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

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+# LinearDeltaSensitivity
+
+- **功能描述：** 在设定Delta后，进一步设定数字输入框变成线性改变以及改变的敏感度（值越大越不敏感）
+- **使用位置：** UPROPERTY
+- **引擎模块：** Numeric Property
+- **元数据类型：** float/int
+- **限制类型：** float,int32
+- **关联项：** [Delta](Delta/Delta.md)
+- **常用程度：** ★★★
+
+生效的条件：
+
+1. 先设置Delta>0
+2. 不设置UIMin, UIMax
+3. 设定LinearDeltaSensitivity >0
+
+## 测试代码：
+
+```cpp
+	UPROPERTY(EditAnywhere, BlueprintReadWrite, Category = DeltaTest, meta = (UIMin = "0", UIMax = "1000", Delta = 10))
+	float MyFloat_Delta10_UIMinMax = 100;
+	UPROPERTY(EditAnywhere, BlueprintReadWrite, Category = DeltaTest, meta = (Delta = 10, LinearDeltaSensitivity = 50))
+	float MyFloat_Delta10_LinearDeltaSensitivity50 = 100;
+	UPROPERTY(EditAnywhere, BlueprintReadWrite, Category = DeltaTest, meta = (UIMin = "0", UIMax = "1000", Delta = 10, LinearDeltaSensitivity = 50))
+	float MyFloat_Delta10_LinearDeltaSensitivity50_UIMinMax = 100;
+```
+
+## 测试效果：
+
+效果解析请参见：Delta的解析
+
+![Delta](Delta/Delta.gif)
+
+## 原理：
+
+可见只有没有UIMinMax且已经设置Delta后才能走进线性改变的代码分支。
+
+```cpp
+, _Delta(0)
+virtual FReply SSpinBox<NumericType>::OnMouseMove(const FGeometry& MyGeometry, const FPointerEvent& MouseEvent) override
+{
+		if (bUnlimitedSpinRange)
+		{
+				// If this control has a specified delta and sensitivity then we use that instead of the current value for determining how much to change.
+				const double Sign = (MouseEvent.GetCursorDelta().X > 0) ? 1.0 : -1.0;
+				
+				if (LinearDeltaSensitivity.IsSet() && LinearDeltaSensitivity.Get() != 0 && Delta.IsSet() && Delta.Get() > 0)
+				{
+								const double MouseDelta = FMath::Abs(MouseEvent.GetCursorDelta().X / (float)LinearDeltaSensitivity.Get());
+								NewValue = InternalValue + (Sign * MouseDelta * FMath::Pow((double)Delta.Get(), (double)SliderExponent.Get())) * Step;
+				}
+				else
+				{
+								const double MouseDelta = FMath::Abs(MouseEvent.GetCursorDelta().X / SliderWidthInSlateUnits);
+								const double CurrentValue = FMath::Clamp<double>(FMath::Abs(InternalValue), 1.0, (double)std::numeric_limits<NumericType>::max());
+								NewValue = InternalValue + (Sign * MouseDelta * FMath::Pow((double)CurrentValue, (double)SliderExponent.Get())) * Step;
+				}
+		}
+}
+
+```