Configurable Mouse-Wheel Scroll Direction for Tool and Document Tab Strips

docfx/articles/dock-controls-reference.md

@@ -83,6 +83,7 @@ Unless noted otherwise, the properties listed are Avalonia styled properties and
 | `IsActive` | `bool` | Active tab strip state (drives `:active`). |
 | `EnableWindowDrag` | `bool` | Allows dragging the host window by the tab strip. |
 | `Orientation` | `Orientation` | Tab strip orientation. |
+| `MouseWheelScrollOrientation` | `Orientation` | Mouse-wheel scroll axis for tab overflow (`Horizontal` by default). |
 | `CreateButtonTheme` | `ControlTheme?` | Theme for the create document button. |
 
 ### DocumentTabStripItem
@@ -97,6 +98,7 @@ Unless noted otherwise, the properties listed are Avalonia styled properties and
 | Property | Type | Description |
 | --- | --- | --- |
 | `CanCreateItem` | `bool` | `true` when the new-tool button is available. |
+| `MouseWheelScrollOrientation` | `Orientation` | Mouse-wheel scroll axis for tab overflow (`Horizontal` by default). |
 
 ### ToolTabStripItem
 

src/Dock.Avalonia/Controls/DocumentTabStrip.axaml.cs

@@ -19,6 +19,8 @@ public class DocumentTabStrip : TabStrip
 {
     private HostWindow? _attachedWindow;
     private Control? _grip;
+    private ScrollViewer? _scrollViewer;
+    private IDisposable? _scrollViewerWheelSubscription;
     private WindowDragHelper? _windowDragHelper;
 
     /// <summary>
@@ -45,6 +47,14 @@ public class DocumentTabStrip : TabStrip
     public static readonly StyledProperty<Orientation> OrientationProperty =
         AvaloniaProperty.Register<DocumentTabStrip, Orientation>(nameof(Orientation));
 
+    /// <summary>
+    /// Defines the <see cref="MouseWheelScrollOrientation"/> property.
+    /// </summary>
+    public static readonly StyledProperty<Orientation> MouseWheelScrollOrientationProperty =
+        AvaloniaProperty.Register<DocumentTabStrip, Orientation>(
+            nameof(MouseWheelScrollOrientation),
+            defaultValue: Orientation.Horizontal);
+
     /// <summary>
     /// Define the <see cref="CreateButtonTheme"/> property.
     /// </summary>
@@ -96,6 +106,15 @@ public Orientation Orientation
         set => SetValue(OrientationProperty, value);
     }
 
+    /// <summary>
+    /// Gets or sets orientation used for mouse wheel scrolling in the tab strip.
+    /// </summary>
+    public Orientation MouseWheelScrollOrientation
+    {
+        get => GetValue(MouseWheelScrollOrientationProperty);
+        set => SetValue(MouseWheelScrollOrientationProperty, value);
+    }
+
     /// <inheritdoc/>
     protected override Type StyleKeyOverride => typeof(DocumentTabStrip);
 
@@ -112,7 +131,13 @@ public DocumentTabStrip()
     protected override void OnApplyTemplate(TemplateAppliedEventArgs e)
     {
         base.OnApplyTemplate(e);
+
+        DetachScrollViewerWheel();
+
         _grip = e.NameScope.Find<Control>("PART_BorderFill");
+        _scrollViewer = e.NameScope.Find<ScrollViewer>("PART_ScrollViewer");
+        AttachScrollViewerWheel();
+
         AttachToWindow();
     }
 
@@ -121,13 +146,15 @@ protected override void OnAttachedToVisualTree(VisualTreeAttachmentEventArgs e)
     {
         base.OnAttachedToVisualTree(e);
 
+        AttachScrollViewerWheel();
         AttachToWindow();
     }
 
     /// <inheritdoc/>
     protected override void OnDetachedFromVisualTree(VisualTreeAttachmentEventArgs e)
     {
         base.OnDetachedFromVisualTree(e);
+        DetachScrollViewerWheel();
         DetachFromWindow();
     }
 
@@ -169,6 +196,11 @@ protected override void OnPropertyChanged(AvaloniaPropertyChangedEventArgs chang
                 DetachFromWindow();
             }
         }
+
+        if (change.Property == MouseWheelScrollOrientationProperty)
+        {
+            AttachScrollViewerWheel();
+        }
     }
 
     private void UpdatePseudoClassesCreate(bool canCreate)
@@ -237,4 +269,16 @@ private void DetachFromWindow()
             _windowDragHelper = null;
         }
     }
+
+    private void DetachScrollViewerWheel()
+    {
+        _scrollViewerWheelSubscription?.Dispose();
+        _scrollViewerWheelSubscription = null;
+    }
+
+    private void AttachScrollViewerWheel()
+    {
+        _scrollViewerWheelSubscription?.Dispose();
+        _scrollViewerWheelSubscription = ScrollViewerMouseWheelHookHelper.Attach(_scrollViewer, MouseWheelScrollOrientation);
+    }
 }

src/Dock.Avalonia/Controls/ToolTabStrip.axaml.cs

@@ -7,8 +7,10 @@
 using Avalonia.Controls.Metadata;
 using Avalonia.Controls.Presenters;
 using Avalonia.Controls.Primitives;
+using Avalonia.Layout;
 using Avalonia.Media;
 using Avalonia.Reactive;
+using Dock.Avalonia.Internal;
 
 namespace Dock.Avalonia.Controls;
 
