keybd_event is not working right =(

Question

I can't get this to work right. This should press left for 1 second then wait 10 seconds, then right 1 second, etc.:

keybd_event(0x25, 0xCB, 0, 0);  // press left
cout << "Ldown\n";              // so i know it worked

Sleep(1000);                    // hold it for 1sec
keybd_event(0x25, 0xCB, KEYEVENTF_KEYUP, 0);// let go of the key
cout << "Lup\n";                // so i know i let go
Sleep(10000);                   // Sleep for 10secs

keybd_event(0x27, 0xCD, 0, 0);  // press right
cout << "Rdown\n";              // so i know i pressed right
Sleep(1000);                    // sleep 1sec
keybd_event(0x27, 0xCD, KEYEVENTF_KEYUP, 0);// let go of the key
cout << "Rdown\n";              // so i know i let go.

This is in a loop but it wont do anything :( Unless I close the program before the key is let go, then it will just keep the key down until I press the key again.

I know you can use only one key code if you want but I need to use both.

So what am I missing?

Answer 1

The code seems to work for me. I cleaned it up a bit (no magic numbers!, use MapVirtualKey, helper functions, etc.):

#include <iostream>
#include <windows.h>

// for key pushing
BYTE scan_code(DWORD pKey)
{
    const DWORD result = MapVirtualKey(pKey, MAPVK_VK_TO_VSC);

    return static_cast<BYTE>(result);
}

void press_key(DWORD pKey)
{
    keybd_event(static_cast<BYTE>(pKey), scan_code(pKey), 0, 0);
}

void release_key(DWORD pKey)
{
    keybd_event(static_cast<BYTE>(pKey), scan_code(pKey), KEYEVENTF_KEYUP, 0);
}

// for testing
#define PRESS(x) press_key(x); std::cout << "Press: " #x << std::endl
#define RELEASE(x) release_key(x); std::cout << "Release: " #x << std::endl

// test
int main(void)
{
    for (;;)
    {
        PRESS(VK_LEFT);
        Sleep(10); // hold it for 1/100'th of a second

        RELEASE(VK_LEFT);
        Sleep(1000); // wait for a second

        PRESS(VK_RIGHT);
        Sleep(10); // hold it for 1/100'th of a second

        RELEASE(VK_RIGHT);
        Sleep(1000); // wait for a second
    }
}

I tested by opening Notepad, typing a bunch of characters, then ran the program. The caret moved back and forth. How are you testing it?

Answer 2

How are you measuring "doesn't do anything"? Is it just that no output appears? Use std::endl to end your lines, as GMan does, instead of "\n", because endl performs a flush in addition to outputting a newline character.