Fixes, enhancements and back porting to macOS 10.11

Demo/Demo.xcodeproj/project.pbxproj

@@ -7,6 +7,7 @@
 	objects = {
 
 /* Begin PBXBuildFile section */
+		293D26F1270870A000333635 /* GroupOutlineViewItem.swift in Sources */ = {isa = PBXBuildFile; fileRef = 293D26F0270870A000333635 /* GroupOutlineViewItem.swift */; };
 		DD61CF5624717B1D00CA0BE9 /* DiffableDataSourceSnapshot+Additions.swift in Sources */ = {isa = PBXBuildFile; fileRef = DD61CF5524717B1D00CA0BE9 /* DiffableDataSourceSnapshot+Additions.swift */; };
 		DD61CF582471882A00CA0BE9 /* MasterOutlineViewItem.swift in Sources */ = {isa = PBXBuildFile; fileRef = DD61CF572471882A00CA0BE9 /* MasterOutlineViewItem.swift */; };
 		DDCAB953246475AB00E5AA41 /* MainViewController.swift in Sources */ = {isa = PBXBuildFile; fileRef = DDCAB952246475AB00E5AA41 /* MainViewController.swift */; };
@@ -22,6 +23,7 @@
 /* End PBXBuildFile section */
 
 /* Begin PBXFileReference section */
+		293D26F0270870A000333635 /* GroupOutlineViewItem.swift */ = {isa = PBXFileReference; fileEncoding = 4; lastKnownFileType = sourcecode.swift; path = GroupOutlineViewItem.swift; sourceTree = "<group>"; };
 		DD61CF5524717B1D00CA0BE9 /* DiffableDataSourceSnapshot+Additions.swift */ = {isa = PBXFileReference; lastKnownFileType = sourcecode.swift; path = "DiffableDataSourceSnapshot+Additions.swift"; sourceTree = "<group>"; };
 		DD61CF572471882A00CA0BE9 /* MasterOutlineViewItem.swift */ = {isa = PBXFileReference; fileEncoding = 4; lastKnownFileType = sourcecode.swift; path = MasterOutlineViewItem.swift; sourceTree = "<group>"; };
 		DDCAB952246475AB00E5AA41 /* MainViewController.swift */ = {isa = PBXFileReference; lastKnownFileType = sourcecode.swift; path = MainViewController.swift; sourceTree = "<group>"; };
@@ -50,6 +52,27 @@
 /* End PBXFrameworksBuildPhase section */
 
