Dock gets stuck on drag

AppDelegate.swift

import Cocoa

@NSApplicationMain
class AppDelegate: NSObject, NSApplicationDelegate {

  @IBOutlet weak var window    : NSWindow!
  @IBOutlet weak var tableView : NSTableView!

  func applicationDidFinishLaunching(_ aNotification: Notification) {
    tableView.delegate   = self
    tableView.dataSource = self
    
    tableView.allowsEmptySelection    = true
    tableView.allowsColumnResizing    = false
    tableView.allowsMultipleSelection = false
    tableView.allowsColumnSelection   = false
    tableView.gridStyleMask = []
    tableView.gridColor     = .clear
    
    // This is required to make the labels selectable!
    tableView.selectionHighlightStyle = .none

    tableView.columnAutoresizingStyle = .firstColumnOnlyAutoresizingStyle

    let tc = tableView.tableColumns[0]
    tc.isEditable   = false
    tc.resizingMask = .autoresizingMask
  }
}

let viewID = NSUserInterfaceItemIdentifier(rawValue: "run-view")

final class MyTextField : NSTextField {
  #if false
  override func draw(_ dirtyRect: NSRect) {
    // Just doing this makes it work
    super.draw(dirtyRect)
  }
  #endif
}

extension AppDelegate : NSTableViewDelegate {
  
  func tableView(_ tableView: NSTableView, heightOfRow row: Int) -> CGFloat {
    return 32
  }

  func tableView(_ tv: NSTableView, viewFor tc: NSTableColumn?, row: Int)
       -> NSView?
  {
    let v = (tv.makeView(withIdentifier: viewID, owner: nil) as? NSTextField)
        ?? MyTextField()
    v.isSelectable = false
    v.isEditable   = false
    v.stringValue  = data[row]
    v.identifier   = viewID
    return v
  }
  
  func tableView(_ tableView: NSTableView, pasteboardWriterForRow row: Int)
       -> NSPasteboardWriting?
  {
    return MyPasteboardItem(value: data[row])
  }
}

final class MyPasteboardItem : NSObject, NSPasteboardWriting {
  
  let value : String
  
  init(value: String) { self.value = value }
  
  func writableTypes(for pasteboard: NSPasteboard) -> [NSPasteboard.PasteboardType] {
    return [ .myOwnType, .string ]
  }
  
  func pasteboardPropertyList(forType type: NSPasteboard.PasteboardType) -> Any? {
    switch type {
      case .string:    return value
      case .myOwnType: return [ "value": value ]
      default:         return nil
    }
  }
}

extension NSPasteboard.PasteboardType {
  static let myOwnType =
    NSPasteboard.PasteboardType(rawValue: "de.zeezide.own-type")
}

extension AppDelegate : NSTableViewDataSource {
  func numberOfRows(in tableView: NSTableView) -> Int { return data.count }
}

fileprivate let data = [
  "Hello",
  "World",
  "Blub"
]

The xib is just the default MainMenu.xib with a plain tableview added to the default window (and hooked up to the AppDelegate outlet).

(this also demos the "white label" issue due to the NSTextLayer not being captured by NSTableView)

The solution for the "Dock-hang" is to call setDraggingSourceOperationMask:

    // THIS FIXES IT!
    tableView.setDraggingSourceOperationMask([.copy], forLocal: false)
    tableView.setDraggingSourceOperationMask([.link], forLocal: true)

The solution for the drawing issue is:

final class MyTextField : NSTextField {
  override func draw(_ dirtyRect: NSRect) {    // Just doing this makes it work
    super.draw(dirtyRect)
  }
}

(though presumably that is suboptimal)