Add Dragging Tabs Between Windows

Author: michael-hawker

TabViewTear/Services/MessageEventArgs.cs

@@ -0,0 +1,33 @@
+using System;
+using System.Collections.Generic;
+using System.Linq;
+using System.Text;
+using System.Threading.Tasks;
+
+namespace TabViewTear.Services
+{
+    /// <summary>
+    /// Information about Message sent between Windows.
+    /// </summary>
+    public class MessageEventArgs: EventArgs
+    {
+        public int FromId { get; private set; }
+
+        public int ToId { get; private set; }
+
+        public string Message { get; private set; }
+
+        /// <summary>
+        /// Extra misc data, should be primitive or thread-safe type.
+        /// </summary>
+        public object Data { get; private set; }
+
+        public MessageEventArgs(int from, int to, string message, object data = null)
+        {
+            FromId = from;
+            ToId = to;
+            Message = message;
+            Data = data;
+        }
+    }
+}

TabViewTear/Services/ViewLifetimeControl.cs

@@ -34,6 +34,8 @@ public sealed class ViewLifetimeControl
         // Optional context to provide from window opener
         public string Context { get; set; }
 
+        public event EventHandler<MessageEventArgs> MessageReceived;
+
         public event ViewReleasedHandler Released
         {
             add
@@ -76,6 +78,11 @@ public static ViewLifetimeControl CreateForCurrentView()
             return new ViewLifetimeControl(CoreWindow.GetForCurrentThread());
         }
 
+        public void SendMessage(string message, int fromid, object data = null)
+        {
+            MessageReceived?.Invoke(this, new MessageEventArgs(fromid, Id, message, data));
+        }
+
         // Signals that the view is being interacted with by another view,
         // so it shouldn't be closed even if it becomes "consolidated"
         public int StartViewInUse()

TabViewTear/Services/WindowManagerService.cs

@@ -28,6 +28,8 @@ public class WindowManagerService
 
         public CoreDispatcher MainDispatcher { get; private set; }
 
+        public event EventHandler<MessageEventArgs> MainWindowMessageReceived;
+
         public void Initialize()
         {
             MainViewId = ApplicationView.GetForCurrentView().Id;
@@ -79,5 +81,21 @@ await CoreApplication.CreateNewView().Dispatcher.RunAsync(CoreDispatcherPriority
         }
 
         public bool IsWindowOpen(string windowTitle) => SecondaryViews.Any(v => v.Title == windowTitle);
+
+        public ViewLifetimeControl GetWindowById(int id) => SecondaryViews.FirstOrDefault(v => v.Id == id);
+
+        public void SendMessage(int toid, string message, object data = null)
+        {
+            if (toid == MainViewId)
+            {
+                // Special case for main window
+                MainWindowMessageReceived?.Invoke(this, new MessageEventArgs(ApplicationView.GetForCurrentView().Id, toid, message, data));
+            }
+            else
+            {
+                // Any secondary window
+                GetWindowById(toid)?.SendMessage(message, ApplicationView.GetForCurrentView().Id, data);
+            }
+        }
     }
 }

TabViewTear/TabViewTear.csproj

@@ -122,6 +122,7 @@
     <Compile Include="Services\DragAndDrop\DropConfiguration.cs" />
     <Compile Include="Services\DragAndDrop\ListViewDropConfiguration.cs" />
     <Compile Include="Services\DragAndDrop\VisualDropConfiguration.cs" />
+    <Compile Include="Services\MessageEventArgs.cs" />
     <Compile Include="Services\NavigationService.cs" />
     <Compile Include="Services\ThemeSelectorService.cs" />
     <Compile Include="Services\ViewLifetimeControl.cs" />

