Embed progress information inside of a `ProgressBar`

[bepri]

I'm wondering if it's currently possible to embed progress bar information inside of the progress chars of a ProgressBar.

An example in the wild of the behavior I'm trying to describe is snapd, as it downloads a file:

I think this may be possible with a custom impl of ProgressTracker, but I'm having a hard time figuring out a way to embed the output of keys like msg inside of my ProgressTracker. Is there a better way? Is there interest in supporting this?

For context on the "why", screen readers for the visually impaired ignore ANSI escape sequences, such as those for color. I wish to leverage this by creating a progress bar that simply changes the background color to indicate progress to avoid clutter in what's read out. I know this is possible already with alternate string styles using console::Style::from_dotted_str, but for visual continuity I'd want to then wrap the progress bar in brackets, such as the one seen in the "download" example in this repository. However, these brackets would then be read by a screen reader, adding noise. I think given these constraints, the "embedded" style is probably the nicest.

[djc]

I guess ProgressTracker doesn't really facilitate this use case. Usually indicatif progress bars show the progress indicator next to the message, rather than behind it, and I'm not sure this is easy to fix. Open to reviewing a PR if it doesn't add too much complexity.