@@ -23,13 +25,22 @@ public class ToolTabStrip : TabStrip
     private Border? _borderRightFill;
     private ItemsPresenter? _itemsPresenter;
     private ScrollViewer? _scrollViewer;
+    private IDisposable? _scrollViewerWheelSubscription;
 
     /// <summary>
     /// Defines the <see cref="CanCreateItem"/> property.
     /// </summary>
     public static readonly StyledProperty<bool> CanCreateItemProperty =
         AvaloniaProperty.Register<ToolTabStrip, bool>(nameof(CanCreateItem));
 
+    /// <summary>
+    /// Defines the <see cref="MouseWheelScrollOrientation"/> property.
+    /// </summary>
+    public static readonly StyledProperty<Orientation> MouseWheelScrollOrientationProperty =
+        AvaloniaProperty.Register<ToolTabStrip, Orientation>(
+            nameof(MouseWheelScrollOrientation),
+            defaultValue: Orientation.Horizontal);
+
     /// <summary>
     /// Gets or sets if tab strop dock can create new items.
     /// </summary>
@@ -39,6 +50,15 @@ public bool CanCreateItem
         set => SetValue(CanCreateItemProperty, value);
     }
 
+    /// <summary>
+    /// Gets or sets orientation used for mouse wheel scrolling in the tab strip.
+    /// </summary>
+    public Orientation MouseWheelScrollOrientation
+    {
+        get => GetValue(MouseWheelScrollOrientationProperty);
+        set => SetValue(MouseWheelScrollOrientationProperty, value);
+    }
+
     /// <inheritdoc/>
     protected override Type StyleKeyOverride => typeof(ToolTabStrip);
 
@@ -55,10 +75,13 @@ protected override void OnApplyTemplate(TemplateAppliedEventArgs e)
     {
         base.OnApplyTemplate(e);
 
+        AttachScrollViewerWheel(null);
+
         _borderLeftFill = e.NameScope.Find<Border>("PART_BorderLeftFill");
         _borderRightFill = e.NameScope.Find<Border>("PART_BorderRightFill");
         _itemsPresenter = e.NameScope.Find<ItemsPresenter>("PART_ItemsPresenter");
         _scrollViewer = e.NameScope.Find<ScrollViewer>("PART_ScrollViewer");
+        AttachScrollViewerWheel(_scrollViewer);
 
         _itemsPresenter?.GetObservable(Border.BoundsProperty)
             .Subscribe(new AnonymousObserver<Rect>(_ => UpdateBorders()));
@@ -75,6 +98,20 @@ protected override void OnApplyTemplate(TemplateAppliedEventArgs e)
         UpdateBorders();
     }
 
+    /// <inheritdoc/>
+    protected override void OnDetachedFromVisualTree(VisualTreeAttachmentEventArgs e)
+    {
+        base.OnDetachedFromVisualTree(e);
+        AttachScrollViewerWheel(null);
+    }
+
+    /// <inheritdoc/>
+    protected override void OnAttachedToVisualTree(VisualTreeAttachmentEventArgs e)
+    {
+        base.OnAttachedToVisualTree(e);
+        AttachScrollViewerWheel(_scrollViewer);
+    }
+
     private void OnContainerAttachedToVisualTree(object? sender, VisualTreeAttachmentEventArgs e)
     {
         if (sender is ToolTabStripItem tabStripItem)
@@ -175,10 +212,21 @@ protected override void OnPropertyChanged(AvaloniaPropertyChangedEventArgs chang
         {
             UpdatePseudoClasses(change.GetNewValue<bool>());
         }
+
+        if (change.Property == MouseWheelScrollOrientationProperty)
+        {
+            AttachScrollViewerWheel(_scrollViewer);
+        }
     }
 
     private void UpdatePseudoClasses(bool canCreate)
     {
         PseudoClasses.Set(":create", canCreate);
     }
+
+    private void AttachScrollViewerWheel(ScrollViewer? scrollViewer)
+    {
+        _scrollViewerWheelSubscription?.Dispose();
+        _scrollViewerWheelSubscription = ScrollViewerMouseWheelHookHelper.Attach(scrollViewer, MouseWheelScrollOrientation);
+    }
 }

