asked on

Need help with setting hooks

I need to set a global hook that raises the callback function whenever a window is minimized,maximized or is set focus. I tried using WH_CBT but this does not seem to work. Is there another hook type I should use? Can you please give sample code that works.

jkr

I'd suggest 'WH_GETMESSAGE', e.g.

#define __DLL

#ifndef _DEBUG
#define WIN32_LEAN_AND_MEAN
#endif
#include <windows.h>

#ifdef _DEBUG
#include <crtdbg.h>

#ifdef __DLL
#define __DYNLINK __declspec(dllexport)
#else
#define __DYNLINK __declspec(dllimport)
#endif

#define HOOL_EVENT_NAME "ElmerFudd"

#pragma warning(disable:4786) // 'identifier truncated to 255 characters'

#pragma data_seg( ".shared")
HHOOK g_hhk = NULL;
#pragma data_seg()

HINSTANCE g_hThisDll;

LRESULT CALLBACK HookProc ( int nCode,
WPARAM wParam,
LPARAM lParam
);

int APIENTRY DllMain ( HINSTANCE hInstance,
DWORD dwReason,
LPVOID lpReserved
)
{
if ( dwReason == DLL_PROCESS_ATTACH)
{
g_hThisDll = hInstance;

return ( DisableThreadLibraryCalls ( g_hThisDll));
}

return( TRUE);
}

LRESULT CALLBACK HookProc ( int nCode, // hook code
WPARAM wParam, // removal flag
LPARAM lParam // address of structure with message
)
{
PMSG pmsg = ( PMSG) lParam;

if ( 0 > nCode || PM_NOREMOVE == wParam)
{
return ( CallNextHookEx ( g_hhk,
nCode,
wParam,
lParam
)
);
}

if ( WM_KEYDOWN == pmsg->message
|| WM_KEYUP == pmsg->message
)
{
/* this one is for us, do whatever is desired */
}

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

LONG __DYNLINK HookInit ( void)
{
HANDLE hev;

if ( g_hhk) return ( ERROR_ALREADY_EXISTS);

g_hhk = SetWindowsHookEx ( WH_GETMESSAGE,
( HOOKPROC) HookProc,
g_hThisDll,
0
);
#ifdef _DEBUG
_ASSERT ( g_hhk);
#endif

if ( !( hev = CreateEvent ( NULL,
FALSE,
FALSE,
HOOK_EVENT_NAME
)
)
)
{
if ( ERROR_ALREADY_EXISTS == GetLastError ())
{
if ( !( hev = OpenEvent ( EVENT_ALL_ACCESS,
FALSE,
HOOK_EVENT_NAME
)
)
)
{
return ( -1);
}
}
else
{
return ( -2);
}
}

WaitForSingleObject ( hev, INFINITE);

Sleep ( 5000);

return ( 0);
}

LONG __DYNLINK HookTerm ( void)
{
HANDLE hev;

UnhookWindowsHookEx ( g_hhk);

Sleep ( 5000);

if ( !( hev = OpenEvent ( EVENT_ALL_ACCESS,
FALSE,
HOOK_EVENT_NAME
)
)
)
{
return ( GetLastError ());
}

PulseEvent ( hev);

return ( 0);
}

All you need to do is calling 'HookInit()' to set the hook and 'HookTerm()' to remove it.

kayhustle

ASKER

Ok, I'm working in .net, when I set the WH_GETMESSAGE hook for some reason the callback function is never called, just like when I set the WH_CBT hook. If I set the WH_MOUSE_LL hook, the callback is called maybe a hundred times before a null reference is raised. This has been an ongoing problem if you can figure this out I will double the points. If I have two of the same processes running then the WH_MOUSE_LL hook will be called maybe 2000 times before the null reference exception is raised. If anybody can figure out why this behavior happens and explain it I'll give double points and even paypal you $20 bucks. If you can just give me an example of how to get it working I'll give at least double the points. Here is the code I have. There is another form that I make a reference to this dll with and do HCallback h = new HCallback(); This class is stored in a dll called testcbthookproc.dll:
using System;
using WindowsFunctions;
using System.Text;
using System.Runtime.InteropServices;
namespace testcbthookproc
{
      /// <summary>
      /// Summary description for Class1.
      /// </summary>
      public class HCallback
      {
            public const int WH_CBT = 5;
            public const int WH_MOUSE = 7;      public const int WH_MOUSE_LL = 14;
            public const int WH_GETMESSAGE = 3;
            public const int WH_CALLWNDPROC = 4;

