Implement a Progress Bar widget.

[rodrigogiraoserrao]

@willmcgugan here is a first prototype that leans heavily on rich.progress.Progress.
Does this feel like the way forward?

Or should we implement things more from scratch so that we can do things like have component styles to style parts of the progress bar?

Screen.Recording.2023-04-19.at.18.24.50.mov

[willmcgugan]

I think we should implement things from scratch, yes.

Functionality would be quite similar to Rich's Progress. Although simpler. It only needs to render a single progress, with percentage and optional ETA.

[rodrigogiraoserrao]

@willmcgugan I think things are going in a pretty good direction as of 8f2fae5.

But I have an issue I don't understand.
I don't know why I need this line:

textual/src/textual/widgets/_progress_bar.py

Line 248 in 8f2fae5

self.percentage = None # Without this, assigning self.total breaks. 🤔

App to reproduce the issue

from textual.app import App, ComposeResult
from textual.widgets import ProgressBar, Footer


class MyApp(App[None]):
    BINDINGS = [
        ("a", "advance", "Advance by 1"),
        ("j", "jump", "Jump to 25"),
        ("u", "update", "Update to start"),
        ("d", "duplicate", "Duplicate total"),
    ]

    def compose(self) -> ComposeResult:
        self.pb = ProgressBar(total=None)
        yield self.pb
        yield Footer()

    def action_update(self):
        self.pb.update(total=100)

    def action_advance(self):
        self.pb.advance()

    def action_jump(self):
        self.pb.progress = 25

    def action_duplicate(self):
        self.pb.total *= 2


if __name__ == "__main__":
    MyApp().run()

Demo of the app with the progress bar:

Screen.Recording.2023-04-21.at.15.29.03.mov

[rodrigogiraoserrao]

Screenshot of a couple of progress bars (left and upper-left corner are indeterminate progress bars; not really on-brand for the app shown, but I tweaked the example just to get an indeterminate bar to show quickly.)

The video demo above is current, up to the colour of the progress bar (which can be styled with CSS either way).

I still need to add tests, but I'll wait for @willmcgugan to determine what features he'd like to see/change before testing everything.

[willmcgugan]

Functionality is about right I think. Looks good. But needs another pass at the implementation.

[rodrigogiraoserrao]

Updated recording of the indeterminate effect with 15 FPS:

Screen.Recording.2023-04-25.at.18.13.42.mov

[willmcgugan]

Looks good! But that private attribute in the examples may be an issue.

We want examples to be show canonical usage, so we shouldn't be using private attributes.

I think we could fake it, show a screenshot with the hack to set the time, but link to the real example.

[willmcgugan]

LGTM. Just some nitpicks to consider.