Dirkster99 · Dirkster99 · Apr 12, 2020 · Mar 29, 2020
diff --git a/source/Components/AvalonDock/Controls/LayoutAnchorablePaneControl.cs b/source/Components/AvalonDock/Controls/LayoutAnchorablePaneControl.cs
@@ -21,9 +21,9 @@ namespace AvalonDock.Controls
 	/// Provides a control to display multible (or just one) LayoutAnchorable(s).
 	/// See also <seealso cref="AnchorablePaneTabPanel"/>.
 	/// </summary>
-	/// <seealso cref="TabControl"/>
+	/// <seealso cref="TabControlEx"/>
 	/// <seealso cref="ILayoutControl"/>
-	public class LayoutAnchorablePaneControl : TabControl, ILayoutControl//, ILogicalChildrenContainer
+	public class LayoutAnchorablePaneControl : TabControlEx, ILayoutControl//, ILogicalChildrenContainer
 	{
 		#region fields
 		private LayoutAnchorablePane _model;

diff --git a/source/Components/AvalonDock/Controls/LayoutDocumentPaneControl.cs b/source/Components/AvalonDock/Controls/LayoutDocumentPaneControl.cs
@@ -22,9 +22,9 @@ namespace AvalonDock.Controls
 	/// TabItem Header (<see cref="LayoutDocumentTabItem"/>) that contains the document titles
 	/// inside the <see cref="DocumentPaneTabPanel"/>.
 	/// </summary>
-	/// <seealso cref="TabControl"/>
+	/// <seealso cref="TabControlEx"/>
 	/// <seealso cref="ILayoutControl"/>
-	public class LayoutDocumentPaneControl : TabControl, ILayoutControl//, ILogicalChildrenContainer
+	public class LayoutDocumentPaneControl : TabControlEx, ILayoutControl//, ILogicalChildrenContainer
 	{
 		#region fields
 		private LayoutDocumentPane _model;

diff --git a/source/Components/AvalonDock/TabControlEx.cs b/source/Components/AvalonDock/TabControlEx.cs
@@ -0,0 +1,201 @@
+using System;
+using System.Collections.Specialized;
+using System.Windows;
+using System.Windows.Controls;
+using System.Windows.Controls.Primitives;
+using System.Windows.Data;
+
+namespace AvalonDock
+{
+    /// <summary>
+    /// This control added to mitigate issue with tab (document) switching speed
+    /// See this https://stackoverflow.com/questions/2080764/how-to-preserve-control-state-within-tab-items-in-a-tabcontrol
+    /// and this https://stackoverflow.com/questions/31030293/cefsharp-in-tabcontrol-not-working/37171847#37171847
+    /// </summary>
+    [TemplatePart(Name = "PART_ItemsHolder", Type = typeof(Panel))]
+    public class TabControlEx : TabControl
+    {
+        private Panel ItemsHolderPanel = null;
+
+        public TabControlEx()
+            : base()
+        {
+            // This is necessary so that we get the initial databound selected item
+            ItemContainerGenerator.StatusChanged += ItemContainerGenerator_StatusChanged;
+        }
+
+        /// <summary>
+        /// If containers are done, generate the selected item
+        /// </summary>
+        /// <param name="sender"></param>
+        /// <param name="e"></param>
+        private void ItemContainerGenerator_StatusChanged(object sender, EventArgs e)
+        {
+            if (this.ItemContainerGenerator.Status == GeneratorStatus.ContainersGenerated)
+            {
+                this.ItemContainerGenerator.StatusChanged -= ItemContainerGenerator_StatusChanged;
+                UpdateSelectedItem();
+            }
+        }
+
+        /// <summary>
+        /// Get the ItemsHolder and generate any children
+        /// </summary>
+        public override void OnApplyTemplate()
+        {
+            base.OnApplyTemplate();
+            ItemsHolderPanel = CreateGrid();
+            // exchange ContentPresenter for Grid
+            var topGrid = (Grid)GetVisualChild(0);
+
+            if (topGrid != null)
+            {
+                if (topGrid.Children != null && topGrid.Children.Count > 2)
+                {
+                    if (topGrid.Children[1] is Border)
+                    {
+                        var border = (Border)topGrid.Children[1];
+                        border.Child = ItemsHolderPanel;
+                    }
+                    else if (topGrid.Children[2] is Border)
+                    {
+                        var border = (Border)topGrid.Children[2];
+                        border.Child = ItemsHolderPanel;
+                    }
+                }
+            }
+
+            UpdateSelectedItem();
+        }
+
+        private Grid CreateGrid()
+        {
+            var grid = new Grid();
+            Binding binding = new Binding(PaddingProperty.Name);
+            binding.Source = this;  // view model?
