From 969eabf4d7f018136eb558a29aa2b6d2f743acd3 Mon Sep 17 00:00:00 2001
From: Emmanuel Hansen <emmausssss@gmail.com>
Date: Fri, 12 Sep 2025 10:41:10 +0000
Subject: [PATCH] Win32 - Fix maximized window being able to resize (#19620)

* fix maximized window being able to resize

* only set border style when client area is extended
---
 src/Windows/Avalonia.Win32/WindowImpl.cs | 6 +++++-
 1 file changed, 5 insertions(+), 1 deletion(-)

diff --git a/src/Windows/Avalonia.Win32/WindowImpl.cs b/src/Windows/Avalonia.Win32/WindowImpl.cs
index 54e464720b..c85b434761 100644
--- a/src/Windows/Avalonia.Win32/WindowImpl.cs
+++ b/src/Windows/Avalonia.Win32/WindowImpl.cs
@@ -1459,7 +1459,7 @@ namespace Avalonia.Win32
                 else
                     style &= ~WindowStyles.WS_MAXIMIZEBOX;
 
-                const WindowStyles fullDecorationFlags = WindowStyles.WS_CAPTION | WindowStyles.WS_SYSMENU | WindowStyles.WS_BORDER;
+                const WindowStyles fullDecorationFlags = WindowStyles.WS_CAPTION | WindowStyles.WS_BORDER;
 
                 if (newProperties.Decorations == SystemDecorations.Full)
                 {
@@ -1473,6 +1473,10 @@ namespace Avalonia.Win32
                     {
                         style |= WindowStyles.WS_THICKFRAME | WindowStyles.WS_BORDER;
                     }
+                    else if(newProperties.WindowState == WindowState.Maximized && _isClientAreaExtended)
+                    {
+                        style |= WindowStyles.WS_THICKFRAME;
+                    }
                 }
 
                 var windowStates = GetWindowStateStyles();