#pragma once

#include "CoreMinimal.h"
#include "Widgets/DeclarativeSyntaxSupport.h"
#include "Widgets/SCompoundWidget.h"

class SDPIScaler;

/**
 * The root of everything the UI puts into the viewport (HUD, window host, gallery). It undoes the engine's UI scale
 * (the project's DPI curve gives 0.67 at 720p, which would shrink the 800 x 450 layout to nothing) and applies the
 * UI's own: one UI unit is one viewport pixel up to 1080p, larger screens scale up (Tune::UI::UiScaleForViewport).
 * Children therefore lay out in UI units; `GetUiScale()` converts back to viewport pixels.
 *
 * The layer itself never takes mouse hits (SelfHitTestInvisible): its children decide.
 */
class THEDESCENT_API SDescentUiLayer : public SCompoundWidget
{
public:
	SLATE_BEGIN_ARGS(SDescentUiLayer) {}
		SLATE_DEFAULT_SLOT(FArguments, Content)
	SLATE_END_ARGS()

	void Construct(const FArguments& InArgs);
	virtual void Tick(const FGeometry& AllottedGeometry, const double InCurrentTime, const float InDeltaTime) override;

	/** Viewport pixels per UI unit as of the last tick. */
	float GetUiScale() const { return UiScale; }
	/** Size of the layer in UI units as of the last tick. */
	FVector2f GetLayoutSize() const { return LayoutSize; }

private:
	float GetChildScale() const { return ChildScale; }

	TSharedPtr<SDPIScaler> Scaler;
	float ChildScale = 1.f;
	float UiScale = 1.f;
	FVector2f LayoutSize = FVector2f(1280.f, 720.f);
};