验证函数，就调用验证函数来验证。如果有错误信息，就一起改变最终输出的颜色和显示文字。
+
+```cpp
+	static FLegacyEdModeWidgetHelper::FPropertyWidgetInfo CreateWidgetInfo(const TArray<FPropertyWidgetInfoChainElement>& Chain, bool bIsTransform, FProperty* CurrentProp, int32 Index = INDEX_NONE)
+	{
+		check(CurrentProp);
+		FEdMode::FPropertyWidgetInfo WidgetInfo;
+		WidgetInfo.PropertyValidationName = FName(*CurrentProp->GetMetaData(FEdMode::MD_ValidateWidgetUsing));
+		
+		return WidgetInfo;
+	}
+	
+void FLegacyEdModeWidgetHelper::FPropertyWidgetInfo::GetTransformAndColor(UObject* BestSelectedItem, bool bIsSelected, FTransform& OutLocalTransform, FString& OutValidationMessage, FColor& OutDrawColor) const
+{
+	// Determine the desired color
+	if (PropertyValidationName != NAME_None)
+	{
+		if (UFunction* ValidateFunc = BestSelectedItem->FindFunction(PropertyValidationName))
+		{
+			BestSelectedItem->ProcessEvent(ValidateFunc, &OutValidationMessage);
+
+			// if we have a negative result, the widget color is red.
+			OutDrawColor = OutValidationMessage.IsEmpty() ? OutDrawColor : FColor::Red;
+		}
+	}
+}
+
+void FLegacyEdModeWidgetHelper::DrawHUD(FEditorViewportClient* ViewportClient, FViewport* Viewport, const FSceneView* View, FCanvas* Canvas)
+{
+	FTransform LocalWidgetTransform;
+	FString ValidationMessage;
+	FColor WidgetColor;
+	WidgetInfo.GetTransformAndColor(BestSelectedItem, bSelected, /*out*/ LocalWidgetTransform, /*out*/ ValidationMessage, /*out*/ WidgetColor);
+	
+	Canvas->DrawItem(TextItem);
+}
+```