UnrealImGui/Source/ImGui/Private/SImGuiWidget.cpp

// Distributed under the MIT License (MIT) (see accompanying LICENSE file)

#include "ImGuiPrivatePCH.h"

#include "SImGuiWidget.h"

#include "ImGuiContextManager.h"
#include "ImGuiContextProxy.h"
#include "ImGuiImplementation.h"
#include "ImGuiInputHandler.h"
#include "ImGuiInputHandlerFactory.h"
#include "ImGuiInteroperability.h"
#include "ImGuiModuleManager.h"
#include "ImGuiSettings.h"
#include "TextureManager.h"
#include "Utilities/Arrays.h"
#include "Utilities/ScopeGuards.h"

#include <Engine/Console.h>

#include <utility>


// High enough z-order guarantees that ImGui output is rendered on top of the game UI.
constexpr int32 IMGUI_WIDGET_Z_ORDER = 10000;


#if IMGUI_WIDGET_DEBUG

DEFINE_LOG_CATEGORY_STATIC(LogImGuiWidget, Warning, All);

#define IMGUI_WIDGET_LOG(Verbosity, Format, ...) UE_LOG(LogImGuiWidget, Verbosity, Format, __VA_ARGS__)

#define TEXT_INPUT_MODE(Val) (\
	(Val) == EInputMode::Full ? TEXT("Full") :\
	(Val) == EInputMode::MousePointerOnly ? TEXT("MousePointerOnly") :\
	TEXT("None"))

#define TEXT_BOOL(Val) ((Val) ? TEXT("true") : TEXT("false"))

#else

#define IMGUI_WIDGET_LOG(...)

#endif // IMGUI_WIDGET_DEBUG

namespace
{
	const FColor CanvasFrameColor = { 16, 16, 16 };
	const FColor ViewportFrameColor = { 204, 74, 10 };
	const FColor ViewportFrameHighlightColor = { 255, 110, 38 };

	constexpr const char* PlainTextureName = "ImGuiModule_Plain";
	constexpr const char* FontAtlasTextureName = "ImGuiModule_FontAtlas";
}

#if IMGUI_WIDGET_DEBUG
namespace CVars
{
	TAutoConsoleVariable<int> DebugWidget(TEXT("ImGui.Debug.Widget"), 0,
		TEXT("Show debug for SImGuiWidget.\n")
		TEXT("0: disabled (default)\n")
		TEXT("1: enabled"),
		ECVF_Default);

	TAutoConsoleVariable<int> DebugInput(TEXT("ImGui.Debug.Input"), 0,
		TEXT("Show debug for input state.\n")
		TEXT("0: disabled (default)\n")
		TEXT("1: enabled"),
		ECVF_Default);
}
#endif // IMGUI_WIDGET_DEBUG

BEGIN_SLATE_FUNCTION_BUILD_OPTIMIZATION
void SImGuiWidget::Construct(const FArguments& InArgs)
{
	checkf(InArgs._ModuleManager, TEXT("Null Module Manager argument"));
	checkf(InArgs._GameViewport, TEXT("Null Game Viewport argument"));

	ModuleManager = InArgs._ModuleManager;
	GameViewport = InArgs._GameViewport;
	ContextIndex = InArgs._ContextIndex;

	// NOTE: We could allow null game viewports (for instance to attach to non-viewport widgets) but we would need
	// to modify a few functions that assume valid viewport pointer.
	GameViewport->AddViewportWidgetContent(SharedThis(this), IMGUI_WIDGET_Z_ORDER);

	// Disable mouse cursor over this widget as we will use ImGui to draw it.
	SetCursor(EMouseCursor::None);

	// Sync visibility with default input enabled state.
	SetVisibilityFromInputEnabled();

	// Register to get post-update notifications, so we can clean frame updates.
	ModuleManager->OnPostImGuiUpdate().AddRaw(this, &SImGuiWidget::OnPostImGuiUpdate);

	// Bind this widget to its context proxy.
	auto* ContextProxy = ModuleManager->GetContextManager().GetContextProxy(ContextIndex);
	checkf(ContextProxy, TEXT("Missing context during widget construction: ContextIndex = %d"), ContextIndex);
#if IMGUI_WIDGET_DEBUG
	ContextProxy->OnDraw().AddRaw(this, &SImGuiWidget::OnDebugDraw);
#endif // IMGUI_WIDGET_DEBUG
	ContextProxy->SetInputState(&InputState);

	// Cache locally software cursor mode.
	UpdateSoftwareCursorMode();

	// Create ImGui Input Handler.
	CreateInputHandler();

	// Register for settings change.
	RegisterImGuiSettingsDelegates();
}
END_SLATE_FUNCTION_BUILD_OPTIMIZATION

SImGuiWidget::~SImGuiWidget()
{
	// Stop listening for settings change.
	UnregisterImGuiSettingsDelegates();

	// Release ImGui Input Handler.
	ReleaseInputHandler();

	// Remove binding between this widget and its context proxy.
	if (auto* ContextProxy = ModuleManager->GetContextManager().GetContextProxy(ContextIndex))
	{
#if IMGUI_WIDGET_DEBUG
		ContextProxy->OnDraw().RemoveAll(this);
#endif // IMGUI_WIDGET_DEBUG
		ContextProxy->RemoveInputState(&InputState);
	}

	// Unregister from post-update notifications.
	ModuleManager->OnPostImGuiUpdate().RemoveAll(this);
}

void SImGuiWidget::Detach()
{
	if (GameViewport.IsValid())
	{
		GameViewport->RemoveViewportWidgetContent(SharedThis(this));
		GameViewport.Reset();
	}
}

void SImGuiWidget::Tick(const FGeometry& AllottedGeometry, const double InCurrentTime, const float InDeltaTime)
{
	Super::Tick(AllottedGeometry, InCurrentTime, InDeltaTime);

	UpdateMouseStatus();

	// Note: Moving that update to console variable sink or callback might seem like a better alternative but input
	// setup in this function is better handled here.
	UpdateInputEnabled();
}

namespace
{
	FReply ToSlateReply(const FImGuiInputResponse& HandlingResponse)
	{
		return HandlingResponse.HasConsumeRequest() ? FReply::Handled() : FReply::Unhandled();
	}
}

FReply SImGuiWidget::OnKeyChar(const FGeometry& MyGeometry, const FCharacterEvent& CharacterEvent)
{
	const FImGuiInputResponse Response = InputHandler->OnKeyChar(CharacterEvent);
	if (Response.HasProcessingRequest())
	{
		InputState.AddCharacter(CharacterEvent.GetCharacter());
	}

	return ToSlateReply(Response);
}

FReply SImGuiWidget::OnKeyDown(const FGeometry& MyGeometry, const FKeyEvent& KeyEvent)
{
	if (KeyEvent.GetKey().IsGamepadKey())
	{
		if (InputState.IsGamepadNavigationEnabled())
		{
			const FImGuiInputResponse Response = InputHandler->OnGamepadKeyDown(KeyEvent);
			if (Response.HasProcessingRequest())
			{
				InputState.SetGamepadNavigationKey(KeyEvent, true);
			}

			return ToSlateReply(Response);
		}
		else
		{
			return Super::OnKeyDown(MyGeometry, KeyEvent);
		}
	}
	else
	{
		UpdateCanvasMapMode(KeyEvent);

		const FImGuiInputResponse Response = InputHandler->OnKeyDown(KeyEvent);
		if (Response.HasProcessingRequest())
		{
			InputState.SetKeyDown(KeyEvent, true);
			CopyModifierKeys(KeyEvent);
		}

		return WithMouseLockRequests(ToSlateReply(Response));
	}
}

FReply SImGuiWidget::OnKeyUp(const FGeometry& MyGeometry, const FKeyEvent& KeyEvent)
{
	if (KeyEvent.GetKey().IsGamepadKey())
	{
		if (InputState.IsGamepadNavigationEnabled())
		{
			// Always handle key up events to protect from leaving accidental keys not cleared in ImGui input state.
			InputState.SetGamepadNavigationKey(KeyEvent, false);

			return ToSlateReply(InputHandler->OnGamepadKeyUp(KeyEvent));
		}
		else
		{
			return Super::OnKeyUp(MyGeometry, KeyEvent);
		}
	}
	else
	{
		UpdateCanvasMapMode(KeyEvent);

