TabViewItem: don't enter the drag visual state when dragging is disallowed

controls/dev/TabView/InteractionTests/TabViewTests.cs

@@ -781,6 +781,56 @@ public void VerifyDragStartedCalledOnItemDrag()
             }
         }
 
+        [TestMethod]
+        [TestProperty("Description", "Verifies that dragging a tab shows the drag visual when the TabView allows dragging.")]
+        public void VerifyTabEntersDragVisualStateWhenDraggingIsEnabled()
+        {
+            using (var setup = new TestSetupHelper("TabView Tests"))
+            {
+                FindElement.ByName<Button>("ResetFirstTabDragDropVisualStateLogButton").InvokeAndWait();
+
+                InputHelper.MouseDragDistance(FindElement.ByName("FirstTab"), 200, Direction.East, 4000);
+
+                FindElement.ByName<Button>("GetFirstTabDragDropVisualStateButton").InvokeAndWait();
+
+                var visitedStates = FindElement.ByName<TextBlock>("FirstTabDragDropVisualStateLogTextBlock").DocumentText;
+                Verify.IsTrue(visitedStates.Contains("DragDropVisualVisible"),
+                    $"The dragged tab should enter the DragDropVisualVisible state. Visited states: '{visitedStates}'.");
+            }
+        }
+
+        [TestMethod]
+        [TestProperty("Description", "Verifies that a tab neither enters nor gets stuck in the drag visual state when the TabView disallows dragging.")]
+        [TestProperty("RegressionBug", "10749")]
+        public void VerifyTabDoesNotEnterDragVisualStateWhenDraggingIsDisabled()
+        {
+            using (var setup = new TestSetupHelper("TabView Tests"))
+            {
+                Log.Comment("Disallow both reordering and dragging of tabs.");
+                FindElement.ByName<CheckBox>("CanDragTabsCheckBox").Uncheck();
+                FindElement.ByName<CheckBox>("CanReorderTabsCheckBox").Uncheck();
+
+                FindElement.ByName<Button>("ResetFirstTabDragDropVisualStateLogButton").InvokeAndWait();
+
+                Log.Comment("Drag the first tab away from the tab strip and release the pointer outside of it.");
+                var firstTab = FindElement.ByName("FirstTab");
+                InputHelper.LeftMouseButtonDown(firstTab);
+                InputHelper.MoveMouse(firstTab, 40, 0);
+                InputHelper.MoveMouse(firstTab, 300, 200);
+                InputHelper.LeftMouseButtonUp();
+
+                FindElement.ByName<Button>("GetFirstTabDragDropVisualStateButton").InvokeAndWait();
+
+                var visitedStates = FindElement.ByName<TextBlock>("FirstTabDragDropVisualStateLogTextBlock").DocumentText;
+                Verify.IsFalse(visitedStates.Contains("DragDropVisualVisible"),
+                    $"The tab should never enter the DragDropVisualVisible state while the TabView disallows dragging. Visited states: '{visitedStates}'.");
+
+                var currentState = FindElement.ByName<TextBlock>("FirstTabDragDropVisualStateTextBlock").DocumentText;
+                Verify.AreNotEqual("DragDropVisualVisible", currentState,
+                    "The tab should not be left in the drag visual state.");
+            }
+        }
+
         [TestMethod]
         public void ScrollButtonToolTipTest()
         {

controls/dev/TabView/TabViewItem.cpp

@@ -485,8 +485,26 @@ bool TabViewItem::ShouldStartDrag(winrt::PointerRoutedEventArgs const& args)
         m_dragPointerId == args.Pointer().PointerId();
 }
 
+// Mirrors the conditions under which ListViewBaseItem captures the pointer to detect a drag gesture.
+// Without that capture this item stops receiving pointer events once the pointer leaves its bounds, so it
+// would never see the PointerReleased that takes it back out of the drag visual state.
+bool TabViewItem::IsDraggingAllowed()
+{
+    if (const auto tabView = GetParentTabView())
+    {
+        return tabView.CanDragTabs() || tabView.CanReorderTabs() || CanDrag();
+    }
+
+    return true;
+}
+
 void TabViewItem::BeginCheckingForDrag(uint32_t const& pointerId)
 {
+    if (!IsDraggingAllowed())
+    {
+        return;
+    }
+
     m_dragPointerId = pointerId;
     m_isCheckingforDrag = true;
 }

controls/dev/TabView/TabViewItem.h

@@ -82,6 +82,7 @@ class TabViewItem :
 
     void UpdateSelectedBackgroundPathTranslateTransform();
 
+    bool IsDraggingAllowed();
     void BeginCheckingForDrag(const uint32_t& pointerId);
     void StopCheckingForDrag(const uint32_t& pointerId);
 

