🚀 go-pugleaf

"Mike Collins" <its@TheBottomOfThePost> wrote:
>
> [...] I did this because it's the only way that i found that
> works in the past, with other callbacks i.e. EnumWindows 
> etc...

This has worked for me:

    protected:
        static  bool __stdcall EnumWindowsCallBack( HWND hWnd, LPARAM lParam );

//-------------------------------------------------------------
TSingleInstance *ThisSingleInstance = NULL;
//-------------------------------------------------------------
__fastcall TSingleInstance::TSingleInstance(TComponent* Owner) : TComponent(Owner)
{
    .....
    ThisSingleInstance = this;
    .....
}
//-------------------------------------------------------------
__fastcall TSingleInstance::~TSingleInstance()
{
    .....
    ThisSingleInstance = NULL;
}
//-------------------------------------------------------------
bool __stdcall TSingleInstance::EnumWindowsCallBack( HWND hWnd, LPARAM lParam )
{
    char WindowClassName[256] = { 0 };
    if( ::GetClassName(hWnd, WindowClassName, 255) )
      {
          if( stricmp(WindowClassName, reinterpret_cast<char*>(lParam)) == 0 )
            {
                if( hWnd != ThisSingleInstance->FParentForm->Handle )
                  {
                      ThisSingleInstance->hFirstInstance = hWnd;
                      return FALSE;
                  }
            }
      }
    return TRUE;
}
//-------------------------------------------------------------

Note the use of ThisSingleInstance in the CallBack.

~ JD