Checking for input while sleeping - c++

Question

Two functions: CheckInput and SendKey
CheckInput checks for Alt-J to be pressed. When Alt-J is pressed, a bool is toggled which allows for SendKey to keep sending the Enter key every 500ms.
I need for CheckInput to still be able to get user input and change the bool - thus stopping enter being sent - whilst the SendKey is still waiting within the sleep, otherwise right now I have to hold down Alt-J until the next 500ms is up.
Any ideas on how to do this? It just seems so basic yet I can't wrap my head around it...
( Basically, a script that presses enter every 500ms and can be toggled on and off without needing to wait 500ms )
void CheckInput() {
if ((GetKeyState(0x12) & 0x8000) && (GetKeyState(0x4A) & 0x8000)) {
Active = !Active;
}
}
void SendKey() {
if (Active) {
keybd_event(0x0D, 0x0A, 0, 0);
Sleep(16);
keybd_event(0x0D, 0X0A, KEYEVENTF_KEYUP, 0);
Sleep(500);
}
}
int main()
{
while (1) {
thread t1(CheckInput);
thread t2(SendKey);
t1.join();
t2.join();
}
return 0;
}

Answer 1

This would go much smoother if you could use a Windows event loop.
If you can't, you should simulate it.
Create a thread-safe queue that can store event information. You need two types of events - keystrokes and timer ticks.
One thread will sleep for 500ms and send a timer tick event - in a loop. The other thread will call Console.ReadKey and send a keystroke event - also in a loop.
Your main thread will wait for events to arrive from the queue and handle them.

Answer 2

As the commenter mentioned, you need to put your loops in the threads, like in this example:
atomic_int temp;
std::thread t( [&temp]()
{
while( temp!= -1){
std::this_thread::sleep_for(std::chrono::milliseconds(500));
temp=0;
}
});
You can use a condition variable and have one thread to wait upon it.
The second thread(or the main loop) would wait for the keyboard input in a loop and signal the condition variable once the input arrives.

Answer 3

I've figured out to just check if the time since last time that Enter was pressed is over 500ms ago, so that it works off of system-time. Unfortunately I still have'nt found a way to have two simultaneous processes running at once, but this seems to work like I needed it to:
void SendKey() {
if (Active){
keybd_event(0x0D, 0x0A, 0, 0);
Sleep(16);
keybd_event(0x0D, 0X0A, KEYEVENTF_KEYUP, 0);
}
}
void CheckInput() {
auto t1 = Clock::now() + chrono::seconds(1);
int temp = 0;
while (temp == 0) {
if ((GetKeyState(0x12) & 0x8000) && (GetKeyState(0x4A) & 0x8000)) {
Active = !Active;
}
if (Clock::now() > t1) {
SendKey();
temp = 1;
}
}
}
int main()
{
while (1) {
thread t1(CheckInput);
t1.join();
}
return 0;
}
This basically stores the time that CheckInput was run at, and sets a set goal thats 1 second in the future. Then it will just keep checking the inputs and it will also check if the time has passed that set goal, which when it has, then it will call SendKey, before repeating again.