First step of new focus management system

Source/Integration/InputEvents.h

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+////////////////////////////////////////////////////////////
+//
+// InputEvents.h
+//
+// Custom input event dispatching system. Uses Unreal's
+// built-in input modes (GameOnly / UIOnly) with an
+// enhanced input component for character mode hotkeys.
+//
+////////////////////////////////////////////////////////////
+
+#pragma once
+
+#include "CoreMinimal.h"
+#include "InputCoreTypes.h"
+#include "Blueprint/UserWidget.h"
+#include "InputEvents.generated.h"
+
+////////////////////////////////////////////////////////////
+//
+// FlxEventRequest
+//
+// A widget's declaration of interest in input events.
+//
+//   Widget:      The widget that wants to receive events.
+//   TakeControl: If true, activating this request puts
+//                the system into Widget Mode.
+//   ShowPointer: If true, the mouse pointer should be
+//                visible when this widget has control.
+//   Hotkeys:     Keys that go to this widget when the
+//                player is in Character mode.
+//
+////////////////////////////////////////////////////////////
+
+USTRUCT(BlueprintType)
+struct FlxEventRequest
+{
+	GENERATED_BODY()
+
+	FlxEventRequest() = default;
+	FlxEventRequest(UUserWidget *InWidget, bool InTakeControl, bool InShowPointer, const TArray<FKey> &InHotkeys)
+		: Widget(InWidget), TakeControl(InTakeControl), ShowPointer(InShowPointer), Hotkeys(InHotkeys) {}
+
+	bool operator == (const FlxEventRequest &Other) const;
+
+	UPROPERTY(BlueprintReadWrite)
+	UUserWidget* Widget = nullptr;
+
+	UPROPERTY(BlueprintReadWrite)
+	bool TakeControl = false;
+
+	UPROPERTY(BlueprintReadWrite)
+	bool ShowPointer = false;
+
+	UPROPERTY(BlueprintReadWrite)
+	TArray<FKey> Hotkeys;
+};
+
+USTRUCT()
+struct FlxEventRequests
+{
+	GENERATED_BODY()
+
+private:
+	UPROPERTY()
+	// High priority requests are always before low-priority.
+	// Otherwise, these are in order of most recent first.
+	TArray<FlxEventRequest> Requests;
+
+	UPROPERTY()
+	bool Dirty = true;
+
+public:
+	enum class InputMode { UIOnly, GameOnly };
+
+	using View = TArrayView<FlxEventRequest>;
+
+	// Get the requests array.
+	const TArray<FlxEventRequest> &GetRequests() const { return Requests; }
+
+	// Sanity check a request to see if it is reasonable.
+	static bool SanityCheck(const FlxEventRequest &Request);
+	
+	// Divide Requests into a high-priority slice and a low-priority slice.
+	void SplitHighLow(View &High, View &Low); 
+
+	// Apply a request.  Replaces any previous request by the same widget.
+	void Request(const FlxEventRequest &NewRequest);
+
+	// Remove all requests by the specified widget.
+	void Remove(UUserWidget *Widget);
+
+	// Remove any requests by dead widgets or widgets with no parents.
+	void GarbageCollect();
+
+	// Return true if the requests have changed since the last ClearDirty.
+	bool IsDirty() { return Dirty; }
+
+	// Clear the dirty flag.
+	void ClearDirty() { Dirty = false; }
+
+	// Set the dirty flag.
+	void SetDirty() { Dirty = true; }
+
+	// Get the currently-requested mode.
+	InputMode GetRequestedMode() const;
+};