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How to access the message queue in Mono on a Linux machine?

I'm writing a game in C# and Mono. I execute the game loop and render whenever the window is idle (that is to say, when the message queue is empty). I understand how to do this on Windows (use P/Invoke to import PeekMessage from "User32.dll"), but I don't know how to get the same information about the state of the message queue on a Linux build. I've browsed the Mono repo on Github, and it doesn't look like direct access to the message queue is exposed. The version of Linux I'm running is Peppermint, if that helps. Any guidance on this would be much appreciated.
bool WindowIsIdle()
{
#if Windows
NativeMessage result;
return PeekMessage(out result, IntPtr.Zero, 0, 0, 0) == 0;
#elif Linux
return false; //how can I get this information?
#endif
}
#if Windows
//Imports a native Win32 function for checking the windows message queue
[System.Runtime.InteropServices.DllImport("User32.dll")]
static extern int PeekMessage(out NativeMessage message, IntPtr handle, uint filterMin, uint filterMax, uint remove);
struct NativeMessage
{
IntPtr Handle;
uint Message;
IntPtr WParameter;
IntPtr LParameter;
uint Time;
Point Location;
}
#endif

Calling WaitForSingleObject from C#

I am trying to call WaitForSingleObject method from C#, as documented here:
https://msdn.microsoft.com/en-us/library/windows/desktop/ms687032(v=vs.85).aspx
In order to call this function I need to create a Handle, or I need to get a Handle of type IntPtr, how can it be done?
I've tried this function that I found:
http://www.pinvoke.net/default.aspx/kernel32.WaitForSingleObject
[DllImport("coredll.dll", SetLastError = true, CallingConvention = CallingConvention.Winapi, CharSet = CharSet.Auto)]
public static extern IntPtr CreateEvent(HANDLE lpEventAttributes, [In, MarshalAs(UnmanagedType.Bool)] bool bManualReset, [In, MarshalAs(UnmanagedType.Bool)] bool bIntialState, [In, MarshalAs(UnmanagedType.BStr)] string lpName);
Or for instance, when I am getting handle from console:
IntPtr handle = Process.GetCurrentProcess().MainWindowHandle;
It throws a DllNotFoundException.
What's the issue here?
I need it in order to run the process with this function call, and to take a dump form its process, for my ClrMd library learning.
Any help will be appreciated.
Code sample:
static void Main(string[] args)
{
var autoEvent = new AutoResetEvent(false);
//this is where I get the DllNotFoundException
WaitForSingleObject(autoEvent.Handle, WAIT_TIMEOUT );
}
[DllImport("kernel32.dll")]
static extern uint WaitForMultipleObjects(uint nCount, IntPtr[] lpHandles, bool bWaitAll, uint dwMilliseconds);
public const Int32 WAIT_TIMEOUT = 0x102;

I would not go through WinApi to get this from C#: you have EventWaitHandler and other synchronization objects in C#, use them:
WaitHandle wh = new EventWaitHandler();
//do whatever you need
...
WaitHandler.WaitOne(wh); // equivalent to WaitForSingleObject in WinApi
you can use wh.SafeWaitHandle if you really need to interop with WinApi
Also I suspect Process.GetCurrentProcess().MainWindowHandle cannot work in a Console Application, that has not any window at all

I want to call native method (WaitForMultipleObjects) which waits for some handle (don't really mind which one), then I want to see it on thread stack using ClrMd library, from dump file
OK, so what about new ManualResetEvent(false).WaitOne()? This should show up in the dump file. And it's reliable.
Just picking any existing handle is not reliable because it might be signaled or be destroyed at any time. Or, you might change its state by waiting. There is no need, a ManualResetEvent can create you a fresh handle.

My mistake I've posted WaitForMultipleObjects instead of WaitForSingleObject, the main issue was that WaitForSingleObject stayed with DllImport("coredll.dll"...) I don't know where did I found it but I did...
Sorry for the confusion

Can WH_MOUSE catch global events?

