docs(examples): simplify the barchart example (ratatui#1079)

The `barchart` example has been split into two examples: `barchart` and
`barchart-grouped`. The `barchart` example now shows a simple barchart
with random data, while the `barchart-grouped` example shows a grouped
barchart with fake revenue data.

This simplifies the examples a bit so they don't cover too much at once.

- Simplify the rendering functions
- Fix several clippy lints that were marked as allowed

---------

Co-authored-by: EdJoPaTo <rfc-conform-git-commit-email@funny-long-domain-label-everyone-hates-as-it-is-too-long.edjopato.de>

Cargo.toml

@@ -18,7 +18,6 @@ exclude = [
   "*.log",
   "tags",
 ]
-autoexamples = true
 edition = "2021"
 rust-version = "1.74.0"
 
@@ -218,6 +217,11 @@ name = "barchart"
 required-features = ["crossterm"]
 doc-scrape-examples = true
 
+[[example]]
+name = "barchart-grouped"
+required-features = ["crossterm"]
+doc-scrape-examples = true
+
 [[example]]
 name = "block"
 required-features = ["crossterm"]

examples/README.md

@@ -23,6 +23,26 @@ This folder might use unreleased code. View the examples for the latest release
 > We don't keep the CHANGELOG updated with unreleased changes, check the git commit history or run
 > `git-cliff -u` against a cloned version of this repository.
 
+## Design choices
+
+The examples contain some opinionated choices in order to make it easier for newer rustaceans to
+easily be productive in creating applications:
+
+- Each example has an App struct, with methods that implement a main loop, handle events and drawing
+  the UI.
+- We use color_eyre for handling errors and panics. See [How to use color-eyre with Ratatui] on the
+  website for more information about this.
+- Common code is not extracted into a separate file. This makes each example self-contained and easy
+  to read as a whole.
+
+Not every example has been updated with all these points in mind yet, however over time they will
+be. None of the above choices are strictly necessary for Ratatui apps, but these choices make
+examples easier to run, maintain and explain. These choices are designed to help newer users fall
+into the pit of success when incorporating example code into their own apps. We may also eventually
+move some of these design choices into the core of Ratatui to simplify apps.
+
+[How to use color-eyre with Ratatui]: https://ratatui.rs/how-to/develop-apps/color_eyre/
+
 ## Demo2
 
 This is the demo example from the main README and crate page. Source: [demo2](./demo2/).

