#include <stdio.h>
#include <gdk/gdk.h>
#include <gdk/gdkx.h>
#include <gtk/gtk.h>

GdkFilterReturn filter(GdkXEvent *xevent, GdkEvent *event, gpointer data) {
    XKeyEvent *ev = (XKeyEvent *) xevent;
    if (ev->type == KeyPress) {
        printf("Ctrl hit.n");
    } else if (ev->type == KeyRelease) {
        printf("Ctrl release.n");
    }
    return GDK_FILTER_CONTINUE;
}

int main(int argc, char *argv[]) {
    gtk_init(&argc, &argv);

    GdkScreen *scr = gdk_screen_get_default();
    GdkWindow *groot = gdk_screen_get_root_window(scr);
    gdk_window_add_filter(groot, filter, NULL);

    Display *d = gdk_x11_get_default_xdisplay();`enter code here`
    Window root = GDK_WINDOW_XID(groot);
    int keycode = XKeysymToKeycode(d, XK_Control_L);
    XGrabKey(d, keycode, AnyModifier, root, 1, GrabModeAsync, GrabModeAsync);

    gtk_main();
}