 /* Begin PBXGroup section */
+		293D26EE2706F38B00333635 /* Left Panel */ = {
+			isa = PBXGroup;
+			children = (
+				DDCAB9542464771600E5AA41 /* MasterViewController.swift */,
+				DD61CF572471882A00CA0BE9 /* MasterOutlineViewItem.swift */,
+				293D26F0270870A000333635 /* GroupOutlineViewItem.swift */,
+			);
+			name = "Left Panel";
+			sourceTree = "<group>";
+		};
+		293D26EF2706F39A00333635 /* Right Panel */ = {
+			isa = PBXGroup;
+			children = (
+				DDCAB9562464785700E5AA41 /* DetailViewController.swift */,
+				DDCAB9582464796400E5AA41 /* EmptyViewController.swift */,
+				DDCAB95A24647B7200E5AA41 /* SingleViewController.swift */,
+				DDCAB95C24647BBF00E5AA41 /* MultiViewController.swift */,
+			);
+			name = "Right Panel";
+			sourceTree = "<group>";
+		};
 		DDCB690F245DDAFD00489647 = {
 			isa = PBXGroup;
 			children = (
@@ -73,16 +96,12 @@
 				DDCB691B245DDAFD00489647 /* AppDelegate.swift */,
 				DDCB691F245DDB0000489647 /* Assets.xcassets */,
 				DDCB6925245DDB0000489647 /* Demo.entitlements */,
-				DDCAB9562464785700E5AA41 /* DetailViewController.swift */,
+				DDCAB952246475AB00E5AA41 /* MainViewController.swift */,
+				293D26EE2706F38B00333635 /* Left Panel */,
+				293D26EF2706F39A00333635 /* Right Panel */,
 				DD61CF5524717B1D00CA0BE9 /* DiffableDataSourceSnapshot+Additions.swift */,
-				DDCAB9582464796400E5AA41 /* EmptyViewController.swift */,
 				DDCB6924245DDB0000489647 /* Info.plist */,
 				DDCB6921245DDB0000489647 /* Main.storyboard */,
-				DDCAB952246475AB00E5AA41 /* MainViewController.swift */,
-				DD61CF572471882A00CA0BE9 /* MasterOutlineViewItem.swift */,
-				DDCAB9542464771600E5AA41 /* MasterViewController.swift */,
-				DDCAB95C24647BBF00E5AA41 /* MultiViewController.swift */,
-				DDCAB95A24647B7200E5AA41 /* SingleViewController.swift */,
 			);
 			path = Demo;
 			sourceTree = "<group>";
@@ -175,6 +194,7 @@
 				DDCAB95B24647B7200E5AA41 /* SingleViewController.swift in Sources */,
 				DD61CF5624717B1D00CA0BE9 /* DiffableDataSourceSnapshot+Additions.swift in Sources */,
 				DDCAB95D24647BBF00E5AA41 /* MultiViewController.swift in Sources */,
+				293D26F1270870A000333635 /* GroupOutlineViewItem.swift in Sources */,
 				DDCB691C245DDAFD00489647 /* AppDelegate.swift in Sources */,
 			);
 			runOnlyForDeploymentPostprocessing = 0;

Demo/Demo/DetailViewController.swift

@@ -20,7 +20,6 @@ final class DetailViewController: NSViewController {
     let viewController = NSTabViewController()
     viewController.tabStyle = .unspecified
     viewController.transitionOptions = []
-    viewController.view.wantsLayer = false
     viewController.tabViewItems = [emptyViewController, singleViewController, multiViewController]
       .map(NSTabViewItem.init(viewController:))
     return viewController

