Struct LogPlugin

pub struct LogPlugin {
    pub filter: String,
    pub level: Level,
    pub custom_layer: fn(_: &mut App) -> Option<Box<dyn Layer<Registry> + Sync + Send>>,
}

Adds logging to Apps. This plugin is part of the DefaultPlugins. Adding this plugin will setup a collector appropriate to your target platform:

• Using tracing-subscriber by default, logging to stdout.
• Using android_log-sys on Android, logging to Android logs.
• Using tracing-wasm in Wasm, logging to the browser console.

You can configure this plugin.

fn main() {
    App::new()
        .add_plugins(DefaultPlugins.set(LogPlugin {
            level: Level::DEBUG,
            filter: "wgpu=error,bevy_render=info,bevy_ecs=trace".to_string(),
            custom_layer: |_| None,
        }))
        .run();
}

Log level can also be changed using the RUST_LOG environment variable. For example, using RUST_LOG=wgpu=error,bevy_render=info,bevy_ecs=trace cargo run ..

It has the same syntax as the field LogPlugin::filter, see EnvFilter. If you define the RUST_LOG environment variable, the LogPlugin settings will be ignored.

Also, to disable color terminal output (ANSI escape codes), you can set the environment variable NO_COLOR to any value. This common convention is documented at no-color.org. For example:

fn main() {
    std::env::set_var("NO_COLOR", "1");
    App::new()
       .add_plugins(DefaultPlugins)
       .run();
}

If you want to setup your own tracing collector, you should disable this plugin from DefaultPlugins:

fn main() {
    App::new()
        .add_plugins(DefaultPlugins.build().disable::<LogPlugin>())
        .run();
}

Panics

This plugin should not be added multiple times in the same process. This plugin sets up global logging configuration for all Apps in a given process, and rerunning the same initialization multiple times will lead to a panic.

Performance

Filters applied through this plugin are computed at runtime, which will have a non-zero impact on performance. To achieve maximum performance, consider using compile time filters provided by the log crate.

# cargo.toml
[dependencies]
log = { version = "0.4", features = ["max_level_debug", "release_max_level_warn"] }

Fields

filter: String

Filters logs using the EnvFilter format

level: Level

Filters out logs that are “less than” the given level. This can be further filtered using the filter setting.

custom_layer: fn(_: &mut App) -> Option<Box<dyn Layer<Registry> + Sync + Send>>

Optionally add an extra Layer to the tracing subscriber

This function is only called once, when the plugin is built.

Because BoxedLayer takes a dyn Layer, Vec<Layer> is also an acceptable return value.

Access to App is also provided to allow for communication between the Subscriber and the App.

Please see the examples/log_layers.rs for a complete example.

Trait Implementations

impl Default for LogPlugin

fn default() -> LogPlugin

Returns the “default value” for a type.

impl Plugin for LogPlugin

fn build(&self, app: &mut App)

Configures the App to which this plugin is added.

fn ready(&self, _app: &App) -> bool

Has the plugin finished its setup? This can be useful for plugins that need something asynchronous to happen before they can finish their setup, like the initialization of a renderer. Once the plugin is ready, finish should be called.

fn finish(&self, _app: &mut App)

Finish adding this plugin to the App, once all plugins registered are ready. This can be useful for plugins that depends on another plugin asynchronous setup, like the renderer.

fn cleanup(&self, _app: &mut App)

Runs after all plugins are built and finished, but before the app schedule is executed. This can be useful if you have some resource that other plugins need during their build step, but after build you want to remove it and send it to another thread.

fn name(&self) -> &str

Configures a name for the Plugin which is primarily used for checking plugin uniqueness and debugging.

fn is_unique(&self) -> bool

If the plugin can be meaningfully instantiated several times in an App, override this method to return false.