		// Always handle key up events to protect from leaving accidental keys not cleared in ImGui input state.
		InputState.SetKeyDown(KeyEvent, false);
		CopyModifierKeys(KeyEvent);

		return WithMouseLockRequests(ToSlateReply(InputHandler->OnKeyUp(KeyEvent)));
	}
}

FReply SImGuiWidget::OnAnalogValueChanged(const FGeometry& MyGeometry, const FAnalogInputEvent& AnalogInputEvent)
{
	if (AnalogInputEvent.GetKey().IsGamepadKey() && InputState.IsGamepadNavigationEnabled())
	{
		const FImGuiInputResponse Response = InputHandler->OnGamepadAxis(AnalogInputEvent);
		if (Response.HasProcessingRequest())
		{
			InputState.SetGamepadNavigationAxis(AnalogInputEvent, AnalogInputEvent.GetAnalogValue());
		}

		return ToSlateReply(Response);
	}
	else
	{
		return Super::OnAnalogValueChanged(MyGeometry, AnalogInputEvent);
	}
}

FReply SImGuiWidget::OnMouseButtonDown(const FGeometry& MyGeometry, const FPointerEvent& MouseEvent)
{
	InputState.SetMouseDown(MouseEvent, true);
	CopyModifierKeys(MouseEvent);

	UpdateCanvasMapMode(MouseEvent);
	UpdateCanvasDraggingConditions(MouseEvent);

	return WithMouseLockRequests(FReply::Handled());
}

FReply SImGuiWidget::OnMouseButtonDoubleClick(const FGeometry& MyGeometry, const FPointerEvent& MouseEvent)
{
	InputState.SetMouseDown(MouseEvent, true);
	CopyModifierKeys(MouseEvent);

	UpdateCanvasMapMode(MouseEvent);
	UpdateCanvasDraggingConditions(MouseEvent);

	return WithMouseLockRequests(FReply::Handled());
}

FReply SImGuiWidget::OnMouseButtonUp(const FGeometry& MyGeometry, const FPointerEvent& MouseEvent)
{
	InputState.SetMouseDown(MouseEvent, false);
	CopyModifierKeys(MouseEvent);

	UpdateCanvasMapMode(MouseEvent);

	return WithMouseLockRequests(FReply::Handled());
}

FReply SImGuiWidget::OnMouseWheel(const FGeometry& MyGeometry, const FPointerEvent& MouseEvent)
{
	if (bCanvasMapMode)
	{
		AddCanvasScale(MouseEvent.GetWheelDelta());
	}
	else
	{
		InputState.AddMouseWheelDelta(MouseEvent.GetWheelDelta());
	}
	CopyModifierKeys(MouseEvent);

	return FReply::Handled();
}

FReply SImGuiWidget::OnMouseMove(const FGeometry& MyGeometry, const FPointerEvent& MouseEvent)
{
	if (bCanvasMapMode)
	{
		UpdateCanvasDragging(MyGeometry, MouseEvent);
	}

	const FVector2D CanvasScreenSpacePosition = MyGeometry.AbsolutePosition + GetCanvasPosition(CanvasScale, CanvasOffset);
	InputState.SetMousePosition((MouseEvent.GetScreenSpacePosition() - CanvasScreenSpacePosition) / CanvasScale);
	CopyModifierKeys(MouseEvent);

	// This event is called in every frame when we have a mouse, so we can use it to raise notifications.
	NotifyMouseEvent();

	UpdateCanvasMapMode(MouseEvent);

	return WithMouseLockRequests(FReply::Handled());
}

FReply SImGuiWidget::OnFocusReceived(const FGeometry& MyGeometry, const FFocusEvent& FocusEvent)
{
	Super::OnFocusReceived(MyGeometry, FocusEvent);

	IMGUI_WIDGET_LOG(VeryVerbose, TEXT("ImGui Widget %d - Focus Received."), ContextIndex);

	// If widget has a keyboard focus we always maintain mouse input. Technically, if mouse is outside of the widget
	// area it won't generate events but we freeze its state until it either comes back or input is completely lost.
	UpdateInputMode(true, IsDirectlyHovered());

	FSlateApplication::Get().ResetToDefaultPointerInputSettings();
	return WithMouseLockRequests(FReply::Handled());
}

void SImGuiWidget::OnFocusLost(const FFocusEvent& FocusEvent)
{
	Super::OnFocusLost(FocusEvent);

	IMGUI_WIDGET_LOG(VeryVerbose, TEXT("ImGui Widget %d - Focus Lost."), ContextIndex);

	UpdateInputMode(false, IsDirectlyHovered());
}

void SImGuiWidget::OnMouseEnter(const FGeometry& MyGeometry, const FPointerEvent& MouseEvent)
{
	Super::OnMouseEnter(MyGeometry, MouseEvent);

	IMGUI_WIDGET_LOG(VeryVerbose, TEXT("ImGui Widget %d - Mouse Enter."), ContextIndex);

	// If mouse enters while input is active then we need to update mouse buttons because there is a chance that we
	// missed some events.
	if (InputMode != EInputMode::None)
	{
		for (const FKey& Button : { EKeys::LeftMouseButton, EKeys::MiddleMouseButton, EKeys::RightMouseButton, EKeys::ThumbMouseButton, EKeys::ThumbMouseButton2 })
		{
			InputState.SetMouseDown(Button, MouseEvent.IsMouseButtonDown(Button));
		}
	}

	UpdateInputMode(HasKeyboardFocus(), true);
}

void SImGuiWidget::OnMouseLeave(const FPointerEvent& MouseEvent)
{
	Super::OnMouseLeave(MouseEvent);

	IMGUI_WIDGET_LOG(VeryVerbose, TEXT("ImGui Widget %d - Mouse Leave."), ContextIndex);

	// We don't get any events when application loses focus, but often this is followed by OnMouseLeave, so we can use
	// this event to immediately disable keyboard input if application lost focus.
	UpdateInputMode(HasKeyboardFocus() && GameViewport->Viewport->IsForegroundWindow(), false);
}

