# Objective
Currently text is recomputed unnecessarily on any changes to its color,
which is extremely expensive.
## Solution
Split up `TextStyle` into two separate components `TextFont` and
`TextColor`.
## Testing
I added this system to `many_buttons`:
```rust
fn set_text_colors_changed(mut colors: Query<&mut TextColor>) {
    for mut text_color in colors.iter_mut() {
        text_color.set_changed();
    }
}
```
reports ~4fps on main, ~50fps with this PR.
## Migration Guide
`TextStyle` has been renamed to `TextFont` and its `color` field has
been moved to a separate component named `TextColor` which newtypes
`Color`.
		
	
			
		
			
				
	
	
		
			217 lines
		
	
	
		
			9.9 KiB
		
	
	
	
		
			Rust
		
	
	
	
	
	
			
		
		
	
	
			217 lines
		
	
	
		
			9.9 KiB
		
	
	
	
		
			Rust
		
	
	
	
	
	
//! Demonstrates how CSS Grid layout can be used to lay items out in a 2D grid
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use bevy::{color::palettes::css::*, prelude::*};
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fn main() {
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    App::new()
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        .add_plugins(DefaultPlugins.set(WindowPlugin {
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            primary_window: Some(Window {
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                resolution: [800., 600.].into(),
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                title: "Bevy CSS Grid Layout Example".to_string(),
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                ..default()
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            }),
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            ..default()
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        }))
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        .add_systems(Startup, spawn_layout)
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        .run();
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}
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fn spawn_layout(mut commands: Commands, asset_server: Res<AssetServer>) {
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    let font = asset_server.load("fonts/FiraSans-Bold.ttf");
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    commands.spawn(Camera2d);
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    // Top-level grid (app frame)
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    commands
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        .spawn(NodeBundle {
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            style: Style {
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                // Use the CSS Grid algorithm for laying out this node
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                display: Display::Grid,
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                // Make node fill the entirety of its parent (in this case the window)
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                width: Val::Percent(100.0),
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                height: Val::Percent(100.0),
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                // Set the grid to have 2 columns with sizes [min-content, minmax(0, 1fr)]
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                //   - The first column will size to the size of its contents
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                //   - The second column will take up the remaining available space
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                grid_template_columns: vec![GridTrack::min_content(), GridTrack::flex(1.0)],
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                // Set the grid to have 3 rows with sizes [auto, minmax(0, 1fr), 20px]
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                //  - The first row will size to the size of its contents
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                //  - The second row take up remaining available space (after rows 1 and 3 have both been sized)
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                //  - The third row will be exactly 20px high
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                grid_template_rows: vec![
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                    GridTrack::auto(),
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                    GridTrack::flex(1.0),
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                    GridTrack::px(20.),
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                ],
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                ..default()
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            },
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            background_color: BackgroundColor(Color::WHITE),
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            ..default()
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        })
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        .with_children(|builder| {
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            // Header
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            builder
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                .spawn(NodeBundle {
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                    style: Style {
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                        display: Display::Grid,
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                        // Make this node span two grid columns so that it takes up the entire top tow
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                        grid_column: GridPlacement::span(2),
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                        padding: UiRect::all(Val::Px(6.0)),
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                        ..default()
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                    },
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                    ..default()
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                })
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                .with_children(|builder| {
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                    spawn_nested_text_bundle(builder, font.clone(), "Bevy CSS Grid Layout Example");
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                });
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            // Main content grid (auto placed in row 2, column 1)
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            builder
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                .spawn(NodeBundle {
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                    style: Style {
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                        // Make the height of the node fill its parent
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                        height: Val::Percent(100.0),
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                        // Make the grid have a 1:1 aspect ratio meaning it will scale as an exact square
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                        // As the height is set explicitly, this means the width will adjust to match the height
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                        aspect_ratio: Some(1.0),
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                        // Use grid layout for this node
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                        display: Display::Grid,
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                        // Add 24px of padding around the grid
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                        padding: UiRect::all(Val::Px(24.0)),
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                        // Set the grid to have 4 columns all with sizes minmax(0, 1fr)
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                        // This creates 4 exactly evenly sized columns
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                        grid_template_columns: RepeatedGridTrack::flex(4, 1.0),
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                        // Set the grid to have 4 rows all with sizes minmax(0, 1fr)
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                        // This creates 4 exactly evenly sized rows
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                        grid_template_rows: RepeatedGridTrack::flex(4, 1.0),
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                        // Set a 12px gap/gutter between rows and columns
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                        row_gap: Val::Px(12.0),
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                        column_gap: Val::Px(12.0),
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                        ..default()
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                    },
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                    background_color: BackgroundColor(Color::srgb(0.25, 0.25, 0.25)),
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                    ..default()
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                })
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                .with_children(|builder| {
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                    // Note there is no need to specify the position for each grid item. Grid items that are
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                    // not given an explicit position will be automatically positioned into the next available
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                    // grid cell. The order in which this is performed can be controlled using the grid_auto_flow
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                    // style property.
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                    item_rect(builder, ORANGE);
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                    item_rect(builder, BISQUE);
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                    item_rect(builder, BLUE);
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                    item_rect(builder, CRIMSON);
