TreeView.h

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// Copyright Epic Games, Inc. All Rights Reserved.
 
#pragma once
 
#include "ListView.h"
#include "Widgets/Views/STreeView.h"
#include "TreeView.generated.h"
 
DECLARE_DYNAMIC_DELEGATE_TwoParams(FOnGetItemChildrenDynamic, UObject*, Item, TArray<UObject*>&, Children);
DECLARE_DYNAMIC_MULTICAST_DELEGATE_TwoParams(FOnItemExpansionChangedDynamic, UObject*, Item, bool, bIsExpanded);
 
UCLASS(MinimalAPI)
class UTreeView : public UListView
{
    GENERATED_BODY()
 
public:
    UMG_API UTreeView(const FObjectInitializer& ObjectInitializer);
    UMG_API virtual void ReleaseSlateResources(bool bReleaseChildren) override;
    
    UFUNCTION(BlueprintCallable, Category = TreeView)
    UMG_API void SetItemExpansion(UObject* Item, bool bExpandItem);
 
    UFUNCTION(BlueprintCallable, Category = TreeView)
    UMG_API void ExpandAll();
 
    UFUNCTION(BlueprintCallable, Category = TreeView)
    UMG_API void CollapseAll();
 
    template <typename ObjectT>
    void SetOnGetItemChildren(ObjectT* InUserObject, typename TSlateDelegates<UObject*>::FOnGetChildren::TMethodPtr<ObjectT> InMethodPtr)
    {
        static_assert(TIsDerivedFrom<ObjectT, UObject>::IsDerived, "Only UObject ptrs can be passed directly when binding to SetOnGetItemChildren. Pass a shared ref for non-UObject binders.");
        OnGetItemChildren = TSlateDelegates<UObject*>::FOnGetChildren::CreateUObject(InUserObject, InMethodPtr);
    }
    template <typename ObjectT>
    void SetOnGetItemChildren(TSharedRef<ObjectT> InUserObject, typename TSlateDelegates<UObject*>::FOnGetChildren::TMethodPtr<ObjectT> InMethodPtr)
    {
        OnGetItemChildren = TSlateDelegates<UObject*>::FOnGetChildren::CreateSP(InUserObject, InMethodPtr);
    }
 
protected:
    UMG_API virtual TSharedRef<STableViewBase> RebuildListWidget() override;
    UMG_API virtual void OnItemClickedInternal(UObject* ListItem) override;
 
    UMG_API virtual void OnItemExpansionChangedInternal(UObject* Item, bool bIsExpanded) override;
    UMG_API virtual void OnGetChildrenInternal(UObject* Item, TArray<UObject*>& OutChildren) const override;
 
    template <template<typename> class TreeViewT = STreeView>
    TSharedRef<TreeViewT<UObject*>> ConstructTreeView()
    {
        FTreeViewConstructArgs Args;
        Args.bClearSelectionOnClick = bClearSelectionOnClick;
        Args.SelectionMode = SelectionMode;
        Args.ConsumeMouseWheel = ConsumeMouseWheel;
        Args.bReturnFocusToSelection = bReturnFocusToSelection;
        Args.TreeViewStyle = &WidgetStyle;
        Args.ScrollBarStyle = &ScrollBarStyle;
 
        MyListView = MyTreeView = ITypedUMGListView<UObject*>::ConstructTreeView<TreeViewT>(this, ListItems, Args);
        MyTreeView->SetOnEntryInitialized(SListView<UObject*>::FOnEntryInitialized::CreateUObject(this, &UTreeView::HandleOnEntryInitializedInternal));
        return StaticCastSharedRef<TreeViewT<UObject*>>(MyTreeView.ToSharedRef());
    }
 
 
    TSharedPtr<STreeView<UObject*>> MyTreeView;
 
private:
    UPROPERTY(EditAnywhere, Category = Events, meta = (IsBindableEvent, AllowPrivateAccess = true, DisplayName = "On Get Item Children"))
    FOnGetItemChildrenDynamic BP_OnGetItemChildren;
 
    UPROPERTY(BlueprintAssignable, Category = Events, meta = (AllowPrivateAccess = true, DisplayName = "On Item Expansion Changed"))
    FOnItemExpansionChangedDynamic BP_OnItemExpansionChanged;
 
    TSlateDelegates<UObject*>::FOnGetChildren OnGetItemChildren;
    FOnItemExpansionChanged OnItemExpansionChangedEvent;
};