01aedc8431
# Objective Now that we can consolidate Bundles and Components under a single insert (thanks to #2975 and #6039), almost 100% of world spawns now look like `world.spawn().insert((Some, Tuple, Here))`. Spawning an entity without any components is an extremely uncommon pattern, so it makes sense to give spawn the "first class" ergonomic api. This consolidated api should be made consistent across all spawn apis (such as World and Commands). ## Solution All `spawn` apis (`World::spawn`, `Commands:;spawn`, `ChildBuilder::spawn`, and `WorldChildBuilder::spawn`) now accept a bundle as input: ```rust // before: commands .spawn() .insert((A, B, C)); world .spawn() .insert((A, B, C); // after commands.spawn((A, B, C)); world.spawn((A, B, C)); ``` All existing instances of `spawn_bundle` have been deprecated in favor of the new `spawn` api. A new `spawn_empty` has been added, replacing the old `spawn` api. By allowing `world.spawn(some_bundle)` to replace `world.spawn().insert(some_bundle)`, this opened the door to removing the initial entity allocation in the "empty" archetype / table done in `spawn()` (and subsequent move to the actual archetype in `.insert(some_bundle)`). This improves spawn performance by over 10%:  To take this measurement, I added a new `world_spawn` benchmark. Unfortunately, optimizing `Commands::spawn` is slightly less trivial, as Commands expose the Entity id of spawned entities prior to actually spawning. Doing the optimization would (naively) require assurances that the `spawn(some_bundle)` command is applied before all other commands involving the entity (which would not necessarily be true, if memory serves). Optimizing `Commands::spawn` this way does feel possible, but it will require careful thought (and maybe some additional checks), which deserves its own PR. For now, it has the same performance characteristics of the current `Commands::spawn_bundle` on main. **Note that 99% of this PR is simple renames and refactors. The only code that needs careful scrutiny is the new `World::spawn()` impl, which is relatively straightforward, but it has some new unsafe code (which re-uses battle tested BundlerSpawner code path).** --- ## Changelog - All `spawn` apis (`World::spawn`, `Commands:;spawn`, `ChildBuilder::spawn`, and `WorldChildBuilder::spawn`) now accept a bundle as input - All instances of `spawn_bundle` have been deprecated in favor of the new `spawn` api - World and Commands now have `spawn_empty()`, which is equivalent to the old `spawn()` behavior. ## Migration Guide ```rust // Old (0.8): commands .spawn() .insert_bundle((A, B, C)); // New (0.9) commands.spawn((A, B, C)); // Old (0.8): commands.spawn_bundle((A, B, C)); // New (0.9) commands.spawn((A, B, C)); // Old (0.8): let entity = commands.spawn().id(); // New (0.9) let entity = commands.spawn_empty().id(); // Old (0.8) let entity = world.spawn().id(); // New (0.9) let entity = world.spawn_empty(); ```
108 lines
3.5 KiB
Rust
108 lines
3.5 KiB
Rust
//! This example illustrates how to create UI text and update it in a system.
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//!
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//! It displays the current FPS in the top left corner, as well as text that changes color
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//! in the bottom right. For text within a scene, please see the text2d example.
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use bevy::{
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diagnostic::{Diagnostics, FrameTimeDiagnosticsPlugin},
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prelude::*,
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};
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fn main() {
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App::new()
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.add_plugins(DefaultPlugins)
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.add_plugin(FrameTimeDiagnosticsPlugin::default())
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.add_startup_system(setup)
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.add_system(text_update_system)
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.add_system(text_color_system)
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.run();
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}
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// A unit struct to help identify the FPS UI component, since there may be many Text components
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#[derive(Component)]
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struct FpsText;
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// A unit struct to help identify the color-changing Text component
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#[derive(Component)]
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struct ColorText;
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fn setup(mut commands: Commands, asset_server: Res<AssetServer>) {
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// UI camera
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commands.spawn(Camera2dBundle::default());
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// Text with one section
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commands.spawn((
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// Create a TextBundle that has a Text with a single section.
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TextBundle::from_section(
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// Accepts a `String` or any type that converts into a `String`, such as `&str`
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"hello\nbevy!",
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TextStyle {
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font: asset_server.load("fonts/FiraSans-Bold.ttf"),
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font_size: 100.0,
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color: Color::WHITE,
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},
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) // Set the alignment of the Text
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.with_text_alignment(TextAlignment::TOP_CENTER)
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// Set the style of the TextBundle itself.
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.with_style(Style {
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align_self: AlignSelf::FlexEnd,
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position_type: PositionType::Absolute,
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position: UiRect {
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bottom: Val::Px(5.0),
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right: Val::Px(15.0),
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..default()
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},
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..default()
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}),
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ColorText,
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));
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// Text with multiple sections
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commands.spawn((
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// Create a TextBundle that has a Text with a list of sections.
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TextBundle::from_sections([
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TextSection::new(
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"FPS: ",
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TextStyle {
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font: asset_server.load("fonts/FiraSans-Bold.ttf"),
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font_size: 60.0,
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color: Color::WHITE,
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},
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),
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TextSection::from_style(TextStyle {
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font: asset_server.load("fonts/FiraMono-Medium.ttf"),
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font_size: 60.0,
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color: Color::GOLD,
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}),
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])
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.with_style(Style {
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align_self: AlignSelf::FlexEnd,
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..default()
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}),
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FpsText,
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));
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}
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fn text_color_system(time: Res<Time>, mut query: Query<&mut Text, With<ColorText>>) {
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for mut text in &mut query {
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let seconds = time.seconds_since_startup() as f32;
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// Update the color of the first and only section.
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text.sections[0].style.color = Color::Rgba {
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red: (1.25 * seconds).sin() / 2.0 + 0.5,
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green: (0.75 * seconds).sin() / 2.0 + 0.5,
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blue: (0.50 * seconds).sin() / 2.0 + 0.5,
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alpha: 1.0,
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};
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}
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}
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fn text_update_system(diagnostics: Res<Diagnostics>, mut query: Query<&mut Text, With<FpsText>>) {
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for mut text in &mut query {
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if let Some(fps) = diagnostics.get(FrameTimeDiagnosticsPlugin::FPS) {
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if let Some(average) = fps.average() {
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// Update the value of the second section
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text.sections[1].value = format!("{average:.2}");
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}
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}
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}
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}
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