MODULE customlayout ;

(*
   m2-GTK4 example - a custom layout manager from Modula-2.

   The shim's M2LayoutManager positions the parent's children in a
   single column using the Modula-2 measure/allocate callbacks.

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

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 GtkWidget IMPORT gtk_widget_set_parent, gtk_widget_get_first_child,
   gtk_widget_get_next_sibling, gtk_widget_set_layout_manager;
FROM M2GtkShim IMPORT m2_gtk_widget_new, m2_layout_manager_new,
   m2_layout_allocate_child;
FROM GtkClosures IMPORT Connect2;
FROM SYSTEM IMPORT ADDRESS, ADR;
FROM libc IMPORT printf;

CONST
   AppId = "org.example.m2gtk4.CustomLayout";
   RowHeight = 36;

PROCEDURE Measure (widget: ADDRESS; orientation: INTEGER; for_size: INTEGER;
                   VAR minimum, natural: INTEGER; user: ADDRESS);
BEGIN
   minimum := 240;
   natural := 240
END Measure;

PROCEDURE Allocate (widget: ADDRESS; width, height, baseline: INTEGER;
                    user: ADDRESS);
VAR
   child: ADDRESS;
   i: INTEGER;
BEGIN
   i := 0;
   child := gtk_widget_get_first_child(widget);
   WHILE child # NIL DO
      m2_layout_allocate_child(child, 8, i * RowHeight, width - 16,
                               RowHeight - 4);
      INC(i);
      child := gtk_widget_get_next_sibling(child)
   END
END Allocate;

PROCEDURE OnActivate (application: ADDRESS; data: ADDRESS);
VAR
   window, parent, manager: ADDRESS;
BEGIN
   parent := m2_gtk_widget_new(NIL, NIL, NIL);
   manager := m2_layout_manager_new(ADR(Measure), ADR(Allocate), NIL, NIL);
   gtk_widget_set_layout_manager(parent, manager);

   gtk_widget_set_parent(gtk_label_new("row one"), parent);
   gtk_widget_set_parent(gtk_label_new("row two"), parent);
   gtk_widget_set_parent(gtk_label_new("row three"), parent);
   gtk_widget_set_parent(gtk_label_new("row four"), parent);

   window := gtk_application_window_new(application);
   gtk_window_set_title(window, "m2-GTK4 Custom Layout");
   gtk_window_set_default_size(window, 300, 220);
   gtk_window_set_child(window, parent);
   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;
   Connect2(app, "activate", OnActivate, NIL);
   g_application_run(app, 0, NIL)
END customlayout.