Robovoice/Robovoice.App/PttHotkey.cs

using System.Runtime.InteropServices;
using System.Windows.Forms;

namespace Robovoice.App;

internal sealed class PttHotkey : IDisposable
{
    private const int WH_KEYBOARD_LL = 13;
    private const int WH_MOUSE_LL = 14;
    private const int WM_KEYDOWN = 0x0100;
    private const int WM_KEYUP = 0x0101;
    private const int WM_SYSKEYDOWN = 0x0104;
    private const int WM_SYSKEYUP = 0x0105;
    private const int WM_LBUTTONDOWN = 0x0201;
    private const int WM_LBUTTONUP = 0x0202;
    private const int WM_RBUTTONDOWN = 0x0204;
    private const int WM_RBUTTONUP = 0x0205;
    private const int WM_MBUTTONDOWN = 0x0207;
    private const int WM_MBUTTONUP = 0x0208;
    private const int WM_XBUTTONDOWN = 0x020B;
    private const int WM_XBUTTONUP = 0x020C;

    private readonly LowLevelKeyboardProc _kbProc;
    private readonly LowLevelMouseProc _msProc;
    private IntPtr _kbHook = IntPtr.Zero;
    private IntPtr _msHook = IntPtr.Zero;
    private bool _isDown;
    private bool _disposed;

    public Keys Key { get; set; } = Keys.F8;

    public static bool IsMouseButton(Keys key) =>
        key is Keys.LButton or Keys.RButton or Keys.MButton or Keys.XButton1 or Keys.XButton2;

    public event EventHandler? Pressed;
    public event EventHandler? Released;

    public event Action<Keys>? CaptureKeyPressed;

    public void InstallCaptureHook()
    {
        ObjectDisposedException.ThrowIf(_disposed, this);
        if (_kbHook != IntPtr.Zero) return;

        IntPtr hModule = GetModuleHandle(null);
        _kbHook = SetWindowsHookEx(WH_KEYBOARD_LL, _kbProc, hModule, 0);
    }

    public PttHotkey()
    {
        _kbProc = KeyboardCallback;
        _msProc = MouseCallback;
    }

    public void Install()
    {
        ObjectDisposedException.ThrowIf(_disposed, this);
        if (_kbHook != IntPtr.Zero || _msHook != IntPtr.Zero) return;

        IntPtr hModule = GetModuleHandle(null);

        if (IsMouseButton(Key))
            _msHook = SetWindowsHookEx(WH_MOUSE_LL, _msProc, hModule, 0);
        else
            _kbHook = SetWindowsHookEx(WH_KEYBOARD_LL, _kbProc, hModule, 0);
    }

    public void Uninstall()
    {
        if (_kbHook != IntPtr.Zero)
        {
            UnhookWindowsHookEx(_kbHook);
            _kbHook = IntPtr.Zero;
        }
        if (_msHook != IntPtr.Zero)
        {
            UnhookWindowsHookEx(_msHook);
            _msHook = IntPtr.Zero;
        }
        _isDown = false;
    }

    private IntPtr KeyboardCallback(int nCode, IntPtr wParam, IntPtr lParam)
    {
        if (nCode >= 0)
        {
            int vkCode = Marshal.ReadInt32(lParam);
            Keys key = (Keys)vkCode;

            bool isDown = wParam == WM_KEYDOWN || wParam == WM_SYSKEYDOWN;
            bool isUp = wParam == WM_KEYUP || wParam == WM_SYSKEYUP;

            if (CaptureKeyPressed is not null && isDown)
            {
                CaptureKeyPressed.Invoke(key);
            }
            else if (key == Key)
            {
                if (isDown && !_isDown)
                {
                    _isDown = true;
                    Pressed?.Invoke(this, EventArgs.Empty);
                }
                else if (isUp && _isDown)
                {
                    _isDown = false;
                    Released?.Invoke(this, EventArgs.Empty);
                }
            }
        }

        return CallNextHookEx(_kbHook, nCode, wParam, lParam);
    }

    private IntPtr MouseCallback(int nCode, IntPtr wParam, IntPtr lParam)
    {
        if (nCode >= 0)
        {
            Keys? button = null;

            switch ((int)wParam)
            {
                case WM_LBUTTONDOWN: button = Keys.LButton; break;
                case WM_LBUTTONUP:   button = Keys.LButton; break;
                case WM_RBUTTONDOWN: button = Keys.RButton; break;
                case WM_RBUTTONUP:   button = Keys.RButton; break;
                case WM_MBUTTONDOWN: button = Keys.MButton; break;
                case WM_MBUTTONUP:   button = Keys.MButton; break;
                case WM_XBUTTONDOWN:
                case WM_XBUTTONUP:
                {
                    int xButton = Marshal.ReadInt32(lParam + 8) >> 16;
                    button = xButton == 1 ? Keys.XButton1 : Keys.XButton2;
                    break;
                }
            }

            if (button is Keys btn && btn == Key)
            {
                bool isDown = wParam == WM_LBUTTONDOWN || wParam == WM_RBUTTONDOWN
                           || wParam == WM_MBUTTONDOWN || wParam == WM_XBUTTONDOWN;
                bool isUp = wParam == WM_LBUTTONUP || wParam == WM_RBUTTONUP
                          || wParam == WM_MBUTTONUP || wParam == WM_XBUTTONUP;

                if (isDown && !_isDown)
                {
                    _isDown = true;
                    Pressed?.Invoke(this, EventArgs.Empty);
                }
                else if (isUp && _isDown)
                {
                    _isDown = false;
                    Released?.Invoke(this, EventArgs.Empty);
                }
            }
        }

        return CallNextHookEx(_msHook, nCode, wParam, lParam);
    }

    public void Dispose()
    {
        if (_disposed) return;
        Uninstall();
        _disposed = true;
    }

    private delegate IntPtr LowLevelKeyboardProc(int nCode, IntPtr wParam, IntPtr lParam);
    private delegate IntPtr LowLevelMouseProc(int nCode, IntPtr wParam, IntPtr lParam);

    [DllImport("user32.dll", SetLastError = true)]
    private static extern IntPtr SetWindowsHookEx(int idHook, LowLevelKeyboardProc lpfn, IntPtr hMod, uint dwThreadId);

    [DllImport("user32.dll", SetLastError = true)]
    private static extern IntPtr SetWindowsHookEx(int idHook, LowLevelMouseProc lpfn, IntPtr hMod, uint dwThreadId);

    [DllImport("user32.dll", SetLastError = true)]
    [return: MarshalAs(UnmanagedType.Bool)]
    private static extern bool UnhookWindowsHookEx(IntPtr hhk);

    [DllImport("user32.dll", SetLastError = true)]
    private static extern IntPtr CallNextHookEx(IntPtr hhk, int nCode, IntPtr wParam, IntPtr lParam);

    [DllImport("kernel32.dll", SetLastError = true, CharSet = CharSet.Unicode)]
    private static extern IntPtr GetModuleHandle(string? lpModuleName);
}