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//! This example illustrates how to create UI text and update it in a system.
//!
//! It displays the current FPS in the top left corner, as well as text that changes color
//! in the bottom right. For text within a scene, please see the text2d example.
use bevy::{
diagnostic::{DiagnosticsStore, FrameTimeDiagnosticsPlugin},
prelude::*,
};
fn main() {
App::new()
.add_plugins((DefaultPlugins, FrameTimeDiagnosticsPlugin))
.add_systems(Startup, setup)
.add_systems(Update, (text_update_system, text_color_system))
.run();
}
// A unit struct to help identify the FPS UI component, since there may be many Text components
#[derive(Component)]
struct FpsText;
// A unit struct to help identify the color-changing Text component
#[derive(Component)]
struct ColorText;
fn setup(mut commands: Commands, asset_server: Res<AssetServer>) {
// UI camera
commands.spawn(Camera2dBundle::default());
// Text with one section
commands.spawn((
// Create a TextBundle that has a Text with a single section.
TextBundle::from_section(
// Accepts a `String` or any type that converts into a `String`, such as `&str`
"hello\nbevy!",
TextStyle {
// This font is loaded and will be used instead of the default font.
font: asset_server.load("fonts/FiraSans-Bold.ttf"),
font_size: 100.0,
..default()
},
) // Set the justification of the Text
.with_text_justify(JustifyText::Center)
// Set the style of the TextBundle itself.
.with_style(Style {
position_type: PositionType::Absolute,
bottom: Val::Px(5.0),
right: Val::Px(5.0),
..default()
}),
ColorText,
));
// Text with multiple sections
commands.spawn((
// Create a TextBundle that has a Text with a list of sections.
TextBundle::from_sections([
TextSection::new(
"FPS: ",
TextStyle {
// This font is loaded and will be used instead of the default font.
font: asset_server.load("fonts/FiraSans-Bold.ttf"),
font_size: 60.0,
..default()
},
),
TextSection::from_style(if cfg!(feature = "default_font") {
TextStyle {
font_size: 60.0,
color: Color::GOLD,
// If no font is specified, the default font (a minimal subset of FiraMono) will be used.
..default()
}
} else {
// "default_font" feature is unavailable, load a font to use instead.
TextStyle {
font: asset_server.load("fonts/FiraMono-Medium.ttf"),
font_size: 60.0,
color: Color::GOLD,
}
}),
]),
FpsText,
));
#[cfg(feature = "default_font")]
commands.spawn(
// Here we are able to call the `From` method instead of creating a new `TextSection`.
// This will use the default font (a minimal subset of FiraMono) and apply the default styling.
TextBundle::from("From an &str into a TextBundle with the default font!").with_style(
Style {
position_type: PositionType::Absolute,
bottom: Val::Px(5.0),
left: Val::Px(15.0),
..default()
},
),
);
#[cfg(not(feature = "default_font"))]
commands.spawn(
TextBundle::from_section(
"Default font disabled",
TextStyle {
font: asset_server.load("fonts/FiraMono-Medium.ttf"),
..default()
},
)
.with_style(Style {
position_type: PositionType::Absolute,
bottom: Val::Px(5.0),
left: Val::Px(15.0),
..default()
}),
);
}
fn text_color_system(time: Res<Time>, mut query: Query<&mut Text, With<ColorText>>) {
for mut text in &mut query {
let seconds = time.elapsed_seconds();
// Update the color of the first and only section.
text.sections[0].style.color = Color::Rgba {
red: (1.25 * seconds).sin() / 2.0 + 0.5,
green: (0.75 * seconds).sin() / 2.0 + 0.5,
blue: (0.50 * seconds).sin() / 2.0 + 0.5,
alpha: 1.0,
};
}
}
fn text_update_system(
diagnostics: Res<DiagnosticsStore>,
mut query: Query<&mut Text, With<FpsText>>,
) {
for mut text in &mut query {
if let Some(fps) = diagnostics.get(&FrameTimeDiagnosticsPlugin::FPS) {
if let Some(value) = fps.smoothed() {
// Update the value of the second section
text.sections[1].value = format!("{value:.2}");
}
}
}
}