EM_Task/UnrealEd/Private/ThumbnailRendering/SlateBrushThumbnailRenderer.cpp

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

#include "ThumbnailRendering/SlateBrushThumbnailRenderer.h"
#include "Styling/SlateBrush.h"
#include "CanvasItem.h"
#include "Engine/Texture2D.h"
#include "ThumbnailRendering/ThumbnailManager.h"
#include "Slate/SlateBrushAsset.h"
// FPreviewScene derived helpers for rendering
#include "CanvasTypes.h"

USlateBrushThumbnailRenderer::USlateBrushThumbnailRenderer(const FObjectInitializer& ObjectInitializer)
    : Super(ObjectInitializer)
{
}

void USlateBrushThumbnailRenderer::Draw(UObject* Object, int32 X, int32 Y, uint32 Width, uint32 Height, FRenderTarget* RenderTarget, FCanvas* Canvas, bool bAdditionalViewFamily)
{
    USlateBrushAsset* SlateBrushAsset = Cast<USlateBrushAsset>(Object);
    if (SlateBrushAsset)
    {
        FSlateBrush Brush   = SlateBrushAsset->Brush;
        UTexture2D* Texture = Cast<UTexture2D>(Brush.GetResourceObject());

        // Draw the background checkboard pattern
        const int32 CheckerDensity = 8;
        auto* Checker              = UThumbnailManager::Get().CheckerboardTexture;
        Canvas->DrawTile(
            0.0f, 0.0f, Width, Height,                   // Dimensions
            0.0f, 0.0f, CheckerDensity, CheckerDensity,  // UVs
            FLinearColor::White, Checker->Resource);     // Tint & Texture

        if (Texture)
        {
            switch (Brush.DrawAs)
            {
                case ESlateBrushDrawType::Image: {
                    FCanvasTileItem CanvasTile(FVector2D(X, Y), Texture->Resource, FVector2D(Width, Height), Brush.TintColor.GetSpecifiedColor());
                    CanvasTile.BlendMode = SE_BLEND_Translucent;
                    CanvasTile.Draw(Canvas);
                }
                break;
                case ESlateBrushDrawType::Border: {
                    FCanvasTileItem CanvasTile(FVector2D(X, Y), Texture->Resource, FVector2D(Width, Height), Brush.TintColor.GetSpecifiedColor());
                    CanvasTile.BlendMode = SE_BLEND_Translucent;
                    CanvasTile.Draw(Canvas);
                }
                break;
                case ESlateBrushDrawType::Box: {
                    float NaturalWidth       = Texture->GetSurfaceWidth();
                    float NaturalHeight      = Texture->GetSurfaceHeight();

                    float TopPx              = FMath::Clamp<float>(NaturalHeight * Brush.Margin.Top, 0, Height);
                    float BottomPx           = FMath::Clamp<float>(NaturalHeight * Brush.Margin.Bottom, 0, Height);
                    float VerticalCenterPx   = FMath::Clamp<float>(Height - TopPx - BottomPx, 0, Height);
                    float LeftPx             = FMath::Clamp<float>(NaturalWidth * Brush.Margin.Left, 0, Width);
                    float RightPx            = FMath::Clamp<float>(NaturalWidth * Brush.Margin.Right, 0, Width);
                    float HorizontalCenterPx = FMath::Clamp<float>(Width - LeftPx - RightPx, 0, Width);

                    // Top-Left
                    FVector2D TopLeftSize(LeftPx, TopPx);
                    {
                        FVector2D UV0(0, 0);
                        FVector2D UV1(Brush.Margin.Left, Brush.Margin.Top);

                        FCanvasTileItem CanvasTile(FVector2D(X, Y), Texture->Resource, TopLeftSize, UV0, UV1, Brush.TintColor.GetSpecifiedColor());
                        CanvasTile.BlendMode = SE_BLEND_Translucent;
                        CanvasTile.Draw(Canvas);
                    }

                    // Bottom-Left
                    FVector2D BottomLeftSize(LeftPx, BottomPx);
                    {
                        FVector2D UV0(0, 1 - Brush.Margin.Bottom);
                        FVector2D UV1(Brush.Margin.Left, 1);

                        FCanvasTileItem CanvasTile(FVector2D(X, Y + Height - BottomPx), Texture->Resource, BottomLeftSize, UV0, UV1, Brush.TintColor.GetSpecifiedColor());
                        CanvasTile.BlendMode = SE_BLEND_Translucent;
                        CanvasTile.Draw(Canvas);
                    }

                    // Top-Right
                    FVector2D TopRightSize(RightPx, TopPx);
                    {
                        FVector2D UV0(1 - Brush.Margin.Right, 0);
                        FVector2D UV1(1, Brush.Margin.Top);

