require 'gtk'

window = Gtk::Window.new(Gtk::WINDOW_TOPLEVEL)

mbar = Gtk::MenuBar.new
filemitem = Gtk::MenuItem.new('File')
filemitem.show
filemenu = Gtk::Menu.new
item1 = Gtk::MenuItem.new('Open')
item1.show
filemenu.add item1
item2 = Gtk::MenuItem.new('Save')
item2.show
filemenu.add item2
item3 = Gtk::MenuItem.new('Quit')
item3.show
filemenu.add item3
filemitem.set_submenu filemenu
mbar.append filemitem
mbar.show

vadj = Gtk::Adjustment.new(0,0,0,0,0,0)
text = Gtk::Text.new(nil, vadj)
vs = Gtk::VScrollbar.new(vadj)
text.set_editable true

hbox = Gtk::HBox.new(false, 0)
hbox.pack_start text, true, true, 0
hbox.pack_start vs, false, false, 0

vbox = Gtk::VBox.new(false, 0)
vbox.pack_start mbar, false, false, 0
vbox.pack_start hbox, true, true, 0
vbox.show

fs = Gtk::FileSelection.new('')
fs.ok_button.signal_connect('clicked') {
  fs.hide
  $callback.call fs.get_filename
}
fs.cancel_button.signal_connect('clicked') {
  fs.hide
}

item1.signal_connect('activate') {
  fs.set_title 'Open File'
  $callback = proc {|filename|
    text.set_point 0
    text.forward_delete text.get_length
    open(filename) {|f| text.insert_text f.read, 0}
  }
  fs.show
}
item2.signal_connect('activate') {
  fs.set_title 'Save File'
  $callback = proc {|filename|
    open(filename, 'w+') {|f| f.write(text.get_chars 0, -1)}
  }
  fs.show
}

item3.signal_connect('activate') {
  exit
}

window.add vbox
text.show
vs.show
hbox.show
window.show
Gtk.main