PDF_Office/PDF Office/PDF Master/Class/Common/Control/KMThumbnailView.swift

//
//  KMThumbnailView.swift
//  PDF Master
//
//  Created by tangchao on 2023/5/4.
//

import Cocoa

@objc enum KMThumbnailViewDragInfoKey: Int {
    case dropOperation = 0
    case draggingInfo = 1
}

@objc protocol KMThumbnailViewDelegate : NSObjectProtocol {
    // layout
    @objc optional func thumbnailView(thumbanView: KMThumbnailView, minimumLineSpacingForSectionAt section: Int) -> CGFloat
    @objc optional func thumbnailView(thumbanView: KMThumbnailView, minimumInteritemSpacingForSectionAt section: Int) -> CGFloat
    @objc optional func thumbnailView(thumbanView: KMThumbnailView, insetForSectionAt section: Int) -> NSEdgeInsets
    
    @objc optional func thumbnailView(thumbanView: KMThumbnailView, sizeForItemAt indexpath: IndexPath) -> NSSize
    
    @objc optional func thumbnailView(thumbanView: KMThumbnailView, numberOfItemsInSection section: Int) -> Int
    @objc optional func thumbnailView(thumbanView: KMThumbnailView, itemForRepresentedObjectAt indexpath: IndexPath) -> NSCollectionViewItem
    
    // Drag & Drop
    @objc optional func thumbnailView(thumbanView: KMThumbnailView, draggingSession session: NSDraggingSession, willBeginAt screenPoint: NSPoint, forItemsAt indexes: IndexSet)
    @objc optional func thumbnailView(thumbanView: KMThumbnailView, draggingSession session: NSDraggingSession, endedAt screenPoint: NSPoint, dragOperation operation: NSDragOperation)
    
    @objc optional func thumbnailView(thumbanView: KMThumbnailView, canPasteboardWriterForItemAt indexPath: IndexPath) -> Bool
    @objc optional func thumbnailView(thumbanView: KMThumbnailView, shouldPasteboardWriterForItemAt indexPath: IndexPath) -> Bool
    @objc optional func thumbnailView(thumbanView: KMThumbnailView, pasteboardWriterForItemAt indexPath: IndexPath) -> NSPasteboardWriting?

    @objc optional func thumbnailView(thumbanView: KMThumbnailView, canDragItemsAt indexPaths: Set<IndexPath>, with event: NSEvent) -> Bool
    @objc optional func thumbnailView(thumbanView: KMThumbnailView, shouldAcceptDrop draggingInfo: NSDraggingInfo, indexPath: IndexPath, dropOperation: NSCollectionView.DropOperation) -> Bool
    // 本地拖拽
    @objc optional func thumbnailView(thumbanView: KMThumbnailView, didDrag dragedIndexPaths: [IndexPath], indexpath: IndexPath, dragInfo:[KMThumbnailViewDragInfoKey.RawValue:Any])
    // 外部拖拽
    @objc optional func thumbnailView(thumbanView: KMThumbnailView, didDragAddFiles files: [URL], indexpath: IndexPath)
    
    @objc optional func thumbnailView(thumbanView: KMThumbnailView, didSelectItemAt indexpath: IndexPath, object: AnyObject?)
    @objc optional func thumbnailView(thumbanView: KMThumbnailView, rightMouseDidClick indexpath: IndexPath, item: NSCollectionViewItem?, object: AnyObject?)
}

private let _KMThumbnailView_collectionViewDrop_lineViewClassName = "NSCollectionViewDropTargetGapIndicator"
@objc class KMThumbnailView_CollectionView: NSCollectionView {
    var hasDragLineView: Bool = true {
        didSet {
            if (!self.hasDragLineView) {
                // 隐藏视图
                for view in self.subviews {
                    guard let lineClass = NSClassFromString(_KMThumbnailView_collectionViewDrop_lineViewClassName) else {
                        continue
                    }
                    if (view.isKind(of: lineClass)) {
//                        view.frame = NSZeroRect
                        view.isHidden = true
                    }
                }
            }
        }
    }
    
