Positioning of Text2D relative to parent when using TextBounds

[keithsharp]

I'm trying to draw a shape and then write some text on top of the shape. The text should be centred vertically and horizontally on the shape, and should wrap on word breaks.

Looking at the documentation and the examples it seems I need some combination of TextLayout and TextBounds. After much experimentation, including trying to use Anchor, I discovered that offsetting the Transform of the Text2D by -(BOUNDS_WIDTH / 4.0) gave me what I was looking for.

My question: is this the best approach? I can't help feeling my solution is a kludge and I'm missing something obvious!

Example code, using Bevy 0.15.3:

use bevy::color::palettes::css::{DIM_GRAY, WHITE};
use bevy::prelude::*;
use bevy::text::TextBounds;

const BOUNDS_WIDTH: f32 = 80.0;

fn main() {
    App::new()
        .insert_resource(ClearColor(Color::Srgba(DIM_GRAY)))
        .add_plugins(DefaultPlugins)
        .add_systems(Startup, setup)
        .run();
}

fn setup(
    mut commands: Commands,
    mut meshes: ResMut<Assets<Mesh>>,
    mut materials: ResMut<Assets<ColorMaterial>>,
) {
    commands.spawn(Camera2d);

    let white = materials.add(Color::Srgba(WHITE));
    let square = meshes.add(Rectangle::new(100.0, 100.0));

    // Short; doesn't need to wrap; no TextBounds
    // Works as expected
    commands
        .spawn((
            Mesh2d(square.clone()),
            MeshMaterial2d(white.clone()),
            Transform::from_xyz(-60.0, 60.0, 0.0),
        ))
        .with_children(|parent| {
            parent.spawn((
                Text2d("No wrap".to_string()),
                TextColor(Color::BLACK),
                TextFont {
                    font_size: 15.0,
                    ..default()
                },
                TextLayout::new(JustifyText::Center, LineBreak::WordBoundary),
            ));
        });

    // Short; doesn't need to wrap; has TextBounds
    // Offset to the right
    commands
        .spawn((
            Mesh2d(square.clone()),
            MeshMaterial2d(white.clone()),
            Transform::from_xyz(60.0, 60.0, 0.0),
        ))
        .with_children(|parent| {
            parent.spawn((
                Text2d("No wrap".to_string()),
                TextColor(Color::BLACK),
                TextFont {
                    font_size: 15.0,
                    ..default()
                },
                TextLayout::new(JustifyText::Center, LineBreak::WordBoundary),
                TextBounds::new_horizontal(BOUNDS_WIDTH),
            ));
        });

    // Longer; needs to wrap; has TextBounds
    // Offset to the right
    commands
        .spawn((
            Mesh2d(square.clone()),
            MeshMaterial2d(white.clone()),
            Transform::from_xyz(-60.0, -60.0, 0.0),
        ))
        .with_children(|parent| {
            parent.spawn((
                Text2d("Long with wrap".to_string()),
                TextColor(Color::BLACK),
                TextFont {
                    font_size: 15.0,
                    ..default()
                },
                TextLayout::new(JustifyText::Center, LineBreak::WordBoundary),
                TextBounds::new_horizontal(BOUNDS_WIDTH),
            ));
        });

    // Longer; needs to wrap; has TextBounds; offset X by BOUNDS_WIDTH / 4.0
    // Expcted visual output, requires manual offset
    commands
        .spawn((
            Mesh2d(square.clone()),
            MeshMaterial2d(white.clone()),
            Transform::from_xyz(60.0, -60.0, 0.0),
        ))
        .with_children(|parent| {
            parent.spawn((
                Text2d("Long with wrap".to_string()),
                TextColor(Color::BLACK),
                TextFont {
                    font_size: 15.0,
                    ..default()
                },
                TextLayout::new(JustifyText::Center, LineBreak::WordBoundary),
                TextBounds::new_horizontal(BOUNDS_WIDTH),
                Transform::from_xyz(-(BOUNDS_WIDTH / 4.0), 0.0, 0.0),
            ));
        });
}

[keithsharp]

Actually, my offset solution doesn't work. If I make one of the words longer than the width of the TextBounds then it loses the horizontal centring.

Add these two additional squares and text to setup() to show the problem:

    // Longer + long word; needs to wrap; has TextBounds; offset X by BOUNDS_WIDTH / 4.0
    // Offset doesn't work
    commands
        .spawn((
            Mesh2d(square.clone()),
            MeshMaterial2d(white.clone()),
            Transform::from_xyz(-60.0, -180.0, 0.0),
        ))
        .with_children(|parent| {
            parent.spawn((
                Text2d("Longword with wrap".to_string()),
                TextColor(Color::BLACK),
                TextFont {
                    font_size: 15.0,
                    ..default()
                },
                TextLayout::new(JustifyText::Center, LineBreak::WordBoundary),
                TextBounds::new_horizontal(BOUNDS_WIDTH),
                Transform::from_xyz(-(BOUNDS_WIDTH / 4.0), 0.0, 0.0),
            ));
        });

    // Longer + long word; needs to wrap; has TextBounds; no offset
    // Visually slightly to the right of centre
    commands
        .spawn((
            Mesh2d(square.clone()),
            MeshMaterial2d(white.clone()),
            Transform::from_xyz(60.0, -180.0, 0.0),
        ))
        .with_children(|parent| {
            parent.spawn((
                Text2d("Longword with wrap".to_string()),
                TextColor(Color::BLACK),
                TextFont {
                    font_size: 15.0,
                    ..default()
                },
                TextLayout::new(JustifyText::Center, LineBreak::WordBoundary),
                TextBounds::new_horizontal(BOUNDS_WIDTH),
            ));
        });

[Henauxg]

This feels a bit like #12319, but with added weirdness.

Anchor::Center + JustifyText::Center with no TextBounds works fine for the centering. But adding the TextBounds messes it up. And It seems like the TextBounds truncation is not applied, at all, if using LineBreak::WordBoundary (but is applied when using LineBreak::AnyCharacter).

The textBounds documentation specifies that "only characters that are completely out of the bounds will be truncated", however, whole words get through when using LineBreak::WordBoundary.

There may be a specific issue to raise about this ?

[keithsharp]

Thanks for the feedback, I've opened #18789 with an example image showing the problem and code to reproduce.

[keithsharp]

It turns out this was a bug and is fixed in 0.16.0.