Add wheel feature.

Terminal.Gui/Views/TabView/TabRowView.cs

@@ -65,20 +65,20 @@ internal class TabRowView : View
             SetFocus ();
         }
 
-        if (!me.IsSingleDoubleOrTripleClicked)
+        if (me is { IsSingleDoubleOrTripleClicked: false, IsWheel: false })
         {
             return false;
         }
 
-        if (me.IsSingleDoubleOrTripleClicked)
+        if (me.IsSingleDoubleOrTripleClicked || me.IsWheel)
         {
             var scrollIndicatorHit = 0;
 
-            if (me.View is { Id: "rightScrollIndicator" })
+            if (me.View is { Id: "rightScrollIndicator" } || me.Flags.HasFlag (MouseFlags.WheeledDown) || me.Flags.HasFlag (MouseFlags.WheeledRight))
             {
                 scrollIndicatorHit = 1;
             }
-            else if (me.View is { Id: "leftScrollIndicator" })
+            else if (me.View is { Id: "leftScrollIndicator" } || me.Flags.HasFlag (MouseFlags.WheeledUp) || me.Flags.HasFlag (MouseFlags.WheeledLeft))
             {
                 scrollIndicatorHit = -1;
             }

UnitTests/Views/TabViewTests.cs

@@ -1490,6 +1490,35 @@ public class TabViewTests (ITestOutputHelper output)
         top.Dispose ();
     }
 
+    [Fact]
+    [SetupFakeDriver]
+    public void Mouse_Wheel_Changes_Tab ()
+    {
+        TabView tv = GetTabView (out Tab tab1, out Tab tab2);
+
+        tv.Width = 20;
+        tv.Height = 5;
+
+        Toplevel top = new ();
+        top.Add (tv);
+        Application.Begin (top);
+
+        Assert.False (tab1.HasFocus);
+
+        Application.RaiseMouseEvent (new () { Position = new (1, 1), Flags = MouseFlags.WheeledDown });
+        Assert.True (tab2.HasFocus);
+
+        Application.RaiseMouseEvent (new () { Position = new (1, 1), Flags = MouseFlags.WheeledUp });
+        Assert.True (tab1.HasFocus);
+
+        Application.RaiseMouseEvent (new () { Position = new (1, 1), Flags = MouseFlags.WheeledRight });
+        Assert.True (tab2.HasFocus);
+
+        Application.RaiseMouseEvent (new () { Position = new (1, 1), Flags = MouseFlags.WheeledLeft });
+        Assert.True (tab1.HasFocus);
+        top.Dispose ();
+    }
+
     private TabView GetTabView () { return GetTabView (out _, out _); }
 
     private TabView GetTabView (out Tab tab1, out Tab tab2, bool initFakeDriver = true)