FCursorReply SImGuiWidget::OnCursorQuery(const FGeometry& MyGeometry, const FPointerEvent& CursorEvent) const
{
	EMouseCursor::Type MouseCursor = EMouseCursor::None;
	if (MouseCursorOverride != EMouseCursor::None)
	{
		MouseCursor = MouseCursorOverride;
	}
	else if (!bUseSoftwareCursor)
	{
		if (FImGuiContextProxy* ContextProxy = ModuleManager->GetContextManager().GetContextProxy(ContextIndex))
		{
			MouseCursor = ContextProxy->GetMouseCursor();
		}
	}

	return FCursorReply::Cursor(MouseCursor);
}

void SImGuiWidget::CreateInputHandler()
{
	if (!InputHandler.IsValid())
	{
		InputHandler = FImGuiInputHandlerFactory::NewHandler(ModuleManager, GameViewport.Get(), ContextIndex);
	}
}

void SImGuiWidget::ReleaseInputHandler()
{
	if (InputHandler.IsValid())
	{
		FImGuiInputHandlerFactory::ReleaseHandler(InputHandler.Get());
		InputHandler.Reset();
	}
}

void SImGuiWidget::RecreateInputHandler()
{
	ReleaseInputHandler();
	CreateInputHandler();
}

void SImGuiWidget::UpdateSoftwareCursorMode()
{
	UImGuiSettings* Settings = GetMutableDefault<UImGuiSettings>();
	bUseSoftwareCursor = Settings && Settings->UseSoftwareCursor();
}

void SImGuiWidget::RegisterImGuiSettingsDelegates()
{
	if (UImGuiSettings* Settings = GetMutableDefault<UImGuiSettings>())
	{
		if (!Settings->OnImGuiInputHandlerClassChanged.IsBoundToObject(this))
		{
			Settings->OnImGuiInputHandlerClassChanged.AddRaw(this, &SImGuiWidget::RecreateInputHandler);
		}
		if (!Settings->OnSoftwareCursorChanged.IsBoundToObject(this))
		{
			Settings->OnSoftwareCursorChanged.AddRaw(this, &SImGuiWidget::UpdateSoftwareCursorMode);
		}
	}
}

void SImGuiWidget::UnregisterImGuiSettingsDelegates()
{
	if (UImGuiSettings* Settings = GetMutableDefault<UImGuiSettings>())
	{
		Settings->OnImGuiInputHandlerClassChanged.RemoveAll(this);
		Settings->OnSoftwareCursorChanged.RemoveAll(this);
	}
}

FReply SImGuiWidget::WithMouseLockRequests(FReply&& Reply)
{
	const bool bNeedMouseLock = bCanvasDragging || bFrameDragging;
	if (bNeedMouseLock != bMouseLock)
	{
		bMouseLock = bNeedMouseLock;
		if (bMouseLock)
		{
			Reply.LockMouseToWidget(SharedThis(this));
		}
		else
		{
			Reply.ReleaseMouseLock();
		}
	}

	return Reply;
}

void SImGuiWidget::CopyModifierKeys(const FInputEvent& InputEvent)
{
	InputState.SetControlDown(InputEvent.IsControlDown());
	InputState.SetShiftDown(InputEvent.IsShiftDown());
	InputState.SetAltDown(InputEvent.IsAltDown());
}

void SImGuiWidget::CopyModifierKeys(const FPointerEvent& MouseEvent)
{
	if (InputMode == EInputMode::MousePointerOnly)
	{
		CopyModifierKeys(static_cast<const FInputEvent&>(MouseEvent));
	}
}

bool SImGuiWidget::IsConsoleOpened() const
{
	return GameViewport->ViewportConsole && GameViewport->ViewportConsole->ConsoleState != NAME_None;
}

void SImGuiWidget::SetMouseCursorOverride(EMouseCursor::Type InMouseCursorOverride)
{
	if (MouseCursorOverride != InMouseCursorOverride)
	{
		MouseCursorOverride = InMouseCursorOverride;
		FSlateApplication::Get().QueryCursor();
		InputState.SetMousePointer(bUseSoftwareCursor && MouseCursorOverride == EMouseCursor::None && IsDirectlyHovered());
	}
}

void SImGuiWidget::SetVisibilityFromInputEnabled()
{
	// If we don't use input disable hit test to make this widget invisible for cursors hit detection.
	SetVisibility(bInputEnabled ? EVisibility::Visible : EVisibility::HitTestInvisible);

	IMGUI_WIDGET_LOG(VeryVerbose, TEXT("ImGui Widget %d - Visibility updated to '%s'."),
		ContextIndex, *GetVisibility().ToString());
}

void SImGuiWidget::UpdateInputEnabled()
{
	const bool bEnabled = ModuleManager && ModuleManager->GetProperties().IsInputEnabled();
	if (bInputEnabled != bEnabled)
	{
		bInputEnabled = bEnabled;

		IMGUI_WIDGET_LOG(Log, TEXT("ImGui Widget %d - Input Enabled changed to '%s'."),
			ContextIndex, TEXT_BOOL(bInputEnabled));

		SetVisibilityFromInputEnabled();

		if (!bInputEnabled)
		{
			auto& Slate = FSlateApplication::Get();
			if (Slate.GetKeyboardFocusedWidget().Get() == this)
			{
				Slate.ResetToDefaultPointerInputSettings();
				Slate.SetUserFocus(Slate.GetUserIndexForKeyboard(),
					PreviousUserFocusedWidget.IsValid() ? PreviousUserFocusedWidget.Pin() : GameViewport->GetGameViewportWidget());
			}

			PreviousUserFocusedWidget.Reset();

			UpdateInputMode(false, false);
		}
	}

	// Note: Some widgets, like console, can reset focus to viewport after we already grabbed it. If we detect that
	// viewport has a focus while input is enabled we will take it.
	if (bInputEnabled && !HasKeyboardFocus() && !IsConsoleOpened())
	{
		const auto& ViewportWidget = GameViewport->GetGameViewportWidget();
		if (ViewportWidget->HasKeyboardFocus() || ViewportWidget->HasFocusedDescendants())
		{
			auto& Slate = FSlateApplication::Get();
			PreviousUserFocusedWidget = Slate.GetUserFocusedWidget(Slate.GetUserIndexForKeyboard());
			Slate.SetKeyboardFocus(SharedThis(this));
		}
	}

	// We don't get any events when application loses focus (we get OnMouseLeave but not always) but we fix it with
	// this manual check. We still allow the above code to run, even if we need to suppress keyboard input right after
	// that.
	if (bInputEnabled && !GameViewport->Viewport->IsForegroundWindow() && InputMode == EInputMode::Full)
	{
		UpdateInputMode(false, IsDirectlyHovered());
	}

	if (bInputEnabled)
	{
		InputState.SetKeyboardNavigationEnabled(ModuleManager && ModuleManager->GetProperties().IsKeyboardNavigationEnabled());
		InputState.SetGamepadNavigationEnabled(ModuleManager && ModuleManager->GetProperties().IsGamepadNavigationEnabled());
		const auto& Application = FSlateApplication::Get().GetPlatformApplication();
		InputState.SetGamepad(Application.IsValid() && Application->IsGamepadAttached());
	}
}

void SImGuiWidget::UpdateInputMode(bool bHasKeyboardFocus, bool bHasMousePointer)
{
	const EInputMode NewInputMode =
		bHasKeyboardFocus ? EInputMode::Full :
		bHasMousePointer ? EInputMode::MousePointerOnly :
		EInputMode::None;

	if (InputMode != NewInputMode)
	{
		IMGUI_WIDGET_LOG(Verbose, TEXT("ImGui Widget %d - Input Mode changed from '%s' to '%s'."),
			ContextIndex, TEXT_INPUT_MODE(InputMode), TEXT_INPUT_MODE(NewInputMode));

