nutmeg

Manage a console/terminal UI that can alternate between showing a progress bar and lines of text output.

Concept

By contrast to other Rust progress-bar libraries, Nutmeg has no built-in concept of what the progress bar or indicator should look like: this is entirely under the control of the application. Nutmeg handles drawing the application's progress bar to the screen and removing it as needed.

The application (or dependent library) is responsible for:

• Defining a type that implements [Model], which holds whatever information is relevant to drawing progress.
• Defining how to render that information into some text lines, by implementing [Model::render]. This returns a String for the progress representation, optionally including ANSI styling.
• Constructing a [View] that will draw progress to the terminal.
• Notifying the [View] when there are model updates, by calling [View::update].
• While a [View] is in use, all text written to stdout/stderr should be sent via that view, to avoid the display getting scrambled. That is to say, use writeln!(view, "hello") rather than println!("hello").

The Nutmeg library is responsible for:

• Periodically drawing the progress bar in response to updates, including
  • Horizontally truncating output to fit on the screen.
  • Handling changes in the number of lines of progress display.
• Removing the progress bar when the view is finished or dropped.
• Coordinating to hide the bar to print text output, and restore it afterwards.
• Limiting the rate at which updates are drawn to the screen.

Errors in writing to the terminal cause a panic.

Potential future features

• Draw updates from a background thread, so that it will keep ticking even if not actively updated, and to better handle applications that send a burst of updates followed by a long pause. The background thread will eventually paint the last drawn update.

• Also set the window title from the progress model, perhaps by a different render function?

License: MIT