How to simulate holding down a keyboard button in C++ - c++

Question

I am trying to make a program that would simulate holding down a keyboard button.
This program is supposed to work in games, where holding down buttons such as W,A,S,D is required. I tested the program both in Grand Theft Auto V and Garry's Mod, but it didn't work in either of them.
I tried using SendInput and keybd_event functions for emulating the input with no luck.
#include <windows.h>
#define VK_W 0x57
using namespace std;
int main(){
while(1){
keybd_event(VK_W, 0, 0, 0);
Sleep(3000); //should hold W for 3 seconds
keybd_event(VK_W, 0, KEYEVENTF_KEYUP, 0);
Sleep(1000);
}
return 0;
}
I've created macros using Razer's keyboard software, which work perfectly, so there must be a way to simulate the key hold input.
I also tried creating an AutoHotkey script, which does work in Garry's Mod, but not in Grand Theft Auto V:
w::
SendInput {w down}
Sleep 3000
SendInput {w up}
This script holds W for 3 seconds when W is pressed.
I tried searching the web, but didn't find any working implementation.
EDIT: I searched around some more and found this: https://stackoverflow.com/a/3647975/1587051
It turns out I was using Unicode instead of keyboard scan codes combined with KEYEVENTF_SCANCODE flag. DirectInput games are now receiving the keystrokes correctly.

Answer 1

For reference sake, as it has already been answered in the comments, you have to use SendInput rather than SendMessage, when filling the INPUT structure required for the SendInput function make sure you combine your Flags with KEYEVENTF_SCANCODE to send hardware signals instead of virtual ones. These will be handled by DirectInput.
Source : Simulating Keyboard with SendInput API in DirectInput applications