How to capture MouseUp event outside the WPF window?

Question

The subject is all in the title. Sorry if it's a duplicate, I really couldn't find anything on SO.

Answer 1

Well, many thanks to Anatoliy Nikolaev for steering me in the right direction! That article helped me much and this answer was useful to make code from the article work. This is what I have now:

internal static class MouseHook
{
    private delegate int HookProc(int nCode, int wParam, IntPtr lParam);
    private static int _mouseHookHandle;
    private static HookProc _mouseDelegate;

    private static event MouseUpEventHandler MouseUp;
    public static event MouseUpEventHandler OnMouseUp
    {
        add
        {
            Subscribe();
            MouseUp += value;
        }
        remove
        {
            MouseUp -= value;
            Unsubscribe();
        }
    }

    private static void Unsubscribe()
    {
        if (_mouseHookHandle != 0)
        {
            int result = UnhookWindowsHookEx(_mouseHookHandle);
            _mouseHookHandle = 0;
            _mouseDelegate = null;
            if (result == 0)
            {
                int errorCode = Marshal.GetLastWin32Error();
                throw new Win32Exception(errorCode);
            }
        }
    }

    private static void Subscribe()
    {
        if (_mouseHookHandle == 0)
        {
            _mouseDelegate = MouseHookProc;
            _mouseHookHandle = SetWindowsHookEx(WH_MOUSE_LL,
                _mouseDelegate,
                GetModuleHandle(Process.GetCurrentProcess().MainModule.ModuleName),
                0);
            if (_mouseHookHandle == 0)
            {
                int errorCode = Marshal.GetLastWin32Error();
                throw new Win32Exception(errorCode);
            }
        }
    }

    private static int MouseHookProc(int nCode, int wParam, IntPtr lParam)
    {
        if (nCode >= 0)
        {
            MSLLHOOKSTRUCT mouseHookStruct = (MSLLHOOKSTRUCT)Marshal.PtrToStructure(lParam, typeof(MSLLHOOKSTRUCT));
            if (wParam == WM_LBUTTONUP)
            {
                if (MouseUp != null)
                {
                    MouseUp.Invoke(null, new Point(mouseHookStruct.pt.x, mouseHookStruct.pt.y));
                }
            }
        }
        return CallNextHookEx(_mouseHookHandle, nCode, wParam, lParam);
    }     

    private const int WH_MOUSE_LL = 14;
    private const int WM_LBUTTONUP = 0x0202;

    [StructLayout(LayoutKind.Sequential)]
    private struct POINT
    {
        public int x;
        public int y;
    }

    [StructLayout(LayoutKind.Sequential)]
    private struct MSLLHOOKSTRUCT
    {
        public POINT pt;
        public uint mouseData;
        public uint flags;
        public uint time;
        public IntPtr dwExtraInfo;
    }

    [DllImport("user32.dll", CharSet = CharSet.Auto,
        CallingConvention = CallingConvention.StdCall, SetLastError = true)]
    private static extern int SetWindowsHookEx(int idHook, HookProc lpfn, IntPtr hMod, int dwThreadId);

    [DllImport("user32.dll", CharSet = CharSet.Auto,
       CallingConvention = CallingConvention.StdCall, SetLastError = true)]
    private static extern int UnhookWindowsHookEx(int idHook);

    [DllImport("user32.dll", CharSet = CharSet.Auto,
         CallingConvention = CallingConvention.StdCall)]
    private static extern int CallNextHookEx(int idHook, int nCode, int wParam, IntPtr lParam);

    [DllImport("kernel32.dll")]
    public static extern IntPtr GetModuleHandle(string name); 
}

public delegate void MouseUpEventHandler(object sender, Point p);

And using it is pretty simple:

MouseHook.OnMouseUp += MouseHookMouseUp;