Prevent first-keystroke UI stalls by suppressing WM_GETOBJECT on the launcher window

Flow.Launcher.Test/MainWindowTest.cs

@@ -0,0 +1,17 @@
+using System.Reflection;
+using NUnit.Framework;
+
+namespace Flow.Launcher.Test;
+
+public class MainWindowTest
+{
+    [Test]
+    public void ShouldSuppressWindowAutomationMessage_ForWmGetObjectOnly()
+    {
+        var method = typeof(MainWindow).GetMethod("ShouldSuppressWindowAutomationMessage", BindingFlags.NonPublic | BindingFlags.Static);
+
+        Assert.That(method, Is.Not.Null);
+        Assert.That((bool)method.Invoke(null, [0x003D]), Is.True);
+        Assert.That((bool)method.Invoke(null, [0x0112]), Is.False);
+    }
+}

Flow.Launcher/MainWindow.xaml.cs

@@ -68,6 +68,7 @@ public partial class MainWindow : IDisposable
         private readonly Lock _soundLock = new();
 
         // Window WndProc
+        private const int WmGetObject = 0x003D;
         private HwndSource _hwndSource;
         private int _initialWidth;
         private int _initialHeight;
@@ -595,8 +596,16 @@ private async void OnContextMenusForSettingsClick(object sender, RoutedEventArgs
 
         #region Window WndProc
 
+        private static bool ShouldSuppressWindowAutomationMessage(int msg) => msg == WmGetObject;
+
         private IntPtr WndProc(IntPtr hwnd, int msg, IntPtr wParam, IntPtr lParam, ref bool handled) 
         {
+            if (ShouldSuppressWindowAutomationMessage(msg))
+            {
+                handled = true;
+                return IntPtr.Zero;
+            }
+
             switch (msg)
             {
                 case Win32Helper.WM_ENTERSIZEMOVE: