Crystal Gtk Application

application.cr

require "gobject/gtk"
require "gobject/gio"

class MyApplication < Gtk::Application
  include Gio::ActionMap

  def self.new
    super "org.example.application", :flags_none
  end

  def initialize(ptr)
    super(ptr)

    on_activate do
      setup_actions

      build_ui
    end
  end

  def setup_actions
    action_entries = [
      LibGio::ActionEntry.new(name: "quit", activate: ->{ puts "quit" }), # works
      # LibGio::ActionEntry.new(name: "quit", activate: ->{ self.quit }), # doesn't work
    ]
    add_action_entries action_entries, action_entries.size, nil
  end

  def build_ui
    title = "Hello World"
    show_menu = !prefers_app_menu()

    headerbar = Gtk::HeaderBar.new
    headerbar.title = title
    headerbar.subtitle = "This is a subtitle"
    headerbar.show_close_button = true

    menu_template = "
    <interface>
    <menu id='app_menu'>
        <submenu>
            <attribute name='label'>_File</attribute>
            <section>
                <item>
                    <attribute name='label'>_Quit</attribute>
                    <attribute name='action'>app.quit</attribute>
                    <attribute name='accel'>&lt;Primary&gt;q</attribute>
                </item>
            </section>
        </submenu>
    </menu>
</interface>
    "
    menuBuilder = Gtk::Builder.new_from_string menu_template, menu_template.size

    menuModel = menuBuilder["app_menu"]

    self.app_menu = menuModel unless show_menu
    self.menubar = menuModel

    window = Gtk::ApplicationWindow.new self
    window.title = title
    window.connect "destroy", &->self.quit
    window.titlebar = headerbar
    window.show_menubar = show_menu
    window.set_default_size 600, 400
    window.icon_name = "applications-development"

    window.show_all
  end
end

app = MyApplication.new
app.run