Keyboard Hook and Change User Input

Question

I want to write a software that intercepts the user input and changes it. In late windows 98 and before our language wasn't supported officially so programmers decided to invent a writing method based on ASCII characters (ArmSCII) and a font so that we could write in our language. The software is just changing the english inpur to relevant characters in ArmSCII. The program is now old. I want to write a new one. and it should be system-wide. Any suggestions how can I hook into keyboard and change the input? C , C++ or C# that doesn't matter. Im fine with all of them..

Answer 1

Here is a Keyboard hook that intercepts user input and changes it to printf("ha ha, I intercepted your [%c] and changed it to [%c]\n", key, key+1);

Win32 console C/C++ code :

#define _WIN32_WINNT 0x0400
#pragma comment( lib, "user32.lib" )

#include <windows.h>
#include <stdio.h>

HHOOK hKeyboardHook;

__declspec(dllexport) LRESULT CALLBACK KeyboardEvent (int nCode, WPARAM wParam, LPARAM lParam)
{
    DWORD SHIFT_key=0;
    DWORD CTRL_key=0;
    DWORD ALT_key=0;

    if  ((nCode == HC_ACTION) &&   ((wParam == WM_SYSKEYDOWN) ||  (wParam == WM_KEYDOWN)))      
    {
        KBDLLHOOKSTRUCT hooked_key =    *((KBDLLHOOKSTRUCT*)lParam);
        DWORD dwMsg = 1;
        dwMsg += hooked_key.scanCode << 16;
        dwMsg += hooked_key.flags << 24;
        char lpszKeyName[1024] = {0};
        //lpszKeyName[0] = '[';

        int i = GetKeyNameText(dwMsg,   (lpszKeyName+1),0xFF) + 1;
        //lpszKeyName[i] = ']';

        int key = hooked_key.vkCode;

        SHIFT_key = GetAsyncKeyState(VK_SHIFT);
        CTRL_key = GetAsyncKeyState(VK_CONTROL);
        ALT_key = GetAsyncKeyState(VK_MENU);

        if (key >= 'A' && key <= 'Z')   
        {

            if  (GetAsyncKeyState(VK_SHIFT)>= 0) key +=32;

            if (CTRL_key !=0 && key == 'y' )
            {
               MessageBox(NULL, "CTRL-y was pressed\nLaunch your app here", "H O T K E Y", MB_OK); 
               CTRL_key=0;
            }

            if (CTRL_key !=0 && key == 'q' )
            {
                MessageBox(NULL, "Shutting down", "H O T K E Y", MB_OK); 
               PostQuitMessage(0);
            }




            //printf("key = %c\n", key);
            printf("ha ha, I intercepted your [%c] and changed it to [%c]\n", key, key+1);

            SHIFT_key = 0;
            CTRL_key = 0;
            ALT_key = 0;

        }

        //printf("lpszKeyName = %s\n",  lpszKeyName );
    //  printf("%s",  lpszKeyName );
    }
    return CallNextHookEx(hKeyboardHook,    nCode,wParam,lParam);
}

void MessageLoop()
{
    MSG message;
    while (GetMessage(&message,NULL,0,0)) 
    {
        TranslateMessage( &message );
        DispatchMessage( &message );
    }
}

DWORD WINAPI my_HotKey(LPVOID lpParm)
{
    HINSTANCE hInstance = GetModuleHandle(NULL);
    if (!hInstance) hInstance = LoadLibrary((LPCSTR) lpParm); 
    if (!hInstance) return 1;

    hKeyboardHook = SetWindowsHookEx (  WH_KEYBOARD_LL, (HOOKPROC) KeyboardEvent,   hInstance,  NULL    );
    MessageLoop();
    UnhookWindowsHookEx(hKeyboardHook);
    return 0;
}

int main(int argc, char** argv)
{
    HANDLE hThread;
    DWORD dwThread;

    hThread = CreateThread(NULL,NULL,(LPTHREAD_START_ROUTINE)   my_HotKey, (LPVOID) argv[0], NULL, &dwThread);

    //ShowWindow(FindWindowA("ConsoleWindowClass", NULL), false);

    if (hThread) return WaitForSingleObject(hThread,INFINITE);
    else return 1;

}