This example is running in WebGL2 and should work in most browsers. You can check the WebGPU examples here.
//! Demonstrates how Display and Visibility work in the UI.
use bevy::{
color::palettes::css::{DARK_CYAN, DARK_GRAY, YELLOW},
prelude::*,
winit::WinitSettings,
};
const PALETTE: [&str; 4] = ["27496D", "466B7A", "669DB3", "ADCBE3"];
const HIDDEN_COLOR: Color = Color::srgb(1.0, 0.7, 0.7);
fn main() {
App::new()
.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,
(
buttons_handler::<Display>,
buttons_handler::<Visibility>,
text_hover,
),
)
.run();
}
#[derive(Component)]
struct Target<T> {
id: Entity,
phantom: std::marker::PhantomData<T>,
}
impl<T> Target<T> {
fn new(id: Entity) -> Self {
Self {
id,
phantom: std::marker::PhantomData,
}
}
}
trait TargetUpdate {
type TargetComponent: Component;
const NAME: &'static str;
fn update_target(&self, target: &mut Self::TargetComponent) -> String;
}
impl TargetUpdate for Target<Display> {
type TargetComponent = Node;
const NAME: &'static str = "Display";
fn update_target(&self, node: &mut Self::TargetComponent) -> String {
node.display = match node.display {
Display::Flex => Display::None,
Display::None => Display::Flex,
Display::Block | Display::Grid => unreachable!(),
};
format!("{}::{:?} ", Self::NAME, node.display)
}
}
impl TargetUpdate for Target<Visibility> {
type TargetComponent = Visibility;
const NAME: &'static str = "Visibility";
fn update_target(&self, visibility: &mut Self::TargetComponent) -> String {
*visibility = match *visibility {
Visibility::Inherited => Visibility::Visible,
Visibility::Visible => Visibility::Hidden,
Visibility::Hidden => Visibility::Inherited,
};
format!("{}::{visibility:?}", Self::NAME)
}
}
fn setup(mut commands: Commands, asset_server: Res<AssetServer>) {
let palette: [Color; 4] = PALETTE.map(|hex| Srgba::hex(hex).unwrap().into());
let text_font = TextFont {
font: asset_server.load("fonts/FiraSans-Bold.ttf"),
..default()
};
commands.spawn(Camera2d);
commands
.spawn((
Node {
width: Val::Percent(100.),
height: Val::Percent(100.),
flex_direction: FlexDirection::Column,
align_items: AlignItems::Center,
justify_content: JustifyContent::SpaceEvenly,
..Default::default()
},
BackgroundColor(Color::BLACK),
))
.with_children(|parent| {
parent.spawn((
Text::new("Use the panel on the right to change the Display and Visibility properties for the respective nodes of the panel on the left"),
text_font.clone(),
TextLayout::new_with_justify(JustifyText::Center),
Node {
margin: UiRect::bottom(Val::Px(10.)),
..Default::default()
},
));
parent
.spawn(Node {
width: Val::Percent(100.),
..default()
})
.with_children(|parent| {
let mut target_ids = vec![];
parent
.spawn(Node {
width: Val::Percent(50.),
height: Val::Px(520.),
justify_content: JustifyContent::Center,
..default()
})
.with_children(|parent| {
target_ids = spawn_left_panel(parent, &palette);
});
parent
.spawn(Node {
width: Val::Percent(50.),
justify_content: JustifyContent::Center,
..default()
})
.with_children(|parent| {
spawn_right_panel(parent, text_font, &palette, target_ids);
});
});
parent
.spawn(Node {
flex_direction: FlexDirection::Row,
align_items: AlignItems::Start,
justify_content: JustifyContent::Start,
column_gap: Val::Px(10.),
..default()
})
.with_children(|builder| {
let text_font = TextFont {
