More work on radial menus

Source/Integration/RadialMenu.h

@@ -0,0 +1,60 @@
+//
+// This class implements the layout calculatations for a radial
+// menu.
+//
+
+#pragma once
+
+#include "CoreMinimal.h"
+#include "RadialMenu.generated.h"
+
+
+USTRUCT(BlueprintType)
+struct FRadialMenuItem
+{
+    GENERATED_BODY()
+
+    FVector2D Point1 = {0,0};
+    FVector2D Point2 = {0,0};
+    FVector2D Point3 = {0,0};
+    bool RightSide = false;
+};
+
+UCLASS(BlueprintType)
+class URadialMenu : public UObject
+{
+    GENERATED_BODY()
+
+public:
+    UFUNCTION(BlueprintCallable)
+    void Configure(int32 NItems, float ItemHeight, float InnerRadius, float MinSpoke, float Spread);
+
+    UFUNCTION(BlueprintCallable)
+    int32 NumItems() const { return Items.Num(); }
+
+    UFUNCTION(BlueprintCallable)
+    const TArray<FRadialMenuItem> GetItems() const { return Items; }
+
+    TArray<FRadialMenuItem> Items;
+
+private:
+    using View = TArrayView<FRadialMenuItem>;
+
+    void CalculateSide(View V);
+    void FlipHorizontal(View V);
+
+    // The half-circle is divided into pie slices.  Returns a direction vector
+    // which aims directly down the center of the pie slice.
+    FVector2D PieSliceToVector(double Slice, double Slices);
+    
+    int32 CNItems = 0;
+    float CItemHeight = 0;
+    float CInnerRadius = 0;
+    float CMinSpoke = 0;
+    float CSpread = 0;
+    int32 CNumLeft = 0;
+    int32 CNumRight = 0;
+    View LeftItems;
+    View RightItems;
+};
+