import patterns
import mywidgets
import time
from PIL import Image

def float_or_zero(x):
    try: return float(x)
    except: return 0.0

class UserInterface(object):
    def __init__(self, factory):
        self.input_a = factory.edit(text='0')
        self.input_b = factory.edit(text='0')
        self.result = factory.label(text='0')
        self.quit_button = factory.button(text='Quit')
        self.kill_gui_func = factory.do_quit

        factory.window().contents = [
            Image.open('i-want-gnu.png'),
            factory.table(contents = [
                [ 'this',           self.input_a ],
                [ 'times this',     self.input_b ],
                [ 'equals this',    self.result ],
              ]),
            '\n',
            self.quit_button,
          ]

class Facade(object):
    def __init__(self, gui):
        self.done = False
        self.gui = gui
        patterns.CallbackObserver(self.gui.input_a, self.input_updated)
        patterns.CallbackObserver(self.gui.input_b, self.input_updated)
        patterns.CallbackObserver(self.gui.quit_button, self.do_quit)
    def do_quit(self, subject):
        self.done = True
        self.gui.kill_gui_func()
    def input_updated(self, subject):
        a = float_or_zero(self.gui.input_a.text)
        b = float_or_zero(self.gui.input_b.text)
        self.gui.result.text = str(a * b)

def main():
    factory = mywidgets.TkWidgetFactory()
    gui = UserInterface(factory)
    facade = Facade(gui)
    while not facade.done:
        time.sleep(.2)

if __name__ == '__main__': main()