		// We need to reset input components if we are either fully shutting down or we are downgrading from full to
		// mouse-only input mode.
		if (NewInputMode == EInputMode::None)
		{
			InputState.ResetState();
		}
		else if (InputMode == EInputMode::Full)
		{
			InputState.ResetKeyboardState();
			InputState.ResetNavigationState();
		}

		InputMode = NewInputMode;

		ClearMouseEventNotification();

		if (InputMode != EInputMode::Full)
		{
			SetCanvasMapMode(false);
		}
	}

	InputState.SetMousePointer(bUseSoftwareCursor && MouseCursorOverride == EMouseCursor::None && bHasMousePointer);
}

void SImGuiWidget::UpdateMouseStatus()
{
	// Note: Mouse leave events can get lost if other viewport takes mouse capture (for instance console is opened by
	// different viewport when this widget is hovered). With that we lose a chance to cleanup and hide ImGui pointer.
	// We could either update ImGui pointer in every frame or like below, use mouse events to catch when mouse is lost.

	if (InputMode == EInputMode::MousePointerOnly)
	{
		if (!HasMouseEventNotification())
		{
			UpdateInputMode(false, IsDirectlyHovered());
		}
		ClearMouseEventNotification();
	}
}

void SImGuiWidget::OnPostImGuiUpdate()
{
	if (InputMode != EInputMode::None)
	{
		InputState.ClearUpdateState();
	}

	// Remember values associated with input state send to ImGui, so we can use them when rendering frame output.
	ImGuiFrameCanvasScale = CanvasScale;
	ImGuiFrameCanvasOffset = CanvasOffset;

	// Update canvas scale.
	UdateCanvasScale(FSlateApplication::Get().GetDeltaTime());
}

void SImGuiWidget::UpdateCanvasMapMode(const FInputEvent& InputEvent)
{
	SetCanvasMapMode(InputEvent.IsLeftAltDown() && InputEvent.IsLeftShiftDown());
}

void SImGuiWidget::SetCanvasMapMode(bool bEnabled)
{
	if (bEnabled != bCanvasMapMode)
	{
		bCanvasMapMode = bEnabled;

		if (!bCanvasMapMode)
		{
			if (TargetCanvasScale != 1.f)
			{
				TargetCanvasScale = 1.f;
			}

			bCanvasDragging = false;
			bFrameDragging = false;
			bFrameDraggingReady = false;
			SetMouseCursorOverride(EMouseCursor::None);
		}
	}
}

void SImGuiWidget::AddCanvasScale(float Delta)
{
	TargetCanvasScale = FMath::Clamp(TargetCanvasScale + Delta * 0.05f, GetMinCanvasScale(), 1.f);
}

void SImGuiWidget::UdateCanvasScale(float DeltaSeconds)
{
	if (CanvasScale != TargetCanvasScale)
	{
		CanvasScale = FMath::Lerp(CanvasScale, TargetCanvasScale, DeltaSeconds * 25.f);

		if (FMath::Abs(CanvasScale - TargetCanvasScale) < KINDA_SMALL_NUMBER)
		{
			CanvasScale = TargetCanvasScale;
		}

		// If viewport frame is being dragged, move mouse to fix de-synchronization caused by scaling.
		if (bFrameDragging)
		{
			const FVector2D Position = GetCanvasPosition(CanvasScale, CanvasOffset) - CanvasScale * CanvasOffset + GetViewportSize() * CanvasScale * 0.5f;
			GameViewport->Viewport->SetMouse((int32)Position.X, (int32)Position.Y);

			// Ignore next mouse movement, so this syncing doesn't change canvas offset.
			bFrameDraggingSkipMouseMove = true;
		}
	}
}

void SImGuiWidget::UpdateCanvasDraggingConditions(const FPointerEvent& MouseEvent)
{
	if (bCanvasMapMode)
	{
		if (MouseEvent.GetEffectingButton() == EKeys::RightMouseButton)
		{
			bCanvasDragging = !bFrameDragging && MouseEvent.IsMouseButtonDown(EKeys::RightMouseButton)
				&& CanvasScale > GetMinCanvasScale();
		}
		else if (MouseEvent.GetEffectingButton() == EKeys::MiddleMouseButton)
		{
			bFrameDragging = bFrameDraggingReady && MouseEvent.IsMouseButtonDown(EKeys::MiddleMouseButton);
			if (bFrameDragging)
			{
				bFrameDraggingReady = false;
			}
		}
	}
}

namespace
{
	FORCEINLINE FVector2D Min(const FVector2D& A, const FVector2D& B)
	{
		return { FMath::Min(A.X, B.X), FMath::Min(A.Y, B.Y) };
	}

	FORCEINLINE FVector2D Max(const FVector2D& A, const FVector2D& B)
	{
		return { FMath::Max(A.X, B.X), FMath::Max(A.Y, B.Y) };
	}

	FORCEINLINE FVector2D Clamp(const FVector2D& V, const FVector2D& Min, const FVector2D& Max)
	{
		return { FMath::Clamp(V.X, Min.X, Max.X), FMath::Clamp(V.Y, Min.Y, Max.Y) };
	}
}

void SImGuiWidget::UpdateCanvasDragging(const FGeometry& MyGeometry, const FPointerEvent& MouseEvent)
{
	// We only start on mouse button down but we handle finishing here, to make sure that we don't miss any release
	// events (possible when tabbing out etc.).
	bCanvasDragging &= MouseEvent.IsMouseButtonDown(EKeys::RightMouseButton);
	bFrameDragging &= MouseEvent.IsMouseButtonDown(EKeys::MiddleMouseButton);

	bool bMouseLeftCanvas = false;

	FImGuiContextProxy* ContextProxy = ModuleManager->GetContextManager().GetContextProxy(ContextIndex);
	if (ContextProxy && GameViewport.IsValid())
	{
		const FVector2D CanvasScreenSpacePosition = MyGeometry.AbsolutePosition + GetCanvasPosition(CanvasScale, CanvasOffset);
		const FVector2D CanvasScreenSpaceMax = CanvasScreenSpacePosition + ContextProxy->GetDisplaySize() * CanvasScale;
		bMouseLeftCanvas = (MouseEvent.GetScreenSpacePosition().X > CanvasScreenSpaceMax.X) || (MouseEvent.GetScreenSpacePosition().Y > CanvasScreenSpaceMax.Y);

		if (bCanvasDragging)
		{
			CanvasOffset += MouseEvent.GetCursorDelta() / CanvasScale;
		}
		else if (bFrameDraggingSkipMouseMove)
		{
			bFrameDraggingSkipMouseMove = false;
		}
		else if (bFrameDragging)
		{
			// We can express canvas offset as a function of a viewport frame position and scale. With position and
			// mouse deltas equal we can find a ratio between canvas offset and mouse position deltas.
			const float DeltaPositionByOffset = (GetNormalizedCanvasScale(CanvasScale) - CanvasScale);

