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bevy/examples/ui/size_constraints.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

360 lines
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Rust
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//! Demonstrates how the to use the size constraints to control the size of a UI node.
use bevy::{color::palettes::css::*, prelude::*};
fn main() {
App::new()
.add_plugins(DefaultPlugins)
.add_event::<ButtonActivatedEvent>()
.add_systems(Startup, setup)
.add_systems(Update, (update_buttons, update_radio_buttons_colors))
.run();
}
const ACTIVE_BORDER_COLOR: Color = Color::Srgba(ANTIQUE_WHITE);
const INACTIVE_BORDER_COLOR: Color = Color::BLACK;
const ACTIVE_INNER_COLOR: Color = Color::WHITE;
const INACTIVE_INNER_COLOR: Color = Color::Srgba(NAVY);
const ACTIVE_TEXT_COLOR: Color = Color::BLACK;
const HOVERED_TEXT_COLOR: Color = Color::WHITE;
const UNHOVERED_TEXT_COLOR: Color = Color::srgb(0.5, 0.5, 0.5);
#[derive(Component)]
struct Bar;
#[derive(Copy, Clone, Debug, Component, PartialEq)]
enum Constraint {
FlexBasis,
Width,
MinWidth,
MaxWidth,
}
#[derive(Copy, Clone, Component)]
struct ButtonValue(Val);
#[derive(Event)]
struct ButtonActivatedEvent(Entity);
fn setup(mut commands: Commands, asset_server: Res<AssetServer>) {
// ui camera
commands.spawn(Camera2d);
let text_font = (
TextFont {
font: asset_server.load("fonts/FiraSans-Bold.ttf"),
font_size: 33.0,
..Default::default()
},
TextColor(Color::srgb(0.9, 0.9, 0.9)),
);
commands
.spawn((
Node {
width: Val::Percent(100.0),
height: Val::Percent(100.0),
justify_content: JustifyContent::Center,
align_items: AlignItems::Center,
..default()
},
BackgroundColor(Color::BLACK),
))
.with_children(|parent| {
parent
.spawn(Node {
flex_direction: FlexDirection::Column,
align_items: AlignItems::Center,
justify_content: JustifyContent::Center,
..default()
})
.with_children(|parent| {
parent.spawn((
Text::new("Size Constraints Example"),
text_font.clone(),
Node {
margin: UiRect::bottom(Val::Px(25.)),
..Default::default()
},
));
spawn_bar(parent);
parent
.spawn((
Node {
flex_direction: FlexDirection::Column,
align_items: AlignItems::Stretch,
padding: UiRect::all(Val::Px(10.)),
margin: UiRect::top(Val::Px(50.)),
..default()
},
BackgroundColor(YELLOW.into()),
))
.with_children(|parent| {
for constraint in [
Constraint::MinWidth,
Constraint::FlexBasis,
Constraint::Width,
Constraint::MaxWidth,
] {
spawn_button_row(parent, constraint, text_font.clone());
}
});
});
});
}
fn spawn_bar(parent: &mut ChildBuilder) {
parent
.spawn((
Node {
flex_basis: Val::Percent(100.0),
align_self: AlignSelf::Stretch,
padding: UiRect::all(Val::Px(10.)),
..default()
},
BackgroundColor(YELLOW.into()),
))
.with_children(|parent| {
parent
.spawn((
Node {
align_items: AlignItems::Stretch,
width: Val::Percent(100.),
height: Val::Px(100.),
padding: UiRect::all(Val::Px(4.)),
..default()
},
BackgroundColor(Color::BLACK),
))
.with_children(|parent| {
parent.spawn((Node::default(), BackgroundColor(Color::WHITE), Bar));
});
});
}
fn spawn_button_row(
parent: &mut ChildBuilder,
constraint: Constraint,
text_style: (TextFont, TextColor),
) {
let label = match constraint {
Constraint::FlexBasis => "flex_basis",
Constraint::Width => "size",
Constraint::MinWidth => "min_size",
Constraint::MaxWidth => "max_size",
};
parent
.spawn((
Node {
flex_direction: FlexDirection::Column,
padding: UiRect::all(Val::Px(2.)),
align_items: AlignItems::Stretch,
..default()
},
BackgroundColor(Color::BLACK),
))
.with_children(|parent| {
parent
.spawn(Node {
flex_direction: FlexDirection::Row,
justify_content: JustifyContent::End,
padding: UiRect::all(Val::Px(2.)),
..default()
})
.with_children(|parent| {
// spawn row label
parent
.spawn((Node {
min_width: Val::Px(200.),
max_width: Val::Px(200.),
justify_content: JustifyContent::Center,
align_items: AlignItems::Center,
..default()
},))
.with_child((Text::new(label), text_style.clone()));