                        FCanvasTileItem CanvasTile(FVector2D(X + Width - RightPx, Y), Texture->Resource, TopRightSize, UV0, UV1, Brush.TintColor.GetSpecifiedColor());
                        CanvasTile.BlendMode = SE_BLEND_Translucent;
                        CanvasTile.Draw(Canvas);
                    }

                    // Bottom-Right
                    FVector2D BottomRightSize(RightPx, BottomPx);
                    {
                        FVector2D UV0(1 - Brush.Margin.Right, 1 - Brush.Margin.Bottom);
                        FVector2D UV1(1, 1);

                        FCanvasTileItem CanvasTile(FVector2D(X + Width - RightPx, Y + Height - BottomPx), Texture->Resource, BottomRightSize, UV0, UV1, Brush.TintColor.GetSpecifiedColor());
                        CanvasTile.BlendMode = SE_BLEND_Translucent;
                        CanvasTile.Draw(Canvas);
                    }

                    //-----------------------------------------------------------------------

                    // Center-Vertical-Left
                    FVector2D CenterVerticalLeftSize(LeftPx, VerticalCenterPx);
                    {
                        FVector2D UV0(0, Brush.Margin.Top);
                        FVector2D UV1(Brush.Margin.Left, 1 - Brush.Margin.Bottom);

                        FCanvasTileItem CanvasTile(FVector2D(X, Y + TopPx), Texture->Resource, CenterVerticalLeftSize, UV0, UV1, Brush.TintColor.GetSpecifiedColor());
                        CanvasTile.BlendMode = SE_BLEND_Translucent;
                        CanvasTile.Draw(Canvas);
                    }

                    // Center-Vertical-Right
                    FVector2D CenterVerticalRightSize(RightPx, VerticalCenterPx);
                    {
                        FVector2D UV0(1 - Brush.Margin.Right, Brush.Margin.Top);
                        FVector2D UV1(1, 1 - Brush.Margin.Bottom);

                        FCanvasTileItem CanvasTile(FVector2D(X + Width - RightPx, Y + TopPx), Texture->Resource, CenterVerticalRightSize, UV0, UV1, Brush.TintColor.GetSpecifiedColor());
                        CanvasTile.BlendMode = SE_BLEND_Translucent;
                        CanvasTile.Draw(Canvas);
                    }

                    //-----------------------------------------------------------------------

                    // Center-Horizontal-Top
                    FVector2D CenterHorizontalTopSize(HorizontalCenterPx, TopPx);
                    {
                        FVector2D UV0(Brush.Margin.Left, 0);
                        FVector2D UV1(1 - Brush.Margin.Right, Brush.Margin.Top);

                        FCanvasTileItem CanvasTile(FVector2D(X + LeftPx, Y), Texture->Resource, CenterHorizontalTopSize, UV0, UV1, Brush.TintColor.GetSpecifiedColor());
                        CanvasTile.BlendMode = SE_BLEND_Translucent;
                        CanvasTile.Draw(Canvas);
                    }

                    // Center-Horizontal-Bottom
                    FVector2D CenterHorizontalBottomSize(HorizontalCenterPx, BottomPx);
                    {
                        FVector2D UV0(Brush.Margin.Left, 1 - Brush.Margin.Bottom);
                        FVector2D UV1(1 - Brush.Margin.Right, 1);

                        FCanvasTileItem CanvasTile(FVector2D(X + LeftPx, Y + Height - BottomPx), Texture->Resource, CenterHorizontalBottomSize, UV0, UV1, Brush.TintColor.GetSpecifiedColor());
                        CanvasTile.BlendMode = SE_BLEND_Translucent;
                        CanvasTile.Draw(Canvas);
                    }

                    //-----------------------------------------------------------------------

                    // Center
                    FVector2D CenterSize(HorizontalCenterPx, VerticalCenterPx);
                    {
                        FVector2D UV0(Brush.Margin.Left, Brush.Margin.Top);
                        FVector2D UV1(1 - Brush.Margin.Right, 1 - Brush.Margin.Bottom);

                        FCanvasTileItem CanvasTile(FVector2D(X + LeftPx, Y + TopPx), Texture->Resource, CenterSize, UV0, UV1, Brush.TintColor.GetSpecifiedColor());
                        CanvasTile.BlendMode = SE_BLEND_Translucent;
                        CanvasTile.Draw(Canvas);
                    }
                }
                break;
                case ESlateBrushDrawType::NoDrawType: {
                    FCanvasTileItem CanvasTile(FVector2D(X, Y), Texture->Resource, FVector2D(Width, Height), Brush.TintColor.GetSpecifiedColor());
                    CanvasTile.BlendMode = SE_BLEND_Translucent;
                    CanvasTile.Draw(Canvas);
                }
                break;
                default:

                    check(false);
            }
        }
    }
}