font: asset_server.load("fonts/FiraSans-Bold.ttf"),
..default()
};
builder.spawn((
Text::new("Display::None\nVisibility::Hidden\nVisibility::Inherited"),
text_font.clone(),
TextColor(HIDDEN_COLOR),
TextLayout::new_with_justify(JustifyText::Center),
));
builder.spawn((
Text::new("-\n-\n-"),
text_font.clone(),
TextColor(DARK_GRAY.into()),
TextLayout::new_with_justify(JustifyText::Center),
));
builder.spawn((Text::new("The UI Node and its descendants will not be visible and will not be allotted any space in the UI layout.\nThe UI Node will not be visible but will still occupy space in the UI layout.\nThe UI node will inherit the visibility property of its parent. If it has no parent it will be visible."), text_font));
});
});
}
fn spawn_left_panel(builder: &mut ChildBuilder, palette: &[Color; 4]) -> Vec<Entity> {
let mut target_ids = vec![];
builder
.spawn((
Node {
padding: UiRect::all(Val::Px(10.)),
..default()
},
BackgroundColor(Color::WHITE),
))
.with_children(|parent| {
parent
.spawn((Node::default(), BackgroundColor(Color::BLACK)))
.with_children(|parent| {
let id = parent
.spawn((
Node {
align_items: AlignItems::FlexEnd,
justify_content: JustifyContent::FlexEnd,
..default()
},
BackgroundColor(palette[0]),
Outline {
width: Val::Px(4.),
color: DARK_CYAN.into(),
offset: Val::Px(10.),
},
))
.with_children(|parent| {
parent.spawn(Node {
width: Val::Px(100.),
height: Val::Px(500.),
..default()
});
let id = parent
.spawn((
Node {
height: Val::Px(400.),
align_items: AlignItems::FlexEnd,
justify_content: JustifyContent::FlexEnd,
..default()
},
BackgroundColor(palette[1]),
))
.with_children(|parent| {
parent.spawn(Node {
width: Val::Px(100.),
height: Val::Px(400.),
..default()
});
let id = parent
.spawn((
Node {
height: Val::Px(300.),
align_items: AlignItems::FlexEnd,
justify_content: JustifyContent::FlexEnd,
..default()
},
BackgroundColor(palette[2]),
))
.with_children(|parent| {
parent.spawn(Node {
width: Val::Px(100.),
height: Val::Px(300.),
..default()
});
let id = parent
.spawn((
Node {
width: Val::Px(200.),
height: Val::Px(200.),
..default()
},
BackgroundColor(palette[3]),
))
.id();
target_ids.push(id);
})
.id();
target_ids.push(id);
})
.id();
target_ids.push(id);
})
.id();
target_ids.push(id);
});
});
target_ids
}
fn spawn_right_panel(
parent: &mut ChildBuilder,
text_font: TextFont,
palette: &[Color; 4],
mut target_ids: Vec<Entity>,
) {
let spawn_buttons = |parent: &mut ChildBuilder, target_id| {
spawn_button::<Display>(parent, text_font.clone(), target_id);
spawn_button::<Visibility>(parent, text_font.clone(), target_id);
};
parent
.spawn((
Node {
padding: UiRect::all(Val::Px(10.)),
..default()
},
BackgroundColor(Color::WHITE),
))
.with_children(|parent| {
parent
.spawn((
Node {
width: Val::Px(500.),
height: Val::Px(500.),
flex_direction: FlexDirection::Column,
align_items: AlignItems::FlexEnd,
justify_content: JustifyContent::SpaceBetween,
padding: UiRect {
left: Val::Px(5.),
top: Val::Px(5.),
..default()
},
..default()
},
BackgroundColor(palette[0]),
Outline {
width: Val::Px(4.),
color: DARK_CYAN.into(),
offset: Val::Px(10.),
},
))
.with_children(|parent| {
spawn_buttons(parent, target_ids.pop().unwrap());
parent
.spawn((
Node {
width: Val::Px(400.),
height: Val::Px(400.),
flex_direction: FlexDirection::Column,
align_items: AlignItems::FlexEnd,