+            grid.SetBinding(Grid.MarginProperty, binding);
+
+            binding = new Binding(SnapsToDevicePixelsProperty.Name);
+            binding.Source = this;  // view model?
+            grid.SetBinding(Grid.SnapsToDevicePixelsProperty, binding);
+
+            return grid;
+        }
+
+        /// <summary>
+        /// When the items change we remove any generated panel children and add any new ones as necessary
+        /// </summary>
+        /// <param name="e"></param>
+        protected override void OnItemsChanged(NotifyCollectionChangedEventArgs e)
+        {
+            base.OnItemsChanged(e);
+
+            if (ItemsHolderPanel == null)
+                return;
+
+            switch (e.Action)
+            {
+                case NotifyCollectionChangedAction.Reset:
+                    ItemsHolderPanel.Children.Clear();
+                    break;
+
+                case NotifyCollectionChangedAction.Add:
+                case NotifyCollectionChangedAction.Remove:
+                    if (e.OldItems != null)
+                    {
+                        foreach (var item in e.OldItems)
+                        {
+                            ContentPresenter cp = FindChildContentPresenter(item);
+                            if (cp != null)
+                                ItemsHolderPanel.Children.Remove(cp);
+                        }
+                    }
+
+                    // Don't do anything with new items because we don't want to
+                    // create visuals that aren't being shown
+
+                    UpdateSelectedItem();
+                    break;
+
+                case NotifyCollectionChangedAction.Replace:
+                    throw new NotImplementedException("Replace not implemented yet");
+            }
+        }
+
+        protected override void OnSelectionChanged(SelectionChangedEventArgs e)
+        {
+            base.OnSelectionChanged(e);
+            UpdateSelectedItem();
+        }
+
+        private void UpdateSelectedItem()
+        {
+            if (ItemsHolderPanel == null)
+                return;
+
+            // Generate a ContentPresenter if necessary
+            TabItem item = GetSelectedTabItem();
+            if (item != null)
+                CreateChildContentPresenter(item);
+
+            // show the right child
+            foreach (ContentPresenter child in ItemsHolderPanel.Children)
+                child.Visibility = ((child.Tag as TabItem).IsSelected) ? Visibility.Visible : Visibility.Collapsed;
+        }
+
+        private ContentPresenter CreateChildContentPresenter(object item)
+        {
+            if (item == null)
+                return null;
+
+            ContentPresenter cp = FindChildContentPresenter(item);
+
+            if (cp != null)
+                return cp;
+
+            // the actual child to be added.  cp.Tag is a reference to the TabItem
+            cp = new ContentPresenter();
+            cp.Content = (item is TabItem) ? (item as TabItem).Content : item;
+            cp.ContentTemplate = this.SelectedContentTemplate;
+            cp.ContentTemplateSelector = this.SelectedContentTemplateSelector;
+            cp.ContentStringFormat = this.SelectedContentStringFormat;
+            cp.Visibility = Visibility.Collapsed;
+            cp.Tag = (item is TabItem) ? item : (this.ItemContainerGenerator.ContainerFromItem(item));
+            ItemsHolderPanel.Children.Add(cp);
+            return cp;
+        }
+
+        private ContentPresenter FindChildContentPresenter(object data)
+        {
+            if (data is TabItem)
+                data = (data as TabItem).Content;
+
+            if (data == null)
+                return null;
+
+            if (ItemsHolderPanel == null)
+                return null;
+
+            foreach (ContentPresenter cp in ItemsHolderPanel.Children)
+            {
+                if (cp.Content == data)
+                    return cp;
+            }
+
+            return null;
+        }
+
+        protected TabItem GetSelectedTabItem()
+        {
+            object selectedItem = base.SelectedItem;
+            if (selectedItem == null)
+                return null;
+
+            TabItem item = selectedItem as TabItem;
+            if (item == null)
+                item = base.ItemContainerGenerator.ContainerFromIndex(base.SelectedIndex) as TabItem;
+
+            return item;
+        }
+    }
+}