winapi GetAsyncKeyState() does not work as described? - c++

Question

According to microsoft's documentation, GetAsyncKeyState() supposedly
Determines whether a key is up or down at the time the function is called
I've been building a UI automation library and the issue boils down to this
#include <Windows.h>
#include <iostream>
#include <chrono>
#include <thread>
using namespace std;
bool IsKeydownAsync(int key) {
return GetAsyncKeyState(key) & 0x8000;
}
int main(){
while (1) {
if (IsKeydownAsync('A')) {
cout << "triggered" << endl;
}
this_thread::sleep_for(chrono::milliseconds(10));
}
}
So my understanding is that it should not matter if my application is in focus or not, the GetAsyncKeyState() should always return whether the physical keys are up or down at the time of being called.
I have tested this over various applications and for most time it behaves as it is described. However, in some games this behavior breaks and it no longer reports whether the key is up or down. cout << "triggered" << endl doesn't get called when the key is held.
Is there something I overlooked?

Answer 1

It has been a while since I worked with native input in Windows, but from experience the Windows API functions only report key-states that are also reported using the synchronzied Windows API functionality, which is to say the normal application message/event input.
Some older games use previous versions of DirectX and alternative ways to capture input, e.g. using a library called the XInput(2) that has been deprecated since Windows 8.1 / 10. While both polling and events/msgs were supported, the input was caught using the DirectX thread and handled entirely differently compared to the Windows API. The main reason for this is that the OS tries to cater to all manufacturers, where the DirectX API did not specificcally address that issue for input.