TabViewTear/Views/MainPage.xaml

@@ -9,14 +9,18 @@
     mc:Ignorable="d">
 
     <controls:TabView
+            x:Name="Items"
             TabWidthBehavior="Equal"
             SelectedTabWidth="200"
-            x:Name="Items"
             CanDragItems="True"
             CanReorderItems="True"
             AllowDrop="True"
             TabDraggedOutside="Items_TabDraggedOutside"
             SelectionChanged="Items_SelectionChanged"
+            DragItemsStarting="Items_DragItemsStarting"
+            DragItemsCompleted="Items_DragItemsCompleted"
+            DragOver="Items_DragOver"
+            Drop="Items_Drop"
             ItemsSource="{x:Bind TabItems}">
         <controls:TabView.Resources>
             <x:Double x:Key="TabViewItemHeaderMinWidth">90</x:Double>

TabViewTear/Views/MainPage.xaml.cs

@@ -6,6 +6,7 @@
 using System.Runtime.CompilerServices;
 using TabViewTear.Models;
 using TabViewTear.Services;
+using Windows.ApplicationModel.DataTransfer;
 using Windows.UI.Core;
 using Windows.UI.ViewManagement;
 using Windows.UI.Xaml;
@@ -16,6 +17,11 @@ namespace TabViewTear.Views
 {
     public sealed partial class MainPage : Page, INotifyPropertyChanged
     {
+        private const string DataIdentifier = "TabData";
+        private const string DataIndex = "TabIndex";
+        private const string DataWindow = "TabWindow";
+        private const string CommandClose = "Close";
+
         ObservableCollection<DataItem> TabItems = new ObservableCollection<DataItem>();
 
         public MainPage()
@@ -26,6 +32,8 @@ public MainPage()
         public event PropertyChangedEventHandler PropertyChanged;
 
         private ViewLifetimeControl _viewLifetimeControl;
+
+        #region Handle Window Lifetime
         protected override void OnNavigatedTo(NavigationEventArgs e)
         {
             base.OnNavigatedTo(e);
@@ -36,6 +44,7 @@ protected override void OnNavigatedTo(NavigationEventArgs e)
                 _viewLifetimeControl.StartViewInUse();
                 // Register for window close
                 _viewLifetimeControl.Released += OnViewLifetimeControlReleased;
+                _viewLifetimeControl.MessageReceived += OnViewLifetimeControlMessageReceived;
                 // Deserialize passed in item to display in this window
                 TabItems.Add(JsonConvert.DeserializeObject<DataItem>(_viewLifetimeControl.Context.ToString()));
                 _viewLifetimeControl.Context = null;
@@ -45,9 +54,18 @@ protected override void OnNavigatedTo(NavigationEventArgs e)
             {
                 // Main Window Start
                 InitializeTestData();
+
+                WindowManagerService.Current.MainWindowMessageReceived += OnViewLifetimeControlMessageReceived;
             }
         }
 
+        private MessageEventArgs _lastMsg;
+
+        private async void OnViewLifetimeControlMessageReceived(object sender, MessageEventArgs e)
+        {
+            _lastMsg = e; // Store to complete in DragItemsCompleted.
+        }
+
         private async void OnViewLifetimeControlReleased(object sender, EventArgs e)
         {
             _viewLifetimeControl.Released -= OnViewLifetimeControlReleased;
@@ -56,7 +74,9 @@ await WindowManagerService.Current.MainDispatcher.RunAsync(CoreDispatcherPriorit
                 WindowManagerService.Current.SecondaryViews.Remove(_viewLifetimeControl);
             });
         }
+        #endregion
 
+        #region Handle Dragging Tab to Create Window
         private async void Items_TabDraggedOutside(object sender, Microsoft.Toolkit.Uwp.UI.Controls.TabDraggedOutsideEventArgs e)
         {
             if (e.Item is DataItem data)
@@ -69,12 +89,15 @@ private async void Items_TabDraggedOutside(object sender, Microsoft.Toolkit.Uwp.
 
                 if (TabItems.Count == 0)
                 {
+                    // TODO: If drag wasn't received by another window and last tab, ignore?
                     // No tabs left on main window, 'switch' to window just created to hide the main view
                     await ApplicationViewSwitcher.SwitchAsync(lifetimecontrol.Id, ApplicationView.GetForCurrentView().Id, ApplicationViewSwitchingOptions.ConsolidateViews);
                 }
             }
         }
+        #endregion
 
