Primary mouse device (#19898) (#19990)

* Primary mouse device

* Addressing feedback

---------

Co-authored-by: Jan Kučera <miloush@users.noreply.github.com>
Co-authored-by: Julien Lebosquain <julien@lebosquain.net>

src/Avalonia.Base/Input/MouseDevice.cs

@@ -18,6 +18,9 @@ namespace Avalonia.Input
     [PrivateApi]
     public class MouseDevice : IMouseDevice, IDisposable
     {
+        private static MouseDevice? _primary;
+        internal static MouseDevice Primary => _primary ??= new MouseDevice();
+
         private int _clickCount;
         private Rect _lastClickRect;
         private ulong _lastClickTime;
@@ -31,6 +34,16 @@ namespace Avalonia.Input
             _pointer = pointer ?? new Pointer(Pointer.GetNextFreeId(), PointerType.Mouse, true);
         }
 
+        internal static TMouseDevice GetOrCreatePrimary<TMouseDevice>() where TMouseDevice : MouseDevice, new()
+        {
+            if (_primary is TMouseDevice device)
+                return device;
+
+            device = new TMouseDevice();
+            _primary = device;
+            return device;
+        }
+
         public void ProcessRawEvent(RawInputEventArgs e)
         {
             if (!e.Handled && e is RawPointerEventArgs margs)
@@ -300,6 +313,8 @@ namespace Avalonia.Input
 
         public void Dispose()
         {
+            System.Diagnostics.Debug.Assert(this != _primary, "Disposing primary mouse device.");
+
             _disposed = true;
             _pointer?.Dispose();
         }

src/Avalonia.Native/TopLevelImpl.cs

@@ -89,7 +89,7 @@ internal class TopLevelImpl : ITopLevelImpl, IFramebufferPlatformSurface
         Factory = factory;
 
         _keyboard = AvaloniaLocator.Current.GetService<IKeyboardDevice>();
-        _mouse = new MouseDevice();
+        _mouse = Avalonia.Input.MouseDevice.Primary;
         _pen = new PenDevice();
         _cursorFactory = AvaloniaLocator.Current.GetService<ICursorFactory>();
     }
@@ -387,8 +387,6 @@ internal class TopLevelImpl : ITopLevelImpl, IFramebufferPlatformSurface
 
         _nativeControlHost?.Dispose();
         _nativeControlHost = null;
-
-        _mouse?.Dispose();
     }
 
     protected virtual bool ChromeHitTest(RawPointerEventArgs e)

src/Avalonia.X11/X11Window.cs

@@ -96,7 +96,7 @@ namespace Avalonia.X11
             _popup = popupParent != null;
             _overrideRedirect = _popup || overrideRedirect;
             _x11 = platform.Info;
-            _mouse = new MouseDevice();
+            _mouse = Avalonia.Input.MouseDevice.Primary;
             _touch = new TouchDevice();
             _keyboard = platform.KeyboardDevice;
 
@@ -1077,7 +1077,6 @@ namespace Avalonia.X11
                 _platform.XI2?.OnWindowDestroyed(_handle);
                 var handle = _handle;
                 _handle = IntPtr.Zero;
-                _mouse.Dispose();
                 _touch.Dispose();
                 if (!fromDestroyNotification) 
                     XDestroyWindow(_x11.Display, handle);

src/Windows/Avalonia.Win32/WindowImpl.AppWndProc.cs

@@ -114,9 +114,9 @@ namespace Avalonia.Win32
                         //Window doesn't exist anymore
                         _hwnd = IntPtr.Zero;
                         //Remove root reference to this class, so unmanaged delegate can be collected
-                        s_instances.Remove(this);
+                        lock (s_instances)
+                            s_instances.Remove(this);
 
-                        _mouseDevice.Dispose();
                         _touchDevice.Dispose();
                         //Free other resources
                         Dispose();
@@ -280,14 +280,6 @@ namespace Avalonia.Win32
                             DipFromLParam(lParam), GetMouseModifiers(wParam));
                         break;
                     }
-                // Mouse capture is lost
-                case WindowsMessage.WM_CANCELMODE:
-                    if (!IsMouseInPointerEnabled)
-                    {
-                        _mouseDevice.Capture(null);
-                    }
-
-                    break;
 
                 case WindowsMessage.WM_MOUSEMOVE:
                     {
@@ -394,13 +386,14 @@ namespace Avalonia.Win32
                         break;
                     }
 
+                // covers WM_CANCELMODE which sends WM_CAPTURECHANGED in DefWindowProc
                 case WindowsMessage.WM_CAPTURECHANGED:
                     {
                         if (IsMouseInPointerEnabled)
                         {
                             break;
                         }
-                        if (_hwnd != lParam)
+                        if (!IsOurWindow(lParam))
                         {
                             _trackingMouse = false;
                             e = new RawPointerEventArgs(
@@ -907,6 +900,22 @@ namespace Avalonia.Win32
             return DefWindowProc(hWnd, msg, wParam, lParam);
         }
 
+        private bool IsOurWindow(IntPtr hwnd)
+        {
+            if (hwnd == IntPtr.Zero)
+                return false;
+
+            if (hwnd == _hwnd)
+                return true;
+
+            lock (s_instances)
+                for (int i = 0; i < s_instances.Count; i++)
+                    if (s_instances[i]._hwnd == hwnd)
+                        return true;
+
+            return false;
+        }
+
         private void OnShowHideMessage(bool shown)
         {
             _shown = shown;

src/Windows/Avalonia.Win32/WindowImpl.cs

@@ -119,7 +119,7 @@ namespace Avalonia.Win32
         public WindowImpl()
         {
             _touchDevice = new TouchDevice();
-            _mouseDevice = new WindowsMouseDevice();
+            _mouseDevice = Avalonia.Input.MouseDevice.GetOrCreatePrimary<WindowsMouseDevice>();
             _penDevice = new PenDevice();
 
 #if USE_MANAGED_DRAG
@@ -177,7 +177,9 @@ namespace Avalonia.Win32
             _nativeControlHost = new Win32NativeControlHost(this, !UseRedirectionBitmap);
             _defaultTransparencyLevel = UseRedirectionBitmap ? WindowTransparencyLevel.None : WindowTransparencyLevel.Transparent;
             _transparencyLevel = _defaultTransparencyLevel;
-            s_instances.Add(this);
+
+            lock (s_instances)
+                s_instances.Add(this);
         }
 
         internal IInputRoot Owner