Text is Unexpectedly Blinking

[eeriemyxi]

I am trying to make a loading animation for my project where the stars in the background would blink and the quote text would stay static. However for whatever reason the text is also blinking. I am aware that I'm using experimental features (alternate screen), but I'd still want to know if this is expected, and if it is, possible solutions to it that is easy to implement.

Even if you merely update art with the same state each time, it would still blink. The only time when it doesn't blink is when you don't print the art text at all and only print the quote text. I have attached a video representation of the issue as well as the possibly reproducible source code.

❯ uv pip show rich
Name: rich
Version: 13.9.4
Location: /home/myxi/Documents/coding/hybrid/scrapes/py-animated-ascii/.venv/lib/python3.12/site-packages
Requires: markdown-it-py, pygments
Required-by:

2025-03-16_22-11-02.mp4

from rich.console import Console, ConsoleOptions
from rich.align import Align
from rich.text import Text
import random

import time

TARGETS = bytearray("*.'+.".encode())

def blink_art(art: bytearray):
    max_changes = random.randint(1, 20)
    changes = [(-1, -1)] * max_changes

    for k in range(max_changes):
        n = random.randint(0, 127)
        for i, s in enumerate(art):
            if s in TARGETS:
                if n == 0:
                    ch = art[i]
                    art[i] = ord(" ")
                    changes[k] = (i, ch)
                    break
                n -= 1

    return changes, art


def start_animation(console, art: bytearray):
    try:
        with console.screen(hide_cursor=True):
            st_time = time.time()

            while True:
                changes, art = blink_art(art)

                console.update_screen(Align(Text(art.decode()), align="center"))
                console.update_screen_lines(
                    [
                        ["            [red bold]C E L E S T I A L"],
                        ["[italic]Beyond the [yellow bold]galaxy[/] and further..."],
                        ["[italic]Higher than usually..."],
                        ["[italic][blue bold]Infinity[/] never ends;"],
                        [
                            "[italic]Stars don't shine [bold green]bright[/] without darkness."
                        ],
                    ],
                    45,
                    9,
                )

                for i, ch in changes:
                    if i == -1 and ch == -1:
                        continue
                    art[i] = ch

                if time.time() - st_time >= 300:
                    break

                time.sleep(0.1)
    except KeyboardInterrupt:
        pass


def main():
    console = Console()

    with open("art.txt", "rb") as file:
        art = bytearray(file.read())

    start_animation(console, art)


if __name__ == "__main__":
    main()

art.txt:

` : | | | |:  ||  :     `  :  |  |+|: | : : :|   .        `              .
      ` : | :|  ||  |:  :    `  |  | :| : | : |:   |  .                    :
         .' ':  ||  |:  |  '       ` || | : | |: : |   .  `           .   :.
                `'  ||  |  ' |   *    ` : | | :| |*|  :   :               :|
        *    *       `  |  : :  |  .      ` ' :| | :| . : :         *   :.||
             .`            | |  |  : .:|       ` | || | : |: |          | ||
      '          .         + `  |  :  .: .         '| | : :| :    .   |:| ||
         .                 .    ` *|  || :       `    | | :| | :      |:| |
 .                .          .        || |.: *          | || : :     :|||
        .                                               + '| |||  .  ||`
     .                                                    . ||||  :.||`
 +                                                          . | :`||+ |||`
     .                                                      | |.| ||`     .
       *     +   '                                          |:`|| `
                            .      .||` .    ..|| | |: '` `| | |`  +
  .       +++                      ||        !|!: `       :| |
              +         .      .    | .      `|||.:      .||    .      .    `
          '                           `|.   .  `:|||   + ||'     `
  __    +      *                         `'       `'|.    `:
"'  `---"""----....____,..^---`^``----.,.___          `.    `.  .    ____,.,-
    ___,--'""`---"'   ^  ^ ^        ^       """'---,..___ __,..---""'
--"'                              ^                         ``--..,__

[willmcgugan]

I'd start by looking at the docs for update_screen_lines, which doesn't take a list of lists of strings.

[eeriemyxi]

Adding an empty console.print statement between the line changes, art = blink_art(art) and the update statement for whatever reason resolves the issue.