    override func addSubview(_ view: NSView) {
        if (self.hasDragLineView) {
            return super.addSubview(view)
        }
        
        if let lineClass = NSClassFromString(_KMThumbnailView_collectionViewDrop_lineViewClassName) {
            if (view.isKind(of: lineClass)) {
                Swift.debugPrint("Find Line View......")
                return
            } else {
                super.addSubview(view)
            }
        }
        
        super.addSubview(view)
    }
}

@objc class KMThumbnailView: NSView {
    
    open weak var delegate: KMThumbnailViewDelegate?
    
    internal let localForDraggedTypes = kKMLocalForDraggedTypes
    internal var dragedIndexPaths: [IndexPath] = []
    var kmAllowedFileTypes: [String]?
    // 记录拖拽移动后的位置
    fileprivate var _dragMoveFlagIndexpath: IndexPath?
    fileprivate var _dragMoveFlagIndexs: IndexSet?
    
    // 是否隐藏拖放线 dragMoveEffectAnimated 属性为false才有效
    var hasDragLineView: Bool = true {
        didSet {
            if (!self.dragMoveEffectAnimated) {
                self.collectionView_.hasDragLineView = self.hasDragLineView
            } else {
                self.collectionView_.hasDragLineView = false
            }
        }
    }
    // 是否显示拖放移动动效 为true时 hasDragLineView属性设置是
    var dragMoveEffectAnimated: Bool = false {
        didSet {
            self.hasDragLineView = !self.dragMoveEffectAnimated
        }
    }

    override init(frame frameRect: NSRect) {
        super.init(frame: frameRect)
        
        self.initDefaultValue()
        self.initSubViews()
    }
    
    required public init?(coder: NSCoder) {
        super.init(coder: coder)
        
        self.initDefaultValue()
        self.initSubViews()
    }
    
    open var minimumLineSpacing: CGFloat = 0.0 {
        didSet {
            self.reloadData()
        }
    }

    open var minimumInteritemSpacing: CGFloat = 0.0 {
        didSet {
            self.reloadData()
        }
    }

    open var itemSize: NSSize = NSMakeSize(60, 80) {
        didSet {
            self.reloadData()
        }
    }

    open var sectionInset: NSEdgeInsets = NSEdgeInsetsZero {
        didSet {
            self.reloadData()
        }
    }
    
    open var numberOfSections: Int = 0 {
        didSet {
            self.reloadData()
        }
    }
    
    var selectionIndexPaths: Set<IndexPath> {
        get {
            return self.collectionView.selectionIndexPaths
        }
        set {
            var indexpaths: Set<IndexPath> = []
            for indexpath in newValue {
                if (indexpath.section >= self.collectionView.numberOfSections) {
                    continue
                }
                if (indexpath.item >= self.collectionView.numberOfItems(inSection: indexpath.section)) {
                    continue
                }
                
                indexpaths.insert(indexpath)
            }
            
            self.collectionView.selectionIndexPaths = indexpaths
        }
    }
    
    // MARK: - Publick Methods
    
    public func initDefaultValue() {
        self.collectionView.registerForDraggedTypes([self.localForDraggedTypes, .fileURL,.string,.pdf])
    }
    
    public func initSubViews() {
        self.addSubview(self.scrollView)
        self.scrollView.frame = self.bounds
        self.scrollView.autoresizingMask = [.width, .height]
        
        self.scrollView.documentView = self.collectionView
    }
    
    // MARK: - register ItemClass
    
    open func register(_ itemClass: AnyClass?) {
        guard let itemClass_ = itemClass else {
            return
        }
        
        self.register(itemClass_, forItemWithIdentifier: NSStringFromClass(itemClass_))
    }
    
    open func register(_ itemClass: AnyClass?, forItemWithIdentifier identifier: String) {
        self.collectionView.register(itemClass, forItemWithIdentifier: NSUserInterfaceItemIdentifier(rawValue: identifier))
    }
    
