This example is running in WebGL2 and should work in most browsers. You can check the WebGPU examples here.
z_index.rs:
//! Demonstrates how to use the z-index component on UI nodes to control their relative depth
//!
//! It uses colored boxes with different z-index values to demonstrate how it can affect the order of
//! depth of nodes compared to their siblings, but also compared to the entire UI.
use bevy::{
color::palettes::basic::{BLUE, GRAY, LIME, PURPLE, RED, YELLOW},
prelude::*,
};
fn main() {
App::new()
.insert_resource(ClearColor(Color::BLACK))
.add_plugins(DefaultPlugins)
.add_systems(Startup, setup)
.run();
}
fn setup(mut commands: Commands) {
commands.spawn(Camera2dBundle::default());
// spawn the container with default z-index.
// the default z-index value is `ZIndex::Local(0)`.
// because this is a root UI node, using local or global values will do the same thing.
commands
.spawn(NodeBundle {
style: Style {
width: Val::Percent(100.),
height: Val::Percent(100.),
align_items: AlignItems::Center,
justify_content: JustifyContent::Center,
..default()
},
..default()
})
.with_children(|parent| {
parent
.spawn(NodeBundle {
background_color: GRAY.into(),
style: Style {
width: Val::Px(180.0),
height: Val::Px(100.0),
..default()
},
..default()
})
.with_children(|parent| {
// spawn a node with default z-index.
parent.spawn(NodeBundle {
background_color: RED.into(),
style: Style {
position_type: PositionType::Absolute,
left: Val::Px(10.0),
bottom: Val::Px(40.0),
width: Val::Px(100.0),
height: Val::Px(50.0),
..default()
},
..default()
});
// spawn a node with a positive local z-index of 2.
// it will show above other nodes in the gray container.
parent.spawn(NodeBundle {
z_index: ZIndex::Local(2),
background_color: BLUE.into(),
style: Style {
position_type: PositionType::Absolute,
left: Val::Px(45.0),
bottom: Val::Px(30.0),
width: Val::Px(100.),
height: Val::Px(50.),
..default()
},
..default()
});
// spawn a node with a negative local z-index.
// it will show under other nodes in the gray container.
parent.spawn(NodeBundle {
z_index: ZIndex::Local(-1),
background_color: LIME.into(),
style: Style {
position_type: PositionType::Absolute,
left: Val::Px(70.0),
bottom: Val::Px(20.0),
width: Val::Px(100.),
height: Val::Px(75.),
..default()
},
..default()
});
// spawn a node with a positive global z-index of 1.
// it will show above all other nodes, because it's the highest global z-index in this example.
// by default, boxes all share the global z-index of 0 that the gray container is added to.
parent.spawn(NodeBundle {
z_index: ZIndex::Global(1),
background_color: PURPLE.into(),
style: Style {
position_type: PositionType::Absolute,
left: Val::Px(15.0),
bottom: Val::Px(10.0),
width: Val::Px(100.),
height: Val::Px(60.),
..default()
},
..default()
});
// spawn a node with a negative global z-index of -1.
// this will show under all other nodes including its parent, because it's the lowest global z-index
// in this example.
parent.spawn(NodeBundle {
z_index: ZIndex::Global(-1),
background_color: YELLOW.into(),
style: Style {
position_type: PositionType::Absolute,
left: Val::Px(-15.0),
bottom: Val::Px(-15.0),
width: Val::Px(100.),
height: Val::Px(125.),
..default()
},
..default()
});
});
});
}