examples/barchart-grouped.rs

@@ -0,0 +1,278 @@
+//! # [Ratatui] `BarChart` example
+//!
+//! The latest version of this example is available in the [examples] folder in the repository.
+//!
+//! Please note that the examples are designed to be run against the `main` branch of the Github
+//! repository. This means that you may not be able to compile with the latest release version on
+//! crates.io, or the one that you have installed locally.
+//!
+//! See the [examples readme] for more information on finding examples that match the version of the
+//! library you are using.
+//!
+//! [Ratatui]: https://github.com/ratatui-org/ratatui
+//! [examples]: https://github.com/ratatui-org/ratatui/blob/main/examples
+//! [examples readme]: https://github.com/ratatui-org/ratatui/blob/main/examples/README.md
+
+use std::iter::zip;
+
+use color_eyre::Result;
+use ratatui::{
+    crossterm::event::{self, Event, KeyCode},
+    prelude::{Color, Constraint, Direction, Frame, Layout, Line, Style},
+    style::Stylize,
+    widgets::{Bar, BarChart, BarGroup, Block},
+};
+
+use self::terminal::Terminal;
+
+const COMPANY_COUNT: usize = 3;
+const PERIOD_COUNT: usize = 4;
+
+struct App {
+    should_exit: bool,
+    companies: [Company; COMPANY_COUNT],
+    revenues: [Revenues; PERIOD_COUNT],
+}
+
+struct Revenues {
+    period: &'static str,
+    revenues: [u32; COMPANY_COUNT],
+}
+
+struct Company {
+    short_name: &'static str,
+    name: &'static str,
+    color: Color,
+}
+
+fn main() -> Result<()> {
+    color_eyre::install()?;
+    let mut terminal = terminal::init()?;
+    let app = App::new();
+    app.run(&mut terminal)?;
+    terminal::restore()?;
+    Ok(())
+}
+
+impl App {
+    const fn new() -> Self {
+        Self {
+            should_exit: false,
+            companies: fake_companies(),
+            revenues: fake_revenues(),
+        }
+    }
+
+    fn run(mut self, terminal: &mut Terminal) -> Result<()> {
+        while !self.should_exit {
+            self.draw(terminal)?;
+            self.handle_events()?;
+        }
+        Ok(())
+    }
+
+    fn draw(&self, terminal: &mut Terminal) -> Result<()> {
+        terminal.draw(|frame| self.render(frame))?;
+        Ok(())
+    }
+
+    fn handle_events(&mut self) -> Result<()> {
+        if let Event::Key(key) = event::read()? {
+            if key.code == KeyCode::Char('q') {
+                self.should_exit = true;
+            }
+        }
+        Ok(())
+    }
+
+    fn render(&self, frame: &mut Frame) {
+        use Constraint::{Fill, Length, Min};
+        let [title, top, bottom] = Layout::vertical([Length(1), Fill(1), Min(20)])
+            .spacing(1)
+            .areas(frame.area());
+
+        frame.render_widget("Grouped Barchart".bold().into_centered_line(), title);
+        frame.render_widget(self.vertical_revenue_barchart(), top);
+        frame.render_widget(self.horizontal_revenue_barchart(), bottom);
+    }
+
+    /// Create a vertical revenue bar chart with the data from the `revenues` field.
+    fn vertical_revenue_barchart(&self) -> BarChart<'_> {
+        let title = Line::from("Company revenues (Vertical)").centered();
+        let mut barchart = BarChart::default()
+            .block(Block::new().title(title))
+            .bar_gap(0)
+            .bar_width(6)
+            .group_gap(2);
+        for group in self
+            .revenues
+            .iter()
+            .map(|revenue| revenue.to_vertical_bar_group(&self.companies))
+        {
+            barchart = barchart.data(group);
+        }
+        barchart
+    }
+
+    /// Create a horizontal revenue bar chart with the data from the `revenues` field.
+    fn horizontal_revenue_barchart(&self) -> BarChart<'_> {
+        let title = Line::from("Company Revenues (Horizontal)").centered();
+        let mut barchart = BarChart::default()
+            .block(Block::new().title(title))
+            .bar_width(1)
+            .group_gap(2)
+            .bar_gap(0)
+            .direction(Direction::Horizontal);
+        for group in self
+            .revenues
+            .iter()
+            .map(|revenue| revenue.to_horizontal_bar_group(&self.companies))
+        {
+            barchart = barchart.data(group);
+        }
+        barchart
+    }
+}
+
+/// Generate fake company data
+const fn fake_companies() -> [Company; COMPANY_COUNT] {
+    [
+        Company::new("BAKE", "Bake my day", Color::LightRed),
+        Company::new("BITE", "Bits and Bites", Color::Blue),
+        Company::new("TART", "Tart of the Table", Color::White),
+    ]
+}
+
+/// Some fake revenue data
+const fn fake_revenues() -> [Revenues; PERIOD_COUNT] {
