m2-GTK4/examples/counter.mod

MODULE counter ;

(*
   m2-GTK4 example - a button that updates a label.

   Demonstrates the widget/layout set (GtkWindow > GtkBox > label &
   button) and a "clicked" signal handler that mutates Modula-2 state.

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

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 GtkBox IMPORT gtk_box_new, gtk_box_append, gtk_box_set_spacing;
FROM GtkEnums IMPORT GtkVertical;
FROM GtkLabel IMPORT gtk_label_new, gtk_label_set_text;
FROM GtkButton IMPORT gtk_button_new_with_label;
FROM GtkUtils IMPORT IntToStr, Connect;
FROM SYSTEM IMPORT ADDRESS, ADR;
FROM libc IMPORT printf;

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

VAR
   label: ADDRESS;
   count: INTEGER;

(* void clicked(GtkButton *button, gpointer user_data) *)
PROCEDURE OnClicked (button: ADDRESS; data: ADDRESS);
VAR
   text: ARRAY [0..31] OF CHAR;
BEGIN
   INC(count);
   IntToStr(count, text);
   gtk_label_set_text(label, text)
END OnClicked;

PROCEDURE OnActivate (application: ADDRESS; data: ADDRESS);
VAR
   window, box, button: ADDRESS;
   text: ARRAY [0..31] OF CHAR;
BEGIN
   window := gtk_application_window_new(application);
   gtk_window_set_title(window, "m2-GTK4 Counter");
   gtk_window_set_default_size(window, 320, 180);

   box := gtk_box_new(GtkVertical, 12);
   gtk_box_set_spacing(box, 12);

   count := 0;
   IntToStr(count, text);
   label := gtk_label_new(text);
   gtk_box_append(box, label);

   button := gtk_button_new_with_label("Click me");
   Connect(button, "clicked", ADR(OnClicked), NIL);
   gtk_box_append(box, button);

   gtk_window_set_child(window, box);
   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 counter.