  TODO: Refactor to include the buttons and the inner separator. Currently it's just a pass-through view only for drag &
  drop due to the drag & drop infrastructure of Cocoa.
  */
+
 fileprivate class ProxyBar: NSView {
 
   fileprivate var isDragOngoing = false

        view.autoPinEdge(toSuperviewEdge: .left),

        view.autoSetDimension(.width, toSize: tool.minimumDimension, relation: .greaterThanOrEqual)
        ])
    }
  }


        view.autoPinEdge(toSuperviewEdge: .left),

        view.autoSetDimension(.height, toSize: tool.minimumDimension, relation: .greaterThanOrEqual)
      ])
    case .left:
      self.layoutConstraints.append(contentsOf: [
        view.autoPinEdge(toSuperviewEdge: .top),
