PowerShell WPF UI detect key combination

Question

I am writing a UI to run in WinPE. I have everything working so far and am trying to make it so the user cannot close the window. I have made it full screen and disabled the close (X) button, but the user can still press Alt+F4 to close the UI. I have been able to make it so that if the user hits F8 the UI is in front so the user cannot Alt+Tab to it. I have read so many ways to do this but nothing covers it for PowerShell I am not sure how to implement it in the script. It is not running in a Runspace.

Here is what I have tried:

$altF4Pressed = {
    [System.Windows.Input.KeyEventArgs]$Alt = $args[1]
    if ( ($Alt.Key -eq 'System') -or ($Alt.Key -eq 'F4') ) {
        if ($_.CloseReason -eq 'UserClosing') {
            $UI.Cancel = $true
        }
    }
}

$null = $UI.add_KeyDown($altF4Pressed)

I have also read to do this (Disabling Alt+F4 in a Powershell form), but this does not work.

#disable closing window using Alt+F4
$UI_KeyDown = [System.Windows.Forms.KeyEventHandler]{
    #Event Argument: $_ = [System.Windows.Forms.KeyEventArgs]

    if ($_.Alt -eq $true -and $_.KeyCode -eq 'F4') {
        $script:altF4Pressed = $true;
    }
}

$UI_Closing = [System.Windows.Forms.FormClosingEventHandler]{
    #Event Argument: $_ = [System.Windows.Forms.FormClosingEventArgs]

    if ($script:altF4Pressed)
    {
        if ($_.CloseReason -eq 'UserClosing') {
            $_.Cancel = $true
            $script:altF4Pressed = $false;
        }
    }
    Else{
        [System.Windows.Forms.Application]::Exit();
        # Stop-Process $pid
    }
}


$UI.Add_Closing({$UI_Closing})
$UI.add_KeyDown({$UI_KeyDown})

I have also tried to do this:

$UI.Add_KeyDown({
    $key = $_.Key
    If ([System.Windows.Input.Keyboard]::IsKeyDown("RightAlt") -OR [System.Windows.Input.Keyboard]::IsKeyDown("LeftAlt")) {
        Switch ($Key) {
            "F4" {
                $script:altF4Pressed = $true;
                write-host "Alt+f4 was pressed"
            }

        }
    }
})

It detects the first keyboard press, but not the next one while the other is pressed. I think I need to use a Keybinding event instead, just not sure how to implement that in Powershell at the App level (not input level). I read you can add a keybinding to XAML code itself, but how do that with Powershell to detect the key combination (Alt+F4) when the UI presents itself?

score 0 · Answer 1 · answered Nov 13 '20 at 19:28

I found the detection of keys with forms or WPF to be well above my skill level. However, I was able to accomplish the same task with a different approach. I needed to do this with an install script in Windows 10.

What I did was disable both left/right alt keys and F4 during the time the script was running and revert the changes, delete the key, after completed.

With WinPE's registry getting "reset" on each reboot it's your call if you want to diable the change after you make it.

# Disable Left & Right ALT keys and F4
Set-ItemProperty -path "HKLM:\SYSTEM\CurrentControlSet\Control\Keyboard Layout" -name "Scancode Map" -Value ([byte[]](0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x04,0x00,0x00,0x00,0x00,0x00,0x3e,0x00,0x00,0x00,0x38,0x00,0x00,0x00,0x38,0xe0,0x00,0x00,0x00,0x00))

To re-enable Alt + F4 simply delete the "Scancode Map" registry value and reboot again.

I found the answer here: http://www.edugeek.net/forums/windows-server-2008-r2/121900-disable-alt-f4.html

score 0 · Accepted Answer · answered Nov 13 '20 at 20:50

You don't have a replicate-able example and I don't want to write one just for this, but I think this may be of assistance.

$altF4Pressed = {
    [System.Windows.Input.KeyEventArgs]$Alt = $args[1]
    if ( ($Alt.Key -eq 'System') -or ($Alt.Key -eq 'F4') ) {
        if ($_.CloseReason -eq 'UserClosing') {
            $UI.Cancel = $true
            $Alt.Handled = $true
        }
    }
}

$null = $UI.add_KeyDown([System.Windows.Input.KeyEventHandler]::new($altF4Pressed))

Also IIRC for WPF, you'll want to use System.Windows.Input not System.Windows.Forms, so the second snippet you posted may actually work if you change the namespace.

PowerShell WPF UI detect key combination

2 Answers2