mcskware/bevy-headless

bevy-headless

This crate supports the Bevy game engine by adding a HeadlessPlugins plugin group. This plugin group will set up similarly to the MinimalPlugins group, with the addition of a new headless plugin which uses the ratatui crate to display to the terminal. You can retrieve the ratatui Terminal via the TerminalResource's get_mut function. You can also retrieve all logged messages via the AllLogs resource.

Example

Here's a simple example which uses clap to accept a command line parameter to launch in windowed or headless mode:

use bevy::{app::ScheduleRunnerPlugin, prelude::*};
use bevy_headless::HeadlessPlugins;
use bevy_utils::Duration;
use clap::Parser;
use bevy_headless::log::AllLogs;
use bevy_headless::terminal::TerminalResource;

use ratatui::widgets::{Block, Borders, Paragraph, Wrap};

#[derive(Parser, Debug)]
#[command(version, about, long_about = None)]
struct ProgramArgs {
    #[arg(short, long)]
    server: bool,
}

fn main() {
    let program_args = ProgramArgs::parse();

    let mut app = &mut App::new();

    if program_args.server {
        app = app.add_plugins(HeadlessPlugins.set(ScheduleRunnerPlugin::run_loop(
            Duration::from_secs_f64(1.0 / 60.0),
        )));
        app = app.add_systems(Update, render);
    } else {
        app = app.add_plugins(DefaultPlugins);
    };

    app.run();
}

pub fn render(logs: Res<AllLogs>, mut terminal: ResMut<TerminalResource>) {
    let _ = terminal.as_mut().get_mut().draw(|frame| {
        let block = Block::default().title("Greeting").borders(Borders::ALL);
        let scroll_count: u16 =
            logs.count() as u16 - (block.inner(frame.size()).height).min(logs.count() as u16);
        let greeting = Paragraph::new(logs.get())
            .block(block)
            .wrap(Wrap { trim: true });
        let greeting = greeting.scroll((scroll_count, 0));
        frame.render_widget(greeting, frame.size());
    });
}

In this example, we add the HeadlessPlugins group, and set our schedule runner to tick 60 times per second. The render function uses standard ratatui code inside the draw closure. Note that we've also used the AllLogs resource in the render method, to retrieve all logged messages in headless mode.