    // MARK: - 刷新UI
    
    public func reloadData(indexs: Set<IndexPath> = []) {
        if (indexs.count == 0) {
            if (Thread.isMainThread) {
                self.collectionView.reloadData()
            } else {
                DispatchQueue.main.async {
                    self.collectionView.reloadData()
                }
            }
        } else {
            var indexpaths: Set<IndexPath> = []
            for index in indexs {
                if (index.section >= self.collectionView.numberOfSections) {
                    continue
                }
                if (index.item >= self.collectionView.numberOfItems(inSection: index.section)) {
                    continue
                }
                
                indexpaths.insert(index)
            }
            if (indexpaths.count == 0) {
                return
            }
            
            if (Thread.isMainThread) {
                self.collectionView.reloadItems(at: indexpaths)
            } else {
                DispatchQueue.main.async {
                    self.collectionView.reloadItems(at: indexpaths)
                }
            }
        }
    }
    
    // MARK: - 属性 【懒加载】
    
    internal lazy var scrollView_: NSScrollView = {
        let view = NSScrollView()
        
        view.hasHorizontalScroller = true
        view.hasVerticalScroller = true
        view.autohidesScrollers = true
        view.minMagnification = 1.0
        view.scrollerStyle = .overlay
        
        view.wantsLayer = true
        view.layer?.backgroundColor = NSColor.clear.cgColor
        
        view.wantsLayer = true
        view.contentView.layer?.backgroundColor = .white
        
        return view
    }()
    var scrollView: NSScrollView {
        get {
            return self.scrollView_
        }
    }
    
    internal lazy var collectionView_: KMThumbnailView_CollectionView = {
        let view = KMThumbnailView_CollectionView()
        view.autoresizingMask = [.width, .height]
        
        let layout = NSCollectionViewFlowLayout()
        layout.sectionInset = NSEdgeInsetsMake(8, 15, 8, 15)
        layout.minimumLineSpacing = 0
        layout.minimumInteritemSpacing = 0
        view.collectionViewLayout = layout
        
        view.delegate = self
        view.dataSource = self
        
        view.register(NSCollectionViewItem.self, forItemWithIdentifier: NSUserInterfaceItemIdentifier(rawValue: "KMPDFThumbnailItem"))
        view.isSelectable = true
        
        view.wantsLayer = true
        view.layer?.backgroundColor = NSColor.km_init(hex: "#F7F8FA").cgColor
        
        return view
    }()
    var collectionView: KMThumbnailView_CollectionView {
        get {
            return self.collectionView_
        }
    }
    
    // MARK: - Private Methods
    
    private func _moveItemForDrag(to toIndexPath: IndexPath) -> Bool {
        if (self.dragedIndexPaths.isEmpty) {
            Swift.debugPrint("not find selected items.\(self.dragedIndexPaths)")
            return false
        }

        if (self.dragedIndexPaths.contains(toIndexPath) == false) { // 目标位置不在拖放数组里
            if (self._dragMoveFlagIndexpath == nil) { // 第一次移动
                self.collectionView.animator().moveItem(at: self.dragedIndexPaths.first!, to: toIndexPath)
                Swift.debugPrint("moveBegin, \(self.dragedIndexPaths.first!.item)->\(toIndexPath.item)")
                
                // 标记位置
                self._dragMoveFlagIndexpath = toIndexPath
                return true
            } else { // 已有移动
                if (self._dragMoveFlagIndexpath! != toIndexPath) {
                    self.collectionView.animator().moveItem(at: self._dragMoveFlagIndexpath!, to: toIndexPath)
                    Swift.debugPrint("move..., \(self._dragMoveFlagIndexpath!.item)->\(toIndexPath.item)")
                    
