XGrabKey

xgrabkey.c

// Original from https://gist.github.com/jouyouyun/669726de58df8d333666
// Compile: gcc xgrabkey.c `pkg-config --cflags --libs x11` -o xgrabkey

#include <stdio.h>
#include <string.h>
#include <X11/Xlib.h>
#include <X11/Xutil.h>

int main()
{
    Window root;
    Display *dpy = NULL;

    dpy = XOpenDisplay(0);
    if (dpy == NULL)
    {
        printf("Open Display Failed\n");
        return -1;
    }

    root = DefaultRootWindow(dpy);

    // unsigned int mod = AnyModifier; // grabs any modifier, or none, will grab Ctrl+C

    unsigned int mods[] = {0, ShiftMask, Mod1Mask, ShiftMask | Mod1Mask};
    // 0 - grabs just the key
    // ShiftMask - grabs if Shift is pressed
    // Mod1Mask - grabs if Alt is pressed
    // ShiftMask | Mod1Mask - grabs if Shift and Alt are pressed

    for (char k = 'a'; k <= 'z'; ++k)
    {
        char key[] = {k, '\0'};

        int sym = XStringToKeysym(key);
        int code = XKeysymToKeycode(dpy, sym);
        for (unsigned int m = 0; m < sizeof(mods) / sizeof(mods[0]); ++m)
        {
            unsigned int mod = mods[m];
            XGrabKey(dpy, code, mod, root, True, GrabModeAsync, GrabModeAsync);
        }
        printf("sym %d code %d\n", sym, code);
    }

    XEvent event;
    for (;;)
    {
        XNextEvent(dpy, &event);
        unsigned int code = event.xkey.keycode;
        KeySym sym = XKeycodeToKeysym(dpy, event.xkey.keycode, 0);
        char *key = XKeysymToString(sym);
        printf("Key event code %u symbol %lu key %s\n",
               code,
               sym,
               key);
        if (event.type == KeyPress)
        {
            printf("Key press\n");
        }
        if (event.type == KeyRelease)
        {
            printf("Key release\n");
        }
        if (sym == XStringToKeysym("z"))
            break;
    }

    XAllowEvents(dpy, AsyncKeyboard, CurrentTime);
    XUngrabKey(dpy, AnyKey, AnyModifier, root);
    XSync(dpy, False);

    XCloseDisplay(dpy);

    return 0;
}