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Prevent first-keystroke UI stalls by suppressing WM_GETOBJECT on the launcher window #4596

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Prevent first-keystroke UI stalls by suppressing WM_GETOBJECT on the launcher window #4596

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Initial plan
Copilot Jul 30, 2026
81ac6c3
Suppress WM_GETOBJECT on main window
Copilot Jul 30, 2026
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17 changes: 17 additions & 0 deletions Flow.Launcher.Test/MainWindowTest.cs
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Original file line number Diff line number Diff line change
@@ -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);
}
}
9 changes: 9 additions & 0 deletions Flow.Launcher/MainWindow.xaml.cs
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Expand Up @@ -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;
Expand Down Expand Up @@ -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;
Comment on lines +603 to +606

@chatgpt-codex-connector chatgpt-codex-connector Bot Aug 16, 2026

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P1 Badge Do not swallow every WM_GETOBJECT request

When Narrator, a screen reader, or another UI Automation/MSAA client queries the launcher, it relies on WM_GETOBJECT to obtain WPF's accessibility provider. Returning zero with handled = true prevents HwndSource from servicing every such request, making the query box and results—including the explicitly configured AutomationProperties.Name in MainWindow.xaml—unavailable to assistive technology. The stall mitigation must preserve normal accessibility-provider requests rather than unconditionally consuming this message.

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}

switch (msg)
{
case Win32Helper.WM_ENTERSIZEMOVE:
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