			// Function for viewport frame positions behaves nicely when zooming but derived function for canvas offset
			// delta has singularity in 1 - which actually makes sense because dragging frame loses context when it
			// takes the whole widget area. We can handle that by preventing dragging when scale is 1.
			if (DeltaPositionByOffset < 0.f)
			{
				// We drag viewport frame in a way that it always remain in the canvas rectangle (see below). But this
				// creates a dead zone around the widget edges, and to handle that we clamp down all the mouse deltas
				// while mouse is in that zone.
				const FVector2D ViewportSizeScaled = GetViewportSize() * CanvasScale;
				const FVector2D ActiveZoneMin = CanvasScreenSpacePosition + ViewportSizeScaled * 0.5f;
				const FVector2D ActiveZoneMax = CanvasScreenSpaceMax - ViewportSizeScaled * 0.5f;
				const FVector2D MaxLimits = Max(MouseEvent.GetScreenSpacePosition() - ActiveZoneMin, FVector2D::ZeroVector);
				const FVector2D MinLimits = Min(MouseEvent.GetScreenSpacePosition() - ActiveZoneMax, FVector2D::ZeroVector);

				CanvasOffset += Clamp(MouseEvent.GetCursorDelta(), MinLimits, MaxLimits) / FMath::Min(DeltaPositionByOffset, -0.1f);
			}
		}

		if (bCanvasDragging || bFrameDragging)
		{
			// Clamping canvas offset keeps the whole viewport frame inside of the canvas rectangle.
			const FVector2D ViewportSize = GetViewportSize();
			const FVector2D DisplaySize = ContextProxy->GetDisplaySize();
			CanvasOffset = Clamp(CanvasOffset, -DisplaySize + ViewportSize, FVector2D::ZeroVector);
		}

		bFrameDraggingReady = !bFrameDragging && !bCanvasDragging && CanvasScale < 1.f
			&& InFrameGrabbingRange(MouseEvent.GetScreenSpacePosition() - MyGeometry.AbsolutePosition, CanvasScale, CanvasOffset);
	}

	const EMouseCursor::Type CursorTypeOverride = (bFrameDragging || bCanvasDragging) ? EMouseCursor::GrabHandClosed
		: (bFrameDraggingReady) ? EMouseCursor::CardinalCross
		: (bMouseLeftCanvas) ? EMouseCursor::Default
		: EMouseCursor::None;

	SetMouseCursorOverride(CursorTypeOverride);
}

float SImGuiWidget::GetMinCanvasScale() const
{
	const FVector2D ViewportSize = GetViewportSize();
	const FVector2D CanvasSize = ModuleManager->GetContextManager().GetContextProxy(ContextIndex)->GetDisplaySize();
	return FMath::Min(ViewportSize.X / CanvasSize.X, ViewportSize.Y / CanvasSize.Y);
}

float SImGuiWidget::GetNormalizedCanvasScale(float Scale) const
{
	const float MinScale = GetMinCanvasScale();
	return (Scale - MinScale) / (1.f - MinScale);
}

FVector2D SImGuiWidget::GetCanvasPosition(float Scale, const FVector2D& Offset) const
{
	// Vast majority of calls will be with scale 1.0f.
	return (Scale == 1.f) ? Offset : Offset * GetNormalizedCanvasScale(Scale);
}

bool SImGuiWidget::InFrameGrabbingRange(const FVector2D& Position, float Scale, const FVector2D& Offset) const
{
	const FVector2D ViewportCenter = GetCanvasPosition(Scale, Offset) - Offset * Scale + GetViewportSize() * Scale * 0.5f;

	// Get the grab range based on cursor shape.
	FVector2D Size, UVMin, UVMax, OutlineUVMin, OutlineUVMax;
	const float Range = ImGuiImplementation::GetCursorData(ImGuiMouseCursor_ResizeAll, Size, UVMin, UVMax, OutlineUVMin, OutlineUVMax)
		? Size.GetMax() * 0.5f + 5.f : 25.f;

	return (Position - ViewportCenter).GetAbsMax() <= Range;
}

FVector2D SImGuiWidget::GetViewportSize() const
{
	FVector2D Size = FVector2D::ZeroVector;
	if (GameViewport.IsValid())
	{
		GameViewport->GetViewportSize(Size);
	}
	return Size;
}

namespace
{
	FORCEINLINE FVector2D RoundToFloat(const FVector2D& Vector)
	{
		return FVector2D{ FMath::RoundToFloat(Vector.X), FMath::RoundToFloat(Vector.Y) };
	}

	void AddLocalRectanglePoints(TArray<FVector2D> &OutPoints, const FGeometry& AllottedGeometry, const FVector2D& AbsoluteMin, const FVector2D& AbsoluteSize)
	{
		FVector2D LocalMin = AllottedGeometry.AbsoluteToLocal(AbsoluteMin) + FVector2D::UnitVector;
		FVector2D LocalMax = AllottedGeometry.AbsoluteToLocal(AbsoluteMin + AbsoluteSize);
		OutPoints.Append({
			FVector2D(LocalMin.X, LocalMin.Y),
			FVector2D(LocalMax.X, LocalMin.Y),
			FVector2D(LocalMax.X, LocalMax.Y),
			FVector2D(LocalMin.X, LocalMax.Y),
			FVector2D(LocalMin.X, LocalMin.Y - 1.f) // -1 to close properly
			});
	}

#if ENGINE_COMPATIBILITY_LEGACY_CLIPPING_API
	void AddQuad(TArray<FSlateVertex>& OutVertexBuffer, TArray<SlateIndex>& OutIndexBuffer, const FVector2D& Position, const FVector2D& Size,
		const FVector2D& UVMin, const FVector2D& UVMax, const FColor& Color, const FSlateRotatedClipRectType& InClipRect)
	{

		const uint32 IndexOffset = static_cast<uint32>(OutVertexBuffer.Num());

		FVector2D Min = RoundToFloat(Position) + FVector2D::UnitVector * 0.5f;
		FVector2D Max = RoundToFloat(Position + Size) + FVector2D::UnitVector * 0.5f;
		OutVertexBuffer.Append({
			FSlateVertex({}, { Min.X, Min.Y }, { UVMin.X, UVMin.Y }, Color, InClipRect),
			FSlateVertex({}, { Max.X, Min.Y }, { UVMax.X, UVMin.Y }, Color, InClipRect),
			FSlateVertex({}, { Max.X, Max.Y }, { UVMax.X, UVMax.Y }, Color, InClipRect),
			FSlateVertex({}, { Min.X, Max.Y }, { UVMin.X, UVMax.Y }, Color, InClipRect)
			});

		OutIndexBuffer.Append({ IndexOffset + 0U, IndexOffset + 1U, IndexOffset + 2U, IndexOffset + 0U, IndexOffset + 2U, IndexOffset + 3U });
	}
#else
	void AddQuad(TArray<FSlateVertex>& OutVertexBuffer, TArray<SlateIndex>& OutIndexBuffer, const FVector2D& Position, const FVector2D& Size,
		const FVector2D& UVMin, const FVector2D& UVMax, const FColor& Color)
	{
		const uint32 IndexOffset = static_cast<uint32>(OutVertexBuffer.Num());

		FVector2D Min = RoundToFloat(Position) + FVector2D::UnitVector * 0.5f;
		FVector2D Max = RoundToFloat(Position + Size) + FVector2D::UnitVector * 0.5f;
		OutVertexBuffer.Append({
			FSlateVertex::Make<ESlateVertexRounding::Disabled>({}, { Min.X, Min.Y }, { UVMin.X, UVMin.Y }, Color),
			FSlateVertex::Make<ESlateVertexRounding::Disabled>({}, { Max.X, Min.Y }, { UVMax.X, UVMin.Y }, Color),
			FSlateVertex::Make<ESlateVertexRounding::Disabled>({}, { Max.X, Max.Y }, { UVMax.X, UVMax.Y }, Color),
			FSlateVertex::Make<ESlateVertexRounding::Disabled>({}, { Min.X, Max.Y }, { UVMin.X, UVMax.Y }, Color)
			});

		OutIndexBuffer.Append({ IndexOffset + 0U, IndexOffset + 1U, IndexOffset + 2U, IndexOffset + 0U, IndexOffset + 2U, IndexOffset + 3U });
	}
#endif // ENGINE_COMPATIBILITY_LEGACY_CLIPPING_API
}

int32 SImGuiWidget::OnPaint(const FPaintArgs& Args, const FGeometry& AllottedGeometry, const FSlateRect& MyClippingRect,
	FSlateWindowElementList& OutDrawElements, int32 LayerId, const FWidgetStyle& WidgetStyle, bool bParentEnabled) const
{
	if (FImGuiContextProxy* ContextProxy = ModuleManager->GetContextManager().GetContextProxy(ContextIndex))
	{
		// Manually update ImGui context to minimise lag between creating and rendering ImGui output. This will also
		// keep frame tearing at minimum because it is executed at the very end of the frame.
		ContextProxy->Tick(FSlateApplication::Get().GetDeltaTime());

		// Calculate offset that will transform vertex positions to screen space - rounded to avoid half pixel offsets.
		const FVector2D CanvasScreenSpacePosition = MyClippingRect.GetTopLeft() + GetCanvasPosition(ImGuiFrameCanvasScale, ImGuiFrameCanvasOffset);

		// Calculate transform between ImGui canvas ans screen space (scale and then offset in Screen Space).
		const FTransform2D Transform{ ImGuiFrameCanvasScale, RoundToFloat(CanvasScreenSpacePosition) };

#if ENGINE_COMPATIBILITY_LEGACY_CLIPPING_API
		// Convert clipping rectangle to format required by Slate vertex.
		const FSlateRotatedRect VertexClippingRect{ MyClippingRect };
#endif // ENGINE_COMPATIBILITY_LEGACY_CLIPPING_API

		for (const auto& DrawList : ContextProxy->GetDrawData())
		{
#if ENGINE_COMPATIBILITY_LEGACY_CLIPPING_API
			DrawList.CopyVertexData(VertexBuffer, Transform, VertexClippingRect);

			// Get access to the Slate scissor rectangle defined in Slate Core API, so we can customize elements drawing.
			extern SLATECORE_API TOptional<FShortRect> GSlateScissorRect;
			auto GSlateScissorRectSaver = ScopeGuards::MakeStateSaver(GSlateScissorRect);
#else
			DrawList.CopyVertexData(VertexBuffer, Transform);
#endif // ENGINE_COMPATIBILITY_LEGACY_CLIPPING_API

			int IndexBufferOffset = 0;
			for (int CommandNb = 0; CommandNb < DrawList.NumCommands(); CommandNb++)
			{
				const auto& DrawCommand = DrawList.GetCommand(CommandNb, Transform);

				DrawList.CopyIndexData(IndexBuffer, IndexBufferOffset, DrawCommand.NumElements);

				// Advance offset by number of copied elements to position it for the next command.
				IndexBufferOffset += DrawCommand.NumElements;

				// Get texture resource handle for this draw command (null index will be also mapped to a valid texture).
				const FSlateResourceHandle& Handle = ModuleManager->GetTextureManager().GetTextureHandle(DrawCommand.TextureId);

				// Transform clipping rectangle to screen space and apply to elements that we draw.
				const FSlateRect ClippingRect = DrawCommand.ClippingRect.IntersectionWith(MyClippingRect);

#if ENGINE_COMPATIBILITY_LEGACY_CLIPPING_API
				GSlateScissorRect = FShortRect{ ClippingRect };
#else
				OutDrawElements.PushClip(FSlateClippingZone{ ClippingRect });
#endif // ENGINE_COMPATIBILITY_LEGACY_CLIPPING_API

				// Add elements to the list.
				FSlateDrawElement::MakeCustomVerts(OutDrawElements, LayerId, Handle, VertexBuffer, IndexBuffer, nullptr, 0, 0);

#if !ENGINE_COMPATIBILITY_LEGACY_CLIPPING_API
				OutDrawElements.PopClip();
#endif // ENGINE_COMPATIBILITY_LEGACY_CLIPPING_API
			}
		}

		// In canvas map mode we need to draw additional information helping with navigation and dragging.
		if (bCanvasMapMode)
		{
			const FVector2D ViewportSizeScaled = GetViewportSize() * ImGuiFrameCanvasScale;
			const FVector2D ViewportScreenSpacePosition = CanvasScreenSpacePosition - ImGuiFrameCanvasOffset * ImGuiFrameCanvasScale;

			const FColor FrameColor = bFrameDraggingReady ? ViewportFrameHighlightColor : ViewportFrameColor;

			TArray<FVector2D> Points;

			if (ImGuiFrameCanvasScale < 1.f)
			{
				// Add a fader outside of the ImGui canvas if it is smaller than widget/viewport area.
				const FVector2D CanvasSizeScaled = ContextProxy->GetDisplaySize() * ImGuiFrameCanvasScale;
				const TextureIndex PlainTextureIndex = ModuleManager->GetTextureManager().FindTextureIndex(FName{ PlainTextureName });
				if (PlainTextureIndex != INDEX_NONE)
				{
					const FVector2D CanvasScreenSpaceMax = CanvasScreenSpacePosition + CanvasSizeScaled;
					const FVector2D WidgetScreenSpaceMax = MyClippingRect.GetBottomRight() - FVector2D::UnitVector;
					FVector2D DeadZoneScreenSpaceMin = MyClippingRect.GetTopLeft();
					if (CanvasScreenSpaceMax.X < WidgetScreenSpaceMax.X)
					{
						DeadZoneScreenSpaceMin.X = CanvasScreenSpaceMax.X;
					}
					else if(CanvasScreenSpaceMax.Y < WidgetScreenSpaceMax.Y)
					{
						DeadZoneScreenSpaceMin.Y = CanvasScreenSpaceMax.Y;
					}

					if (!DeadZoneScreenSpaceMin.Equals(MyClippingRect.GetTopLeft()))
					{
						IndexBuffer.SetNum(0, false);
						VertexBuffer.SetNum(0, false);
#if ENGINE_COMPATIBILITY_LEGACY_CLIPPING_API
						AddQuad(VertexBuffer, IndexBuffer, DeadZoneScreenSpaceMin, MyClippingRect.GetBottomRight() - DeadZoneScreenSpaceMin,
							FVector2D::ZeroVector, FVector2D::ZeroVector, CanvasFrameColor.WithAlpha(128), VertexClippingRect);
#else
						AddQuad(VertexBuffer, IndexBuffer, DeadZoneScreenSpaceMin, MyClippingRect.GetBottomRight() - DeadZoneScreenSpaceMin,
							FVector2D::ZeroVector, FVector2D::ZeroVector, CanvasFrameColor.WithAlpha(128));
#endif // ENGINE_COMPATIBILITY_LEGACY_CLIPPING_API

						const FSlateResourceHandle& Handle = ModuleManager->GetTextureManager().GetTextureHandle(PlainTextureIndex);
						FSlateDrawElement::MakeCustomVerts(OutDrawElements, LayerId, Handle, VertexBuffer, IndexBuffer, nullptr, 0, 0);
					}
				}

				// Draw a scaled canvas border.
				AddLocalRectanglePoints(Points, AllottedGeometry, CanvasScreenSpacePosition, CanvasSizeScaled);
#if ENGINE_COMPATIBILITY_LEGACY_CLIPPING_API
				FSlateDrawElement::MakeLines(OutDrawElements, LayerId, AllottedGeometry.ToPaintGeometry(), Points, MyClippingRect,
					ESlateDrawEffect::None, FLinearColor{ CanvasFrameColor }, false);
#else
				FSlateDrawElement::MakeLines(OutDrawElements, LayerId, AllottedGeometry.ToPaintGeometry(), Points,
					ESlateDrawEffect::None, FLinearColor{ CanvasFrameColor }, false);
#endif // ENGINE_COMPATIBILITY_LEGACY_CLIPPING_API

				// Draw a movement gizmo (using ImGui move cursor).
				FVector2D Size, UVMin, UVMax, OutlineUVMin, OutlineUVMax;
				if (ImGuiImplementation::GetCursorData(ImGuiMouseCursor_ResizeAll, Size, UVMin, UVMax, OutlineUVMin, OutlineUVMax))
				{
					const TextureIndex FontAtlasIndex = ModuleManager->GetTextureManager().FindTextureIndex(FName{ FontAtlasTextureName });
					if (FontAtlasIndex != INDEX_NONE)
					{
						IndexBuffer.SetNum(0, false);
						VertexBuffer.SetNum(0, false);
#if ENGINE_COMPATIBILITY_LEGACY_CLIPPING_API
						AddQuad(VertexBuffer, IndexBuffer, ViewportScreenSpacePosition + ViewportSizeScaled * 0.5f - Size * 0.375f, Size * 0.75f,
							UVMin, UVMax, FrameColor.WithAlpha(bCanvasDragging ? 32 : 128), VertexClippingRect);
#else
						AddQuad(VertexBuffer, IndexBuffer, ViewportScreenSpacePosition + ViewportSizeScaled * 0.5f - Size * 0.375f, Size * 0.75f,
							UVMin, UVMax, FrameColor.WithAlpha(bCanvasDragging ? 32 : 128));
#endif // ENGINE_COMPATIBILITY_LEGACY_CLIPPING_API
						const FSlateResourceHandle& Handle = ModuleManager->GetTextureManager().GetTextureHandle(FontAtlasIndex);
						FSlateDrawElement::MakeCustomVerts(OutDrawElements, LayerId, Handle, VertexBuffer, IndexBuffer, nullptr, 0, 0);
					}
				}
			}

			// Draw frame representing area of the ImGui canvas that is visible when scale is 1.
			Points.SetNum(0, false);
			AddLocalRectanglePoints(Points, AllottedGeometry, ViewportScreenSpacePosition, ViewportSizeScaled);
#if ENGINE_COMPATIBILITY_LEGACY_CLIPPING_API
				FSlateDrawElement::MakeLines(OutDrawElements, LayerId, AllottedGeometry.ToPaintGeometry(), Points, MyClippingRect,
					ESlateDrawEffect::None, FLinearColor{ FrameColor }, false);
#else
				FSlateDrawElement::MakeLines(OutDrawElements, LayerId, AllottedGeometry.ToPaintGeometry(), Points,
				ESlateDrawEffect::None, FLinearColor{ FrameColor }, false);
#endif // ENGINE_COMPATIBILITY_LEGACY_CLIPPING_API
		}
	}

	return LayerId;
}

FVector2D SImGuiWidget::ComputeDesiredSize(float) const
{
	return FVector2D{ 3840.f, 2160.f };
}

#if IMGUI_WIDGET_DEBUG

static TArray<FKey> GetImGuiMappedKeys()
{
	TArray<FKey> Keys;
	Keys.Reserve(Utilities::ArraySize<ImGuiInterops::ImGuiTypes::FKeyMap>::value + 8);

	// ImGui IO key map.
	Keys.Emplace(EKeys::Tab);
	Keys.Emplace(EKeys::Left);
	Keys.Emplace(EKeys::Right);
	Keys.Emplace(EKeys::Up);
	Keys.Emplace(EKeys::Down);
	Keys.Emplace(EKeys::PageUp);
	Keys.Emplace(EKeys::PageDown);
	Keys.Emplace(EKeys::Home);
	Keys.Emplace(EKeys::End);
	Keys.Emplace(EKeys::Delete);
	Keys.Emplace(EKeys::BackSpace);
	Keys.Emplace(EKeys::Enter);
	Keys.Emplace(EKeys::Escape);
	Keys.Emplace(EKeys::A);
	Keys.Emplace(EKeys::C);
	Keys.Emplace(EKeys::V);
	Keys.Emplace(EKeys::X);
	Keys.Emplace(EKeys::Y);
	Keys.Emplace(EKeys::Z);

	// Modifier keys.
	Keys.Emplace(EKeys::LeftShift);
	Keys.Emplace(EKeys::RightShift);
	Keys.Emplace(EKeys::LeftControl);
	Keys.Emplace(EKeys::RightControl);
	Keys.Emplace(EKeys::LeftAlt);
	Keys.Emplace(EKeys::RightAlt);
	Keys.Emplace(EKeys::LeftCommand);
	Keys.Emplace(EKeys::RightCommand);

	return Keys;
}

// Column layout utilities.
namespace Columns
{
	template<typename FunctorType>
	static void CollapsingGroup(const char* Name, int Columns, FunctorType&& DrawContent)
	{
		if (ImGui::CollapsingHeader(Name, ImGuiTreeNodeFlags_DefaultOpen))
		{
			const int LastColumns = ImGui::GetColumnsCount();
			ImGui::Columns(Columns, nullptr, false);
			DrawContent();
			ImGui::Columns(LastColumns);
		}
	}
}

// Controls tweaked for 2-columns layout.
namespace TwoColumns
{
	template<typename FunctorType>
	static inline void CollapsingGroup(const char* Name, FunctorType&& DrawContent)
	{
		Columns::CollapsingGroup(Name, 2, std::forward<FunctorType>(DrawContent));
	}

	namespace
	{
		void LabelText(const char* Label)
		{
			ImGui::Text("%s:", Label);
		}

		void LabelText(const wchar_t* Label)
		{
			ImGui::Text("%ls:", Label);
		}
	}

	template<typename LabelType>
	static void Value(LabelType&& Label, int32 Value)
	{
		LabelText(Label); ImGui::NextColumn();
		ImGui::Text("%d", Value); ImGui::NextColumn();
	}

	template<typename LabelType>
	static void Value(LabelType&& Label, uint32 Value)
	{
		LabelText(Label); ImGui::NextColumn();
		ImGui::Text("%u", Value); ImGui::NextColumn();
	}

	template<typename LabelType>
	static void Value(LabelType&& Label, float Value)
	{
		LabelText(Label); ImGui::NextColumn();
		ImGui::Text("%f", Value); ImGui::NextColumn();
	}

