Port DragMove logic from WPF (#14186)

* Port DragMove logic from WPF to fix missing PointerReleased event on drag out. * remove WindowState.Normal check
AvaloniaUI · Jan 17, 2024 · 366a935 · 366a935
1 parent d0267c8
commit 366a935
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Showing 2 changed files with 22 additions and 3 deletions.
diff --git a/src/Windows/Avalonia.Win32/Interop/UnmanagedMethods.cs b/src/Windows/Avalonia.Win32/Interop/UnmanagedMethods.cs
@@ -1180,7 +1180,12 @@ public static extern IntPtr CreateWindowEx(
 
         [DllImport("user32.dll", EntryPoint = "DefWindowProcW")]
         public static extern IntPtr DefWindowProc(IntPtr hWnd, uint msg, IntPtr wParam, IntPtr lParam);
-
+
+        public const int SC_MOUSEMOVE = 0xf012;
+
+        [DllImport("user32.dll", CharSet = CharSet.Unicode, EntryPoint = "SendMessageW")]
+        public static extern IntPtr SendMessage(IntPtr hWnd, int Msg, IntPtr wParam, IntPtr lParam);
+
         [DllImport("user32.dll", EntryPoint = "DispatchMessageW")]
         public static extern IntPtr DispatchMessage(ref MSG lpmsg);
 

diff --git a/src/Windows/Avalonia.Win32/WindowImpl.cs b/src/Windows/Avalonia.Win32/WindowImpl.cs
@@ -695,8 +695,22 @@ public void SetParent(IWindowImpl? parent)
         public void BeginMoveDrag(PointerPressedEventArgs e)
         {
             e.Pointer.Capture(null);
-            DefWindowProc(_hwnd, (int)WindowsMessage.WM_NCLBUTTONDOWN,
-                new IntPtr((int)HitTestValues.HTCAPTION), IntPtr.Zero);
+
+            // Mouse.LeftButton actually reflects the primary button user is using.
+            // So we don't need to check whether the button has been swapped here.
+            if (e.Pointer.IsPrimary)
+            {
+                // SendMessage's return value is dependent on the message send.  WM_SYSCOMMAND
+                // and WM_LBUTTONUP return value just signify whether the WndProc handled the
+                // message or not, so they are not interesting
+
+                SendMessage(_hwnd, (int)WindowsMessage.WM_SYSCOMMAND, (IntPtr)SC_MOUSEMOVE, IntPtr.Zero);
+                SendMessage(_hwnd, (int)WindowsMessage.WM_LBUTTONUP, IntPtr.Zero, IntPtr.Zero);
+            }
+            else
+            {
+                throw new InvalidOperationException("BeginMoveDrag Failed");
+            }
         }
 
         public void BeginResizeDrag(WindowEdge edge, PointerPressedEventArgs e)