Stop a Program from Stealing Focus

The window that appeared last owns the foreground. Logging the foreground window over a minute names the app instead of guessing.

Add-Type @'
using System; using System.Runtime.InteropServices;
public class Fg { [DllImport("user32.dll")] public static extern IntPtr GetForegroundWindow(); [DllImport("user32.dll")] public static extern int GetWindowText(IntPtr h, System.Text.StringBuilder s, int n); }
'@
1..10 | ForEach-Object { $b = New-Object System.Text.StringBuilder 256; [Fg]::GetWindowText([Fg]::GetForegroundWindow(), $b, 256) | Out-Null; "{0} {1}" -f (Get-Date -Format HH:mm:ss), $b.ToString(); Start-Sleep -Seconds 6 }

**ForegroundLockTimeout** decides how long a background process must wait before it may take the foreground. The default is 200000 ms, and a smaller value makes stealing easier.

Get-ItemProperty 'HKCU:\Control Panel\Desktop' | Select-Object ForegroundLockTimeout,ForegroundFlashCount
Get-ItemProperty 'HKCU:\Control Panel\Desktop' | Select-Object * -ExcludeProperty PS*

A long timeout makes Windows flash the taskbar button instead of switching. The value is in milliseconds and needs a sign-out to take full effect.

Set-ItemProperty 'HKCU:\Control Panel\Desktop' -Name ForegroundLockTimeout -Value 200000 -Type DWord
Set-ItemProperty 'HKCU:\Control Panel\Desktop' -Name ForegroundFlashCount -Value 3 -Type DWord
Get-ItemProperty 'HKCU:\Control Panel\Desktop' | Select-Object ForegroundLockTimeout,ForegroundFlashCount

Most focus steals come from an updater or a launcher starting at logon. Removing that entry removes the cause, which is more reliable than any timeout.

Get-CimInstance Win32_StartupCommand | Select-Object Name,Command,Location
Get-ItemProperty 'HKCU:\Software\Microsoft\Windows\CurrentVersion\Run' | Select-Object * -ExcludeProperty PS*
Get-ScheduledTask | Where-Object { $_.Triggers.CimClass.CimClassName -contains 'MSFT_TaskLogonTrigger' } | Select-Object TaskName,State

An app that sets a topmost window stays visible over everything without stealing focus in the normal sense. Its window style is visible in the window list.

Get-Process | Where-Object MainWindowTitle | Select-Object Name,Id,MainWindowTitle
Get-Process -Id (Get-Process | Where-Object MainWindowTitle | Select-Object -First 1).Id | Select-Object Name,MainWindowHandle

The test is a full hour of typing without an interruption. If a window still grabs focus, log it again and check the app's update settings rather than Windows.

Get-ItemProperty 'HKCU:\Control Panel\Desktop' | Select-Object ForegroundLockTimeout
Get-Process | Sort-Object StartTime -Descending | Select-Object -First 5 Name,Id,StartTime
Get-WinEvent -LogName Application -MaxEvents 30 | Where-Object LevelDisplayName -eq 'Information' | Select-Object TimeCreated,ProviderName -First 5