bevy/examples/window/multiple_windows.rs
Carter Anderson 015f2c69ca
Merge Style properties into Node. Use ComputedNode for computed properties. (#15975)
# Objective

Continue improving the user experience of our UI Node API in the
direction specified by [Bevy's Next Generation Scene / UI
System](https://github.com/bevyengine/bevy/discussions/14437)

## Solution

As specified in the document above, merge `Style` fields into `Node`,
and move "computed Node fields" into `ComputedNode` (I chose this name
over something like `ComputedNodeLayout` because it currently contains
more than just layout info. If we want to break this up / rename these
concepts, lets do that in a separate PR). `Style` has been removed.

This accomplishes a number of goals:

## Ergonomics wins

Specifying both `Node` and `Style` is now no longer required for
non-default styles

Before:
```rust
commands.spawn((
    Node::default(),
    Style {
        width:  Val::Px(100.),
        ..default()
    },
));
```

After:

```rust
commands.spawn(Node {
    width:  Val::Px(100.),
    ..default()
});
```

## Conceptual clarity

`Style` was never a comprehensive "style sheet". It only defined "core"
style properties that all `Nodes` shared. Any "styled property" that
couldn't fit that mold had to be in a separate component. A "real" style
system would style properties _across_ components (`Node`, `Button`,
etc). We have plans to build a true style system (see the doc linked
above).

By moving the `Style` fields to `Node`, we fully embrace `Node` as the
driving concept and remove the "style system" confusion.

## Next Steps

* Consider identifying and splitting out "style properties that aren't
core to Node". This should not happen for Bevy 0.15.

---

## Migration Guide

Move any fields set on `Style` into `Node` and replace all `Style`
component usage with `Node`.

Before:
```rust
commands.spawn((
    Node::default(),
    Style {
        width:  Val::Px(100.),
        ..default()
    },
));
```

After:

```rust
commands.spawn(Node {
    width:  Val::Px(100.),
    ..default()
});
```

For any usage of the "computed node properties" that used to live on
`Node`, use `ComputedNode` instead:

Before:
```rust
fn system(nodes: Query<&Node>) {
    for node in &nodes {
        let computed_size = node.size();
    }
}
```

After:
```rust
fn system(computed_nodes: Query<&ComputedNode>) {
    for computed_node in &computed_nodes {
        let computed_size = computed_node.size();
    }
}
```
2024-10-18 22:25:33 +00:00

69 lines
2 KiB
Rust

//! Uses two windows to visualize a 3D model from different angles.
use bevy::{prelude::*, render::camera::RenderTarget, window::WindowRef};
fn main() {
App::new()
// By default, a primary window gets spawned by `WindowPlugin`, contained in `DefaultPlugins`
.add_plugins(DefaultPlugins)
.add_systems(Startup, setup_scene)
.run();
}
fn setup_scene(mut commands: Commands, asset_server: Res<AssetServer>) {
// add entities to the world
commands.spawn(SceneRoot(
asset_server.load(GltfAssetLabel::Scene(0).from_asset("models/torus/torus.gltf")),
));
// light
commands.spawn((
DirectionalLight::default(),
Transform::from_xyz(3.0, 3.0, 3.0).looking_at(Vec3::ZERO, Vec3::Y),
));
let first_window_camera = commands
.spawn((
Camera3d::default(),
Transform::from_xyz(0.0, 0.0, 6.0).looking_at(Vec3::ZERO, Vec3::Y),
))
.id();
// Spawn a second window
let second_window = commands
.spawn(Window {
title: "Second window".to_owned(),
..default()
})
.id();
let second_window_camera = commands
.spawn((
Camera3d::default(),
Transform::from_xyz(6.0, 0.0, 0.0).looking_at(Vec3::ZERO, Vec3::Y),
Camera {
target: RenderTarget::Window(WindowRef::Entity(second_window)),
..default()
},
))
.id();
let node = Node {
position_type: PositionType::Absolute,
top: Val::Px(12.0),
left: Val::Px(12.0),
..default()
};
commands.spawn((
Text::new("First window"),
node.clone(),
// Since we are using multiple cameras, we need to specify which camera UI should be rendered to
TargetCamera(first_window_camera),
));
commands.spawn((
Text::new("Second window"),
node,
TargetCamera(second_window_camera),
));
}