C loop printing integers in GTK4 box

[HelloYes1]

Excuses, this is way below your level, no doubt.

I want to merge two scripts. 1 C-script and 1 for a box in GTK4.

The target is a digital clock (with seconds) in a box.
In case there is a better option with GTK4 please let me know.

Can you please tell me how I can integrate the C-script (with integer types) in the GTK4 script?

Sorry again for bothering.

Just hope to see more fun things (for me).

Thanks a lot, greetings!

The C-script with the loop (time as integers):

#include <stdio.h>
#include <time.h>
#include <unistd.h>

//example: 'https://www.geeksforgeeks.org/c-program-print-digital-clock-current-time/' 

int main()

{

for (;;){

    time_t s, val = 1;
    struct tm* current_time;

    // time in seconds
    s = time(NULL);

    // to get current time
    current_time = localtime(&s);

    // print time in minutes,
    // hours and seconds
    printf("\r%02d:%02d:%02d",
        current_time->tm_hour,
        current_time->tm_min,
        current_time->tm_sec);

fflush(stdout);
usleep(10);
	
	}

    return 0;
    
  }

GTK4 example box:

#include <gtk/gtk.h>

//Source: 'https://github.com/ToshioCP/Gtk4-tutorial/blob/main/gfm/sec4.md'

static void
app_activate (GApplication *app, gpointer user_data) {
  GtkWidget *win;
  GtkWidget *lab;

  win = gtk_application_window_new (GTK_APPLICATION (app));
  gtk_window_set_title (GTK_WINDOW (win), "lb1");
  gtk_window_set_default_size (GTK_WINDOW (win), 400, 300);

  (int) lab = 1;
  gtk_window_set_child (GTK_WINDOW (win), lab);

  gtk_widget_show (win);
}

int
main (int argc, char **argv) {
  GtkApplication *app;
  int stat;

  app = gtk_application_new ("com.github.ToshioCP.lb1", G_APPLICATION_FLAGS_NONE);
  g_signal_connect (app, "activate", G_CALLBACK (app_activate), NULL);
  stat =g_application_run (G_APPLICATION (app), argc, argv);
  g_object_unref (app);
  return stat;
}