Global/Local WH_MESSAGE Hook

ManagedHook.cs

    public enum HookType
    {
        MessageQueue = 3, //WH_GETMESSAGE
        Shell = 10, //WH_SHELL
    }

    public abstract class ManagedHook : IDisposable
    {
        private delegate IntPtr MessageDelegate(int code, IntPtr wparam, IntPtr lparam);

        private const int HcAction = 0;

        [DllImport("user32", EntryPoint = "SetWindowsHookExA", SetLastError = true)]
        private static extern IntPtr SetWindowsHookEx(int hookId, [MarshalAs(UnmanagedType.FunctionPtr)] MessageDelegate messageDelegate, IntPtr moduleHandle, IntPtr threadId);

        [DllImport("user32", EntryPoint = "UnhookWindowsHookEx", SetLastError = true)]
        private static extern int UnhookWindowsHookEx(IntPtr hHook);

        [DllImport("user32", EntryPoint = "CallNextHookEx", SetLastError = true)]
        private static extern IntPtr CallNextHook(IntPtr hHook, int ncode, IntPtr wParam, IntPtr lParam);

        [DllImport("kernel32.dll")]
        static extern IntPtr GetCurrentThreadId();

        private readonly IntPtr _hookHandle;

        protected ManagedHook(HookType hookType, bool installGlobally = false)
        {
            _hookHandle = SetWindowsHookEx((int)hookType, ProcessMessage, IntPtr.Zero, installGlobally ? IntPtr.Zero : GetCurrentThreadId());

            if (_hookHandle == IntPtr.Zero)
            {
                throw new Exception(Marshal.GetLastWin32Error().ToString("X"));
            }
        }

        private IntPtr ProcessMessage(int code, IntPtr wparam, IntPtr lparam)
        {
            if (code == HcAction)
            {
                try
                {
                    if (Handle(wparam, lparam)) return new IntPtr(1);
                }
                catch
                {
                    // ignored
                }
            }
            return CallNextHook(_hookHandle, code, wparam, lparam);
        }

        protected abstract bool Handle(IntPtr wparam, IntPtr lparam);

        public void Dispose()
        {
            UnhookWindowsHookEx(_hookHandle);
        }
    }

    class WmNcPaintHook : ManagedHook
    {
        [StructLayout(LayoutKind.Sequential)]
        public struct MSG
        {
            public IntPtr hwnd;
            public UInt32 message;
            public IntPtr wParam;
            public IntPtr lParam;
            public UInt32 time;
            public Point pt;
        }

        public WmNcPaintHook()
            : base(WindowsFormsApp4.HookType.MessageQueue)
        {
        }

        protected override bool Handle(IntPtr wparam, IntPtr lparam)
        {
            var msg = Marshal.PtrToStructure<MSG>(lparam);

            Debug.WriteLine($"wparam: {wparam} lParam: {lparam} msg.wnd: {msg.hwnd} msg.msg: {msg.message}");
            return true;
        }
    }