From c4516a3444c368fbf604aec636f80873276c4f8d Mon Sep 17 00:00:00 2001
From: Alex Fort <imphasing@gmail.com>
Date: Tue, 9 Nov 2010 15:22:49 -0500
Subject: [PATCH] Add support for the CancelKeyPress event on Windows

Adds a call to the Win32 function SetConsoleCtrlHandler for Windows, which adds the DoWindowsConsoleCancelEvent wrapper for DoConsoleCancelEvent to the Ctrl-C handler when an event handler is added, and removes the handler once all event handlers are removed.
---
 mcs/class/corlib/System/Console.cs | 37 ++++++++++++++++++++++++++++++
 1 file changed, 37 insertions(+)

diff --git a/mcs/class/corlib/System/Console.cs b/mcs/class/corlib/System/Console.cs
index 9457016a431d..8b68f4f505f3 100644
--- a/mcs/class/corlib/System/Console.cs
+++ b/mcs/class/corlib/System/Console.cs
@@ -44,11 +44,26 @@ public static class Console
 #if !NET_2_1
 		private class WindowsConsole
 		{
+			public static bool ctrlHandlerAdded = false;
+			private delegate bool WindowsCancelHandler (int keyCode);
+			private static WindowsCancelHandler cancelHandler = new WindowsCancelHandler (DoWindowsConsoleCancelEvent);
+
 			[DllImport ("kernel32.dll", CharSet=CharSet.Auto, ExactSpelling=true)]
 			private static extern int GetConsoleCP ();
 			[DllImport ("kernel32.dll", CharSet=CharSet.Auto, ExactSpelling=true)]
 			private static extern int GetConsoleOutputCP ();
 
+			[DllImport ("kernel32.dll", CharSet=CharSet.Auto, ExactSpelling=true)]
+			private static extern bool SetConsoleCtrlHandler (WindowsCancelHandler handler, bool addHandler);
+
+			// Only call the event handler if Control-C was pressed (code == 0), nothing else
+			private static bool DoWindowsConsoleCancelEvent (int keyCode)
+			{
+				if (keyCode == 0)
+					DoConsoleCancelEvent ();
+				return keyCode == 0;
+			}
+
 			[MethodImpl (MethodImplOptions.NoInlining)]
 			public static int GetInputCodePage ()
 			{
@@ -60,6 +75,18 @@ public static int GetOutputCodePage ()
 			{
 				return GetConsoleOutputCP ();
 			}
+
+			public static void AddCtrlHandler ()
+			{
+				SetConsoleCtrlHandler (cancelHandler, true);
+				ctrlHandlerAdded = true;
+			}
+			
+			public static void RemoveCtrlHandler ()
+			{
+				SetConsoleCtrlHandler (cancelHandler, false);
+				ctrlHandlerAdded = false;
+			}
 		}
 #endif
 		internal static TextWriter stdout;
@@ -682,12 +709,22 @@ public static event ConsoleCancelEventHandler CancelKeyPress {
 					ConsoleDriver.Init ();
 
 				cancel_event += value;
+
+				if (Environment.IsRunningOnWindows && !WindowsConsole.ctrlHandlerAdded)
+					WindowsConsole.AddCtrlHandler();
 			}
 			remove {
 				if (ConsoleDriver.Initialized == false)
 					ConsoleDriver.Init ();
 
 				cancel_event -= value;
+
+				if (cancel_event == null && Environment.IsRunningOnWindows)
+				{
+					// Need to remove our hook if there's nothing left in the event
+					if (WindowsConsole.ctrlHandlerAdded)
+						WindowsConsole.RemoveCtrlHandler();
+				}
 			}
 		}