+    [
+        Revenues::new("Jan", [8500, 6500, 7000]),
+        Revenues::new("Feb", [9000, 7500, 8500]),
+        Revenues::new("Mar", [9500, 4500, 8200]),
+        Revenues::new("Apr", [6300, 4000, 5000]),
+    ]
+}
+
+impl Revenues {
+    /// Create a new instance of `Revenues`
+    const fn new(period: &'static str, revenues: [u32; COMPANY_COUNT]) -> Self {
+        Self { period, revenues }
+    }
+
+    /// Create a `BarGroup` with vertical bars for each company
+    fn to_vertical_bar_group<'a>(&self, companies: &'a [Company]) -> BarGroup<'a> {
+        let bars: Vec<Bar> = zip(companies, self.revenues)
+            .map(|(company, revenue)| company.vertical_revenue_bar(revenue))
+            .collect();
+        BarGroup::default()
+            .label(Line::from(self.period).centered())
+            .bars(&bars)
+    }
+
+    /// Create a `BarGroup` with horizontal bars for each company
+    fn to_horizontal_bar_group<'a>(&'a self, companies: &'a [Company]) -> BarGroup<'a> {
+        let bars: Vec<Bar> = zip(companies, self.revenues)
+            .map(|(company, revenue)| company.horizontal_revenue_bar(revenue))
+            .collect();
+        BarGroup::default()
+            .label(Line::from(self.period).centered())
+            .bars(&bars)
+    }
+}
+
+impl Company {
+    /// Create a new instance of `Company`
+    const fn new(short_name: &'static str, name: &'static str, color: Color) -> Self {
+        Self {
+            short_name,
+            name,
+            color,
+        }
+    }
+
+    /// Create a vertical revenue bar for the company
+    ///
+    /// The label is the short name of the company, and will be displayed under the bar
+    fn vertical_revenue_bar(&self, revenue: u32) -> Bar {
+        let text_value = format!("{:.1}M", f64::from(revenue) / 1000.);
+        Bar::default()
+            .label(self.short_name.into())
+            .value(u64::from(revenue))
+            .text_value(text_value)
+            .style(self.color)
+            .value_style(Style::new().fg(Color::Black).bg(self.color))
+    }
+
+    /// Create a horizontal revenue bar for the company
+    ///
+    /// The label is the long name of the company combined with the revenue and will be displayed
+    /// on the bar
+    fn horizontal_revenue_bar(&self, revenue: u32) -> Bar {
+        let text_value = format!("{} ({:.1} M)", self.name, f64::from(revenue) / 1000.);
+        Bar::default()
+            .value(u64::from(revenue))
+            .text_value(text_value)
+            .style(self.color)
+            .value_style(Style::new().fg(Color::Black).bg(self.color))
+    }
+}
+
+/// Contains functions common to all examples
+mod terminal {
+    use std::{
+        io::{self, stdout, Stdout},
+        panic,
+    };
+
+    use ratatui::{
+        backend::CrosstermBackend,
+        crossterm::{
+            execute,
+            terminal::{
+                disable_raw_mode, enable_raw_mode, Clear, ClearType, EnterAlternateScreen,
+                LeaveAlternateScreen,
+            },
+        },
+    };
+
+    // A type alias to simplify the usage of the terminal and make it easier to change the backend
+    // or choice of writer.
+    pub type Terminal = ratatui::Terminal<CrosstermBackend<Stdout>>;
+
+    /// Initialize the terminal by enabling raw mode and entering the alternate screen.
+    ///
+    /// This function should be called before the program starts to ensure that the terminal is in
+    /// the correct state for the application.
+    pub fn init() -> io::Result<Terminal> {
+        install_panic_hook();
+        enable_raw_mode()?;
+        execute!(stdout(), EnterAlternateScreen)?;
+        let backend = CrosstermBackend::new(stdout());
+        let terminal = Terminal::new(backend)?;
+        Ok(terminal)
+    }
+
+    /// Restore the terminal by leaving the alternate screen and disabling raw mode.
+    ///
+    /// This function should be called before the program exits to ensure that the terminal is
+    /// restored to its original state.
+    pub fn restore() -> io::Result<()> {
+        disable_raw_mode()?;
+        execute!(
+            stdout(),
+            LeaveAlternateScreen,
+            Clear(ClearType::FromCursorDown),
+        )
+    }
+
+    /// Install a panic hook that restores the terminal before printing the panic.
+    ///
+    /// This prevents error messages from being messed up by the terminal state.
+    fn install_panic_hook() {
+        let panic_hook = panic::take_hook();
+        panic::set_hook(Box::new(move |panic_info| {
+            let _ = restore();
+            panic_hook(panic_info);
+        }));
+    }
+}