The new progressbar flickers badly

[bjorn3]

Verification

• I searched for recent similar issues at https://github.com/rust-lang/rustup/issues?q=is%3Aissue and found no duplicates.
• I am on the latest version of Rustup according to https://github.com/rust-lang/rustup/tags and am still able to reproduce my issue.

Problem

When there are multiple progressbars being updated at the same time, there is heavy flickering when using Konsole.

Steps

1. rustup update

Possible Solution(s)

Reduce update interval to at most twice every second and/or use the synchronized update escape codes: https://gitlab.com/gnachman/iterm2/-/wikis/synchronized-updates-spec

Notes

No response

Rustup version

rustup 1.29.0 (28d1352db 2026-03-05)

Installed toolchains

Not relevant

OS version

Linux

[rami3l]

@bjorn3 Thanks for reporting! I think @djc has lowered the tickrate to 20 per second in #4602... Would you mind testing a little bit on your side by editing that value to see how low we could go without making the animation super laggy?

Or, alternatively, maybe we can add an env var to tweak that value?

[djc]

Or, alternatively, maybe we can add an env var to tweak that value?

Pff, let's not go there for this. Adding more configuration surface does not make things better in the grand scheme of things, it just requires users to build more expertise.

[ehuss]

I'm experiencing significant flicker on Windows as well. This is with Windows Terminal using a build from latest main (0a96a33):

rustup-flicker.mp4

[rami3l]

@ehuss What would be a better value in your opinion? Will 2 ticks per second as mentioned above suffice?

[ChrisDenton]

I'm admittedly not too familiar with the library we use for the progressbar.

Is there a way to stop it redrawing the whole line when only a part has changed?

Could the update itself be faster? I mean from the video it looks like it first clears the output then prints the new output. Could it just overwrite in a single pass? Or somehow reduce the delay between the two so it's unnoticeable?

[rami3l]

@ChrisDenton Possibly .set_move_cursor() is here to help but since I don't have the environment to reproduce the issue, I'm not sure what will fix or mitigate this...

If I understand it correctly, the flickering is happening because the terminal emulator is too slow for our output mode. If you can reproduce it with Windows Terminal then maybe give it a try?

[ChrisDenton]

Using set_move_cursor does seem to help. I'll put up a PR and hopefully others can test it.