Use Terminal background color to determine color mode

[sealor]

My example app recognizes the Terminal background color at start-up and adjusts the color mode accordingly.
So, the light and dark mode is set automatically depending on the users Terminal.

import fcntl
import os
import re
import sys
import termios
import time
import tty

from textual.app import App, ComposeResult
from textual.color import Color
from textual.widgets import Static


# see: https://stackoverflow.com/questions/37726138/disable-buffering-of-sys-stdin-in-python-3
class raw(object):
    def __init__(self, stream):
        self.stream = stream

    def __enter__(self):
        self.original_stty = termios.tcgetattr(self.stream)
        tty.setcbreak(self.stream)

    def __exit__(self, *args):
        termios.tcsetattr(self.stream, termios.TCSANOW, self.original_stty)


class nonblocking(object):
    def __init__(self, stream):
        self.stream = stream
        self.fd = self.stream.fileno()

    def __enter__(self):
        self.orig_fl = fcntl.fcntl(self.fd, fcntl.F_GETFL)
        fcntl.fcntl(self.fd, fcntl.F_SETFL, self.orig_fl | os.O_NONBLOCK)

    def __exit__(self, *args):
        fcntl.fcntl(self.fd, fcntl.F_SETFL, self.orig_fl)


COLOR_REGEX = re.compile("\033]11;rgb:([0-9a-f]{4})/([0-9a-f]{4})/([0-9a-f]{4})\033\\\\")


# see: https://github.com/Canop/terminal-light/blob/main/src/xterm.rs
def resolve_terminal_background_color(stdin, stdout) -> Color:
    with raw(stdin):
        with nonblocking(stdin):
            stdout.write("\033]11;?\033\\")
            stdout.flush()
            time.sleep(0.1)
            line = ""
            while True:
                char = stdin.read(1)

                if not char:
                    return Color(0, 0, 0)

                line += char

                if char == "\\":
                    break

            match = COLOR_REGEX.match(line)
            if not match:
                return Color(0, 0, 0)

            r = match.group(1)[0:2]
            g = match.group(2)[0:2]
            b = match.group(3)[0:2]

            return Color.parse(f"#{r}{g}{b}")


class DynamicBackgroundApp(App):
    def __init__(self):
        super().__init__()
        terminal_background_color = resolve_terminal_background_color(sys.stdin, sys.stdout)
        self.dark = terminal_background_color.brightness < 0.5  # noqa

    def compose(self) -> ComposeResult:
        yield Static("Hello, World!")


app = DynamicBackgroundApp()
app.run()