From 366a935b3617142b1ab850839492cd75d7510ac7 Mon Sep 17 00:00:00 2001
From: Jumar Macato <16554748+jmacato@users.noreply.github.com>
Date: Sat, 13 Jan 2024 10:16:19 +0800
Subject: [PATCH] Port DragMove logic from WPF (#14186)

* Port DragMove logic from WPF to fix missing PointerReleased event on drag out.

* remove WindowState.Normal check
---
 .../Avalonia.Win32/Interop/UnmanagedMethods.cs |  7 ++++++-
 src/Windows/Avalonia.Win32/WindowImpl.cs       | 18 ++++++++++++++++--
 2 files changed, 22 insertions(+), 3 deletions(-)

diff --git a/src/Windows/Avalonia.Win32/Interop/UnmanagedMethods.cs b/src/Windows/Avalonia.Win32/Interop/UnmanagedMethods.cs
index 445bec979e..6c64603377 100644
--- a/src/Windows/Avalonia.Win32/Interop/UnmanagedMethods.cs
+++ b/src/Windows/Avalonia.Win32/Interop/UnmanagedMethods.cs
@@ -1180,7 +1180,12 @@ namespace Avalonia.Win32.Interop
 
         [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
index 0a75732182..50ed39193c 100644
--- a/src/Windows/Avalonia.Win32/WindowImpl.cs
+++ b/src/Windows/Avalonia.Win32/WindowImpl.cs
@@ -695,8 +695,22 @@ namespace Avalonia.Win32
         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)