🚀 go-pugleaf

I'm trying to write an application that creates a global key hook. I
have the MainForm project and the DLL project in a project group. I
can't seem to get this working right.

If I uncomment the ShowMessage in the KeyboardProc function, it comes up
on keystroke TWICE. Why is this?

Or am I going abou this the wrong way?

What I'm trying to do is cature keystrokes globally and trigger an event 
in my form.

Thanks for any help.


KeyCap_MainForm.h:
[...]
publuc:
     [...]
     bool __fastcall OnSystemKeyStroke(char Key);

KeyCap_MainForm.cpp:
[...]
typedef bool (__stdcall *DLLFunc_SetHook)  (TKeyCapForm *KeyCapForm);
typedef bool (__stdcall *DLLFunc_UnsetHook)(void);

DLLFunc_SetHook   SetHook;
DLLFunc_UnsetHook UnsetHook;

HINSTANCE DllHandle;
//------------------------------------------------------------------------------

__fastcall TKeyCapForm::TKeyCapForm(TComponent* Owner) // constructor
        : TForm(Owner)
{
   // LOAD DLL
   DllHandle = LoadLibrary("KeyCap.dll");

   if (DllHandle != NULL) {
      SetHook = (DLLFunc_SetHook)GetProcAddress(DllHandle, "SetHook");

      // To set the keyboard hook
      if (SetHook != NULL) {
         if (!SetHook(this)) ShowMessage("Can't set hook");
      }
   }
}
//------------------------------------------------------------------------------

__fastcall TKeyCapForm::~TKeyCapForm() { // Destructor
   if (DllHandle != NULL) {
      UnsetHook = (DLLFunc_UnsetHook)GetProcAddress(DllHandle,
"UnsetHook");

      // To release the keyboard hook
      if (UnsetHook != NULL) {
         if (!UnsetHook()) ShowMessage("Can't unset hook");
      }
   }
}
//------------------------------------------------------------------------------

bool __fastcall TKeyCapForm::OnSystemKeyStroke(char Key) {
   /*if (wParam == VK_SNAPSHOT) {
       // Print Screen key caught, do something
       // return 0 to allow Windows to finish processing the key
       // or return non-zero to prevent further processing
       return 1;
   }
   else return 0;*/

   // Add a line to the Memo.
   Out->Lines->Add(Key);

   return 1;
}
//------------------------------------------------------------------------------


KeyCap_DLL.cpp:
#include <vcl.h>
#include <windows.h>

#include "KeyCap_MainForm.h"

#pragma hdrstop
#pragma argsused

HINSTANCE DllInstance;
HHOOK KeyHookHandle;
TKeyCapForm *Form;
//------------------------------------------------------------------------------

extern "C" {
    BOOL __declspec(dllexport) __stdcall SetHook(TKeyCapForm
*KeyCapForm);
    BOOL __declspec(dllexport) __stdcall UnsetHook(void);
}
//------------------------------------------------------------------------------

LRESULT CALLBACK KeyboardProc(int code, WPARAM wParam, LPARAM lParam){
   if (code < 0) return CallNextHookEx(KeyHookHandle, code, wParam,
lParam);

   //ShowMessage("Test [" + String((char)wParam) + "]");

   // Use TKeyCapForm::OnSystemKeyStroke function to handle this !
   return Form->OnSystemKeyStroke((char)wParam);
}
//------------------------------------------------------------------------------

BOOL __stdcall SetHook(TKeyCapForm *KeyCapForm) {
   KeyHookHandle = SetWindowsHookEx(WH_KEYBOARD, (HOOKPROC)KeyboardProc,
DllInstance, 0);
   Form = KeyCapForm;
   return (KeyHookHandle != NULL);
}
//------------------------------------------------------------------------------

BOOL __stdcall UnsetHook(void) {
   BOOL ret = TRUE;

   if (KeyHookHandle != NULL) {
      ret = UnhookWindowsHookEx(KeyHookHandle);
      if (ret == TRUE) KeyHookHandle = NULL;
   }
   return ret;
}
//------------------------------------------------------------------------------

int WINAPI DllEntryPoint(HINSTANCE hinst, unsigned long reason, void*
lpReserved)
{
    DllInstance = hinst;
    return 1;
}
//------------------------------------------------------------------------------

--
Stan R.