Detect function keys in c++ console.

Question

I want to detect function keys such as f1 to save f2 to refresh in console using c++ so I can add further functionality.

Answer 1

Check this example:

#include <conio.h>

using namespace std;

int main()
{
    cout << "Press any key! CTRL-D to end" << endl;
    while(1)
    {
        unsigned char x = _getch();
        if (0 == x)
        {
            printf("Function key!\n");
            x = _getch();
        }
        printf("key = %02x\n", x);
        if (x == 4) break;
    }
    return 0;
}

When you press a function key, you'll get a zero followed by another code. Use that code to determine which F-key you got.

Answer 2

If you are on windows console, you can use ReadConsoleInput() to detect and process keyboard events.

All keys are mapped as virtual keys. The F function keys are mapped as VK_F1 to VK_F12.

Below is an implementation of console keyboard handling.

#include <stdio.h>
#include <windows.h>
#include <iostream>
using namespace std;


void save();
void refresh();


int main(){
    DWORD        mode;          /* Preserved console mode */
    INPUT_RECORD event;         /* Input event */
    BOOL         QUIT = FALSE;  /* Program termination flag */

    /* Get the console input handle */
    HANDLE hstdin = GetStdHandle( STD_INPUT_HANDLE );

    /* Preserve the original console mode */
    GetConsoleMode( hstdin, &mode );

    /* Set to no line-buffering, no echo, no special-key-processing */
    SetConsoleMode( hstdin, 0 );


    while (!QUIT){           


        if (WaitForSingleObject( hstdin, 0 ) == WAIT_OBJECT_0){  /* if kbhit */

            DWORD count;  /* ignored */

            /* Get the input event */
            ReadConsoleInput( hstdin, &event, 1, &count );
            cout<<"Key Code   = "<<event.Event.KeyEvent.wVirtualKeyCode <<" \n";

        }

            /* Only respond to key release events */
            if ((event.EventType == KEY_EVENT)
            &&  !event.Event.KeyEvent.bKeyDown){        


                    switch (event.Event.KeyEvent.wVirtualKeyCode){

                        case VK_ESCAPE:
                           QUIT = TRUE;
                         break;


                        case VK_F1:
                                  save();
                         break;


                       case VK_F2:
                                  refresh();
                         break;


                       case VK_F5:

                         break;


                       case VK_F8:

                         break;


                    }//switch

                   event.Event.KeyEvent.wVirtualKeyCode=-1;             

        }
    }

 return 0; 
}



void save(){

}


void refresh(){

}

More key mappings : https://msdn.microsoft.com/en-us/library/windows/desktop/dd375731%28v=vs.85%29.aspx?f=255&MSPPError=-2147217396

Answer 3

F1-F12 work cross-platform with this solution.

On Windows, F11 toggles fullscreen mode in the command prompt and thus cannot be detected as key press.

Answer 4

Try this :

#include <iostream>
#include <system.h>
int main(){
while(true){
Sleep(10);
if(GetKeyState('R') & 0x8000){
std::cout << "R Pressed";
}
}
return 0;
}