controls/dev/TabView/TestUI/TabViewPage.xaml

@@ -25,6 +25,8 @@
                     <CheckBox x:Name="HandleTabItemCloseRequestedCheckBox" AutomationProperties.Name="HandleTabItemCloseRequestedCheckBox" Content="Handle TabViewItem close"/>
                     <CheckBox x:Name="IsAddButtonVisibleCheckBox" AutomationProperties.Name="IsAddButtonVisibleCheckBox" Content="Add button visible" IsChecked="{x:Bind Tabs.IsAddTabButtonVisible, Mode=TwoWay}"/>
                     <CheckBox x:Name="IsDisabledTabVisibleCheckBox" AutomationProperties.Name="IsDisabledTabVisibleCheckBox" Checked="IsDisabledTabVisibleCheckBox_CheckChanged" Unchecked="IsDisabledTabVisibleCheckBox_CheckChanged" Content="Disabled tab visible" IsChecked="True"/>
+                    <CheckBox x:Name="CanDragTabsCheckBox" AutomationProperties.Name="CanDragTabsCheckBox" Content="CanDragTabs" IsChecked="{x:Bind Tabs.CanDragTabs, Mode=TwoWay}"/>
+                    <CheckBox x:Name="CanReorderTabsCheckBox" AutomationProperties.Name="CanReorderTabsCheckBox" Content="CanReorderTabs" IsChecked="{x:Bind Tabs.CanReorderTabs, Mode=TwoWay}"/>
                     <StackPanel Orientation="Horizontal" Margin="0,0,0,8">
                         <TextBlock VerticalAlignment="Center">Tab Width:</TextBlock>
                         <ComboBox x:Name="TabWidthComboBox" AutomationProperties.Name="TabWidthComboBox" Margin="4,0,0,0" SelectedIndex="0" SelectionChanged="TabWidthComboBox_SelectionChanged">
@@ -125,6 +127,15 @@
                         <TextBlock x:Name="TabsItemChangedEventArgsIndexTextBlock" AutomationProperties.Name="TabsItemChangedEventArgsIndexTextBlock" Margin="4,0,0,0" Text="" />
                     </StackPanel>
 
+                    <StackPanel Orientation="Horizontal" Margin="0,0,0,8">
+                        <Button x:Name="ResetFirstTabDragDropVisualStateLogButton" AutomationProperties.Name="ResetFirstTabDragDropVisualStateLogButton" Content="Reset FirstTab drag state" Click="ResetFirstTabDragDropVisualStateLogButton_Click"/>
+                        <Button x:Name="GetFirstTabDragDropVisualStateButton" AutomationProperties.Name="GetFirstTabDragDropVisualStateButton" Content="Get FirstTab drag state" Margin="4,0,0,0" Click="GetFirstTabDragDropVisualStateButton_Click"/>
+                    </StackPanel>
+                    <StackPanel Orientation="Horizontal" Margin="0,0,0,8">
+                        <TextBlock x:Name="FirstTabDragDropVisualStateTextBlock" AutomationProperties.Name="FirstTabDragDropVisualStateTextBlock" Margin="4,0,0,0" Text=""/>
+                        <TextBlock x:Name="FirstTabDragDropVisualStateLogTextBlock" AutomationProperties.Name="FirstTabDragDropVisualStateLogTextBlock" Margin="4,0,0,0" Text=""/>
+                    </StackPanel>
+
                     <TextBlock x:Name="TabDraggedResultsTextBlock" AutomationProperties.Name="TabDraggedResultsTextBlock" />
                 </StackPanel>
             </ScrollViewer>

controls/dev/TabView/TestUI/TabViewPage.xaml.cs

@@ -12,6 +12,7 @@
 using Microsoft.UI.Xaml.Automation;
 using Microsoft.UI.Xaml.Shapes;
 using System.Reflection;
+using System.Collections.Generic;
 
 using System.Collections.ObjectModel;
 using Windows.Devices.PointOfService;
@@ -33,6 +34,8 @@ public sealed partial class TabViewPage : TestPage
     {
         int _newTabNumber = 1;
         SymbolIconSource _iconSource;
+        VisualStateGroup firstTabDragDropVisualStateGroup;
+        readonly List<string> firstTabDragDropVisualStateLog = new List<string>();
 
         public TabViewPage()
         {
@@ -175,6 +178,57 @@ public void GetTab1ToolTipButton_Click(object sender, RoutedEventArgs e)
             GetToolTipStringForUIElement(SecondTab, Tab1ToolTipTextBlock);
         }
 
+        public void ResetFirstTabDragDropVisualStateLogButton_Click(object sender, RoutedEventArgs e)
+        {
+            if (firstTabDragDropVisualStateGroup == null)
+            {
+                firstTabDragDropVisualStateGroup = FindDragDropVisualStateGroup(FirstTab);
+
+                if (firstTabDragDropVisualStateGroup != null)
+                {
+                    firstTabDragDropVisualStateGroup.CurrentStateChanged +=
+                        (s, args) => firstTabDragDropVisualStateLog.Add(args.NewState?.Name ?? "none");
+                }
+            }
+
+            firstTabDragDropVisualStateLog.Clear();
+            FirstTabDragDropVisualStateTextBlock.Text = string.Empty;
+            FirstTabDragDropVisualStateLogTextBlock.Text = string.Empty;
+        }
+
+        public void GetFirstTabDragDropVisualStateButton_Click(object sender, RoutedEventArgs e)
+        {
+            FirstTabDragDropVisualStateTextBlock.Text = firstTabDragDropVisualStateGroup?.CurrentState?.Name ?? "none";
+            FirstTabDragDropVisualStateLogTextBlock.Text = string.Join(",", firstTabDragDropVisualStateLog);
+        }
+
+        // The drag/drop visual state group in the TabViewItem template is unnamed, so find it by the states it holds.
+        private static VisualStateGroup FindDragDropVisualStateGroup(TabViewItem tabViewItem)
+        {
+            if (VisualTreeHelper.GetChildrenCount(tabViewItem) == 0)
+            {
+                return null;
+            }
+
+            if (VisualTreeHelper.GetChild(tabViewItem, 0) is not FrameworkElement templateRoot)
+            {
+                return null;
+            }
+
+            foreach (var group in VisualStateManager.GetVisualStateGroups(templateRoot))
+            {
+                foreach (var state in group.States)
+                {
+                    if (state.Name == "DragDropVisualVisible")
+                    {
+                        return group;
+                    }
+                }
+            }
+
+            return null;
+        }
+
         public void GetToolTipStringForUIElement(UIElement item, TextBlock textBlock)
         {
             var tooltip = ToolTipService.GetToolTip(item);