                    // 标记位置
                    self._dragMoveFlagIndexpath = toIndexPath
                    return true
                } else {
                    Swift.debugPrint("drag... ")
                }
            }
        } else if (self._dragMoveFlagIndexpath != nil) { // 目标位置在拖放数组里且已有移动
            if (self._dragMoveFlagIndexpath! != toIndexPath) {
                self.collectionView.animator().moveItem(at: self._dragMoveFlagIndexpath!, to: toIndexPath)
                Swift.debugPrint("move..., \(self._dragMoveFlagIndexpath!.item)->\(toIndexPath.item)")
                
                // 标记位置
                self._dragMoveFlagIndexpath = toIndexPath
                return true
            } else {
                Swift.debugPrint("drag... ")
            }
        }
        
        return false
    }
    
    private func _moveItemsForDrag(at itemIndexPaths: Set<IndexPath>, to toIndexPath: IndexPath) -> Bool {
        if (itemIndexPaths.isEmpty) {
            return false
        }
        
        var itemIndexs = IndexSet()
        for ip in itemIndexPaths {
            itemIndexs.insert(ip.item)
        }
        return self._moveItemsForDrag(at: itemIndexs, to: toIndexPath.item)
    }
    
    private func _moveItemsForDrag(at itemIndexs: IndexSet, to toIndex: Int) -> Bool {
        if (itemIndexs.isEmpty) {
            return false
        }
        
        var flagIndexs = IndexSet()
        if (itemIndexs.first! > toIndex) { // 往前拖放
            // 3,4 -> 2
            // 3->2,4->3
            var cnt: Int = 0
            for item in itemIndexs {
                let indexpath = IndexPath(item: item, section: 0)
                let _toIndexPath = IndexPath(item: toIndex+cnt, section: 0)
                self.collectionView.animator().moveItem(at: indexpath, to: _toIndexPath)
                
                // 标记位置
                flagIndexs.insert(_toIndexPath.item)
                cnt += 1
            }
        } else if (itemIndexs.last! < toIndex) { // 往后拖放
            // 1,2 -> 3
            // 2->3, 1->2
            
            // 1,2 -> 4
            // 2->4, 1->3
            
            // 1,3 -> 4
            // 3->4, 1->3
            var cnt: Int = 0
            for item in itemIndexs.reversed() {
                let indexpath = IndexPath(item: item, section: 0)
                let _toIndexPath = IndexPath(item: toIndex-cnt, section: 0)
                self.collectionView.animator().moveItem(at: indexpath, to: _toIndexPath)
                
                // 标记位置
                flagIndexs.insert(_toIndexPath.item)
                cnt += 1
            }
        } else { // 往中间拖放(选中不连续)
            // 1,3 -> 2
            // 1->2, ...
            var cnt: Int = 0
            for item in itemIndexs {
                let indexpath = IndexPath(item: item, section: 0)
                
                if (cnt == 0) { // 第一个
                    let _toIndexPath = IndexPath(item: toIndex, section: 0)
                    self.collectionView.animator().moveItem(at: indexpath, to: _toIndexPath)
                    
                    flagIndexs.insert(toIndex)
                } else { // 第二个...
                    if (indexpath.item == toIndex + cnt) { // 已在对应的位置
                        // no doings
                        flagIndexs.insert(toIndex+cnt)
                    } else { // 需要移动
                        let _toIndexPath = IndexPath(item: toIndex+cnt, section: 0)
                        self.collectionView.animator().moveItem(at: indexpath, to: _toIndexPath)
                        
                        flagIndexs.insert(_toIndexPath.item)
                    }
                }
                cnt += 1
            }
        }
        
