d8fa57bd7b
# Objective In #17905 we swapped to a named field on `ChildOf` to help resolve variable naming ambiguity of child vs parent (ex: `child_of.parent` clearly reads as "I am accessing the parent of the child_of relationship", whereas `child_of.0` is less clear). Unfortunately this has the side effect of making initialization less ideal. `ChildOf { parent }` reads just as well as `ChildOf(parent)`, but `ChildOf { parent: root }` doesn't read nearly as well as `ChildOf(root)`. ## Solution Move back to `ChildOf(pub Entity)` but add a `child_of.parent()` function and use it for all accesses. The downside here is that users are no longer "forced" to access the parent field with `parent` nomenclature, but I think this strikes the right balance. Take a look at the diff. I think the results provide strong evidence for this change. Initialization has the benefit of reading much better _and_ of taking up significantly less space, as many lines go from 3 to 1, and we're cutting out a bunch of syntax in some cases. Sadly I do think this should land in 0.16 as the cost of doing this _after_ the relationships migration is high.
126 lines
4.2 KiB
Rust
126 lines
4.2 KiB
Rust
//! This example demonstrates the use of Ghost Nodes.
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//!
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//! UI layout will ignore ghost nodes, and treat their children as if they were direct descendants of the first non-ghost ancestor.
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//!
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//! # Warning
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//!
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//! This is an experimental feature, and should be used with caution,
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//! especially in concert with 3rd party plugins or systems that may not be aware of ghost nodes.
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//!
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//! In order to use [`GhostNode`]s you must enable the `ghost_nodes` feature flag.
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use bevy::{prelude::*, ui::experimental::GhostNode, winit::WinitSettings};
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fn main() {
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App::new()
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.add_plugins(DefaultPlugins)
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.insert_resource(WinitSettings::desktop_app())
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.add_systems(Startup, setup)
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.add_systems(Update, button_system)
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.run();
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}
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#[derive(Component)]
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struct Counter(i32);
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fn setup(mut commands: Commands, asset_server: Res<AssetServer>) {
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let font_handle = asset_server.load("fonts/FiraSans-Bold.ttf");
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commands.spawn(Camera2d);
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// Ghost UI root
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commands.spawn(GhostNode).with_children(|ghost_root| {
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ghost_root.spawn(Node::default()).with_child(create_label(
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"This text node is rendered under a ghost root",
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font_handle.clone(),
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));
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});
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// Normal UI root
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commands
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.spawn(Node {
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width: Val::Percent(100.0),
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height: Val::Percent(100.0),
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align_items: AlignItems::Center,
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justify_content: JustifyContent::Center,
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..default()
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})
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.with_children(|parent| {
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parent
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.spawn((Node::default(), Counter(0)))
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.with_children(|layout_parent| {
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layout_parent
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.spawn((GhostNode, Counter(0)))
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.with_children(|ghost_parent| {
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// Ghost children using a separate counter state
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// These buttons are being treated as children of layout_parent in the context of UI
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ghost_parent
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.spawn(create_button())
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.with_child(create_label("0", font_handle.clone()));
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ghost_parent
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.spawn(create_button())
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.with_child(create_label("0", font_handle.clone()));
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});
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// A normal child using the layout parent counter
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layout_parent
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.spawn(create_button())
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.with_child(create_label("0", font_handle.clone()));
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});
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});
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}
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fn create_button() -> impl Bundle {
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(
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Button,
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Node {
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width: Val::Px(150.0),
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height: Val::Px(65.0),
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border: UiRect::all(Val::Px(5.0)),
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// horizontally center child text
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justify_content: JustifyContent::Center,
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// vertically center child text
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align_items: AlignItems::Center,
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..default()
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},
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BorderColor(Color::BLACK),
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BorderRadius::MAX,
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BackgroundColor(Color::srgb(0.15, 0.15, 0.15)),
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)
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}
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fn create_label(text: &str, font: Handle<Font>) -> (Text, TextFont, TextColor) {
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(
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Text::new(text),
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TextFont {
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font,
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font_size: 33.0,
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..default()
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},
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TextColor(Color::srgb(0.9, 0.9, 0.9)),
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)
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}
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fn button_system(
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mut interaction_query: Query<(&Interaction, &ChildOf), (Changed<Interaction>, With<Button>)>,
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labels_query: Query<(&Children, &ChildOf), With<Button>>,
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mut text_query: Query<&mut Text>,
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mut counter_query: Query<&mut Counter>,
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) {
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// Update parent counter on click
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for (interaction, child_of) in &mut interaction_query {
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if matches!(interaction, Interaction::Pressed) {
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let mut counter = counter_query.get_mut(child_of.parent()).unwrap();
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counter.0 += 1;
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}
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}
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// Update button labels to match their parent counter
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for (children, child_of) in &labels_query {
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let counter = counter_query.get(child_of.parent()).unwrap();
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let mut text = text_query.get_mut(children[0]).unwrap();
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**text = counter.0.to_string();
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}
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}
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