bevy/examples/app/logs.rs
UkoeHB c2c19e5ae4
Text rework (#15591)
**Ready for review. Examples migration progress: 100%.**

# Objective

- Implement https://github.com/bevyengine/bevy/discussions/15014

## Solution

This implements [cart's
proposal](https://github.com/bevyengine/bevy/discussions/15014#discussioncomment-10574459)
faithfully except for one change. I separated `TextSpan` from
`TextSpan2d` because `TextSpan` needs to require the `GhostNode`
component, which is a `bevy_ui` component only usable by UI.

Extra changes:
- Added `EntityCommands::commands_mut` that returns a mutable reference.
This is a blocker for extension methods that return something other than
`self`. Note that `sickle_ui`'s `UiBuilder::commands` returns a mutable
reference for this reason.

## Testing

- [x] Text examples all work.

---

## Showcase

TODO: showcase-worthy

## Migration Guide

TODO: very breaking

### Accessing text spans by index

Text sections are now text sections on different entities in a
hierarchy, Use the new `TextReader` and `TextWriter` system parameters
to access spans by index.

Before:
```rust
fn refresh_text(mut query: Query<&mut Text, With<TimeText>>, time: Res<Time>) {
    let text = query.single_mut();
    text.sections[1].value = format_time(time.elapsed());
}
```

After:
```rust
fn refresh_text(
    query: Query<Entity, With<TimeText>>,
    mut writer: UiTextWriter,
    time: Res<Time>
) {
    let entity = query.single();
    *writer.text(entity, 1) = format_time(time.elapsed());
}
```

### Iterating text spans

Text spans are now entities in a hierarchy, so the new `UiTextReader`
and `UiTextWriter` system parameters provide ways to iterate that
hierarchy. The `UiTextReader::iter` method will give you a normal
iterator over spans, and `UiTextWriter::for_each` lets you visit each of
the spans.

---------

Co-authored-by: ickshonpe <david.curthoys@googlemail.com>
Co-authored-by: Carter Anderson <mcanders1@gmail.com>
2024-10-09 18:35:36 +00:00

81 lines
2.8 KiB
Rust

//! This example illustrates how to use logs in bevy.
use bevy::{log::once, prelude::*};
fn main() {
App::new()
.add_plugins(DefaultPlugins.set(bevy::log::LogPlugin {
// Uncomment this to override the default log settings:
// level: bevy::log::Level::TRACE,
// filter: "wgpu=warn,bevy_ecs=info".to_string(),
..default()
}))
.add_systems(Startup, setup)
.add_systems(Update, log_system)
.add_systems(Update, log_once_system)
.add_systems(Update, panic_on_p)
.run();
}
fn setup(mut commands: Commands) {
commands.spawn(Camera2d);
commands.spawn((
Text::new("Press P to panic"),
Style {
position_type: PositionType::Absolute,
top: Val::Px(12.0),
left: Val::Px(12.0),
..default()
},
));
}
fn panic_on_p(keys: Res<ButtonInput<KeyCode>>) {
if keys.just_pressed(KeyCode::KeyP) {
panic!("P pressed, panicking");
}
}
fn log_system() {
// here is how you write new logs at each "log level" (in "least important" to "most important"
// order)
trace!("very noisy");
debug!("helpful for debugging");
info!("helpful information that is worth printing by default");
warn!("something bad happened that isn't a failure, but thats worth calling out");
error!("something failed");
// by default, trace and debug logs are ignored because they are "noisy"
// you can control what level is logged by setting up the LogPlugin
// alternatively you can set the log level via the RUST_LOG=LEVEL environment variable
// ex: RUST_LOG=trace, RUST_LOG=info,bevy_ecs=warn
// the format used here is super flexible. check out this documentation for more info:
// https://docs.rs/tracing-subscriber/*/tracing_subscriber/filter/struct.EnvFilter.html
}
fn log_once_system() {
// The 'once' variants of each log level are useful when a system is called every frame,
// but we still wish to inform the user only once. In other words, use these to prevent spam :)
trace_once!("one time noisy message");
debug_once!("one time debug message");
info_once!("some info which is printed only once");
warn_once!("some warning we wish to call out only once");
error_once!("some error we wish to report only once");
for i in 0..10 {
info_once!("logs once per call site, so this works just fine: {}", i);
}
// you can also use the `once!` macro directly,
// in situations where you want to do something expensive only once
// within the context of a continuous system.
once!({
info!("doing expensive things");
let mut a: u64 = 0;
for i in 0..100000000 {
a += i;
}
info!("result of some expensive one time calculation: {}", a);
});
}