CODEWITHSUNDEEP
c++linuxkeyboardhook
David Polák
David Polák

Reputation: 1691

How to capture any key in X?

I am building an application for which I need to periodically get information about users keyboard. It is going to be user idle detection application. I have a fairly simple solution to periodically check if the mouse has been moved. But I can't figure any reasonable non root way to detect if the keyboard has been pressed.

I was thinking about registering a hook every timer timeout and on any key press to unregister it. So if there is no key press for a long time then my program will know if the user is idle.

Anyway, I couldn't find any global hooks for any key, including modifiers. Is there an easy way to do this? Or would someone have a better way to detect keyboard idleness?

Thanks

Upvotes: 5

Views: 1695

Answers (3)

Phi
Phi

Reputation: 230

I have some code that can track keyboard activity for you.

#include "stdafx.h"

#include <stdio.h>

#include "windows.h"

#include "iostream"
using namespace std;


int main(void)
 {

HANDLE hStdInput, hStdOutput, hEvent;

INPUT_RECORD ir[128];

DWORD nRead;

COORD xy;
UINT i;

hStdInput = GetStdHandle(STD_INPUT_HANDLE);
hStdOutput = GetStdHandle(STD_OUTPUT_HANDLE);
FlushConsoleInputBuffer(hStdInput);
hEvent = CreateEvent(NULL, FALSE, FALSE, NULL);
HANDLE handles[2] = { hEvent, hStdInput };


while (WaitForMultipleObjects(2, handles, FALSE, INFINITE))
{

    ReadConsoleInput(hStdInput, ir, 128, &nRead);
    for (i = 0; i<nRead; i++)
    {
        switch (ir[i].EventType)
        {
        case KEY_EVENT:
            if (ir[i].Event.KeyEvent.wVirtualKeyCode == VK_ESCAPE)
                SetEvent(hEvent);
            else
            {
                xy.X = 0; xy.Y = 0;
                SetConsoleCursorPosition(hStdOutput, xy);
                printf
                    (
                    "AsciiCode = %d: symbol = %c\n",
                    ir[i].Event.KeyEvent.uChar.AsciiChar,
                    ir[i].Event.KeyEvent.uChar.AsciiChar
                    );
            // note that some keys have a AsciiCode of 0 such as shift, ctrl, and the 
            // rest you can try out yourself

            }
            break;

        }
    }
};

return 0;
}

In this code it tracks keyboard activity and for now it shows the key you pressed and its AsciiCode, also for shift,ctrl, etc the key name won't be shown.

Upvotes: -3

David Pol&#225;k
David Pol&#225;k

Reputation: 1691

After a lot of searching I found this:

bool kbdActivity(Display* display)  // checks for key presses
{
    XQueryKeymap(display, keymap);  // asks x server for current keymap
    for (int i=0; i<32; i++)        // for 0 to 32 (keymap size)
    {
        if (prevKeymap[i] != keymap[i])   // if previous keymap does not
        {                               // equal current keymap 
            XQueryKeymap(display, prevKeymap);  // ask for new keymap
            return true;                // exit with true
        }
    }
    return false;                   // no change == no activity
}

When I call it every 100-300ms it detects any pressed key anywhere in X.

Upvotes: 4

unbeli
unbeli

Reputation: 30248

Have a look at xautolock source, which does exactly what you need, for both keyboard and mouse. http://www.ibiblio.org/pub/Linux/X11/screensavers/xautolock-2.2.tgz

Upvotes: 1

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