// Copyright Epic Games, Inc. All Rights Reserved.

/**
 *
 * This is an abstract base class that is used to define the interface that
 * UnrealEd will use when rendering a given object's thumbnail. The editor
 * only calls the virtual rendering function.
 */

#pragma once

#include "CoreMinimal.h"
#include "UObject/ObjectMacros.h"
#include "UObject/Object.h"
#include "ThumbnailRenderer.generated.h"

class FCanvas;
class FRenderTarget;

UCLASS(abstract, MinimalAPI)
class UThumbnailRenderer: public UObject
{
    GENERATED_UCLASS_BODY()

public:
    /**
     * Returns true if the renderer is capable of producing a thumbnail for the specified asset.
     *
     * @param Object the asset to attempt to render
     */
    virtual bool CanVisualizeAsset(UObject* Object) { return true; }

    /**
     * Calculates the size the thumbnail would be at the specified zoom level
     *
     * @param Object the object the thumbnail is of
     * @param Zoom the current multiplier of size
     * @param OutWidth the var that gets the width of the thumbnail
     * @param OutHeight the var that gets the height
     */
    virtual void GetThumbnailSize(UObject* Object, float Zoom, uint32& OutWidth, uint32& OutHeight) const PURE_VIRTUAL(UThumbnailRenderer::GetThumbnailSize, );

    /**
     * Draws a thumbnail for the object that was specified.
     *
     * @param Object the object to draw the thumbnail for
     * @param X the X coordinate to start drawing at
     * @param Y the Y coordinate to start drawing at
     * @param Width the width of the thumbnail to draw
     * @param Height the height of the thumbnail to draw
     * @param Viewport the viewport being drawn in
     * @param Canvas the render interface to draw with
     */
    UE_DEPRECATED(4.25, "Please override the other prototype of the Draw function.")
    virtual void Draw(UObject* Object, int32 X, int32 Y, uint32 Width, uint32 Height, FRenderTarget* Viewport, FCanvas* Canvas) { Draw(Object, X, Y, Width, Height, Viewport, Canvas, false); }

    /**
     * Draws a thumbnail for the object that was specified.
     *
     * @param Object the object to draw the thumbnail for
     * @param X the X coordinate to start drawing at
     * @param Y the Y coordinate to start drawing at
     * @param Width the width of the thumbnail to draw
     * @param Height the height of the thumbnail to draw
     * @param Viewport the viewport being drawn in
     * @param Canvas the render interface to draw with
     * @param bAdditionalViewFamily whether this draw should write over the render target (true) or clear it before (false)
     */
    virtual void Draw(UObject* Object, int32 X, int32 Y, uint32 Width, uint32 Height, FRenderTarget* Viewport, FCanvas* Canvas, bool bAdditionalViewFamily) PURE_VIRTUAL(UThumbnailRenderer::Draw, );

    /**
     * Checks to see if the specified asset supports realtime thumbnails, which will cause them to always be rerendered to reflect any changes
     * made to the asset. If this is false, thumbnails should render once and then not update again.
     * For most renderers, this should remain as true.
     *
     * @param	Object	The asset to draw the thumbnail for
     *
     * @return True if the thumbnail needs to always be redrawn, false if it can be just drawn once and then reused.
     */
    virtual bool AllowsRealtimeThumbnails(UObject* Object) const { return true; }

protected:
    /** Renders the thumbnail's view family. */
    UNREALED_API static void RenderViewFamily(FCanvas* Canvas, class FSceneViewFamily* ViewFamily);
};