Large OptionList widgets are slow to load (since 0.86.0)

[TomJGooding]

I've noticed that OptionList widgets with a large number of options take significantly longer to load since Textual 0.86.0.

The example below is an extreme scenario, but it demonstrates the difference in loading times.

Textual 0.85.2:
Loading OptionList with 10,000 options took 4.02s

Textual 0.86.0:
Loading OptionList with 10,000 options took 9.17s

Textual 1.0.0:
Loading OptionList with 10,000 options took 13.28s

from time import perf_counter

from textual import __version__
from textual.app import App, ComposeResult
from textual.widgets import OptionList

TOTAL_OPTIONS = 10_000


class ExampleApp(App):
    def compose(self) -> ComposeResult:
        content = [f"Option {i}/{TOTAL_OPTIONS}" for i in range(TOTAL_OPTIONS)]
        yield OptionList(*content)

    def on_ready(self) -> None:
        self.call_after_refresh(self.exit)


if __name__ == "__main__":
    start = perf_counter()

    app = ExampleApp()
    app.run()

    elapsed = perf_counter() - start
    print(f"**Textual {__version__}:**")
    print(f"Loading OptionList with {TOTAL_OPTIONS:,} options took {elapsed:.2f}s")

[github-actions]

We found the following entries in the FAQ which you may find helpful:

• How do I center a widget in a screen?
• No widget called TextLog

Feel free to close this issue if you found an answer in the FAQ. Otherwise, please give us a little time to review.

This is an automated reply, generated by FAQtory

[willmcgugan]

Previous iteration of the OptionList were lazy in calculating dimensions, which cause all sorts of flakiness. Now it does more work up-front. I suspect the timings look better in older versions because it is exiting before that lazy work is done.

It takes 6.45s on my machine currently with a feature branch that should speed up rendering.

The OptionList is also due for a re-write.

Closing this for now, will revisit after these changes are in.

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[TomJGooding]

It takes 6.45s on my machine currently with a feature branch that should speed up rendering.

@willmcgugan Can I ask which feature branch so I can give it a go? That's quite a difference, though I suspect my old Thinkpad won’t keep up with your machine!

[willmcgugan]

It's in main now

[TomJGooding]

Ah, that's what I feared. It takes ~16s on main on my machine, so actually 3s longer than before.

[TomJGooding]

Thanks for reopening this issue. That's quite an impressive difference on the new option list branch (currently down to 1.27s on my machine)!

[willmcgugan]

It's a wee bit faster now!

[TomJGooding]

Closed by #5510.

[github-actions]

Don't forget to star the repository!

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