GTK borderless window

main.c

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

void hello(GtkWidget* widget, gpointer data)
{
  printf("Hello World!\n");
}

int main(int argc, char* argv[])
{
  GtkWidget* window;
  GtkWidget* button;

  gtk_init(&argc, &argv);
  
  window = gtk_window_new(GTK_WINDOW_TOPLEVEL);
  button = gtk_button_new_with_label("Hello World");
  gtk_container_add(GTK_CONTAINER(window), button);
  gtk_window_set_decorated((GtkWindow*)window, 0);
  
  g_signal_connect(G_OBJECT(button), "clicked",
                   G_CALLBACK(hello), NULL);
  g_signal_connect(G_OBJECT(window), "delete-event",
                   G_CALLBACK(gtk_main_quit), NULL);

  gtk_widget_show_all(window);
  gtk_main();
  return(0);
}

@EntityPlantt yes

Thanks @jeandudey!