Demo/Demo/DiffableDataSourceSnapshot+Additions.swift

@@ -2,47 +2,62 @@ import Foundation
 import OutlineViewDiffableDataSource
 
 extension DiffableDataSourceSnapshot {
-
+  
   /// Appends items from the text view.
   mutating func fillItem(_ selectedItem: Item?, with string: String) {
     let lines = string.components(separatedBy: .newlines)
+
     for line in lines {
+      // Each line should have a "parent (/ child)?". Since this is a free-form text field, we need to find
+      // existing items in the side bar
       let titles = line.components(separatedBy: "/").map { $0.trimmingCharacters(in: .whitespaces) }.filter { $0.isEmpty == false }
+
+      guard !titles.isEmpty else { continue }
+
+      // Use title as the unique ID in this case
+      let rootItem = getItemForID(titles[0]) ?? MasterGroupOutlineViewItem(id: titles[0], title: titles[0])
+      let sideBarItem = getItemForID(titles[0]) ?? MasterOutlineViewItem(id: titles[0], title: titles[0])
+
+      let foundRootItem = containsItem(rootItem)
+      let foundSidebarItem = containsItem(sideBarItem)
+
       switch titles.count {
-      case 1:
-        let groupItem = GroupOutlineViewItem(id: titles[0], title: titles[0])
-        let masterItem = MasterOutlineViewItem(title: titles[0])
-        if containsItem(groupItem) == false, containsItem(masterItem) == false {
-          if selectedItem == nil {
-            appendItems([groupItem])
-          } else {
-            appendItems([masterItem], into: selectedItem)
+        case 1:
+          // No child specified
+          if foundRootItem == false, foundSidebarItem == false {
+            if let selectedItem = selectedItem {
+              appendItems([sideBarItem], into: selectedItem)
+            }
+            else {
+              appendItems([rootItem], into: nil)
+            }
           }
-        }
-      case 2:
-        let parentGroupItem = GroupOutlineViewItem(id: titles[0], title: titles[0])
-        let parentMasterItem = MasterOutlineViewItem(title: titles[0])
-        var parentItem: NSObject?
-        if containsItem(parentGroupItem) == false, containsItem(parentMasterItem) == false {
-          if selectedItem == nil {
-            appendItems([parentGroupItem])
-            parentItem = parentGroupItem
-
-          } else {
-            appendItems([parentMasterItem], into: selectedItem)
-            parentItem = parentMasterItem
+        case 2:
+          let childItemToAdd = MasterOutlineViewItem(id: titles[1], title: titles[1])
+
+          if containsItem(childItemToAdd) == false {
+            // Parent / Child specified. Find
+            var parentItemToUse: OutlineViewItem?
+
+            if foundRootItem == false, foundSidebarItem == false {
+              if selectedItem == nil {
+                appendItems([rootItem])
+                parentItemToUse = rootItem
+
+              } else {
+                appendItems([sideBarItem], into: selectedItem)
+                parentItemToUse = sideBarItem
+              }
+            } else if foundRootItem {
+              parentItemToUse = rootItem
+            } else if foundSidebarItem {
+              parentItemToUse = sideBarItem
+            }
+
+            appendItems([childItemToAdd], into: parentItemToUse)
           }
-        } else if containsItem(parentGroupItem) {
-          parentItem = parentGroupItem
-        } else if containsItem(parentMasterItem) {
-          parentItem = parentMasterItem
-        }
-        let childItem = MasterOutlineViewItem(title: titles[1])
-        if containsItem(childItem) == false {
-          appendItems([childItem], into: parentItem)
-        }
-      default:
-        continue
+        default:
+          continue
       }
     }
   }

Demo/Demo/EmptyViewController.swift

@@ -4,7 +4,6 @@ import OutlineViewDiffableDataSource
 
 /// The number of controls for an empty outline view selection.
 final class EmptyViewController: NSViewController {
-
   /// Multiline text editor for the outline contents.
   private lazy var scrollableEditor: NSScrollView = {
     let scrollView = NSTextView.scrollablePlainDocumentContentTextView()
@@ -56,17 +55,25 @@ extension EmptyViewController {
 
     guard let textView = scrollableEditor.documentView as? NSTextView, textView.string.isEmpty else { return }
     textView.string = """
-      Parent 1 / Child 11
-      Parent 1 / Child 12
-      Parent 1 / Child 13
-      Parent 2
-      Parent 2 / Child 21
-      Child 21 / Leaf 211
-      Child 21 / Leaf 212
-      Parent 3 / Child 31
-      Parent 3 / Child 32
-      Parent 3 / Child 33
+      Cars / Toyota
+      Cars / Honda
+      Cars / Tesla
+      Phones
+      Phones / Samsung
+      Samsung / Samsung Note
+      Samsung / Samsung Nexus
+      Samsung Nexus / Nexus 5
+      OS / macOS
+      OS / Windows
+      OS / Linux
       """
+
+//    Parent 3
+//    Parent 3 / Child 31
+//    Child 31 / Child 33
+//    Child 33 / Child 32
+
+    fillSidebar(nil)
   }
 }
 
@@ -77,9 +84,11 @@ private extension EmptyViewController {
   /// Replaces the whole tree with the given contents.
   @IBAction func fillSidebar(_ sender: Any?) {
     guard let textView = scrollableEditor.documentView as? NSTextView else { return }
+
+    // Create a new snapshot from entered Parent / Child items.
     var snapshot: DiffableDataSourceSnapshot = .init()
     snapshot.fillItem(nil, with: textView.string)
-    snapshotBinding.wrappedValue = snapshot
+    snapshotBinding.wrappedValue = snapshot    
   }
 