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                    item_rect(builder, AQUA);
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                    item_rect(builder, ORANGE_RED);
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                    item_rect(builder, DARK_GREEN);
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                    item_rect(builder, FUCHSIA);
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                    item_rect(builder, TEAL);
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                    item_rect(builder, ALICE_BLUE);
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                    item_rect(builder, CRIMSON);
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                    item_rect(builder, ANTIQUE_WHITE);
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                    item_rect(builder, YELLOW);
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                    item_rect(builder, DEEP_PINK);
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                    item_rect(builder, YELLOW_GREEN);
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                    item_rect(builder, SALMON);
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                });
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            // Right side bar (auto placed in row 2, column 2)
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            builder
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                .spawn(NodeBundle {
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                    style: Style {
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                        display: Display::Grid,
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                        // Align content towards the start (top) in the vertical axis
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                        align_items: AlignItems::Start,
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                        // Align content towards the center in the horizontal axis
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                        justify_items: JustifyItems::Center,
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                        // Add 10px padding
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                        padding: UiRect::all(Val::Px(10.)),
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                        // Add an fr track to take up all the available space at the bottom of the column so that the text nodes
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                        // can be top-aligned. Normally you'd use flexbox for this, but this is the CSS Grid example so we're using grid.
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                        grid_template_rows: vec![GridTrack::auto(), GridTrack::auto(), GridTrack::fr(1.0)],
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                        // Add a 10px gap between rows
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                        row_gap: Val::Px(10.),
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                        ..default()
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                    },
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                    background_color: BackgroundColor(BLACK.into()),
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                    ..default()
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                })
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                .with_children(|builder| {
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                    builder.spawn((Text::new("Sidebar"),
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                        TextFont {
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                            font: font.clone(),
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                            ..default()
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                        },
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                    ));
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                    builder.spawn((Text::new("A paragraph of text which ought to wrap nicely. A paragraph of text which ought to wrap nicely. A paragraph of text which ought to wrap nicely. A paragraph of text which ought to wrap nicely. A paragraph of text which ought to wrap nicely. A paragraph of text which ought to wrap nicely. A paragraph of text which ought to wrap nicely."),
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                        TextFont {
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                            font: font.clone(),
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                            font_size: 13.0,
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                            ..default()
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                        },
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                    ));
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                    builder.spawn(NodeBundle::default());
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                });
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            // Footer / status bar
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            builder.spawn(NodeBundle {
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                style: Style {
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                    // Make this node span two grid column so that it takes up the entire bottom row
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                    grid_column: GridPlacement::span(2),
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                    ..default()
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                },
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                background_color: BackgroundColor(WHITE.into()),
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                ..default()
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            });
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            // Modal (absolutely positioned on top of content - currently hidden: to view it, change its visibility)
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            builder.spawn(NodeBundle {
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                visibility: Visibility::Hidden,
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                style: Style {
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                    position_type: PositionType::Absolute,
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                    margin: UiRect {
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                        top: Val::Px(100.),
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                        bottom: Val::Auto,
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                        left: Val::Auto,
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                        right: Val::Auto,
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                    },
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                    width: Val::Percent(60.),
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                    height: Val::Px(300.),
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                    max_width: Val::Px(600.),
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                    ..default()
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                },
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                background_color: BackgroundColor(Color::WHITE.with_alpha(0.8)),
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                ..default()
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            });
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        });
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}
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/// Create a coloured rectangle node. The node has size as it is assumed that it will be
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/// spawned as a child of a Grid container with `AlignItems::Stretch` and `JustifyItems::Stretch`
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/// which will allow it to take its size from the size of the grid area it occupies.
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fn item_rect(builder: &mut ChildBuilder, color: Srgba) {
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    builder
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        .spawn(NodeBundle {
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            style: Style {
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                display: Display::Grid,
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                padding: UiRect::all(Val::Px(3.0)),
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                ..default()
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            },
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            background_color: BackgroundColor(BLACK.into()),
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            ..default()
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        })
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        .with_children(|builder| {
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            builder.spawn(NodeBundle {
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                background_color: BackgroundColor(color.into()),
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                ..default()
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            });
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        });
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}
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fn spawn_nested_text_bundle(builder: &mut ChildBuilder, font: Handle<Font>, text: &str) {
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    builder.spawn((
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        Text::new(text),
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        TextFont { font, ..default() },
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        TextColor::BLACK,
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    ));
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}
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