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

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

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+# WheelStep
+
+- **功能描述：** 指定数字输入框上鼠标轮上下滚动产生的变化值
+- **使用位置：** UPROPERTY
+- **引擎模块：** Numeric Property
+- **元数据类型：** float/int
+- **常用程度：** ★★★
+
+指定数字输入框上鼠标轮上下滚动产生的变化值。
+
+## 默认值的规则：
+
+如果属性是浮点数且UI滚动条范围小于10，则WheelStep=0.1，否则为1
+
+如果属性是整数，则WheelStep=1
+
+## 测试代码：
+
+```cpp
+	UPROPERTY(EditAnywhere, BlueprintReadWrite, Category = WheelStepTest)
+	float MyFloat_DefaultWheelStep = 50;
+	UPROPERTY(EditAnywhere, BlueprintReadWrite, Category = WheelStepTest, meta = (UIMin = "0", UIMax = "10"))
+	float MyFloat_SmallWheelStep = 1;
+	UPROPERTY(EditAnywhere, BlueprintReadWrite, Category = WheelStepTest, meta = (WheelStep = 10))
+	float MyFloat_HasWheelStep = 50;
+```
+
+## 效果图：
+
+默认值不指定UIMin，UIMax也可以鼠标轮滚动变化值。默认为1
+
+MyFloat_SmallWheelStep的UI范围只有10，则默认改变幅度0.1
+
+指定WheelStep =10，则一下子变化10
+
+![WheelStep2](WheelStep2.gif)
+
+## 原理：
+
+通过代码可知，如果设置了WheelStep则用该值。
+
+否则如果是浮点数且UI滚动条范围小于10，则WheelStep=0.1，否则为1
+
+否则如果是整数，则WheelStep=1
+
+```cpp
+	virtual FReply SSpinBox<NumericType>::OnMouseWheel(const FGeometry& MyGeometry, const FPointerEvent& MouseEvent) override
+	{
+		if (bEnableWheel && PointerDraggingSliderIndex == INDEX_NONE && HasKeyboardFocus())
+		{
+			// If there is no WheelStep defined, we use 1.0 (Or 0.1 if slider range is <= 10)
+			constexpr bool bIsIntegral = TIsIntegral<NumericType>::Value;
+			const bool bIsSmallStep = !bIsIntegral && (GetMaxSliderValue() - GetMinSliderValue()) <= 10.0;
+			double Step = WheelStep.IsSet() && WheelStep.Get().IsSet() ? WheelStep.Get().GetValue() : (bIsSmallStep ? 0.1 : 1.0);
+
+			if (MouseEvent.IsControlDown())
+			{
+				// If no value is set for WheelSmallStep, we use the DefaultStep multiplied by the CtrlMultiplier
+				Step *= CtrlMultiplier.Get();
+			}
+			else if (MouseEvent.IsShiftDown())
+			{
+				// If no value is set for WheelBigStep, we use the DefaultStep multiplied by the ShiftMultiplier
+				Step *= ShiftMultiplier.Get();
+			}
+
+			const double Sign = (MouseEvent.GetWheelDelta() > 0) ? 1.0 : -1.0;
+			const double NewValue = InternalValue + (Sign * Step);
+			const NumericType RoundedNewValue = RoundIfIntegerValue(NewValue);
+
+			return FReply::Handled();
+		}
+
+		return FReply::Unhandled();
+	}
+```