urwid_double_spiral.py

# Info:
#
# To run this script, install urwid (http://urwid.org/) via your favourite
# package manager.

import math

import urwid


class TestWidget(urwid.WidgetWrap):
    DELTA = 0.05
    CHARS = "  ░▒▓██"
    #CHARS = " ░▒▓█"
    #CHARS = " ▁▂▃▄▅▆▇█"

    def __init__(self):
        self.text = urwid.Text("<placeholder text>", align=urwid.CENTER)
        self.filler = urwid.Filler(self.text)
        super().__init__(self.filler)

        self.t = 0

    def render(self, size, focus):
        self.width, self.height = size
        return super().render(size, focus)

    def func(self, x, y, t):
        # FULL of magic numbers!
        x -= self.width/2
        y -= self.height/2
        x /= 2

        x /= 7
        y /= 7

        t *= 2

        d = math.sqrt(x**2 + y**2)
        th = math.atan2(y, x) * 5

        f = max(-1, min(1, (d - 2)))
        g = 1 if f > 0 else -1
        h = 1 if f > 0 else 2
        n = math.sin(5*d - t*h + th*g)
        n *= f
        return n

    def value_to_char(self, val):
        val = max(-1, min(1, val))
        val = (val + 1) / 2
        l = len(self.CHARS)
        d = 1 / l

        for n in range(l):
            if val <= (n + 1) * d:
                return self.CHARS[n]

    def text_from_func(self, width, height, t):
        lines = []
        for y in range(height):
            line = []
            for x in range(width):
                value = self.func(x, y, t)
                line.append(self.value_to_char(value))
            lines.append("".join(line))
        return "\n".join(lines)

    def update_text(self, loop, user_data):
        self.t += self.DELTA

        new_text = self.text_from_func(self.width, self.height, self.t)
        self.text.set_text(new_text)

        loop.set_alarm_in(self.DELTA, self.update_text)

widget = TestWidget()
loop = urwid.MainLoop(
        widget,
)
loop.set_alarm_in(widget.DELTA, widget.update_text)
loop.run()