SScrollBar.h

Go to the documentation of this file.

// Copyright Epic Games, Inc. All Rights Reserved.
 
#pragma once
 
#include "CoreMinimal.h"
#include "Misc/Attribute.h"
#include "Styling/SlateColor.h"
#include "Input/Reply.h"
#include "Layout/Visibility.h"
#include "Widgets/DeclarativeSyntaxSupport.h"
#include "Styling/SlateTypes.h"
#include "Styling/CoreStyle.h"
#include "Widgets/Layout/SBorder.h"
#include "Styling/SlateWidgetStyleAsset.h"
 
class SScrollBarTrack;
class SSpacer;
class SImage;
 
DECLARE_DELEGATE_OneParam(
    FOnUserScrolled,
    float );    
DECLARE_DELEGATE_OneParam(FOnScrollBarVisibilityChanged, EVisibility);  
class SScrollBarTrack;
 
class SScrollBar : public SBorder
{
public:
 
    inline static const float DefaultUniformPadding = 2.0f;
 
    SLATE_BEGIN_ARGS( SScrollBar )
        : _Style( &FAppStyle::Get().GetWidgetStyle<FScrollBarStyle>("Scrollbar") )
        , _OnUserScrolled()
        , _AlwaysShowScrollbar(false)
        , _AlwaysShowScrollbarTrack(true)
#if PLATFORM_UI_HAS_MOBILE_SCROLLBARS
        , _HideWhenNotInUse(true)
#else
        , _HideWhenNotInUse(false)
#endif
        , _PreventThrottling(false)
        , _Orientation( Orient_Vertical )
        , _DragFocusCause( EFocusCause::Mouse )
        , _Thickness()
        , _Padding( DefaultUniformPadding )
        {}
 
        SLATE_STYLE_ARGUMENT( FScrollBarStyle, Style )
        SLATE_EVENT( FOnUserScrolled, OnUserScrolled )
        SLATE_EVENT( FOnScrollBarVisibilityChanged, OnScrollBarVisibilityChanged )
        SLATE_ARGUMENT( bool, AlwaysShowScrollbar )
        SLATE_ARGUMENT( bool, AlwaysShowScrollbarTrack )
        SLATE_ARGUMENT( bool, HideWhenNotInUse )
        SLATE_ARGUMENT( bool, PreventThrottling )
        SLATE_ARGUMENT( EOrientation, Orientation )
        SLATE_ARGUMENT( EFocusCause, DragFocusCause )
        SLATE_ATTRIBUTE( FVector2D, Thickness )
        SLATE_ATTRIBUTE( FMargin, Padding )
    SLATE_END_ARGS()
 
    
    SLATE_API void Construct(const FArguments& InArgs);
 
    SLATE_API void SetOnUserScrolled( const FOnUserScrolled& InHandler );
 
    SLATE_API void SetOnScrollBarVisibilityChanged( const FOnScrollBarVisibilityChanged& InHandler );
 
    SLATE_API virtual void SetState( float InOffsetFraction, float InThumbSizeFraction, bool bCallOnUserScrolled = false);
 
    // SWidget
    SLATE_API virtual void Tick(const FGeometry& AllottedGeometry, const double InCurrentTime, const float InDeltaTime) override;
    SLATE_API virtual FReply OnMouseButtonDown( const FGeometry& MyGeometry, const FPointerEvent& MouseEvent ) override;
    SLATE_API virtual FReply OnMouseButtonUp( const FGeometry& MyGeometry, const FPointerEvent& MouseEvent ) override;
    SLATE_API virtual FReply OnMouseMove( const FGeometry& MyGeometry, const FPointerEvent& MouseEvent ) override;
    SLATE_API virtual void OnMouseEnter(const FGeometry& MyGeometry, const FPointerEvent& MouseEvent) override;
    SLATE_API virtual void OnMouseLeave(const FPointerEvent& MouseEvent) override;
    // SWidget
 
    SLATE_API bool IsNeeded() const;
 
    SLATE_API float DistanceFromTop() const;
 
    SLATE_API float DistanceFromBottom() const;
 
    SLATE_API float ThumbSizeFraction() const;
 
    SLATE_API EVisibility ShouldBeVisible() const;
 
    SLATE_API bool IsScrolling() const;
 
    SLATE_API EOrientation GetOrientation() const; 
 
    SLATE_API void SetStyle(const FScrollBarStyle* InStyle);
 
    SLATE_API void InvalidateStyle();
 
    void SetUserVisibility(TAttribute<EVisibility> InUserVisibility) { UserVisibility = InUserVisibility; }
 
    SLATE_API void SetDragFocusCause(EFocusCause InDragFocusCause);
 
    SLATE_API void SetThickness(TAttribute<FVector2D> InThickness);
 
    SLATE_API void SetScrollBarAlwaysVisible(bool InAlwaysVisible);
 
    SLATE_API void SetScrollBarTrackAlwaysVisible(bool InAlwaysVisible);
 
    SLATE_API void SetScrollbarDisabledVisibility(EVisibility InVisibility);
 
    SLATE_API bool AlwaysShowScrollbar() const;
 
    SLATE_API virtual void BeginScrolling();
 
    SLATE_API virtual void EndScrolling();
 
    SLATE_API SScrollBar();
    SLATE_API ~SScrollBar();
 
protected:
    
    SLATE_API void ExecuteOnUserScrolled( const FGeometry& MyGeometry, const FPointerEvent& MouseEvent );
 
    SLATE_API FSlateColor GetTrackOpacity() const;
 
    SLATE_API FLinearColor GetThumbOpacity() const;
 
    SLATE_API const FSlateBrush* GetDragThumbImage() const;
 
    TAttribute<EVisibility> UserVisibility;
 
    TSharedPtr<SImage> TopImage;
    TSharedPtr<SImage> BottomImage;
    TSharedPtr<SBorder> DragThumb;
    TSharedPtr<SSpacer> ThicknessSpacer;
    bool bDraggingThumb;
    TSharedPtr<SScrollBarTrack> Track;
    FOnUserScrolled OnUserScrolled;
    FOnScrollBarVisibilityChanged OnScrollBarVisibilityChanged;
    float DragGrabOffset;
    EOrientation Orientation;
    bool bAlwaysShowScrollbar;
    bool bAlwaysShowScrollbarTrack;
    EFocusCause DragFocusCause;
    bool bHideWhenNotInUse;
    EVisibility ScrollbarDisabledVisibility = EVisibility::Collapsed;
    /*
     * Holds whether or not to prevent throttling during mouse capture
     * When true, the viewport will be updated with every single change to the value during dragging
     */
    bool bPreventThrottling;
    bool bIsScrolling;
    double LastInteractionTime;
 
    const FSlateBrush* NormalThumbImage;
    const FSlateBrush* HoveredThumbImage;
    const FSlateBrush* DraggedThumbImage;
    const FSlateBrush* BackgroundBrush;
    const FSlateBrush* TopBrush;
    const FSlateBrush* BottomBrush;
};