//! This example illustrates the various features of Bevy UI. use bevy::{ a11y::{ accesskit::{NodeBuilder, Role}, AccessibilityNode, }, color::palettes::basic::LIME, input::mouse::{MouseScrollUnit, MouseWheel}, picking::focus::HoverMap, prelude::*, winit::WinitSettings, }; fn main() { let mut app = App::new(); app.add_plugins(DefaultPlugins) // Only run the app when there is user input. This will significantly reduce CPU/GPU use. .insert_resource(WinitSettings::desktop_app()) .add_systems(Startup, setup) .add_systems(Update, update_scroll_position); #[cfg(feature = "bevy_dev_tools")] { app.add_plugins(bevy::dev_tools::ui_debug_overlay::DebugUiPlugin) .add_systems(Update, toggle_overlay); } app.run(); } fn setup(mut commands: Commands, asset_server: Res) { // Camera commands.spawn((Camera2d, IsDefaultUiCamera, UiBoxShadowSamples(6))); // root node commands .spawn(Node { width: Val::Percent(100.0), height: Val::Percent(100.0), justify_content: JustifyContent::SpaceBetween, ..default() }) .insert(PickingBehavior::IGNORE) .with_children(|parent| { // left vertical fill (border) parent .spawn(( Node { width: Val::Px(200.), border: UiRect::all(Val::Px(2.)), ..default() }, BackgroundColor(Color::srgb(0.65, 0.65, 0.65)), )) .with_children(|parent| { // left vertical fill (content) parent .spawn(( Node { width: Val::Percent(100.), flex_direction: FlexDirection::Column, padding: UiRect::all(Val::Px(5.)), row_gap: Val::Px(5.), ..default() }, BackgroundColor(Color::srgb(0.15, 0.15, 0.15)), )) .with_children(|parent| { // text parent.spawn(( Text::new("Text Example"), TextFont { font: asset_server.load("fonts/FiraSans-Bold.ttf"), font_size: 25.0, ..default() }, // Because this is a distinct label widget and // not button/list item text, this is necessary // for accessibility to treat the text accordingly. Label, )); #[cfg(feature = "bevy_dev_tools")] // Debug overlay text parent.spawn(( Text::new("Press Space to enable debug outlines."), TextFont { font: asset_server.load("fonts/FiraSans-Bold.ttf"), ..default() }, Label, )); #[cfg(not(feature = "bevy_dev_tools"))] parent.spawn(( Text::new("Try enabling feature \"bevy_dev_tools\"."), TextFont { font: asset_server.load("fonts/FiraSans-Bold.ttf"), ..default() }, Label, )); }); }); // right vertical fill parent .spawn(Node { flex_direction: FlexDirection::Column, justify_content: JustifyContent::Center, align_items: AlignItems::Center, width: Val::Px(200.), ..default() }) .with_children(|parent| { // Title parent.spawn(( Text::new("Scrolling list"), TextFont { font: asset_server.load("fonts/FiraSans-Bold.ttf"), font_size: 21., ..default() }, Label, )); // Scrolling list parent .spawn(( Node { flex_direction: FlexDirection::Column, align_self: AlignSelf::Stretch, height: Val::Percent(50.), overflow: Overflow::scroll_y(), ..default() }, BackgroundColor(Color::srgb(0.10, 0.10, 0.10)), )) .with_children(|parent| { // List items for i in 0..25 { parent .spawn(( Text(format!("Item {i}")), TextFont { font: asset_server.load("fonts/FiraSans-Bold.ttf"), ..default() }, Label, AccessibilityNode(NodeBuilder::new(Role::ListItem)), )) .insert(PickingBehavior { should_block_lower: false, ..default() }); } }); }); parent .spawn(( Node { width: Val::Px(200.0), height: Val::Px(200.0), position_type: PositionType::Absolute, left: Val::Px(210.), bottom: Val::Px(10.), border: UiRect::all(Val::Px(20.)), ..default() }, BorderColor(LIME.into()), BackgroundColor(Color::srgb(0.4, 0.4, 1.)), )) .with_children(|parent| { parent.spawn(( Node { width: Val::Percent(100.0), height: Val::Percent(100.0), ..default() }, BackgroundColor(Color::srgb(0.8, 0.8, 1.)), )); }); let shadow = BoxShadow { color: