run.rb

require "gtk3"

builder_file = "#{File.expand_path(File.dirname(__FILE__))}/builder-thread.ui"
builder = Gtk::Builder.new(:file => builder_file)
window = builder.get_object("window")

window.signal_connect("destroy") do
  Gtk.main_quit
end

button = builder.get_object("button")

button.signal_connect("clicked") do
  Gtk.main_quit
end

def thread(button)
  Thread.new do
    count = 0
    while(true)
      button.label="Click to Quit (#{count})"
      count = count + 1
      sleep(0.1)
    end
  end
end

thread(button)

Gtk.main