GetKeyState C++

[Jameslat]

How can i find the key state of individual characters/numbers?
I guess what i mean is i need some help understanding VK and the hexedecimal pointer.
Anyone care to explain? thanks alot!

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

using namespace std;

int main()
{
while(1)
{
    if(GetKeyState(VK_CONTROL) & 0x80)
    {
        cout<<"hey"<<endl;
    }
        
    // continue looping regardless, without waiting for any input.
}

system("pause");
return 0;
}

[Jameslat]

I guess what i mean is instead of just using VK_CONTROL i'd like to be able to use
VK_KEY_A
or
VK_KEY_L etc...
but i can't get them to work.
what am i doing wrong?

[ninja9578]

Well, first & 0x80 is not a hexidecimal pointer. In this case & is acting as a binary AND.

Other than that I can't help, I don't know windows.

[jeron]

Try 'A' ....'Z' in place of VK_KEY_A....VK_KEY_A.

[Jameslat]

thanks a lot!
now i have run into another problem.
everytime i press my key (a)
it runs the command like 100 times.
How can i make it only run once per evertime a is pressed?
thanks.

[nuzzle]

thanks a lot!
now i have run into another problem.
everytime i press my key (a)
it runs the command like 100 times.
How can i make it only run once per evertime a is pressed?
thanks.

You're in the wrong forum. There's a special forum for windows issues called C++ and WinAPI.

[monarch_dodra]

thanks a lot!
now i have run into another problem.
everytime i press my key (a)
it runs the command like 100 times.
How can i make it only run once per evertime a is pressed?
thanks.

"sleep(10)" to add a 10ms pause between each iteration. That's just one solution. More advanced solutions would be to use keyboard hooks and notifications, but that's a whole other level.

Depending on your needs though, the program called AutoHotKey could be what you are looking for.

[Jameslat]

I'll check out autohotkey
but what are these keyboard hooks?

[jeron]

Could you put the returned by GetKeyState() into a variable, then compare the next GetKeyState() with that variable and do something only when they are different?

[Jameslat]

That is a good idea.

[Jameslat]

I am running into some errors tho.
How should i best put it into a varible?

[jeron]

Something along the lines of this, note that I have not compiled or run it though.

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

using namespace std;

int main()
{
	SHORT last = 0;
while(1)
{
    if(last != (last = (GetKeyState(VK_CONTROL) & 0x80)))
    {
        cout<<"hey"<<endl;
    }
        
    // continue looping regardless, without waiting for any input.
}

system("pause");
return 0;
}

[Joeman]

now i have run into another problem.
everytime i press my key (a)
it runs the command like 100 times.
How can i make it only run once per evertime a is pressed?

if you want to capture keys from the keyboard, do this with a keyboard hook

#include <iostream>
#include <windows.h>
 
using namespace std;
HHOOK hooked = 0;
 
LRESULT CALLBACK LowLevelKeyboardProc( int nCode, WPARAM wParam, LPARAM lParam)
{
    KBDLLHOOKSTRUCT* ABoutKeyboard = (KBDLLHOOKSTRUCT*)lParam;
 
    cout << "Recieved key" << ABoutKeyboard->vkCode << endl;
 
    return CallNextHookEx ( hooked, nCode , wParam, lParam );
}
 
int WINAPI WinMain (HINSTANCE hThisInstance, HINSTANCE hPrevInstance, LPSTR lpszArgument, int nCmdShow)
{
 
    hooked = SetWindowsHookEx(WH_KEYBOARD_LL, &LowLevelKeyboardProc, hThisInstance, NULL);
    if (hooked == NULL)
    {
        cout << "Error" << endl;
        return 1;
    }
 
    MSG messages;
 
    while (GetMessage (&messages, NULL, 0, 0))
    {
        TranslateMessage(&messages);
        DispatchMessage(&messages);
    }
 
    return messages.wParam;
}

[monarch_dodra]

if(last != (last = (GetKeyState(VK_CONTROL) & 0x80)))[/code]

This, while fancy, is undefined behavior. C++ does not guarantee which side of operator!= is evaluated first. The right side could be evaluated first, making the condition always true.

Just take the time to create both a "current" and "previous" variable. The execution cost is virtually null. The code is longer, but easier to read and with clearer intent.

Section 1.9 of the standard.

[jeron]

This, while fancy, is undefined behavior. C++ does not guarantee which side of operator!= is evaluated first. The right side could be evaluated first, making the condition always true.

Just take the time to create both a "current" and "previous" variable. The execution cost is virtually null. The code is longer, but easier to read and with clearer intent.

Section 1.9 of the standard.

Excellent points!