+        #region Handle Tab Change Updating Window Title
         private void Items_SelectionChanged(object sender, SelectionChangedEventArgs e)
         {
             // Update window title with current item
@@ -84,6 +107,100 @@ private void Items_SelectionChanged(object sender, SelectionChangedEventArgs e)
                 ApplicationView.GetForCurrentView().Title = data.Title;
             }
         }
+        #endregion
+
+        #region Handle Dragging Tabs between windows
+        private void Items_DragItemsStarting(object sender, DragItemsStartingEventArgs e)
+        {
+            // In Initial Window we need to serialize our tab data.
+            var item = e.Items.FirstOrDefault();
+
+            if (item is DataItem data)
+            {
+                // Add actual data
+                e.Data.Properties.Add(DataIdentifier, JsonConvert.SerializeObject(data));
+                // Add our index so we know where to remove from later (if needed)
+                e.Data.Properties.Add(DataIndex, Items.IndexFromContainer(Items.ContainerFromItem(data)));
+                // Add Window Id to know if we're transferring to a different window.
+                e.Data.Properties.Add(DataWindow, ApplicationView.GetForCurrentView().Id);
+            }
+        }
+
+        private void Items_DragOver(object sender, DragEventArgs e)
+        {
+            // Called before we drop to see if we will accept a drop.
+
+            // Do we have Tab Data?
+            if (e.DataView.Properties.ContainsKey(DataIdentifier))
+            {
+                // Tell OS that we allow moving item.
+                e.AcceptedOperation = DataPackageOperation.Move;
+            }
+        }
+
+        private void Items_Drop(object sender, DragEventArgs e)
+        {
+            // Called when we actually get the drop, let's get the data and add our tab.
+            var pos = e.GetPosition(this);
+
+            if (e.DataView.Properties.TryGetValue(DataIdentifier, out object value) && value is string str)
+            {
+                var data = JsonConvert.DeserializeObject<DataItem>(str);
+
+                if (data != null)
+                {
+                    //var minpos = pos;
+                    //var mindist = 1000.0;
+                    //var minindex = -1;
+                    //foreach (var item in Items.Items)
+                    //{
+                    //    var tab = Items.ContainerFromItem(item);
+                    //    var p = e.GetPosition(tab as UIElement);
+                    //    var amt = Math.Abs(p.X - minpos.X) + Math.Abs(p.Y - minpos.Y);
+                    //    if (amt < mindist)
+                    //    {
+                    //        minindex = Items.IndexFromContainer(tab);
+                    //        mindist = amt;
+                    //        minpos = p;
+                    //    }
+                    //}
+
+
+                    // TODO: Figure out how to insert this in the right place.
+                    TabItems.Add(data);
+
+                    Items.SelectedItem = data; // Select new item.
+
+                    // Send message to origintator to remove the tab.
+                    WindowManagerService.Current.SendMessage((e.DataView.Properties[DataWindow] as int?).Value, CommandClose, e.DataView.Properties[DataIndex]);
+                }
+            }
+        }
+
+        private async void Items_DragItemsCompleted(ListViewBase sender, DragItemsCompletedEventArgs args)
+        {
+            if (args.DropResult == DataPackageOperation.Move && _lastMsg != null)
+            {
+                switch (_lastMsg.Message)
+                {
+                    case CommandClose:
+                        if (_lastMsg.Data is int value)
+                        {
+                            TabItems.RemoveAt(value);
+
+                            if (TabItems.Count == 0)
+                            {
+                                // No tabs left on main window, 'switch' to window just created to hide the main view
+                                await ApplicationViewSwitcher.SwitchAsync(_lastMsg.FromId, ApplicationView.GetForCurrentView().Id, ApplicationViewSwitchingOptions.ConsolidateViews);
+                            }
+                        }
+
+                        _lastMsg = null;
+                        break;
+                }
+            }
+        }
+        #endregion
 
         private void Set<T>(ref T storage, T value, [CallerMemberName]string propertyName = null)
         {