bevy/examples/ui/ui_texture_atlas.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

77 lines
2.6 KiB
Rust

//! This example illustrates how to use `TextureAtlases` within ui
use bevy::{color::palettes::css::*, prelude::*, winit::WinitSettings};
fn main() {
App::new()
.add_plugins(DefaultPlugins.set(
// This sets image filtering to nearest
// This is done to prevent textures with low resolution (e.g. pixel art) from being blurred
// by linear filtering.
ImagePlugin::default_nearest(),
))
// 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, increment_atlas_index)
.run();
}
fn setup(
mut commands: Commands,
asset_server: Res<AssetServer>,
mut texture_atlases: ResMut<Assets<TextureAtlasLayout>>,
) {
// Camera
commands.spawn(Camera2d);
let text_font = TextFont::default();
let texture_handle = asset_server.load("textures/rpg/chars/gabe/gabe-idle-run.png");
let texture_atlas = TextureAtlasLayout::from_grid(UVec2::splat(24), 7, 1, None, None);
let texture_atlas_handle = texture_atlases.add(texture_atlas);
// root node
commands
.spawn(Node {
width: Val::Percent(100.0),
height: Val::Percent(100.0),
flex_direction: FlexDirection::Column,
justify_content: JustifyContent::Center,
align_items: AlignItems::Center,
row_gap: Val::Px(text_font.font_size * 2.),
..default()
})
.with_children(|parent| {
parent.spawn((
UiImage::new(texture_handle),
Node {
width: Val::Px(256.),
height: Val::Px(256.),
..default()
},
BackgroundColor(ANTIQUE_WHITE.into()),
TextureAtlas::from(texture_atlas_handle),
Outline::new(Val::Px(8.0), Val::ZERO, CRIMSON.into()),
));
parent
.spawn((Text::new("press "), text_font.clone()))
.with_child((
TextSpan::new("space"),
TextColor(YELLOW.into()),
text_font.clone(),
))
.with_child((TextSpan::new(" to advance frames"), text_font));
});
}
fn increment_atlas_index(
mut atlas_images: Query<&mut TextureAtlas>,
keyboard: Res<ButtonInput<KeyCode>>,
) {
if keyboard.just_pressed(KeyCode::Space) {
for mut atlas_image in &mut atlas_images {
atlas_image.index = (atlas_image.index + 1) % 6;
}
}
}