How to block printing functionality(CTRL + P) on windows text editors? - c

Question

I want to block printing functionality(CTRL + P) on windows platform for specific applications. I am doing it using keyboard hook. I am able to detect CTRL + P but I am not able to stop it. I am returning from hook procedure in case of CTRL + P but application still receives this message and process printing.
LRESULT __declspec(dllexport)__stdcall CALLBACK KeyboardProc(
int nCode,
WPARAM wParam,
LPARAM lParam)
{
FILE* f1;
static WPARAM wPrevParam;
if (((DWORD)lParam & 0x40000000) && (HC_ACTION == nCode))
{
if ((wParam == VK_SPACE) || (wParam == VK_RETURN) || (wParam == VK_CONTROL) || (wParam >= 0x2f) && (wParam <= 0x100))
{
char ch;
f1 = fopen("d:\\report.txt", "a+");
if (wParam == VK_CONTROL)
{
if (wPrevParam == 0x50)// 0x50 = P
{
const char* text = "CTRL-P detected.";
fwrite(text, strlen(text), 1, f1);
fclose(f1);
wParam = 0;
lParam = 0;
return 1;
}
const char *text = "CTRL";
fwrite(text, strlen(text), 1, f1);
fprintf(f1, "%02X\n", (unsigned char)wParam);
}
else
{
wPrevParam = wParam;
}
fclose(f1);
}
}
LRESULT RetVal = CallNextHookEx(hkb, nCode, wParam, lParam);
return RetVal;
}

Answer 1

I want to block printing functionality(CTRL + P) on windows platform
for specific applications. I am doing it using keyboard hook. I am
able to detect CTRL + P but I am not able to stop it.
This blocks [Ctrl] + "P" in a WH_KEYBOARD_LL hook... but won't prevent printing by [File] [Print] or other way of course... =>
LRESULT CALLBACK LowLevelKeyboardProc(int nCode, WPARAM wParam, LPARAM lParam)
{
DWORD dwKey = 0;
if (HC_ACTION == nCode)
{
KBDLLHOOKSTRUCT *pkbdll = (KBDLLHOOKSTRUCT*)lParam;
dwKey = pkbdll->vkCode;
BOOL bCtlDown = GetKeyState(VK_CONTROL) < 0;
if (bCtlDown && dwKey == 'P')
{
Beep(6000, 10);
return 1;
}
}
return CallNextHookEx(hKeyboardHook, nCode, wParam, lParam);
}

Answer 2

Windows application to block CTRL + P using WH_KEYBORAD_LL hook works. So working code snippet will be as follows:
#include<fstream>
#include<windows.h>
using namespace std;
ofstream out("logs.txt", ios::out);
LRESULT CALLBACK keyboardHookProc(int nCode, WPARAM wParam, LPARAM lParam)
{
static bool controlPressed = false;
PKBDLLHOOKSTRUCT p = (PKBDLLHOOKSTRUCT)(lParam);
if (wParam == WM_KEYDOWN)
{
if (p->vkCode == VK_LCONTROL || p->vkCode == VK_RCONTROL)
{
controlPressed = true;
}
else if (char(tolower(p->vkCode)) == 'p' && true == controlPressed)
{
out << "<CONTROL + P Detected>";
return 1;
}
else
{
controlPressed = false;
}
}
return CallNextHookEx(NULL, nCode, wParam, lParam);
}
int APIENTRY wWinMain(_In_ HINSTANCE hInstance,
_In_opt_ HINSTANCE hPrevInstance,
_In_ LPWSTR lpCmdLine,
_In_ int nCmdShow)
{
UNREFERENCED_PARAMETER(hPrevInstance);
UNREFERENCED_PARAMETER(lpCmdLine);
HHOOK keyboardHook = SetWindowsHookEx(WH_KEYBOARD_LL,
keyboardHookProc,
hInstance,
0
);
MessageBox(NULL, TEXT("Press OK to stop blocking of printing."), TEXT("Information"), MB_OK);
out.close();
return 0;
}