GetAsyncKeyState() during a Sleep() does not register immediately

[gunman353]

In the program I am writing when I hit the 'escape' key, I want it to exit immediately. Currently it waits until the end of the sleep statement before registering. In the program that I am writing, sleep statements can be several minutes long, and I do not want to wait until the end for key presses to be registered. Thank you in advance!

int main()
{
	bool ESCAPE = false;

	while (!ESCAPE) {
		// Stop program when Escape is pressed
		if (GetAsyncKeyState(VK_ESCAPE)) {
			cout << "Exit triggered" << endl;
			ESCAPE = true;
		}

		Sleep(10000);
	}
	system("PAUSE");
	return 0;
}

EDIT: To clarify, the sleep is because I am performing an action after a given period of time

[Handy Andy]

Hello gunman353,

You could try this:

	if (GetAsyncKeyState(VK_ESCAPE))
        {
	        cout << "\nExit triggered" << endl;  // <--- You may want the "\n" for better readability.
		ESCAPE = true;
                continue;  //  <--- Continues to the next while condition.
                break;  // <--- will leave the while loop.
                or
                exit (1); //  <--- Will leave the program.
	}

Not sure if the "Sleep(10000);" is worth keeping here?

Hope that helps,

Andy

[gunman353]

The sleep time is important for my program, as the user needs to define the time between repeating events.

[coder777]

as the user needs to define the time between repeating events.

Consider using timer for this:

https://msdn.microsoft.com/en-us/library/windows/desktop/ms644906(v=vs.85).aspx

[Chervil]

A rather clunky approach using Sleep().

Here the escape key is tested 4 times per second during the delay period. That's a compromise, you could change that to say 50 times per second if you like, to make it a bit more responsive if essential. Though if the required sleep time is several minutes, a response within a second or two might suffice.

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

using std::cout;
using std::endl;

bool testEscape(unsigned millisec)
{
    bool result = false;
    unsigned delay = 250;

    for (unsigned i=0; !result && i<millisec; i += delay)
    {
        result = GetAsyncKeyState(VK_ESCAPE);
        Sleep(delay);
    }
        
    return result;      
}

int main()
{
    cout << "start\n";
    
    bool escape = false;

    while (!escape) 
    {
        cout << ".";

        escape = testEscape(10000);
        if (escape)
            cout << "Exit triggered" << endl;
        
    }

    cout << "done\n";
    system("pause");
    return 0;
}