bevy/examples/2d/2d_shapes.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

86 lines
2.5 KiB
Rust

//! Shows how to render simple primitive shapes with a single color.
//!
//! You can toggle wireframes with the space bar except on wasm. Wasm does not support
//! `POLYGON_MODE_LINE` on the gpu.
use bevy::prelude::*;
#[cfg(not(target_arch = "wasm32"))]
use bevy::sprite::{Wireframe2dConfig, Wireframe2dPlugin};
fn main() {
let mut app = App::new();
app.add_plugins((
DefaultPlugins,
#[cfg(not(target_arch = "wasm32"))]
Wireframe2dPlugin,
))
.add_systems(Startup, setup);
#[cfg(not(target_arch = "wasm32"))]
app.add_systems(Update, toggle_wireframe);
app.run();
}
const X_EXTENT: f32 = 900.;
fn setup(
mut commands: Commands,
mut meshes: ResMut<Assets<Mesh>>,
mut materials: ResMut<Assets<ColorMaterial>>,
) {
commands.spawn(Camera2d);
let shapes = [
meshes.add(Circle::new(50.0)),
meshes.add(CircularSector::new(50.0, 1.0)),
meshes.add(CircularSegment::new(50.0, 1.25)),
meshes.add(Ellipse::new(25.0, 50.0)),
meshes.add(Annulus::new(25.0, 50.0)),
meshes.add(Capsule2d::new(25.0, 50.0)),
meshes.add(Rhombus::new(75.0, 100.0)),
meshes.add(Rectangle::new(50.0, 100.0)),
meshes.add(RegularPolygon::new(50.0, 6)),
meshes.add(Triangle2d::new(
Vec2::Y * 50.0,
Vec2::new(-50.0, -50.0),
Vec2::new(50.0, -50.0),
)),
];
let num_shapes = shapes.len();
for (i, shape) in shapes.into_iter().enumerate() {
// Distribute colors evenly across the rainbow.
let color = Color::hsl(360. * i as f32 / num_shapes as f32, 0.95, 0.7);
commands.spawn((
Mesh2d(shape),
MeshMaterial2d(materials.add(color)),
Transform::from_xyz(
// Distribute shapes from -X_EXTENT/2 to +X_EXTENT/2.
-X_EXTENT / 2. + i as f32 / (num_shapes - 1) as f32 * X_EXTENT,
0.0,
0.0,
),
));
}
#[cfg(not(target_arch = "wasm32"))]
commands.spawn((
Text::new("Press space to toggle wireframes"),
Node {
position_type: PositionType::Absolute,
top: Val::Px(12.0),
left: Val::Px(12.0),
..default()
},
));
}
#[cfg(not(target_arch = "wasm32"))]
fn toggle_wireframe(
mut wireframe_config: ResMut<Wireframe2dConfig>,
keyboard: Res<ButtonInput<KeyCode>>,
) {
if keyboard.just_pressed(KeyCode::Space) {
wireframe_config.global = !wireframe_config.global;
}
}