   /// Replaces text with sidebar contents.
@@ -89,8 +98,8 @@ private extension EmptyViewController {
     var items: [String] = []
     snapshot.enumerateItems { item, parentItem in
       items.append([
-        (parentItem as? GroupOutlineViewItem)?.title ?? (parentItem as? MasterOutlineViewItem)?.title,
-        (item as? GroupOutlineViewItem)?.title ?? (item as? MasterOutlineViewItem)?.title,
+        (parentItem as? MasterGroupOutlineViewItem)?.title ?? (parentItem as? MasterOutlineViewItem)?.title,
+        (item as? MasterGroupOutlineViewItem)?.title ?? (item as? MasterOutlineViewItem)?.title,
       ].compactMap { $0 }.joined(separator: " / "))
     }
     textView.string = items.joined(separator: "\n")

Sources/OutlineViewItem+Group.swift → Demo/Demo/GroupOutlineViewItem.swift

@@ -1,37 +1,22 @@
 import AppKit
+import OutlineViewDiffableDataSource
 
 /// Default root item with buttons ‘Show’ and ‘Hide’, not intended for subclassing.
-public final class GroupOutlineViewItem: NSObject, OutlineViewItem {
-
-  /// Unique identifier for diffing.
-  public let id: String
-
+public final class MasterGroupOutlineViewItem: GroupOutlineViewItem {
   /// Display string.
   public let title: String
 
-  /// Show as Group.
-  public let isGroup: Bool = true
-
-  /// Deny selection.
-  public let isSelectable: Bool = false
-
   /// Creates a “standard” root item for the sidebar.
   public init(id: String, title: String) {
-    self.id = id
     self.title = title
+    super.init(id: id)
   }
 
   /// Returns an appropriate cell view type.
-  public func cellViewType(for tableColumn: NSTableColumn?) -> NSTableCellView.Type { GroupTableCellView.self }
+  public override func cellViewType(for tableColumn: NSTableColumn?) -> NSTableCellView.Type { GroupTableCellView.self }
 
   /// Necessary for sets.
   public override var hash: Int { title.hash }
-
-  /// Necessary for outline view reloading.
-  public override func isEqual(_ object: Any?) -> Bool {
-    guard let groupItem = object as? GroupOutlineViewItem else { return false }
-    return groupItem.id == id
-  }
 }
 
 // MARK: - Private API
@@ -86,7 +71,7 @@ private final class GroupTableCellView: NSTableCellView {
   /// Retrieves new title from the associated group item.
   override var objectValue: Any? {
     didSet {
-      if let label = textField, let groupItem = objectValue as? GroupOutlineViewItem {
+      if let label = textField, let groupItem = objectValue as? MasterGroupOutlineViewItem {
         label.stringValue = groupItem.title
       }
     }

Demo/Demo/MasterOutlineViewItem.swift

@@ -2,25 +2,21 @@ import AppKit
 import OutlineViewDiffableDataSource
 
 /// Sidebar iitems.
-class MasterOutlineViewItem: NSObject, OutlineViewItem {
-
+class MasterOutlineViewItem: OutlineViewItem {
   /// Visible string.
   let title: String
 
   /// Creates a new item ready for insertion into the sidebar.
-  init(title: String) { self.title = title }
-
+  init(id: String, title: String) {
+    self.title = title
+    super.init(id: id)
+  }
+
   /// Returns a private cell view type.
-  func cellViewType(for tableColumn: NSTableColumn?) -> NSTableCellView.Type { MasterCellView.self }
+  override func cellViewType(for tableColumn: NSTableColumn?) -> NSTableCellView.Type { MasterCellView.self }
 
-  /// Necessary for sets.
+  /// Necessary for supporting drag-n-drop and expand-collapse.
   override var hash: Int { title.hash }
-
-  /// Necessary for outline view reloading.
-  override func isEqual(_ object: Any?) -> Bool {
-    guard let masterItem = object as? MasterOutlineViewItem else { return false }
-    return masterItem.title == title
-  }
 }
 
 // MARK: - Private API