IItemsSource.h

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// Copyright Epic Games, Inc. All Rights Reserved.
 
#pragma once
 
#include "CoreMinimal.h"
#include "Containers/ArrayView.h"
#include "Containers/ObservableArray.h"
#include "Widgets/Views/STableViewBase.h"
 
namespace UE::Slate::ItemsSource
{
template<typename ArgType>
struct ForwardedSlateItemsSourceArgument
{
    const TArray<ArgType>* ArrayPointer;
    ::UE::Slate::Containers::TObservableArray<ArgType>* ObservableArrayPointer;
    TSharedPtr<::UE::Slate::Containers::TObservableArray<ArgType>> SharedObservableArray;
};
 
#define SLATE_ITEMS_SOURCE_ARGUMENT( ArgType, ArgName ) \
    private: \
        const TArray<ArgType>* _##ArgName##_ArrayPointer = nullptr; \
        ::UE::Slate::Containers::TObservableArray<ArgType>* _##ArgName##_ObservableArrayPointer = nullptr; \
        TSharedPtr<::UE::Slate::Containers::TObservableArray<ArgType>> _##ArgName##_SharedObservableArray; \
        void _Reset##ArgName() \
        { \
            _##ArgName##_ArrayPointer = nullptr; \
            _##ArgName##_ObservableArrayPointer = nullptr; \
            _##ArgName##_SharedObservableArray.Reset(); \
        } \
    public: \
        WidgetArgsType& ArgName(const TArray<ArgType>* InArg) \
        { \
            _Reset##ArgName(); \
            _##ArgName##_ArrayPointer = InArg; \
            return static_cast<WidgetArgsType*>(this)->Me(); \
        } \
        WidgetArgsType& ArgName(::UE::Slate::Containers::TObservableArray<ArgType>* InArg) \
        { \
            _Reset##ArgName(); \
            _##ArgName##_ObservableArrayPointer = InArg; \
            return static_cast<WidgetArgsType*>(this)->Me(); \
        } \
        WidgetArgsType& ArgName(TSharedPtr<::UE::Slate::Containers::TObservableArray<ArgType>> InArg) \
        { \
            _Reset##ArgName(); \
            _##ArgName##_SharedObservableArray = InArg; \
            return static_cast<WidgetArgsType*>(this)->Me(); \
        } \
        WidgetArgsType& ArgName(TSharedRef<::UE::Slate::Containers::TObservableArray<ArgType>> InArg) \
        { \
            _Reset##ArgName(); \
            _##ArgName##_SharedObservableArray = InArg; \
            return static_cast<WidgetArgsType*>(this)->Me(); \
        } \
        WidgetArgsType& ArgName(::UE::Slate::ItemsSource::ForwardedSlateItemsSourceArgument<ArgType> InArg) \
        { \
            _Reset##ArgName(); \
            _##ArgName##_ArrayPointer = InArg.ArrayPointer; \
            _##ArgName##_ObservableArrayPointer = InArg.ObservableArrayPointer; \
            _##ArgName##_SharedObservableArray = InArg.SharedObservableArray; \
            return static_cast<WidgetArgsType*>(this)->Me(); \
        } \
        ::UE::Slate::ItemsSource::ForwardedSlateItemsSourceArgument<ArgType> Get##ArgName() const \
        { \
            return {_##ArgName##_ArrayPointer, _##ArgName##_ObservableArrayPointer, _##ArgName##_SharedObservableArray}; \
        } \
        TUniquePtr<::UE::Slate::ItemsSource::IItemsSource<ArgType>> Make##ArgName(TSharedRef<STableViewBase> InWidget) const \
        { \
            if (_##ArgName##_ArrayPointer) \
            { \
                return MakeUnique<::UE::Slate::ItemsSource::FArrayPointer<ArgType>>(_##ArgName##_ArrayPointer); \
            } \
            else if (_##ArgName##_ObservableArrayPointer) \
            { \
                return MakeUnique<::UE::Slate::ItemsSource::FObservableArrayPointer<ArgType>>(InWidget, _##ArgName##_ObservableArrayPointer); \
            } \
            else if (_##ArgName##_SharedObservableArray) \
            { \
                return MakeUnique<::UE::Slate::ItemsSource::FSharedObservableArray<ArgType>>(InWidget, _##ArgName##_SharedObservableArray.ToSharedRef()); \
            } \
            return TUniquePtr<::UE::Slate::ItemsSource::IItemsSource<ArgType>>(); \
        }
        