        // 标记位置
        self._dragMoveFlagIndexs = flagIndexs
        return true
    }
    
    private func _doDragMoveEffect(to toIndexPath: IndexPath) -> Bool {
        if (self.dragedIndexPaths.isEmpty) {
            Swift.debugPrint("not find selected items.\(self.dragedIndexPaths)")
            return false
        }

        if (self.dragedIndexPaths.contains(toIndexPath) == false) { // 目标位置不在拖放数组里
            if (self._dragMoveFlagIndexs == nil) { // 第一次移动
                var itemIndexPaths = Set<IndexPath>()
                for indexpath in self.dragedIndexPaths {
                    itemIndexPaths.insert(indexpath)
                }
                return self._moveItemsForDrag(at: itemIndexPaths, to: toIndexPath)
            } else { // 已有移动
                if (self._dragMoveFlagIndexs!.contains(toIndexPath.item) == false) {
                    return self._moveItemsForDrag(at: self._dragMoveFlagIndexs!, to: toIndexPath.item)
                } else {
                    Swift.debugPrint("drag... ")
                }
            }
        } else if (self._dragMoveFlagIndexs != nil) { // 目标位置在拖放数组里且已有移动
            if (self._dragMoveFlagIndexs!.contains(toIndexPath.item) == false) {
                return self._moveItemsForDrag(at: self._dragMoveFlagIndexs!, to: toIndexPath.item)
            } else {
                Swift.debugPrint("drag... ")
            }
        }
        
        return false
    }
}

// MARK: - NSCollectionViewDataSource, NSCollectionViewDelegate

extension KMThumbnailView: NSCollectionViewDataSource {
    public func collectionView(_ collectionView: NSCollectionView, numberOfItemsInSection section: Int) -> Int {
        if let items = self.delegate?.thumbnailView?(thumbanView: self, numberOfItemsInSection: section) {
            return items
        }
        return self.numberOfSections
    }
    
    func collectionView(_ collectionView: NSCollectionView, itemForRepresentedObjectAt indexPath: IndexPath) -> NSCollectionViewItem {
        if let item = self.delegate?.thumbnailView?(thumbanView: self, itemForRepresentedObjectAt: indexPath) {
            return item
        }
        return NSCollectionViewItem()
    }
}

// MARK: -  NSCollectionViewDelegate
extension KMThumbnailView: NSCollectionViewDelegate {
//    func collectionView(_ collectionView: NSCollectionView, shouldSelectItemsAt indexPaths: Set<IndexPath>) -> Set<IndexPath> {
//        return indexPaths
//    }
    
    func collectionView(_ collectionView: NSCollectionView, shouldSelectItemsAt indexPaths: Set<IndexPath>) -> Set<IndexPath> {
        if let lastSelectedIndexPath = collectionView.selectionIndexPaths.first {
            if NSApp.currentEvent?.modifierFlags.contains(.shift) == true {
                // Shift 键按住，进行连续多选
                let selectedIndexPaths = collectionView.selectionIndexPaths
                var allIndexPaths = Set<IndexPath>(selectedIndexPaths)

                // 获取两个 IndexPath 之间的所有 IndexPath
                let startIndex = lastSelectedIndexPath.item
                let endIndex = indexPaths.first?.item ?? startIndex
                let range = startIndex < endIndex ? startIndex...endIndex : endIndex...startIndex
                for index in range {
                    let indexPath = IndexPath(item: index, section: lastSelectedIndexPath.section)
                    allIndexPaths.insert(indexPath)
                }

                return allIndexPaths
            }
        }

        return indexPaths
    }
    
    func collectionView(_ collectionView: NSCollectionView, didSelectItemsAt indexPaths: Set<IndexPath>) {}
    
    func collectionView(_ collectionView: NSCollectionView, shouldDeselectItemsAt indexPaths: Set<IndexPath>) -> Set<IndexPath> {
        return indexPaths
    }
    
    func collectionView(_ collectionView: NSCollectionView, didDeselectItemsAt indexPaths: Set<IndexPath>) {}
    