            public delegate int HookProc(int nCode, IntPtr wParam, IntPtr lParam);
            [DllImport("kernel32",CharSet=CharSet.Auto,
                   CallingConvention=CallingConvention.StdCall)]
            internal static extern int LoadLibrary(string lpLibFileName);

            [DllImport("user32.dll",CharSet=CharSet.Auto,
                   CallingConvention=CallingConvention.StdCall)]
            internal static extern int SetWindowsHookEx(int idHook, HookProc lpfn,
                  IntPtr hInstance, int threadId);

            [DllImport("user32.dll",CharSet=CharSet.Auto,
                   CallingConvention=CallingConvention.StdCall)]
            internal static extern int GetWindowText(int hWnd, StringBuilder lpString, int nMaxCount);
            [DllImport("user32.dll",CharSet=CharSet.Auto,
                   CallingConvention=CallingConvention.StdCall)]
            internal static extern int CallNextHookEx(int idHook, int nCode,IntPtr wParam, IntPtr lParam);
            public static int hHook;
            private bool cbt = false;
            public HCallback()
            {
                  int lib = LoadLibrary("testcbthookproc.dll");
                  int mess = WH_GETMESSAGE;
                  if(mess==WH_CBT)
                        cbt=true;
                  HCallback.hHook=SetWindowsHookEx(mess,new HookProc(CBTHookProc2),
                        (IntPtr)lib,0);

            }
            public int CBTHookProc2(int nCode, IntPtr wParam, IntPtr lParam)
            {
                  if(nCode>=0)
                  {
                        StringBuilder s = new StringBuilder(1000);
                        GetWindowText((int)wParam,s,100);
                        if(cbt)
                        {
                              switch((HCBTType)nCode)
                              {
                                    case HCBTType.HCBT_SETFOCUS:
                                          Console.WriteLine(s);
                                          Console.WriteLine("Focus "+((int)wParam).ToString());//+","+((int)wh.LParam).ToString());
                                          break;
                                    case HCBTType.HCBT_CREATEWND:
                                          Console.WriteLine(s);
                                          Console.WriteLine("Created."+((int)wParam).ToString());
                                          break;
                                    case HCBTType.HCBT_MINMAX:
                                          Console.WriteLine(s);
                                          Console.WriteLine("Min max."+((int)wParam).ToString());
                                          break;
                              }
                        }
                  }
                  else
                  {
                        if(nCode==-1)
                              Console.WriteLine("Got -1 code");
                  }
                  return CallNextHookEx(hHook, nCode, wParam, lParam);
            }
      }
}

kayhustle

ASKER

oh, ignore the include WindowsFunctions, its just a dll with this enum specified:
public enum HCBTType
      {
            HCBT_MOVESIZE = 0,
            HCBT_MINMAX = 1,
            HCBT_QS = 2,
            HCBT_CREATEWND = 3,
            HCBT_DESTROYWND = 4,
            HCBT_ACTIVATE = 5,
            HCBT_CLICKSKIPPED = 6,
            HCBT_KEYSKIPPED = 7,
            HCBT_SYSCOMMAND = 8,
            HCBT_SETFOCUS = 9,
      }

ASKER CERTIFIED SOLUTION

chandru_in

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kayhustle

ASKER

https://www.experts-exchange.com/questions/21529436/Mysterious-behavior-with-setting-hooks.html

Go there and leave the same answer so I can leave you double the points for telling me why it wasn't working.

chandru_in

Thanx for that.

I've done it.