🚀 go-pugleaf

Hi Remy,

Following your instructions I completely redesigned my DLL, and
now I have placed HWND in the shared memory, at least I think I did.

The code now works as I expect, and so far I haven't noticed crashes
of other VCL programs on their termination like it was the case when
I used FindWindow (from a DLL) to get the App HWND.

Anyway, can you please take a short look at the code and see if
I should make any (maybe code security) corrections to it.

Also, I have few questions:

1) Is there any sigifficant difference if I use SendMessage() or
PostMessage() from my DLL, in my case?

2) In the API CreateFileMapping(), I named a last argument "DiHook",
and I never used it after that. Is that OK? Should I use NULL?

3) Is that normal that I haven't any chages (because of shared memory
changes in y DLL) at my App side, except that I passed the HWND
argument to install a DLL?

--- DLL CODE ---

#include <vcl.h>
#include <windows.h>
#pragma hdrstop

#define WM_KEYHOOK       (WM_USER + 1002)

HINSTANCE ghInst;

typedef struct _HookInfo
{
   HHOOK ghhookKB;
   HWND hAppWnd;

} HOOKINFO, *PHOOKINFO;

HANDLE hFileMapping = NULL;
PHOOKINFO pHookInfo = NULL;

#pragma argsused

//---------------------------------------------------------------------------
extern "C" __declspec(dllexport) __stdcall void SetHook(HWND);
extern "C" __declspec(dllexport) __stdcall void RemoveHook(void);
extern "C" __declspec(dllexport) __stdcall DWORD CheckKey(int, WORD,LONG);
//---------------------------------------------------------------------------

int WINAPI DllEntryPoint(HINSTANCE hinst, unsigned long reason, void 
*lpReserved)
{
   ghInst = hinst;

   switch ( reason )
   {
      case DLL_PROCESS_ATTACH:
           hFileMapping = CreateFileMapping( INVALID_HANDLE_VALUE,
                                             NULL,
                                             PAGE_READWRITE,
                                             0,
                                             sizeof(HOOKINFO),
                                             "DiHook" );
           if ( hFileMapping )
              pHookInfo = (PHOOKINFO)MapViewOfFile( hFileMapping,
                                                    FILE_MAP_WRITE,
                                                    0,
                                                    0,
                                                    0 );
           break;

      case DLL_PROCESS_DETACH:
           UnmapViewOfFile( pHookInfo );
           pHookInfo = NULL;
           CloseHandle( hFileMapping );
           hFileMapping = NULL;
           break;

   }

   return ( 1 );
}

void __stdcall SetHook( HWND hWnd )
{
   if ( pHookInfo )
   {
      if( pHookInfo->ghhookKB == NULL )
         pHookInfo->ghhookKB = SetWindowsHookEx( WH_KEYBOARD, 
(HOOKPROC)CheckKey, ghInst, NULL );
      pHookInfo->hAppWnd = hWnd;
   }
}

void __stdcall RemoveHook( void )
{
   if ( pHookInfo )
   {
      if ( pHookInfo->ghhookKB )
      {
         UnhookWindowsHookEx( pHookInfo->ghhookKB );
         pHookInfo->ghhookKB = NULL;
      }
   }

}

DWORD __stdcall CheckKey( int nCode, WORD wParam, LONG lParam )
{
   if ( ( nCode < 0 ) || ( nCode == HC_NOREMOVE ) )
     return CallNextHookEx( pHookInfo->ghhookKB, nCode, wParam, lParam );

   // Skip if it's a repeat
   if ( lParam & 0x40000000 )
      return CallNextHookEx( pHookInfo->ghhookKB, nCode, wParam, lParam );

   // Check if Alt is pressed
   if ( !( lParam & ( 1<<29 ) ) )
      return CallNextHookEx( pHookInfo->ghhookKB, nCode, wParam, lParam );

   // Send key information to the main window
   if ( pHookInfo && pHookInfo->hAppWnd )
      PostMessage( pHookInfo->hAppWnd, WM_KEYHOOK, 0, lParam );

   return CallNextHookEx( pHookInfo->ghhookKB, nCode, wParam, lParam );
}






-- 
Best regards,
Vladimir Stefanovic
"Remy Lebeau (TeamB)" <no.spam@no.spam.com> wrote in message 
news:4277c28c$1@newsgroups.borland.com...
>
> "Vladimir Stefanovic" <antivari@po.sbb.co.yu> wrote in message
> news:427748eb@newsgroups.borland.com...
>
>>    HWND hAppWnd;
>
> You should always initialize your variables, especially when used 
> globally:
>
>    HWND hAppWnd = NULL;;
>
>>    ghhookKB = SetWindowsHookEx( WH_KEYBOARD, (HOOKPROC)CheckKey, ghInst,
> NULL)
>
> You did not specify whether the HHOOK was in shared memory or not.  It 
> must
> be.  Otherwise, the hook will only work in your own application and not in
> others.  When you place your icon in the System Tray and hide your window,
> your window won't be focused anymore, and won't be the window receiving
> keyboard input.  If you do not set up your hook properly to begin with, 
> then
> you will not be hooking the keyboard input of other applications properly.
>
>>    // Send key information to the main window
>>    SendMessage( hAppWnd, WM_KEYHOOK, 0, lParam );
>
> Check the HWND for NULL before calling SendMessage():
>
>    if( hAppWnd )
>        SendMessage( hAppWnd, WM_KEYHOOK, 0, lParam );
>
>
> Gambit
>
>