    func collectionView(_ collectionView: NSCollectionView, canDragItemsAt indexPaths: Set<IndexPath>, with event: NSEvent) -> Bool {
        if let can = self.delegate?.thumbnailView?(thumbanView: self, canDragItemsAt: indexPaths, with: event) {
            return can
        }
        return true
    }
    
    func collectionView(_ collectionView: NSCollectionView, writeItemsAt indexPaths: Set<IndexPath>, to pasteboard: NSPasteboard) -> Bool {
        let data: Data = try! NSKeyedArchiver.archivedData(withRootObject: indexPaths, requiringSecureCoding: true)
        pasteboard.declareTypes([self.localForDraggedTypes], owner: self)
        pasteboard.setData(data, forType: self.localForDraggedTypes)
        
        self.dragedIndexPaths.removeAll()
        for indexPath in indexPaths {
            self.dragedIndexPaths.append(indexPath)
        }
        return true
    }
    
    func collectionView(_ collectionView: NSCollectionView, draggingSession session: NSDraggingSession, willBeginAt screenPoint: NSPoint, forItemsAt indexes: IndexSet) {
        self.delegate?.thumbnailView?(thumbanView: self, draggingSession: session, willBeginAt: screenPoint, forItemsAt: indexes)
    }
    
    func collectionView(_ collectionView: NSCollectionView, draggingSession session: NSDraggingSession, endedAt screenPoint: NSPoint, dragOperation operation: NSDragOperation) {
        self._dragMoveFlagIndexpath = nil
        self._dragMoveFlagIndexs = nil
        self.delegate?.thumbnailView?(thumbanView: self, draggingSession: session, endedAt: screenPoint, dragOperation: operation)
    }
    
    func collectionView(_ collectionView: NSCollectionView, validateDrop draggingInfo: NSDraggingInfo, proposedIndexPath proposedDropIndexPath: AutoreleasingUnsafeMutablePointer<NSIndexPath>, dropOperation proposedDropOperation: UnsafeMutablePointer<NSCollectionView.DropOperation>) -> NSDragOperation {
        let pboard = draggingInfo.draggingPasteboard
        if (pboard.availableType(from: [self.localForDraggedTypes]) != nil) {
            return .move
        } else if (pboard.availableType(from: [.localDraggedTypes]) != nil) {
            if (proposedDropOperation.pointee == .on && self.dragMoveEffectAnimated) {
                _ = self._doDragMoveEffect(to: proposedDropIndexPath.pointee as IndexPath)
            }
            
            return .move
        } else if ((pboard.availableType(from: [.fileURL])) != nil) {
            guard let pbItems = pboard.pasteboardItems else {
                return NSDragOperation(rawValue: 0)
            }
            guard let _allowedFileTypes = self.kmAllowedFileTypes else {
                return .generic
            }
            
            var hasValidFile = false
            for item in pbItems {
                guard let data = item.string(forType: .fileURL), let _url = URL(string: data) else {
                    continue
                }
                let type = _url.pathExtension.lowercased()
                if (_allowedFileTypes.contains(type)) {
                    hasValidFile = true
                    break
                }
            }
            
            if (!hasValidFile) {
                return NSDragOperation(rawValue: 0)
            }
        }
        
        return .generic
    }
    
    func collectionView(_ collectionView: NSCollectionView, acceptDrop draggingInfo: NSDraggingInfo, indexPath: IndexPath, dropOperation: NSCollectionView.DropOperation) -> Bool {
        if let should = self.delegate?.thumbnailView?(thumbanView: self, shouldAcceptDrop: draggingInfo, indexPath: indexPath, dropOperation: dropOperation), !should {
            return should
        }
        
