Adds some low level mouse hooks to a WPF app, turning any left click into a double click.

LowLevelMouseHooks.cs

using System;
using System.Diagnostics;
using System.Runtime.InteropServices;

namespace Dawson.Accessibility
{
    /// <summary>
    /// Interaction logic for MouseHooker.xaml
    /// Derived from http://blogs.msdn.com/b/toub/archive/2006/05/03/589468.aspx
    /// </summary>
    public partial class MouseHooker
    {
        public MouseHooker()
        {
            _hookID = SetHook(_proc);
            InitializeComponent();
        }

        private static readonly LowLevelMouseProc _proc = HookCallback;
        private static IntPtr _hookID = IntPtr.Zero;


        private static IntPtr SetHook(LowLevelMouseProc proc)
        {
            using (Process curProcess = Process.GetCurrentProcess())
            using (ProcessModule curModule = curProcess.MainModule)
            {
                return SetWindowsHookEx(WH_MOUSE_LL, proc,
                    GetModuleHandle(curModule.ModuleName), 0);
            }
        }

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

        [Flags]
        private enum MouseEventFlags
        {
            LEFTDOWN = 0x00000002,
            LEFTUP = 0x00000004,
            MIDDLEDOWN = 0x00000020,
            MIDDLEUP = 0x00000040,
            MOVE = 0x00000001,
            ABSOLUTE = 0x00008000,
            RIGHTDOWN = 0x00000008,
            RIGHTUP = 0x00000010
        }
        private enum MouseMessages
        {
            WM_LBUTTONDOWN = 0x0201,
            WM_LBUTTONUP = 0x0202,
            WM_MOUSEMOVE = 0x0200,
            WM_MOUSEWHEEL = 0x020A,
            WM_RBUTTONDOWN = 0x0204,
            WM_RBUTTONUP = 0x0205
        }

        private static IntPtr HookCallback(
            int nCode, IntPtr wParam, IntPtr lParam)
        {
            if (nCode >= 0 &&
                MouseMessages.WM_LBUTTONDOWN == (MouseMessages)wParam)
            {
                var hookStruct = (MSLLHOOKSTRUCT)Marshal.PtrToStructure(lParam, typeof(MSLLHOOKSTRUCT));
                Console.WriteLine(@"Left clicked: " + hookStruct.pt.x + @", " + hookStruct.pt.y);

                UnhookWindowsHookEx(_hookID);
                mouse_event((int)(MouseEventFlags.LEFTDOWN), 0, 0, 0, 0);
                mouse_event((int)(MouseEventFlags.LEFTUP), 0, 0, 0, 0);
                _hookID = SetHook(_proc);
            }
            return CallNextHookEx(_hookID, nCode, wParam, lParam);
        }

        private const int WH_MOUSE_LL = 14;

        [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")]
        static extern void mouse_event(int dwFlags, int dx, int dy, int dwData, int dwExtraInfo);

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

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

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

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