        
 /*
  * A generic container for TableView items.
  */
 template <typename ItemType>
class IItemsSource
{
public:
    virtual ~IItemsSource() = default;
    virtual const TArrayView<const ItemType> GetItems() const = 0;
    virtual bool IsSame(const void* RawPointer) const = 0;
};
 
 
/*
 *
 */
template <typename ItemType>
class FArrayPointer : public IItemsSource<ItemType>
{
public:
    explicit FArrayPointer(const TArray<ItemType>* InItemsSource)
        : ItemsSource(InItemsSource)
    {
    }
 
    virtual const TArrayView<const ItemType> GetItems() const override
    {
        return *ItemsSource;
    }
 
    virtual bool IsSame(const void* RawPointer) const override
    {
        return RawPointer == reinterpret_cast<const void*>(ItemsSource);
    }
 
private:
    const TArray<ItemType>* ItemsSource;
};
 
 
/*
 *
 */
template<typename InItemType>
class FObservableArrayPointer : public IItemsSource<InItemType>
{
public:
    using WidgetType = STableViewBase;
    using ItemType = InItemType;
 
    explicit FObservableArrayPointer(TSharedRef<WidgetType> InListView, ::UE::Slate::Containers::TObservableArray<ItemType>* InItemsSource)
        : ItemsSource(InItemsSource)
        , ListViewOwner(InListView)
    {
        ArrayChangedHandle = InItemsSource->OnArrayChanged().AddRaw(this, &FObservableArrayPointer::HandleArrayChanged);
    }
 
    virtual ~FObservableArrayPointer()
    {
        checkf(ListViewOwner.IsValid(), TEXT("The View widget has a source needed to be released to prevent bad memory access."));
        ItemsSource->OnArrayChanged().Remove(ArrayChangedHandle);
    }
 
    virtual const TArrayView<const ItemType> GetItems() const override
    {
        return TArrayView<const ItemType>(ItemsSource->GetData(), ItemsSource->Num());
    }
 
    virtual bool IsSame(const void* RawPointer) const override
    {
        return RawPointer == reinterpret_cast<const void*>(&ItemsSource);
    }
 
private:
    void HandleArrayChanged(typename ::UE::Slate::Containers::TObservableArray<ItemType>::ObservableArrayChangedArgsType Args)
    {
        if (TSharedPtr<WidgetType> ListViewOwnerPin = ListViewOwner.Pin())
        {
            ListViewOwnerPin->RequestListRefresh();
        }
    }
 
private:
    UE::Slate::Containers::TObservableArray<ItemType>* ItemsSource;
    TWeakPtr<WidgetType> ListViewOwner;
    FDelegateHandle ArrayChangedHandle;
};
 
/*
 *
 */
template<typename InItemType>
class FSharedObservableArray : public IItemsSource<InItemType>
{
public:
    using WidgetType = STableViewBase;
    using ItemType = InItemType;
 
    explicit FSharedObservableArray(TSharedRef<WidgetType> InListView, TSharedRef<::UE::Slate::Containers::TObservableArray<ItemType>> InItemsSource)
        : ItemsSource(InItemsSource)
        , ListViewOwner(InListView)
    {
        ArrayChangedHandle = InItemsSource->OnArrayChanged().AddRaw(this, &FSharedObservableArray::HandleArrayChanged);
    }
 
    virtual ~FSharedObservableArray()
    {
        ItemsSource->OnArrayChanged().Remove(ArrayChangedHandle);
    }
 
    virtual const TArrayView<const ItemType> GetItems() const override
    {
        return TArrayView<const ItemType>(ItemsSource->GetData(), ItemsSource->Num());
    }
 
    virtual bool IsSame(const void* RawPointer) const override
    {
        UE::Slate::Containers::TObservableArray<ItemType>* ValueToTest = &(ItemsSource.Get());
        return RawPointer == reinterpret_cast<const void*>(ValueToTest);
    }
 
private:
    void HandleArrayChanged(typename ::UE::Slate::Containers::TObservableArray<ItemType>::ObservableArrayChangedArgsType Args)
    {
        if (TSharedPtr<WidgetType> ListViewOwnerPin = ListViewOwner.Pin())
        {
            ListViewOwnerPin->RequestListRefresh();
        }
    }
 
private:
    TSharedRef<UE::Slate::Containers::TObservableArray<ItemType>> ItemsSource;
    TWeakPtr<WidgetType> ListViewOwner;
    FDelegateHandle ArrayChangedHandle;
};
 
} //UE::Slate::ItemsSource