Lots of work on focus management

Source/Integration/InputModeRequest.h

@@ -0,0 +1,99 @@
+////////////////////////////////////////////////////////////
+//
+// InputModeRequest.h
+//
+// Custom input event dispatching system. Uses Unreal's
+// built-in input modes (GameOnly / UIOnly) with an
+// enhanced input component for GameOnly mode hotkeys.
+//
+////////////////////////////////////////////////////////////
+
+#pragma once
+
+#include "CoreMinimal.h"
+#include "Blueprint/UserWidget.h"
+#include "InputModeRequest.generated.h"
+
+
+
+////////////////////////////////////////////////////////////
+//
+// FlxInputModeRequest
+//
+// Using this struct, a Widget can express a need for a
+// particular input mode.  These requests go to the player
+// controller, which arbitrates.
+//
+////////////////////////////////////////////////////////////
+
+USTRUCT(BlueprintType)
+struct FlxInputModeRequest
+{
+	GENERATED_BODY()
+
+	FlxInputModeRequest() = default;
+
+	bool operator == (const FlxInputModeRequest &Other) const;
+
+	// True if this request wants any high-priority resource:
+	// keyboard focus, the mouse pointer, or input blocking.
+	bool IsHighPrio() const { return Focus != nullptr || ShowPointer || BlockInput; }
+
+	UPROPERTY(BlueprintReadWrite)
+	UUserWidget* Widget = nullptr;
+
+	UPROPERTY(BlueprintReadWrite)
+	UWidget* Focus = nullptr;
+
+	UPROPERTY(BlueprintReadWrite)
+	bool ShowPointer = false;
+
+	UPROPERTY(BlueprintReadWrite)
+	bool BlockInput = false;
+
+	UPROPERTY(BlueprintReadWrite)
+	bool EnableInputComponent = true;
+
+	UPROPERTY()
+	int32 SequenceNumber = 0;
+
+};
+
+USTRUCT()
+struct FlxInputModeRequests
+{
+	GENERATED_BODY()
+
+private:
+	UPROPERTY()
+	// Sorted by highest priority first, then most recent first.
+	TArray<FlxInputModeRequest> Requests;
+
+	UPROPERTY()
+	int32 NextSequenceNumber = 0;
+
+public:
+	using View = TArrayView<FlxInputModeRequest>;
+
+	// Get the requests array.
+	const TArray<FlxInputModeRequest> &GetRequests() const { return Requests; }
+
+	// Sanity check a request to see if it is reasonable.
+	static bool SanityCheck(const FlxInputModeRequest &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 FlxInputModeRequest &NewRequest);
+
+	// Find the specified widget, and modify the 'EnableInputComponent'
+	// flag.  Adds the widget if it's not already present.
+	void SetEnableInputComponent(UUserWidget *Widget, bool EnableInputComponent);
+
+	// Remove all requests by the specified widget.
+	void Remove(UUserWidget *Widget);
+
+	// Remove any requests by dead widgets or widgets with no parents.
+	void GarbageCollect();
+};