I'm trying to develop a WPF C# application that captures mouse clicks even (especially) if it's in background in order to start another task.
On MSDN documentation ( http://msdn.microsoft.com/en-us/library/windows/desktop/ms644990(v=vs.85).aspx ) I can read that WH_MOUSE should have either a global or thread scope.
I instantiate my hook handle this way:
hHook = SetWindowsHookEx(WH_MOUSE,
MouseHookProcedure,
(IntPtr)0,
AppDomain.GetCurrentThreadId());
where MouseHookProcedure is the delegate of my callback function and WH_MOUSE value is 7 (following Winuser.h).
The code works but it can only catch local clicks (I just need WM_LBUTTONDOWN messages), the clicks inside the window. I need to catch clicks also outside the window, and when the window is in background.
I tried hooking to WH_MOUSE_LL (with a value of 14), but it's not working.
For the most part I followed this:
http://support.microsoft.com/kb/318804
with some changes since I am using WPF and not WinForms.
The documentation about Hooks is a bit confusing.
All in all I'd like to know:
Can WH_MOUSE detect mouse messages globally? If yes, what am I doing wrong?
Can I hook from a .NET C# code to a WH_MOUSE_LL? If yes, how?
Thanks in advance.

It's possible with WH_MOUSE_LL and you need it.
In my case I developed a global keyboard maybe this could help you.
I needed to call LoadLibrary in the third parameters.
[DllImport("kernel32", SetLastError = true, CharSet = CharSet.Auto)]
private static extern IntPtr LoadLibrary(string fileName);
[DllImport("user32.dll", CharSet = CharSet.Auto, SetLastError = true)]
private static extern IntPtr SetWindowsHookEx(int idHook, KeyboardProc lpfn, IntPtr hMod, uint dwThreadId);
void MyFunction(){
[...]
SetWindowsHookEx(WH_KEYBOARD_LL, KeyboardHookProcedure, LoadLibrary("user32.dll"), 0);
}

Technically you should be able to have a global mouse hook implemented in C#. You would then pass zero as the last arguments to SetWindowsHookEx and your hook procedure must reside in a DLL, not an EXE. That's because the DLL will be injected into every process that has windows belonging to the same desktop as the hooking application. For this same reason writing global hooks in .NET is not actually recommended by most because it causes the CLR to be loaded into every desktop process, which can carry substantial overhead.

