Gathering keyboard input doesn't work (winui 3)

Describe the bug

I simply can’t believe that this is an issue in 2022:

There’s simply no reliable way to capture keyboard in winui – I have no idea what to do.

I won’t reiterate what Gavin Williams already said in #3986 – we don’t have a CoreWindow in WinUI 3, and I don’t see any way to reliably capture keys.

Steps to reproduce the bug

I have a DataGrid and I want to capture keyboard input for it. Obviously, since I don’t have access to CoreWindow, I tried to capture its KeyDown or PreviewKeyDown Of course it doesn’t work.

Then I tried to capture the parent’s Keydown:

var grid = Parent as Grid;
Debug.Assert(grid != null);

grid.IsTabStop = true;
grid.IsHitTestVisible = true;
grid.Background = new SolidColorBrush(Colors.Transparent);
grid.PreviewKeyDown += DecentDataGrid_KeyDown;

This doesn’t work either. There’s simply no way to capture this. How am I supposed to create a half decent app when I can’t even handle an INS hotkey?

LATER EDIT: Turns out the issue with the datagrid not handling KeyDown happens when it’s placed on a pivot.

Expected behavior

1. There should be a way to globally capture keyboard, like in UWP
2. When capturing KeyDown, this should work reliably (see below, when Datagrid is on a Pivot)

Screenshots

No response

NuGet package version

WinUI 3 - Windows App SDK 1.0.4

Windows app type

• UWP
• Win32

Device form factor

Desktop

Windows version

Windows 10 (21H1): Build 19043

Additional context

No response

[MYPOSConnect]

I got it going, thanks to Castorix and some digging around on Google. It needs some tidying up after being hacked together but seems to work ok.

1. Put this class WinAPI.cs in Platforms/Windows folder

using System.Runtime.InteropServices;
using System.Text;
using System.Threading.Tasks;

namespace YourApp { 

    public class WinAPI
    {
        public delegate void HookProc(int nCode, IntPtr wParam, IntPtr lParam);

        [DllImport("User32.dll", SetLastError = true, CharSet = CharSet.Auto, CallingConvention = CallingConvention.StdCall)]
        public static extern int SetWindowsHookEx(int idHook, HookProc lpfn, IntPtr hInstance, int threadId);

        [DllImport("User32.dll", SetLastError = true, CharSet = CharSet.Auto, CallingConvention = CallingConvention.StdCall)]
        public static extern bool UnhookWindowsHookEx(int idHook);

        [DllImport("User32.dll", SetLastError = true, CharSet = CharSet.Auto, CallingConvention = CallingConvention.StdCall)]
        public static extern int CallNextHookEx(int idHook, int nCode, IntPtr wParam, IntPtr lParam);

        [DllImport("Kernel32.dll", SetLastError = true, CharSet = CharSet.Unicode)]
        public static extern uint GetCurrentThreadId();

        [DllImport("user32.dll")]
        public static extern int MapVirtualKey(uint uCode, uint uMapType);

     [DllImport("user32.dll")]
        public static extern int ToUnicode(uint virtualKeyCode, uint scanCode,
    byte[] keyboardState,
    [Out, MarshalAs(UnmanagedType.LPWStr, SizeConst = 64)]
    StringBuilder receivingBuffer,
    int bufferSize, uint flags);

        public const int WH_MIN = (-1);
        public const int WH_MSGFILTER = (-1);
        public const int WH_JOURNALRECORD = 0;
        public const int WH_JOURNALPLAYBACK = 1;
        public const int WH_KEYBOARD = 2;
        public const int WH_GETMESSAGE = 3;
        public const int WH_CALLWNDPROC = 4;
        public const int WH_CBT = 5;
        public const int WH_SYSMSGFILTER = 6;
        public const int WH_MOUSE = 7;
        public const int WH_HARDWARE = 8;
        public const int WH_DEBUG = 9;
        public const int WH_SHELL = 10;
        public const int WH_FOREGROUNDIDLE = 11;
        public const int WH_CALLWNDPROCRET = 12;
        public const int WH_KEYBOARD_LL = 13;
        public const int WH_MOUSE_LL = 14;
        public const int WH_MAX = 14;
        public const int WH_MINHOOK = WH_MIN;
        public const int WH_MAXHOOK = WH_MAX;

        public const int KF_EXTENDED = 0x0100;
        public const int KF_DLGMODE = 0x0800;
        public const int KF_MENUMODE = 0x1000;
        public const int KF_ALTDOWN = 0x2000;
        public const int KF_REPEAT = 0x4000;
        public const int KF_UP = 0x8000;

        internal static int HIWORD(IntPtr wParam)
        {
            return (int)((wParam.ToInt64() >> 16) & 0xffff);
        }

        internal static int LOWORD(IntPtr wParam)
        {
            return (int)(wParam.ToInt64() & 0xffff);
        }

    }
}

1. Add this using to Platform/Windows/App.xaml.cs:

using static YourApp.WinAPI;

1. Add these as properties in Platforms/Windows/App.xaml.cs

 private static int m_hHook = 0;
 private HookProc m_HookProcedure;

1. Add these methods to same file

  protected override void OnLaunched(Microsoft.UI.Xaml.LaunchActivatedEventArgs e)
    {
        base.OnLaunched(e);
        m_HookProcedure = new HookProc(HookProcedure);
        m_hHook = SetWindowsHookEx(WH_KEYBOARD, m_HookProcedure, (IntPtr)0, (int)GetCurrentThreadId());

    }
    
    private void HookProcedure(int nCode, IntPtr wParam, IntPtr lParam)
    {
        if (nCode < 0) return;

        bool shift = (Microsoft.UI.Input.InputKeyboardSource.GetKeyStateForCurrentThread(Windows.System.VirtualKey.Shift).HasFlag(Windows.UI.Core.CoreVirtualKeyStates.Down));

        string s = GetCharFromKey((uint)wParam, shift, false);

        if (s == "") return;

        Debug.WriteLine(s);

    }

    static string GetCharFromKey(uint key, bool shift, bool altGr)
    {
        var buf = new StringBuilder(256);
        var keyboardState = new byte[256];
        if (shift)
            keyboardState[(int)VirtualKey.Shift] = 0xff;
        if (altGr)
        {
            keyboardState[(int)VirtualKey.Control] = 0xff;
            keyboardState[(int)VirtualKey.Menu] = 0xff;
        }
        WinAPI.ToUnicode(key, 0, keyboardState, buf, 256, 0);

        if (buf.Length == 0) return "";
        return buf[0].ToString();
    }
    

[applefanbois]

Can’t believe we are here because Microsoft forgot that a PC use a mouse and … a keyboard.