# 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(); } } ```
		
			
				
	
	
		
			325 lines
		
	
	
		
			11 KiB
		
	
	
	
		
			Rust
		
	
	
	
	
	
			
		
		
	
	
			325 lines
		
	
	
		
			11 KiB
		
	
	
	
		
			Rust
		
	
	
	
	
	
//! Shows various text layout options.
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use std::{collections::VecDeque, time::Duration};
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use bevy::{
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    color::palettes::css::*,
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    diagnostic::{DiagnosticsStore, FrameTimeDiagnosticsPlugin},
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    prelude::*,
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    ui::widget::TextUiWriter,
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    window::PresentMode,
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};
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fn main() {
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    App::new()
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        .add_plugins((
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            DefaultPlugins.set(WindowPlugin {
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                primary_window: Some(Window {
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                    present_mode: PresentMode::AutoNoVsync,
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                    ..default()
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                }),
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                ..default()
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            }),
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            FrameTimeDiagnosticsPlugin,
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        ))
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        .add_systems(Startup, infotext_system)
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        .add_systems(Update, change_text_system)
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        .run();
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}
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#[derive(Component)]
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struct TextChanges;
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fn infotext_system(mut commands: Commands, asset_server: Res<AssetServer>) {
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    let font = asset_server.load("fonts/FiraSans-Bold.ttf");
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    let background_color = MAROON.into();
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    commands.spawn(Camera2d);
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    let root_uinode = commands
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        .spawn(Node {
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            width: Val::Percent(100.),
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            height: Val::Percent(100.),
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            justify_content: JustifyContent::SpaceBetween,
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            ..default()
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        })
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        .id();
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    let left_column = commands
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        .spawn(Node {
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            flex_direction: FlexDirection::Column,
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            justify_content: JustifyContent::SpaceBetween,
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            align_items: AlignItems::Start,
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            flex_grow: 1.,
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            margin: UiRect::axes(Val::Px(15.), Val::Px(5.)),
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            ..default()
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        }).with_children(|builder| {
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        builder.spawn((
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            Text::new("This is\ntext with\nline breaks\nin the top left."),
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            TextFont {
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                font: font.clone(),
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                font_size: 25.0,
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                ..default()
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            },
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            BackgroundColor(background_color)
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        ));
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        builder.spawn((
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            Text::new(
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                "This text is right-justified. The `JustifyText` component controls the horizontal alignment of the lines of multi-line text relative to each other, and does not affect the text node's position in the UI layout.",
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            ),
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            TextFont {
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                font: font.clone(),
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                font_size: 25.0,
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                ..default()
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            },
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            TextColor(YELLOW.into()),
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            TextLayout::new_with_justify(JustifyText::Right),
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            Node {
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                max_width: Val::Px(300.),
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                ..default()
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            },
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            BackgroundColor(background_color)
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        ));
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        builder.spawn((
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            Text::new(
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                "This\ntext has\nline breaks and also a set width in the bottom left."),
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            TextFont {
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                font: font.clone(),
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                font_size: 25.0,
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                ..default()
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            },
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            Node {
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                max_width: Val::Px(300.),
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                ..default()
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            },
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            BackgroundColor(background_color)
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        )
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        );
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    }).id();
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    let right_column = commands
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        .spawn(Node {
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            flex_direction: FlexDirection::Column,
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            justify_content: JustifyContent::SpaceBetween,
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            align_items: AlignItems::End,
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            flex_grow: 1.,
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            margin: UiRect::axes(Val::Px(15.), Val::Px(5.)),
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            ..default()
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        })
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        .with_children(|builder| {
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            builder.spawn((
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                Text::new("This text is very long, has a limited width, is center-justified, is positioned in the top right and is also colored pink."),
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                TextFont {
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                    font: font.clone(),
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                    font_size: 33.0,
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                    ..default()
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                },
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                TextColor(Color::srgb(0.8, 0.2, 0.7)),
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                TextLayout::new_with_justify(JustifyText::Center),
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                Node {
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                    max_width: Val::Px(400.),
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                    ..default()
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                },
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                BackgroundColor(background_color),
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            ));
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            builder.spawn((
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                Text::new("This text is left-justified and is vertically positioned to distribute the empty space equally above and below it."),
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                TextFont {
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                    font: font.clone(),
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                    font_size: 29.0,
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                    ..default()
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                },
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                TextColor(YELLOW.into()),
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                TextLayout::new_with_justify(JustifyText::Left),
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                Node {
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                    max_width: Val::Px(300.),
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                    ..default()
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                },
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                BackgroundColor(background_color),
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            ));
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            builder.spawn((
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                Text::new("This text is fully justified and is positioned in the same way."),
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                TextFont {
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                    font: font.clone(),
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                    font_size: 29.0,
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                    ..default()
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                },
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                TextLayout::new_with_justify(JustifyText::Justified),
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                TextColor(GREEN_YELLOW.into()),
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                Node {
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                    max_width: Val::Px(300.),
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                    ..default()
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                },
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                BackgroundColor(background_color),
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            ));
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            builder
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                .spawn((
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                    Text::default(),
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                    TextFont {
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                        font: font.clone(),
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                        font_size: 21.0,