src/Dock.Avalonia/Internal/ScrollViewerMouseWheelHookHelper.cs

@@ -0,0 +1,51 @@
+// Copyright (c) Wiesław Šoltés. All rights reserved.
+// Licensed under the MIT license. See LICENSE file in the project root for details.
+using System;
+using Avalonia.Controls;
+using Avalonia.Input;
+using Avalonia.Layout;
+
+namespace Dock.Avalonia.Internal;
+
+internal static class ScrollViewerMouseWheelHookHelper
+{
+    public static IDisposable? Attach(ScrollViewer? scrollViewer, Orientation orientation)
+    {
+        if (scrollViewer is null)
+        {
+            return null;
+        }
+
+        void OnPointerWheelChanged(object? sender, PointerWheelEventArgs e)
+        {
+            if (e.Handled)
+            {
+                return;
+            }
+
+            if (TabStripMouseWheelScrollHelper.TryHandle(scrollViewer, orientation, e.Delta))
+            {
+                e.Handled = true;
+            }
+        }
+
+        scrollViewer.PointerWheelChanged += OnPointerWheelChanged;
+        return new DelegateDisposable(() => scrollViewer.PointerWheelChanged -= OnPointerWheelChanged);
+    }
+
+    private sealed class DelegateDisposable : IDisposable
+    {
+        private Action? _dispose;
+
+        public DelegateDisposable(Action dispose)
+        {
+            _dispose = dispose;
+        }
+
+        public void Dispose()
+        {
+            _dispose?.Invoke();
+            _dispose = null;
+        }
+    }
+}

src/Dock.Avalonia/Internal/TabStripMouseWheelScrollHelper.cs

@@ -0,0 +1,73 @@
+// Copyright (c) Wiesław Šoltés. All rights reserved.
+// Licensed under the MIT license. See LICENSE file in the project root for details.
+using System;
+using Avalonia;
+using Avalonia.Controls;
+using Avalonia.Layout;
+
+namespace Dock.Avalonia.Internal;
+
+internal static class TabStripMouseWheelScrollHelper
+{
+    public static bool TryHandle(ScrollViewer? scrollViewer, Orientation orientation, Vector delta)
+    {
+        if (scrollViewer is null)
+        {
+            return false;
+        }
+
+        var deltaY = delta.Y;
+        if (Math.Abs(deltaY) <= double.Epsilon)
+        {
+            return false;
+        }
+
+        var steps = Math.Max(1, (int)Math.Ceiling(Math.Abs(deltaY)));
+
+        switch (orientation)
+        {
+            case Orientation.Horizontal:
+                if (scrollViewer.Extent.Width <= scrollViewer.Viewport.Width)
+                {
+                    return false;
+                }
+
+                var initialHorizontalOffset = scrollViewer.Offset;
+                for (var i = 0; i < steps; i++)
+                {
+                    if (deltaY > 0)
+                    {
+                        scrollViewer.LineLeft();
+                    }
+                    else
+                    {
+                        scrollViewer.LineRight();
+                    }
+                }
+
+                return !scrollViewer.Offset.Equals(initialHorizontalOffset);
+            case Orientation.Vertical:
+                if (scrollViewer.Extent.Height <= scrollViewer.Viewport.Height)
+                {
+                    return false;
+                }
+
+                var initialVerticalOffset = scrollViewer.Offset;
+                for (var i = 0; i < steps; i++)
+                {
+                    if (deltaY > 0)
+                    {
+                        scrollViewer.LineUp();
+                    }
+                    else
+                    {
+                        scrollViewer.LineDown();
+                    }
+                }
+
+                return !scrollViewer.Offset.Equals(initialVerticalOffset);
+            default:
+                return false;
+        }
+    }
+}

tests/Dock.Avalonia.Diagnostics.UnitTests/DockControlInstantiationTests.cs

@@ -23,6 +23,13 @@ public void DocumentTabStrip_Default_Orientation_Horizontal()
         Assert.Equal(LayoutOrientation.Horizontal, control.Orientation);
     }
 
+    [AvaloniaFact]
+    public void DocumentTabStrip_Default_MouseWheelScrollOrientation_Horizontal()
+    {
+        var control = new DocumentTabStrip();
+        Assert.Equal(LayoutOrientation.Horizontal, control.MouseWheelScrollOrientation);
+    }
+
     [AvaloniaFact]
     public void DockableControl_Default_TrackingMode_Visible()
     {
@@ -197,6 +204,13 @@ public void ToolTabStrip_Can_Instantiate()
         Assert.NotNull(control);
     }
 
+    [AvaloniaFact]
+    public void ToolTabStrip_Default_MouseWheelScrollOrientation_Horizontal()
+    {
+        var control = new ToolTabStrip();
+        Assert.Equal(LayoutOrientation.Horizontal, control.MouseWheelScrollOrientation);
+    }
+
     [AvaloniaFact]
     public void ToolTabStripItem_Can_Instantiate()
     {