Color::BLACK.with_alpha(0.5), blur_radius: Val::Px(2.), x_offset: Val::Px(10.), y_offset: Val::Px(10.), ..Default::default() }; // render order test: reddest in the back, whitest in the front (flex center) parent .spawn(Node { width: Val::Percent(100.0), height: Val::Percent(100.0), position_type: PositionType::Absolute, align_items: AlignItems::Center, justify_content: JustifyContent::Center, ..default() }) .insert(PickingBehavior::IGNORE) .with_children(|parent| { parent .spawn(( Node { width: Val::Px(100.0), height: Val::Px(100.0), ..default() }, BackgroundColor(Color::srgb(1.0, 0.0, 0.)), shadow, )) .with_children(|parent| { parent.spawn(( Node { // Take the size of the parent node. width: Val::Percent(100.0), height: Val::Percent(100.0), position_type: PositionType::Absolute, left: Val::Px(20.), bottom: Val::Px(20.), ..default() }, BackgroundColor(Color::srgb(1.0, 0.3, 0.3)), shadow, )); parent.spawn(( Node { width: Val::Percent(100.0), height: Val::Percent(100.0), position_type: PositionType::Absolute, left: Val::Px(40.), bottom: Val::Px(40.), ..default() }, BackgroundColor(Color::srgb(1.0, 0.5, 0.5)), shadow, )); parent.spawn(( Node { width: Val::Percent(100.0), height: Val::Percent(100.0), position_type: PositionType::Absolute, left: Val::Px(60.), bottom: Val::Px(60.), ..default() }, BackgroundColor(Color::srgb(0.0, 0.7, 0.7)), shadow, )); // alpha test parent.spawn(( Node { width: Val::Percent(100.0), height: Val::Percent(100.0), position_type: PositionType::Absolute, left: Val::Px(80.), bottom: Val::Px(80.), ..default() }, BackgroundColor(Color::srgba(1.0, 0.9, 0.9, 0.4)), BoxShadow { color: Color::BLACK.with_alpha(0.3), ..shadow }, )); }); }); // bevy logo (flex center) parent .spawn(Node { width: Val::Percent(100.0), position_type: PositionType::Absolute, justify_content: JustifyContent::Center, align_items: AlignItems::FlexStart, ..default() }) .with_children(|parent| { // bevy logo (image) parent .spawn(( UiImage::new(asset_server.load("branding/bevy_logo_dark_big.png")), Node { width: Val::Px(500.0), height: Val::Px(125.0), margin: UiRect::top(Val::VMin(5.)), ..default() }, )) .with_children(|parent| { // alt text // This UI node takes up no space in the layout and the `Text` component is used by the accessibility module // and is not rendered. parent.spawn(( Node { display: Display::None, ..default() }, Text::new("Bevy logo"), )); }); }); }); } #[cfg(feature = "bevy_dev_tools")] // The system that will enable/disable the debug outlines around the nodes fn toggle_overlay( input: Res>, mut options: ResMut, ) { info_once!("The debug outlines are enabled, press Space to turn them on/off"); if input.just_pressed(KeyCode::Space) { // The toggle method will enable the debug_overlay if disabled and disable if enabled options.toggle(); } } /// Updates the scroll position of scrollable nodes in response to mouse input pub fn update_scroll_position( mut mouse_wheel_events: EventReader, hover_map: Res, mut scrolled_node_query: Query<&mut ScrollPosition>, keyboard_input: Res>, ) { for mouse_wheel_event in mouse_wheel_events.read() { let (mut dx, mut dy) = match mouse_wheel_event.unit { MouseScrollUnit::Line => (mouse_wheel_event.x * 20., mouse_wheel_event.y * 20.), MouseScrollUnit::Pixel => (mouse_wheel_event.x, mouse_wheel_event.y), }; if keyboard_input.pressed(KeyCode::ShiftLeft) || keyboard_input.pressed(KeyCode::ShiftRight) { std::mem::swap(&mut dx, &mut dy); } for (_pointer, pointer_map) in hover_map.iter() { for (entity, _hit) in pointer_map.iter() { if let Ok(mut scroll_position) = scrolled_node_query.get_mut(*entity) { scroll_position.offset_x -= dx; scroll_position.offset_y -= dy; } } } } }