Receiving Windows Message on C# from managed Dll using p/invoke

I have to call some native C functions from C# using p/invoke. So far, I had no problems marshaling the different methods and structures to C#. Where my problem resides is in the fact that many of the methods I have to call are asynchronous, and return their final results to my WinForms application through Windows Messages. For instance, I have a call to a method that has the following signature in C:
HRESULT AsyncOpenSession( LPSTR lpszLogicalName,
HANDLE hApp,
LPSTR lpszAppID,
DWORD dwTraceLevel,
DWORD dwTimeOut,
USHORT lphService,
HWND hWnd,
DWORD dwSrvcVersionsRequired,
LPWFSVERSION lpSrvcVersion,
LPWFSVERSION lpSPIVersion,
ULONG lpRequestID );
Where lpszAppID expects to receive the NAME of my application (MyApp.exe) and hWnd is a pointer to the WINDOW HANDLE of my application, which I obtain with a call to
[DllImport("user32.dll")]
private static extern IntPtr GetForegroundWindow();
public static IntPtr GetCurrentWindowHandle()
{
IntPtr handle = GetForegroundWindow();
return handle;
}
The imported signature is:
[DllImport("MSXFS.DLL", BestFitMapping = true, CharSet = CharSet.Auto, SetLastError = true)]
private static extern int AsyncOpenSession([MarshalAs(UnmanagedType.LPStr)] string lpszLogicalName,
IntPtr hApp,
[MarshalAs(UnmanagedType.LPStr)] string lpszAppID,
UInt32 dwTraceLevel,
UInt32 dwTimeOut,
out Int32 lphService,
IntPtr hWnd,
UInt32 dwSrvcVersionsRequired,
out WFSVersion lpSrvcVersion,
out WFSVersion lpSPIVersion,
out Int32 lpRequestID);
I call the method as follows:
Int32 r = AsyncOpenSession(lpszLogicalName,
appHanlder,
"MyApp.exe",
dwTraceLevel,
dwTimeOut,
out hServ,
GetCurrentWindowHandle(),
dwSrvcVersionsRequired,
out srvcVersion,
out spiVersion,
out requestID);
Initially, the method call returns a result code that indicates the requested call has been put to the execution queue. Any time after the original call the native Dll completes the execution of the request and send a Windows Message to the application by means of its windows handle and name. The Windows Message code for this method is defined as follows:
#define WM_USER 0x0400
#define OPEN_SESSION_COMPLETE (WM_USER + 1)
More info about Windows Messages here: http://msdn.microsoft.com/en-us/library/windows/desktop/ms644931(v=vs.85).aspx
In my application I have overridden the method WndProc to be able to control the Windows Messages as follows:
protected override void WndProc(ref Message m)
{
const int wm_user = 0x0400;
const int OPEN_SESSION_COMPLETE = wm_user + 1;
switch (m.Msg)
{
case OPEN_SESSION_COMPLETE:
txtEventsState.Text = m.ToString();
break;
}
base.WndProc(ref m);
}
But I never receive a Windows Message with this code. There are no error in logs or event viewer. I know my call to the method succeeded because I do not get any error code and because it is mandatory to have an opened session before calling other methods, and I can call other methods that need a session handler successfully (no error code either).
My imported signature and call to the method is in a class library project that my application is referencing. Am I doing something wrong here? Can anyone give a light on what could be happening? I do not have access to the native code, just to a test application the shows that the Windows Messages are being sent by the native C Dll.
Thank to everybody in advance.

So, here it the deal: GetForegroundWindow() is not retriving the correct Window Handle. It happens that my application has two windows. One is the main form that I use for my test and the other displays all results and logging I am doing. So, the method was actually returning the Handle of the loggin window and not the form windows.
Using this.Handle and passing that value to the native methods made everything work correctly.
Thanks to Hans for pointing this out.

Simulating Keys C# .Net

I am working on VS 2010 Ultimate. I have created a simple console application about 25-30 rows. So I want in the Main() function simply to simulate pressing "ALT+TAB" in a while cycle. Hoh can I do that - I cant use SendKeys class cause it "Provides methods for sending keystrokes to an application." I want just when I start my console application to simulate 1000 times pressing "ALT+TAB" without attaching it to anny applications. Something like this:
using System;
using System.Windows.Forms;
namespace nagradite
{
class Program
{
static void Main()
{
int i = 1000;
while( i > 0 )
{
// PRESS "ALT+TAB"
i--;
}
}
}
}
what should I type instead of // PRESS "ALT+TAB"

Use "%{TAB}" for Alt+TAB
SendKeys.Send("%{TAB}");
SendKeys.Send("%{TAB} 1000"); //if you want to do same by 1000 times as you stated
Reference http://msdn.microsoft.com/en-us/library/system.windows.forms.sendkeys.send.aspx

I think you can use SendMessage for finding keys you can see http://www.blizzhackers.cc/viewtopic.php?t=396398, your parent window is null (desktop)
[DllImport("user32.dll", CharSet = CharSet.Auto)]
static extern IntPtr SendMessage(IntPtr hWnd, UInt32 Msg, IntPtr wParam, IntPtr lParam);

You can try a Win32 API called SendInput. It allows you to simulate keyboard/mouse input events and does not require a HWND target. However, I don't know if this will actually trigger system-wide keyboard shortcuts such as ALT+TAB.
MSDN - http://msdn.microsoft.com/en-us/library/ms646310(v=vs.85).aspx
PInvoke.Net - http://www.pinvoke.net/default.aspx/user32.sendinput