// The 15 second timeout allows enough time to cancel if someone's using the computer.
// The config class on line 7 can be used to customize what happens.

using System; using System.Text; using System.Windows.Forms; using System.Runtime.InteropServices;
public static class DisplayFusionFunction
{
    internal static class config {
        // The text in the messagebox
        internal const string Text = "This computer will be logged off 15 seconds.";
        // The title of the window.
        internal const string Title = "System logging off...";
        // The icon. Valid icons are described at https://msdn.microsoft.com/en-us/library/system.windows.forms.messageboxicon(v=vs.110).aspx
        internal const MessageBoxIcon icon = MessageBoxIcon.Exclamation;
        // number of seconds to wait (remove the *1000 on line 37 to use milliseconds instead)
        internal const uint Timeout = 15;
    }
    
    [DllImport("user32")]
    public static extern bool ExitWindowsEx(uint uFlags, uint dwReason);
	public static void Run(IntPtr windowHandle)
	{
        DialogResult DoShutdown = MessageBoxEx.Show(config.Text,config.Title,MessageBoxButtons.OKCancel,config.icon,config.Timeout*1000);
        if(DoShutdown != DialogResult.Cancel) { ExitWindowsEx(0,0); }
	}
}

//borrowed from http://www.codeproject.com/Articles/7968/MessageBox-with-a-timeout-for-NET
//unnecessary stuff removed
namespace System.Windows.Forms
{
	public class MessageBoxEx
	{
		public static DialogResult Show(string text, string caption, MessageBoxButtons buttons, MessageBoxIcon icon, uint uTimeout)
		{
			Setup(caption, uTimeout);
			return MessageBox.Show(text, caption, buttons, icon);
		}
		
		public delegate IntPtr HookProc(int nCode, IntPtr wParam, IntPtr lParam);
		public delegate void TimerProc(IntPtr hWnd, uint uMsg, UIntPtr nIDEvent, uint dwTime);
		
		public const int WH_CALLWNDPROCRET = 12;
		public const int WM_DESTROY = 0x0002;
		public const int WM_INITDIALOG = 0x0110;
		public const int WM_TIMER = 0x0113;
		public const int WM_USER = 0x400;
		public const int DM_GETDEFID = WM_USER + 0;

		[DllImport("User32.dll")]
		public static extern UIntPtr SetTimer(IntPtr hWnd, UIntPtr nIDEvent, uint uElapse, TimerProc lpTimerFunc);

		[DllImport("User32.dll")]
		public static extern IntPtr SendMessage(IntPtr hWnd, int Msg, IntPtr wParam, IntPtr lParam);

		[DllImport("user32.dll")]
		public static extern IntPtr SetWindowsHookEx(int idHook, HookProc lpfn, IntPtr hInstance, int threadId);

		[DllImport("user32.dll")]
		public static extern int UnhookWindowsHookEx(IntPtr idHook);
			
		[DllImport("user32.dll")]
		public static extern IntPtr CallNextHookEx(IntPtr idHook, int nCode, IntPtr wParam, IntPtr lParam);

		[DllImport("user32.dll")]
		public static extern int GetWindowTextLength(IntPtr hWnd);

		[DllImport("user32.dll")]
		public static extern int GetWindowText(IntPtr hWnd, StringBuilder text, int maxLength);

		[DllImport("user32.dll")]
		public static extern int EndDialog(IntPtr hDlg, IntPtr nResult);

		[StructLayout(LayoutKind.Sequential)]
		public struct CWPRETSTRUCT
		{
			public IntPtr lResult;
			public IntPtr lParam;
			public IntPtr wParam;
			public uint   message;
			public IntPtr hwnd;
		};

		private const int TimerID = 42;
		private static HookProc hookProc;
		private static TimerProc hookTimer;
		private static uint hookTimeout;
		private static string hookCaption;
		private static IntPtr hHook;
		
		static MessageBoxEx()
		{
			hookProc = new HookProc(MessageBoxHookProc);
			hookTimer = new TimerProc(MessageBoxTimerProc);
			hookTimeout = 0;
			hookCaption = null;
			hHook = IntPtr.Zero;
		}
		
		private static void Setup(string caption, uint uTimeout)
		{
			if (hHook != IntPtr.Zero)
				throw new NotSupportedException("multiple calls are not supported");
			
			hookTimeout = uTimeout;
			hookCaption = caption != null ? caption : "";
			hHook = SetWindowsHookEx(WH_CALLWNDPROCRET, hookProc, IntPtr.Zero, AppDomain.GetCurrentThreadId());
		}
		
		private static IntPtr MessageBoxHookProc(int nCode, IntPtr wParam, IntPtr lParam)
		{
			if (nCode < 0)
				return CallNextHookEx(hHook, nCode, wParam, lParam);

			CWPRETSTRUCT msg = (CWPRETSTRUCT)Marshal.PtrToStructure(lParam, typeof(CWPRETSTRUCT));
			IntPtr hook = hHook;

			if (hookCaption != null && msg.message == WM_INITDIALOG)
			{
				int nLength = GetWindowTextLength(msg.hwnd);
				StringBuilder text = new StringBuilder(nLength + 1);

				GetWindowText(msg.hwnd, text, text.Capacity);

				if (hookCaption == text.ToString())
				{
					hookCaption = null;
					SetTimer(msg.hwnd, (UIntPtr)TimerID, hookTimeout, hookTimer);
					UnhookWindowsHookEx(hHook);
					hHook = IntPtr.Zero;
				}
			}

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

		private static void MessageBoxTimerProc(IntPtr hWnd, uint uMsg, UIntPtr nIDEvent, uint dwTime)
		{
			if (nIDEvent == (UIntPtr)TimerID)
			{
				short dw = (short)SendMessage(hWnd, DM_GETDEFID, IntPtr.Zero, IntPtr.Zero);
			
				EndDialog(hWnd, (IntPtr)dw);
			}
		}
	}
}