examples/app/headless.rs implies presence of non-existent feature

[ndarilek]

// This example disables the default plugins by not registering them during setup.
// You can also completely remove rendering / windowing Plugin code from bevy
// by making your import look like this in your Cargo.toml
//
// [dependencies]
// bevy = { version = "0.1.3", default-features = false, features = ["headless"] }

Building with that feature doesn't work and claims it doesn't exist. Not sure if the comment should go or if the feature should materialize. :)

Thanks.

[memoryruins]

The fix for this may be to remove that feature from the example's comments and leave it as

// [dependencies]
// bevy = { version = "0.1.3", default-features = false }

since disabling the default features essentially makes it headless.
https://github.com/bevyengine/bevy/blob/master/docs/cargo_features.md

[ndarilek]

Unfortunately not. If I do, then initialize:

    App::build()
        .add_default_plugins()
        .add_resource(terminal)
        .add_system(render_system.system())
        .run();

I get:

thread 'thread '<unnamed><unnamed>' panicked at '' panicked at 'Resource does no
t exist alloc::boxed::Box<dyn bevy_render::renderer::render_resource_context::Re
nderResourceContext>Resource does not exist alloc::boxed::Box<dyn bevy_render::r
enderer::render_resource_context::RenderResourceContext>', ', C:\Users\Nolan Dar
ilek\scoop\persist\rustup\.rustup\toolchains\stable-x86_64-pc-windows-msvc\lib/r
ustlib/src/rust\src\libstd\macros.rsC:\Users\Nolan Darilek\scoop\persist\rustup\
.rustup\toolchains\stable-x86_64-pc-windows-msvc\lib/rustlib/src/rust\src\libstd
\macros.rs::1616::99

Here, render_system is a function that calls terminal-rendering functions. It shouldn't trigger this failure, and doesn't if I initialize a plugin subset.

I did have this working if I initialized a subset of plugins, namely just the scheduler, but a feature or disabling defaults would certainly be nice.

Thanks.

[memoryruins]

Good point, I did not try it with add_default_plugins earlier. #485 recently added a render feature that makes the entire render pipeline optional. With default-features disabled, It now runs on master branch without a panic.

[dependencies.bevy]
git = "https://github.com/bevyengine/bevy"
rev = "b9f549efaac3215e63a2d2022d58f58648adf8cb"
default-features = false

use std::time::Duration;
use bevy::{app::ScheduleRunnerPlugin, prelude::*};

struct SystemTimer(Timer);

fn a(time: Res<Time>, mut timer: ResMut<SystemTimer>) {
    timer.0.tick(time.delta_seconds);
    if timer.0.finished {
        println!("-");
        timer.0.reset();
    }
}

fn main() {
    let wait_duration = Duration::from_secs_f64(1.0 / 60.0);
    App::build()
        .add_plugin(ScheduleRunnerPlugin::run_loop(wait_duration))
        .add_resource(SystemTimer(Timer::from_seconds(1.0, true)))
        .add_system(a.system())
        .add_default_plugins()
        .run();
}

   Compiling bevy_ui_tools v0.1.0
    Finished dev [optimized + debuginfo] target(s) in 1.29s
     Running `target\debug\bevy_ui_tools.exe`
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