	template<typename LabelType>
	static void Value(LabelType&& Label, bool bValue)
	{
		LabelText(Label); ImGui::NextColumn();
		ImGui::Text("%ls", TEXT_BOOL(bValue)); ImGui::NextColumn();
	}

	template<typename LabelType>
	static void Value(LabelType&& Label, const TCHAR* Value)
	{
		LabelText(Label); ImGui::NextColumn();
		ImGui::Text("%ls", Value); ImGui::NextColumn();
	}
}

namespace Styles
{
	template<typename FunctorType>
	static void TextHighlight(bool bHighlight, FunctorType&& DrawContent)
	{
		if (bHighlight)
		{
			ImGui::PushStyleColor(ImGuiCol_Text, { 1.f, 1.f, 0.5f, 1.f });
		}
		DrawContent();
		if (bHighlight)
		{
			ImGui::PopStyleColor();
		}
	}
}

void SImGuiWidget::OnDebugDraw()
{
	if (CVars::DebugWidget.GetValueOnGameThread() > 0)
	{
		bool bDebug = true;
		ImGui::SetNextWindowSize(ImVec2(380, 480), ImGuiSetCond_Once);
		if (ImGui::Begin("ImGui Widget Debug", &bDebug))
		{
			ImGui::Spacing();

			TwoColumns::CollapsingGroup("Context", [&]()
			{
				TwoColumns::Value("Context Index", ContextIndex);
				FImGuiContextProxy* ContextProxy = ModuleManager->GetContextManager().GetContextProxy(ContextIndex);
				TwoColumns::Value("Context Name", ContextProxy ? *ContextProxy->GetName() : TEXT("< Null >"));
				TwoColumns::Value("Game Viewport", *GameViewport->GetName());
			});

			TwoColumns::CollapsingGroup("Input Mode", [&]()
			{
				TwoColumns::Value("Input Enabled", bInputEnabled);
				TwoColumns::Value("Input Mode", TEXT_INPUT_MODE(InputMode));
				TwoColumns::Value("Input Has Mouse Pointer", InputState.HasMousePointer());
			});

			TwoColumns::CollapsingGroup("Widget", [&]()
			{
				TwoColumns::Value("Visibility", *GetVisibility().ToString());
				TwoColumns::Value("Is Hovered", IsHovered());
				TwoColumns::Value("Is Directly Hovered", IsDirectlyHovered());
				TwoColumns::Value("Has Keyboard Input", HasKeyboardFocus());
			});

			TwoColumns::CollapsingGroup("Viewport", [&]()
			{
				const auto& ViewportWidget = GameViewport->GetGameViewportWidget();
				TwoColumns::Value("Is Foreground Window", GameViewport->Viewport->IsForegroundWindow());
				TwoColumns::Value("Is Hovered", ViewportWidget->IsHovered());
				TwoColumns::Value("Is Directly Hovered", ViewportWidget->IsDirectlyHovered());
				TwoColumns::Value("Has Mouse Capture", ViewportWidget->HasMouseCapture());
				TwoColumns::Value("Has Keyboard Input", ViewportWidget->HasKeyboardFocus());
				TwoColumns::Value("Has Focused Descendants", ViewportWidget->HasFocusedDescendants());
				auto Widget = PreviousUserFocusedWidget.Pin();
				TwoColumns::Value("Previous User Focused", Widget.IsValid() ? *Widget->GetTypeAsString() : TEXT("None"));
			});
		}
		ImGui::End();

		if (!bDebug)
		{
			CVars::DebugWidget->Set(0, ECVF_SetByConsole);
		}
	}

	if (CVars::DebugInput.GetValueOnGameThread() > 0)
	{
		bool bDebug = true;
		ImGui::SetNextWindowSize(ImVec2(460, 480), ImGuiSetCond_Once);
		if (ImGui::Begin("ImGui Input State", &bDebug))
		{
			const ImVec4 HiglightColor{ 1.f, 1.f, 0.5f, 1.f };
			Columns::CollapsingGroup("Mapped Keys", 4, [&]()
			{
				static const auto& Keys = GetImGuiMappedKeys();

				const int32 Num = Keys.Num();

				// Simplified when slicing for two 2.
				const int32 RowsNum = (Num + 1) / 2;

				for (int32 Row = 0; Row < RowsNum; Row++)
				{
					for (int32 Col = 0; Col < 2; Col++)
					{
						const int32 Idx = Row + Col * RowsNum;
						if (Idx < Num)
						{
							const FKey& Key = Keys[Idx];
							const uint32 KeyIndex = ImGuiInterops::GetKeyIndex(Key);
							Styles::TextHighlight(InputState.GetKeys()[KeyIndex], [&]()
							{
								TwoColumns::Value(*Key.GetDisplayName().ToString(), KeyIndex);
							});
						}
						else
						{
							ImGui::NextColumn(); ImGui::NextColumn();
						}
					}
				}
			});

			Columns::CollapsingGroup("Modifier Keys", 4, [&]()
			{
				Styles::TextHighlight(InputState.IsShiftDown(), [&]() { ImGui::Text("Shift"); }); ImGui::NextColumn();
				Styles::TextHighlight(InputState.IsControlDown(), [&]() { ImGui::Text("Control"); }); ImGui::NextColumn();
				Styles::TextHighlight(InputState.IsAltDown(), [&]() { ImGui::Text("Alt"); }); ImGui::NextColumn();
				ImGui::NextColumn();
			});

			Columns::CollapsingGroup("Mouse Buttons", 4, [&]()
			{
				static const FKey Buttons[] = { EKeys::LeftMouseButton, EKeys::RightMouseButton,
					EKeys::MiddleMouseButton, EKeys::ThumbMouseButton, EKeys::ThumbMouseButton2 };

				const int32 Num = Utilities::GetArraySize(Buttons);

				// Simplified when slicing for two 2.
				const int32 RowsNum = (Num + 1) / 2;

				for (int32 Row = 0; Row < RowsNum; Row++)
				{
					for (int32 Col = 0; Col < 2; Col++)
					{
						const int32 Idx = Row + Col * RowsNum;
						if (Idx < Num)
						{
							const FKey& Button = Buttons[Idx];
							const uint32 MouseIndex = ImGuiInterops::GetMouseIndex(Button);
							Styles::TextHighlight(InputState.GetMouseButtons()[MouseIndex], [&]()
							{
								TwoColumns::Value(*Button.GetDisplayName().ToString(), MouseIndex);
							});
						}
						else
						{
							ImGui::NextColumn(); ImGui::NextColumn();
						}
					}
				}
			});

			Columns::CollapsingGroup("Mouse Axes", 4, [&]()
			{
				TwoColumns::Value("Position X", InputState.GetMousePosition().X);
				TwoColumns::Value("Position Y", InputState.GetMousePosition().Y);
				TwoColumns::Value("Wheel Delta", InputState.GetMouseWheelDelta());
				ImGui::NextColumn(); ImGui::NextColumn();
			});

			if (!bDebug)
			{
				CVars::DebugInput->Set(0, ECVF_SetByConsole);
			}
		}
		ImGui::End();
	}
}

#undef TEXT_INPUT_MODE
#undef TEXT_BOOL

#endif // IMGUI_WIDGET_DEBUG

#undef IMGUI_WIDGET_LOG