async GTK 3 4 gui example vala nim

async_GTK_gui_example.vala

using Gtk;
Button button;

void main (string[] args) {
   Gtk.init (ref args);

   var window = new Window ();
  
   button = new Button.with_label ("Start counting");
   button.clicked.connect (() => {
      count.begin();
   });

   with (window){
      title = "Count without blocking the UI";
      border_width = 10;
      window_position = WindowPosition.CENTER;
      set_default_size (350, 70);
      destroy.connect (Gtk.main_quit);
      child = button;
      show_all ();
   }

   Gtk.main ();
}

async void count(){

    for(int i = 0; i < 10000; i++){
         button.label = i.to_string();
         Idle.add (count.callback);
         yield;
    }
}

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