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                        ..default()
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                    },
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                    TextChanges,
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                    BackgroundColor(background_color),
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                ))
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                .with_children(|p| {
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                    p.spawn((
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                        TextSpan::new("\nThis text changes in the bottom right"),
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                        TextFont {
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                            font: font.clone(),
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                            font_size: 21.0,
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                            ..default()
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                        },
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                    ));
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                    p.spawn((
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                        TextSpan::new(" this text has zero fontsize"),
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                        TextFont {
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                            font: font.clone(),
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                            font_size: 0.0,
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                            ..default()
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                        },
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                        TextColor(BLUE.into()),
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                    ));
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                    p.spawn((
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                        TextSpan::new("\nThis text changes in the bottom right - "),
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                        TextFont {
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                            font: font.clone(),
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                            font_size: 21.0,
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                            ..default()
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                        },
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                        TextColor(RED.into()),
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                    ));
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                    p.spawn((
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                        TextSpan::default(),
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                        TextFont {
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                            font: font.clone(),
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                            font_size: 21.0,
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                            ..default()
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                        },
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                        TextColor(ORANGE_RED.into()),
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                    ));
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                    p.spawn((
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                        TextSpan::new(" fps, "),
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                        TextFont {
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                            font: font.clone(),
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                            font_size: 10.0,
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                            ..default()
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                        },
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                        TextColor(YELLOW.into()),
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                    ));
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                    p.spawn((
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                        TextSpan::default(),
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                        TextFont {
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                            font: font.clone(),
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                            font_size: 21.0,
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                            ..default()
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                        },
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                        TextColor(LIME.into()),
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                    ));
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                    p.spawn((
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                        TextSpan::new(" ms/frame"),
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                        TextFont {
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                            font: font.clone(),
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                            font_size: 42.0,
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                            ..default()
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                        },
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                        TextColor(BLUE.into()),
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                    ));
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                    p.spawn((
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                        TextSpan::new(" this text has negative fontsize"),
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                        TextFont {
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                            font: font.clone(),
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                            font_size: -42.0,
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                            ..default()
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                        },
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                        TextColor(BLUE.into()),
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                    ));
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                });
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        })
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        .id();
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    commands
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        .entity(root_uinode)
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        .add_children(&[left_column, right_column]);
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}
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fn change_text_system(
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    mut fps_history: Local<VecDeque<f64>>,
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    mut time_history: Local<VecDeque<Duration>>,
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    time: Res<Time>,
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    diagnostics: Res<DiagnosticsStore>,
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    query: Query<Entity, With<TextChanges>>,
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    mut writer: TextUiWriter,
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) {
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    time_history.push_front(time.elapsed());
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    time_history.truncate(120);
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    let avg_fps = (time_history.len() as f64)
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        / (time_history.front().copied().unwrap_or_default()
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            - time_history.back().copied().unwrap_or_default())
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        .as_secs_f64()
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        .max(0.0001);
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    fps_history.push_front(avg_fps);
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    fps_history.truncate(120);
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    let fps_variance = std_deviation(fps_history.make_contiguous()).unwrap_or_default();
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    for entity in &query {
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        let mut fps = 0.0;
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        if let Some(fps_diagnostic) = diagnostics.get(&FrameTimeDiagnosticsPlugin::FPS) {
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            if let Some(fps_smoothed) = fps_diagnostic.smoothed() {
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                fps = fps_smoothed;
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            }
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        }
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        let mut frame_time = time.delta_secs_f64();
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        if let Some(frame_time_diagnostic) =
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            diagnostics.get(&FrameTimeDiagnosticsPlugin::FRAME_TIME)
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        {
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            if let Some(frame_time_smoothed) = frame_time_diagnostic.smoothed() {
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                frame_time = frame_time_smoothed;
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            }
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        }
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        *writer.text(entity, 0) =
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            format!("{avg_fps:.1} avg fps, {fps_variance:.1} frametime variance",);
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        *writer.text(entity, 1) = format!(
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            "\nThis text changes in the bottom right - {fps:.1} fps, {frame_time:.3} ms/frame",
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        );
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        *writer.text(entity, 4) = format!("{fps:.1}");
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        *writer.text(entity, 6) = format!("{frame_time:.3}");
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    }
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}
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fn mean(data: &[f64]) -> Option<f64> {
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    let sum = data.iter().sum::<f64>();
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    let count = data.len();
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    match count {
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        positive if positive > 0 => Some(sum / count as f64),
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        _ => None,
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    }
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}
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fn std_deviation(data: &[f64]) -> Option<f64> {
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    match (mean(data), data.len()) {
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        (Some(data_mean), count) if count > 0 => {
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            let variance = data
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                .iter()
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                .map(|value| {
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                    let diff = data_mean - *value;
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                    diff * diff
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                })
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                .sum::<f64>()
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                / count as f64;
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            Some(variance.sqrt())
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        }
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        _ => None,
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    }
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}
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