Restrict document window drag docking to chrome targets

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

@@ -16,6 +16,7 @@
 using Avalonia.Styling;
 using Dock.Avalonia.Contract;
 using Dock.Avalonia.Automation.Peers;
+using Dock.Settings;
 
 namespace Dock.Avalonia.Controls;
 
@@ -631,7 +632,8 @@ private WindowDragHelper CreateDragHelper()
                     DataContext is Dock.Model.Core.IDock { CanCloseLastDockable: false };
 
                 return baseAllow || overrideAllow;
-            });
+            },
+            getDockScope: _ => DockSettings.DocumentWindowDragScope);
     }
 
     private void AttachToWindow()

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

@@ -87,6 +87,8 @@ public bool DocumentChromeControlsWholeWindow
     /// <inheritdoc/>
     public IHostWindowState HostWindowState => _hostWindowState;
 
+    internal WindowDragDockScope WindowDragDockScope { get; set; } = WindowDragDockScope.FullWindow;
+
     /// <inheritdoc/>
     public bool IsTracked { get; set; }
 

src/Dock.Avalonia/Internal/DockHelpers.cs

@@ -210,6 +210,11 @@ public static void LogDropAreas(Visual? root, string context)
             return localHit;
         }
 
+        return GetExternalControl(dockControl, point, property);
+    }
+
+    public static Control? GetExternalControl(DockControl dockControl, Point point, StyledProperty<bool> property)
+    {
         if (dockControl.GetVisualRoot() is not Visual visualRoot)
         {
             return null;

src/Dock.Avalonia/Internal/HostWindowState.cs

@@ -396,7 +396,9 @@ public void Process(PixelPoint point, EventType eventType)
                     }
 
                     var dockControlPoint = dockControl.PointToClient(screenPoint);
-                    var dropControl = DockHelpers.GetControlIncludingExternal(dockControl, dockControlPoint, DockProperties.IsDropAreaProperty);
+                    var dropControl = _hostWindow.WindowDragDockScope == WindowDragDockScope.WindowChrome
+                        ? DockHelpers.GetExternalControl(dockControl, dockControlPoint, DockProperties.IsDropAreaProperty)
+                        : DockHelpers.GetControlIncludingExternal(dockControl, dockControlPoint, DockProperties.IsDropAreaProperty);
                     if (dropControl is { })
                     {
                         var isDropEnabled = dropControl.GetValue(DockProperties.IsDropEnabledProperty);

src/Dock.Avalonia/Internal/WindowDragHelper.cs

@@ -20,23 +20,31 @@ internal class WindowDragHelper
     private readonly Control _owner;
     private readonly Func<bool> _isEnabled;
     private readonly Func<Control?, bool> _canStartDrag;
+    private readonly Func<Control?, WindowDragDockScope> _getDockScope;
     private readonly bool _handlePointerPressed;
     private bool _handledPointerPressed;
     private Point _dragStartPoint;
     private bool _pointerPressed;
     private bool _isDragging;
+    private WindowDragDockScope _dockScope = WindowDragDockScope.FullWindow;
     private PointerPressedEventArgs? _lastPointerPressedArgs;
     private Window? _dragWindow;
     private EventHandler<PixelPointEventArgs>? _positionChangedHandler;
     private IDisposable[]? _disposables;
     private IDisposable? _releasedEventDisposable;
 
-    public WindowDragHelper(Control owner, Func<bool> isEnabled, Func<Control?, bool> canStartDrag, bool handlePointerPressed = true)
+    public WindowDragHelper(
+        Control owner,
+        Func<bool> isEnabled,
+        Func<Control?, bool> canStartDrag,
+        bool handlePointerPressed = true,
+        Func<Control?, WindowDragDockScope>? getDockScope = null)
     {
         _owner = owner;
         _isEnabled = isEnabled;
         _canStartDrag = canStartDrag;
         _handlePointerPressed = handlePointerPressed;
+        _getDockScope = getDockScope ?? (_ => WindowDragDockScope.FullWindow);
     }
 
     public void Attach()
@@ -74,6 +82,7 @@ public void Detach()
         _pointerPressed = false;
         _isDragging = false;
         _handledPointerPressed = false;
+        _dockScope = WindowDragDockScope.FullWindow;
         _lastPointerPressedArgs = null;
     }
 
@@ -97,6 +106,7 @@ private void OnPointerPressed(object? sender, PointerPressedEventArgs e)
         {
             _dragStartPoint = e.GetPosition(_owner);
             _pointerPressed = true;
+            _dockScope = _getDockScope(source);
             if (_handlePointerPressed)
             {
                 e.Handled = true;
@@ -135,6 +145,8 @@ private void OnPointerReleased(object? sender, PointerReleasedEventArgs e)
 
             if (_dragWindow is HostWindow hostWindow)
             {
+                hostWindow.WindowDragDockScope = WindowDragDockScope.FullWindow;
+
                 if (hostWindow.HostWindowState is HostWindowState state)
                 {
                     var point = hostWindow.PointToScreen(e.GetPosition(hostWindow)) -
@@ -147,6 +159,7 @@ private void OnPointerReleased(object? sender, PointerReleasedEventArgs e)
         }
 
         _dragWindow = null;
+        _dockScope = WindowDragDockScope.FullWindow;
 
         if (shouldHandleRelease)
         {
@@ -221,6 +234,7 @@ private void OnPointerMoved(object? sender, PointerEventArgs e)
         }
 
         _dragWindow = hostWindow;
+        hostWindow.WindowDragDockScope = _dockScope;
 
         _positionChangedHandler = (_, _) =>
         {

src/Dock.Settings/DockSettings.cs

@@ -74,6 +74,12 @@ public static class DockSettings
     /// </summary>
     public static bool BringWindowsToFrontOnDrag = true;
 
+    /// <summary>
+    /// Controls which background-window docking targets are considered when a floating document
+    /// window is dragged by its document tab strip.
+    /// </summary>
+    public static WindowDragDockScope DocumentWindowDragScope = WindowDragDockScope.WindowChrome;
+
     /// <summary>
     /// Close all floating windows when the main (non-host) window closes.
     /// </summary>
@@ -262,3 +268,19 @@ public enum DockCommandBarMergingScope
     /// </summary>
     ActiveDockable
 }
+
+/// <summary>
+/// Controls which docking targets are considered during window move-drag operations.
+/// </summary>
+public enum WindowDragDockScope
+{
+    /// <summary>
+    /// Consider all window docking targets, including the main dock area.
+    /// </summary>
+    FullWindow,
+
+    /// <summary>
+    /// Consider only chrome-like targets such as external tab strips and titlebars.
+    /// </summary>
+    WindowChrome
+}