MODULE hello ;

(*
   m2-GTK4 example - the canonical GTK4 "Hello, world".

   A GtkApplication is created, its "activate" signal opens a window
   with a label, and g_application_run() drives the main loop until the
   window is closed.

   Build:  make examples
   Run:    ./build/examples/hello
*)

FROM Gio IMPORT g_application_run;
FROM GtkApplication IMPORT gtk_application_new;
FROM GtkWindow IMPORT gtk_application_window_new, gtk_window_set_title,
   gtk_window_set_default_size, gtk_window_set_child, gtk_window_present;
FROM GtkLabel IMPORT gtk_label_new;
FROM GtkUtils IMPORT Connect;
FROM SYSTEM IMPORT ADDRESS, ADR;
FROM libc IMPORT printf;

CONST
   AppId = "org.example.m2gtk4.Hello";

PROCEDURE OnActivate (application: ADDRESS; data: ADDRESS);
VAR
   window, label: ADDRESS;
BEGIN
   window := gtk_application_window_new(application);
   gtk_window_set_title(window, "m2-GTK4 Hello");
   gtk_window_set_default_size(window, 360, 120);

   label := gtk_label_new("Hello, GNU Modula-2 + GTK4!");
   gtk_window_set_child(window, label);

   gtk_window_present(window)
END OnActivate;

VAR
   app: ADDRESS;
BEGIN
   app := gtk_application_new(AppId, 0);
   IF app = NIL THEN
      printf("gtk_application_new failed\n");
      HALT(1)
   END;
   Connect(app, "activate", ADR(OnActivate), NIL);
   g_application_run(app, 0, NIL)
END hello.