// spawn row buttons
parent.spawn(Node::default()).with_children(|parent| {
spawn_button(
parent,
constraint,
ButtonValue(Val::Auto),
"Auto".to_string(),
text_style.clone(),
true,
);
for percent in [0., 25., 50., 75., 100., 125.] {
spawn_button(
parent,
constraint,
ButtonValue(Val::Percent(percent)),
format!("{percent}%"),
text_style.clone(),
false,
);
}
});
});
});
}
fn spawn_button(
parent: &mut ChildBuilder,
constraint: Constraint,
action: ButtonValue,
label: String,
text_style: (TextFont, TextColor),
active: bool,
) {
parent
.spawn((
Button,
Node {
align_items: AlignItems::Center,
justify_content: JustifyContent::Center,
border: UiRect::all(Val::Px(2.)),
margin: UiRect::horizontal(Val::Px(2.)),
..Default::default()
},
BorderColor(if active {
ACTIVE_BORDER_COLOR
} else {
INACTIVE_BORDER_COLOR
}),
constraint,
action,
))
.with_children(|parent| {
parent
.spawn((
Node {
width: Val::Px(100.),
justify_content: JustifyContent::Center,
..default()
},
BackgroundColor(if active {
ACTIVE_INNER_COLOR
} else {
INACTIVE_INNER_COLOR
}),
))
.with_child((
Text::new(label),
text_style.0,
TextColor(if active {
ACTIVE_TEXT_COLOR
} else {
UNHOVERED_TEXT_COLOR
}),
TextLayout::new_with_justify(JustifyText::Center),
));
});
}
fn update_buttons(
mut button_query: Query<
(Entity, &Interaction, &Constraint, &ButtonValue),
Changed<Interaction>,
>,
mut bar_node: Single<&mut Node, With<Bar>>,
mut text_query: Query<&mut TextColor>,
children_query: Query<&Children>,
mut button_activated_event: EventWriter<ButtonActivatedEvent>,
) {
for (button_id, interaction, constraint, value) in button_query.iter_mut() {
match interaction {
Interaction::Pressed => {
button_activated_event.send(ButtonActivatedEvent(button_id));
match constraint {
Constraint::FlexBasis => {
bar_node.flex_basis = value.0;
}
Constraint::Width => {
bar_node.width = value.0;
}
Constraint::MinWidth => {
bar_node.min_width = value.0;
}
Constraint::MaxWidth => {
bar_node.max_width = value.0;
}
}
}
Interaction::Hovered => {
if let Ok(children) = children_query.get(button_id) {
for &child in children {
if let Ok(grand_children) = children_query.get(child) {
for &grandchild in grand_children {
if let Ok(mut text_color) = text_query.get_mut(grandchild) {
if text_color.0 != ACTIVE_TEXT_COLOR {
text_color.0 = HOVERED_TEXT_COLOR;
}
}
}
}
}
}
}
Interaction::None => {
if let Ok(children) = children_query.get(button_id) {
for &child in children {
if let Ok(grand_children) = children_query.get(child) {
for &grandchild in grand_children {
if let Ok(mut text_color) = text_query.get_mut(grandchild) {
if text_color.0 != ACTIVE_TEXT_COLOR {
text_color.0 = UNHOVERED_TEXT_COLOR;
}
}
}
}
}
}
}
}
}
}
fn update_radio_buttons_colors(
mut event_reader: EventReader<ButtonActivatedEvent>,
button_query: Query<(Entity, &Constraint, &Interaction)>,
mut border_query: Query<&mut BorderColor>,
mut color_query: Query<&mut BackgroundColor>,
mut text_query: Query<&mut TextColor>,
children_query: Query<&Children>,
) {
for &ButtonActivatedEvent(button_id) in event_reader.read() {
let (_, target_constraint, _) = button_query.get(button_id).unwrap();
for (id, constraint, interaction) in button_query.iter() {
if target_constraint == constraint {
let (border_color, inner_color, label_color) = if id == button_id {
(ACTIVE_BORDER_COLOR, ACTIVE_INNER_COLOR, ACTIVE_TEXT_COLOR)
} else {
(
INACTIVE_BORDER_COLOR,
INACTIVE_INNER_COLOR,
if matches!(interaction, Interaction::Hovered) {
HOVERED_TEXT_COLOR
} else {
UNHOVERED_TEXT_COLOR
},
)
};
border_query.get_mut(id).unwrap().0 = border_color;
for &child in children_query.get(id).into_iter().flatten() {
color_query.get_mut(child).unwrap().0 = inner_color;
for &grandchild in children_query.get(child).into_iter().flatten() {
if let Ok(mut text_color) = text_query.get_mut(grandchild) {
text_color.0 = label_color;
}
}
}
}
}
}
}
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