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font_atlas_debug.rs
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font_atlas_debug.rs
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//! This example illustrates how `FontAtlas`'s are populated.
//! Bevy uses `FontAtlas`'s under the hood to optimize text rendering.
use bevy::{prelude::*, text::FontAtlasSets};
fn main() {
App::new()
.init_resource::<State>()
.insert_resource(ClearColor(Color::BLACK))
.add_plugins(DefaultPlugins)
.add_systems(Startup, setup)
.add_systems(Update, (text_update_system, atlas_render_system))
.run();
}
#[derive(Resource)]
struct State {
atlas_count: u32,
handle: Handle<Font>,
timer: Timer,
}
impl Default for State {
fn default() -> Self {
Self {
atlas_count: 0,
handle: Handle::default(),
timer: Timer::from_seconds(0.05, TimerMode::Repeating),
}
}
}
fn atlas_render_system(
mut commands: Commands,
mut state: ResMut<State>,
font_atlas_sets: Res<FontAtlasSets>,
) {
if let Some(set) = font_atlas_sets.get(&state.handle) {
if let Some((_size, font_atlas)) = set.iter().next() {
let x_offset = state.atlas_count as f32;
if state.atlas_count == font_atlas.len() as u32 {
return;
}
let font_atlas = &font_atlas[state.atlas_count as usize];
state.atlas_count += 1;
commands.spawn(ImageBundle {
image: font_atlas.texture.clone().into(),
style: Style {
position_type: PositionType::Absolute,
top: Val::ZERO,
left: Val::Px(512.0 * x_offset),
..default()
},
..default()
});
}
}
}
fn text_update_system(mut state: ResMut<State>, time: Res<Time>, mut query: Query<&mut Text>) {
if state.timer.tick(time.delta()).finished() {
for mut text in &mut query {
let c = rand::random::<u8>() as char;
let string = &mut text.sections[0].value;
if !string.contains(c) {
string.push(c);
}
}
state.timer.reset();
}
}
fn setup(mut commands: Commands, asset_server: Res<AssetServer>, mut state: ResMut<State>) {
let font_handle = asset_server.load("fonts/FiraSans-Bold.ttf");
state.handle = font_handle.clone();
commands.spawn(Camera2dBundle::default());
commands
.spawn(NodeBundle {
background_color: Color::NONE.into(),
style: Style {
position_type: PositionType::Absolute,
bottom: Val::ZERO,
..default()
},
..default()
})
.with_children(|parent| {
parent.spawn(TextBundle::from_section(
"a",
TextStyle {
font: font_handle,
font_size: 60.0,
color: Color::YELLOW,
},
));
});
}