Flickering in Terminal UI

[sluongng]

This is probably a minor nit, but a new user might notice the flickering in the progress UI by quite a bit. There seem to be 2 main problems with the current UI:

1. The action progress flickers quite a lot when the build is on-going.

2. The cursor jumped all over the place during build, assuming because redraw process left it there.

Most of the relevant code is in UiEventHandler.java. I am not quite sure just yet how to fix/improve this 🤔

[meisterT]

What terminal / OS are you using? I don't see any flickering (or perhaps I am not looking at the right thing).

[sluongng]

I am using Ghostty terminal on MacOS with a layer of Tmux on top.
I also see the same problem when using Kitty terminal to open the same Tmux session.
Opening a vertical Tmux split during the build showed no flickering, so that should also exclude problems originating from Tmux.

Most terminal CLI I use renders just fine.
Newer ones created in Rust are working with a very high frame rate.

Here is an asciinema I recorded just now building Bazel.git https://asciinema.org/a/OR9wg9ktndKtc2URPHTtAUe9A

If you download it and replay it with asciinema play frame by frame, you would be able to see instances like this:

• Frame 0:

• Frame 1:

• Frame 2:

• Frame 3:

This also explains why I see the cursor jump to different places.

And if you speed up the playback, you can see the flickering intensify, matching what I experienced on my end.