"""Proof of concept: integrate tkinter, asyncio and async iterator.

Terry Jan Reedy, 2016 July 25
"""

import asyncio
import tkinter as tk
import datetime


class App(tk.Tk):
    
    def __init__(self, loop, interval=.01):
        super().__init__()
        self.loop = loop
        self.protocol("WM_DELETE_WINDOW", self.close)
        self.tasks = []
        self.create_widgets()
        self.updater(interval)

    def create_widgets(self):
        self.hello = tk.Label(self, text='Hello World', bg='white')
        self.dtime = tk.Label(self)
        self.hello.pack()
        self.dtime.pack()
        self.tasks.append(loop.create_task(self.clock(1)))
        self.tasks.append(loop.create_task(
                self.bg_flip(.337, self.hello, 'red')))

    async def clock(self, interval):
        while True:
            self.dtime['text'] = datetime.datetime.now()
            await asyncio.sleep(interval)

    async def bg_flip(self, interval, widget, color):
        while True:
            await asyncio.sleep(interval)
            bg = widget['bg']
            widget['bg'] = color if bg == 'white' else 'white'

    def updater(self, interval):
        self.update()
        self.loop.call_later(interval, self.updater, interval)

    def close(self):
        for task in self.tasks:
            task.cancel()
        self.loop.stop()
        self.destroy()


loop = asyncio.get_event_loop()
app = App(loop)
loop.run_forever()
loop.close()