justify_content: JustifyContent::SpaceBetween,
padding: UiRect {
left: Val::Px(5.),
top: Val::Px(5.),
..default()
},
..default()
},
BackgroundColor(palette[1]),
))
.with_children(|parent| {
spawn_buttons(parent, target_ids.pop().unwrap());
parent
.spawn((
Node {
width: Val::Px(300.),
height: Val::Px(300.),
flex_direction: FlexDirection::Column,
align_items: AlignItems::FlexEnd,
justify_content: JustifyContent::SpaceBetween,
padding: UiRect {
left: Val::Px(5.),
top: Val::Px(5.),
..default()
},
..default()
},
BackgroundColor(palette[2]),
))
.with_children(|parent| {
spawn_buttons(parent, target_ids.pop().unwrap());
parent
.spawn((
Node {
width: Val::Px(200.),
height: Val::Px(200.),
align_items: AlignItems::FlexStart,
justify_content: JustifyContent::SpaceBetween,
flex_direction: FlexDirection::Column,
padding: UiRect {
left: Val::Px(5.),
top: Val::Px(5.),
..default()
},
..default()
},
BackgroundColor(palette[3]),
))
.with_children(|parent| {
spawn_buttons(parent, target_ids.pop().unwrap());
parent.spawn(Node {
width: Val::Px(100.),
height: Val::Px(100.),
..default()
});
});
});
});
});
});
}
fn spawn_button<T>(parent: &mut ChildBuilder, text_font: TextFont, target: Entity)
where
T: Default + std::fmt::Debug + Send + Sync + 'static,
Target<T>: TargetUpdate,
{
parent
.spawn((
Button,
Node {
align_self: AlignSelf::FlexStart,
padding: UiRect::axes(Val::Px(5.), Val::Px(1.)),
..default()
},
BackgroundColor(Color::BLACK.with_alpha(0.5)),
Target::<T>::new(target),
))
.with_children(|builder| {
builder.spawn((
Text(format!("{}::{:?}", Target::<T>::NAME, T::default())),
text_font,
TextLayout::new_with_justify(JustifyText::Center),
));
});
}
fn buttons_handler<T>(
mut left_panel_query: Query<&mut <Target<T> as TargetUpdate>::TargetComponent>,
mut visibility_button_query: Query<(&Target<T>, &Interaction, &Children), Changed<Interaction>>,
mut text_query: Query<(&mut Text, &mut TextColor)>,
) where
T: Send + Sync,
Target<T>: TargetUpdate + Component,
{
for (target, interaction, children) in visibility_button_query.iter_mut() {
if matches!(interaction, Interaction::Pressed) {
let mut target_value = left_panel_query.get_mut(target.id).unwrap();
for &child in children {
if let Ok((mut text, mut text_color)) = text_query.get_mut(child) {
**text = target.update_target(target_value.as_mut());
text_color.0 = if text.contains("None") || text.contains("Hidden") {
Color::srgb(1.0, 0.7, 0.7)
} else {
Color::WHITE
};
}
}
}
}
}
fn text_hover(
mut button_query: Query<(&Interaction, &mut BackgroundColor, &Children), Changed<Interaction>>,
mut text_query: Query<(&Text, &mut TextColor)>,
) {
for (interaction, mut color, children) in button_query.iter_mut() {
match interaction {
Interaction::Hovered => {
*color = Color::BLACK.with_alpha(0.6).into();
for &child in children {
if let Ok((_, mut text_color)) = text_query.get_mut(child) {
// Bypass change detection to avoid recomputation of the text when only changing the color
text_color.bypass_change_detection().0 = YELLOW.into();
}
}
}
_ => {
*color = Color::BLACK.with_alpha(0.5).into();
for &child in children {
if let Ok((text, mut text_color)) = text_query.get_mut(child) {
text_color.bypass_change_detection().0 =
if text.contains("None") || text.contains("Hidden") {
HIDDEN_COLOR
} else {
Color::WHITE
};
}
}
}
}
}
}