SColorValueSlider.h

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// Copyright Epic Games, Inc. All Rights Reserved.
 
#pragma once
 
// HEADER_UNIT_SKIP - Bad header, does not compile
 
#include "CoreMinimal.h"
#include "Misc/Attribute.h"
#include "InputCoreTypes.h"
#include "Input/Reply.h"
#include "Rendering/DrawElements.h"
#include "Widgets/DeclarativeSyntaxSupport.h"
#include "Styling/CoreStyle.h"
#include "Widgets/SLeafWidget.h"
#include "Framework/SlateDelegates.h"
 
class FPaintArgs;
class FSlateRect;
class FWidgetStyle;
struct FGeometry;
struct FPointerEvent;
struct FSlateBrush;
 
class SColorValueSlider
    : public SLeafWidget
{
public:
 
    SLATE_BEGIN_ARGS( SColorValueSlider )
        : _SelectedColor()
        , _OnValueChanged()
        , _OnMouseCaptureBegin()
        , _OnMouseCaptureEnd()
    { }
        
        SLATE_ATTRIBUTE(FLinearColor, SelectedColor)
        
        
        SLATE_EVENT(FOnLinearColorValueChanged, OnValueChanged)
        
        
        SLATE_EVENT(FSimpleDelegate, OnMouseCaptureBegin)
 
        
        SLATE_EVENT(FSimpleDelegate, OnMouseCaptureEnd)
 
    SLATE_END_ARGS()
    
    void Construct( const FArguments& InArgs )
    {
        SelectorImage = FCoreStyle::Get().GetBrush("ColorPicker.Selector");
 
        OnValueChanged = InArgs._OnValueChanged;
        OnMouseCaptureBegin = InArgs._OnMouseCaptureBegin;
        OnMouseCaptureEnd = InArgs._OnMouseCaptureEnd;
        SelectedColor = InArgs._SelectedColor;
    }
 
    virtual int32 OnPaint( const FPaintArgs& Args, const FGeometry& AllottedGeometry, const FSlateRect& MyCullingRect, FSlateWindowElementList& OutDrawElements, int32 LayerId, const FWidgetStyle& InWidgetStyle, bool bParentEnabled ) const
    {
        const bool bIsEnabled = ShouldBeEnabled(bParentEnabled);
        const ESlateDrawEffect DrawEffects = bIsEnabled ? ESlateDrawEffect::None : ESlateDrawEffect::DisabledEffect;
    
        FLinearColor FullValueColor = SelectedColor.Get();
        FullValueColor.B = FullValueColor.A = 1.f;
        FLinearColor StopColor = FullValueColor.HSVToLinearRGB();
 
        TArray<FSlateGradientStop> GradientStops;
        GradientStops.Add(FSlateGradientStop(FVector2D::ZeroVector, FLinearColor(0.0f, 0.0f, 0.0f, 1.0f)));
        GradientStops.Add(FSlateGradientStop(AllottedGeometry.Size, StopColor));
 
        FSlateDrawElement::MakeGradient(
            OutDrawElements,
            LayerId,
            AllottedGeometry.ToPaintGeometry(),
            GradientStops,
            Orient_Vertical,
            MyCullingRect,
            DrawEffects
        );
    
        float Value = SelectedColor.Get().B;
        FVector2D RelativeSelectedPosition = FVector2D(Value, 0.5f);
 
        FSlateDrawElement::MakeBox(
            OutDrawElements,
            LayerId + 1,
            AllottedGeometry.ToPaintGeometry( RelativeSelectedPosition*AllottedGeometry.Size - SelectorImage->ImageSize*0.5, SelectorImage->ImageSize ),
            SelectorImage,
            MyCullingRect,
            DrawEffects,
            InWidgetStyle.GetColorAndOpacityTint() * SelectorImage->GetTint( InWidgetStyle ) );
 
        return LayerId + 1;
    }
    
    virtual FReply OnMouseButtonDown( const FGeometry& MyGeometry, const FPointerEvent& MouseEvent )
    {
        if ( MouseEvent.GetEffectingButton() == EKeys::LeftMouseButton )
        {
            OnMouseCaptureBegin.ExecuteIfBound();
 
            return FReply::Handled().CaptureMouse( SharedThis(this) );
        }
        else
        {
            return FReply::Unhandled();
        }
    }
    
    virtual FReply OnMouseButtonUp( const FGeometry& MyGeometry, const FPointerEvent& MouseEvent )
    {
        if ( MouseEvent.GetEffectingButton() == EKeys::LeftMouseButton && HasMouseCapture() )
        {
            OnMouseCaptureEnd.ExecuteIfBound();
 
            return FReply::Handled().ReleaseMouseCapture();
        }
        else
        {
            return FReply::Unhandled();
        }
    }
 
    virtual FReply OnMouseMove( const FGeometry& MyGeometry, const FPointerEvent& MouseEvent )
    {
        if (!HasMouseCapture())
        {
            return FReply::Unhandled();
        }
 
        FVector2D LocalMouseCoordinate = MyGeometry.AbsoluteToLocal( MouseEvent.GetScreenSpacePosition() );
        FVector2D Location = LocalMouseCoordinate / (MyGeometry.Size);
        float Value = FMath::Clamp(Location.X, 0.f, 1.f);
 
        FLinearColor NewColor = SelectedColor.Get();
        NewColor.B = Value;
 
        OnValueChanged.ExecuteIfBound(NewColor);
 
        return FReply::Handled();
    }
    
    virtual FReply OnMouseButtonDoubleClick( const FGeometry& InMyGeometry, const FPointerEvent& InMouseEvent )
    {
        return FReply::Handled();
    }
 
    virtual FVector2D ComputeDesiredSize(float) const
    {
        return SelectorImage->ImageSize * 2.f;
    }
    
protected:
 
    const FSlateBrush* SelectorImage;
    
    TAttribute< FLinearColor > SelectedColor;
 
    FOnLinearColorValueChanged OnValueChanged;
 
    FSimpleDelegate OnMouseCaptureBegin;
 
    FSimpleDelegate OnMouseCaptureEnd;
};