        let pboard = draggingInfo.draggingPasteboard
        if (pboard.availableType(from: [self.localForDraggedTypes]) != nil) {
            let dragInfo = [
                KMThumbnailViewDragInfoKey.draggingInfo.rawValue : draggingInfo,
                KMThumbnailViewDragInfoKey.dropOperation.rawValue : dropOperation
            ] as [Int : Any]
            self.delegate?.thumbnailView?(thumbanView: self, didDrag: self.dragedIndexPaths, indexpath: indexPath, dragInfo: dragInfo)
            self.dragedIndexPaths.removeAll()
            return true
        } else if (pboard.availableType(from: [.localDraggedTypes]) != nil) {
            var _dragIndexpaths = Set<IndexPath>()
            draggingInfo.enumerateDraggingItems(
                options: NSDraggingItemEnumerationOptions.concurrent,
                for: collectionView,
                classes: [NSPasteboardItem.self],
                searchOptions: [:],
                using: {(draggingItem, idx, stop) in
                    if let pasteboardItem = draggingItem.item as? NSPasteboardItem {
                        do {
                            if let indexPathData = pasteboardItem.data(forType: .localDraggedTypes), let _indexPath =
                                try NSKeyedUnarchiver.unarchiveTopLevelObjectWithData(indexPathData) as? IndexPath {
                                
                                _dragIndexpaths.insert(_indexPath)
                            }
                        } catch {
                            Swift.debugPrint("failed to unarchive indexPath for dropped photo item.")
                        }
                    }
                })
            
            let dragInfo = [
                KMThumbnailViewDragInfoKey.draggingInfo.rawValue : draggingInfo,
                KMThumbnailViewDragInfoKey.dropOperation.rawValue : dropOperation
            ] as [Int : Any]
            self.delegate?.thumbnailView?(thumbanView: self, didDrag: _dragIndexpaths.sorted(), indexpath: indexPath, dragInfo: dragInfo)
            self.dragedIndexPaths.removeAll()
            return true
        } else if ((pboard.availableType(from: [.fileURL])) != nil) {
            var array: [URL] = []
            for item: NSPasteboardItem in pboard.pasteboardItems! {
                let string: String = item.string(forType: NSPasteboard.PasteboardType.fileURL)!
                let url = NSURL(string: string)
                array.append(url! as URL)
            }
            
            self.delegate?.thumbnailView?(thumbanView: self, didDragAddFiles: array, indexpath: indexPath)
            return true
        }
        
        return false
    }
}

// MARK: - NSCollectionViewDelegateFlowLayout

extension KMThumbnailView: NSCollectionViewDelegateFlowLayout {
    func collectionView(_ collectionView: NSCollectionView, layout collectionViewLayout: NSCollectionViewLayout, sizeForItemAt indexPath: IndexPath) -> NSSize {
        if let size_ = self.delegate?.thumbnailView?(thumbanView: self, sizeForItemAt: indexPath) {
            return size_
        }
        
        return self.itemSize
    }
    
    func collectionView(_ collectionView: NSCollectionView, layout collectionViewLayout: NSCollectionViewLayout, minimumLineSpacingForSectionAt section: Int) -> CGFloat {
        if let minimumLineSpacing_ = self.delegate?.thumbnailView?(thumbanView: self, minimumLineSpacingForSectionAt: section) {
            return minimumLineSpacing_
        }
        return self.minimumLineSpacing
    }
    
    func collectionView(_ collectionView: NSCollectionView, layout collectionViewLayout: NSCollectionViewLayout, minimumInteritemSpacingForSectionAt section: Int) -> CGFloat {
        if let minimumInteritemSpacing_ = self.delegate?.thumbnailView?(thumbanView: self, minimumInteritemSpacingForSectionAt: section) {
            return minimumInteritemSpacing_
        }
        return self.minimumInteritemSpacing
    }
    
    func collectionView(_ collectionView: NSCollectionView, layout collectionViewLayout: NSCollectionViewLayout, insetForSectionAt section: Int) -> NSEdgeInsets {
        if let inset = self.delegate?.thumbnailView?(thumbanView: self, insetForSectionAt: section) {
            return inset
        }
        return self.sectionInset
    }
}