Text 2d alignment fix

[ickshonpe]

Objective

Text2d ignores TextBounds when calculating the offset for text aligment.
On main a text entity positioned in the center of the window with center justification and 600px horizontal text bounds isn't centered like it should be but shifted off to the right:

(second example in the testing section below)

Fixes #14266

I already had a PR in review for this (#14270) but it used post layout adjustment (which we want to avoid) and ignored TextBounds.

Solution

• If TextBounds are present for an axis, use them instead of the size of the computed text layout size to calculate the offset.
• Adjust the vertical offset of text so it's top is aligned with the top of the texts bounding rect (when present).

Testing

use bevy::prelude::*;
use bevy::color::palettes;
use bevy::sprite::Anchor;
use bevy::text::TextBounds;

fn main() {
    App::new()
        .add_plugins(DefaultPlugins)
        .add_systems(Startup, setup)
        .run();
}

fn example(commands: &mut Commands, dest: Vec3, justify: JustifyText) {
    commands.spawn((
        Sprite {
            color: palettes::css::YELLOW.into(),
            custom_size: Some(10. * Vec2::ONE),
            anchor: Anchor::Center,
            ..Default::default()
        },
        Transform::from_translation(dest),
    ));

    for a in [
        Anchor::TopLeft,
        Anchor::TopRight,
        Anchor::BottomRight,
        Anchor::BottomLeft,
    ] {
        commands.spawn((
            Text2d(format!("L R\n{:?}\n{:?}", a, justify)),
            TextFont {
                font_size: 14.0,
                ..default()
            },
            TextLayout {
                justify,
                ..Default::default()
            },
            TextBounds::new(300., 75.),
            Transform::from_translation(dest + Vec3::Z),
            a,
        ));
    }
}

fn setup(mut commands: Commands) {
    commands.spawn(Camera2d::default());

    for (i, j) in [
        JustifyText::Left,
        JustifyText::Right,
        JustifyText::Center,
        JustifyText::Justified,
    ]
    .into_iter()
    .enumerate()
    {
        example(&mut commands, (300. - 150. * i as f32) * Vec3::Y, j);
    }

    commands.spawn(Sprite {
        color: palettes::css::YELLOW.into(),
        custom_size: Some(10. * Vec2::ONE),
        anchor: Anchor::Center,
        ..Default::default()
    });
}

This probably looks really confusing but it should make sense if you imagine each block of text surrounded by a 300x75 rectangle that is anchored to the center of the yellow square.

use bevy::prelude::*;
use bevy::sprite::Anchor;
use bevy::text::TextBounds;

fn main() {
    App::new()
        .add_plugins(DefaultPlugins)
        .add_systems(Startup, setup)
        .run();
}

fn setup(mut commands: Commands) {
    commands.spawn(Camera2d::default());

    commands.spawn((
        Text2d::new("hello"),
        TextFont {
            font_size: 60.0,
            ..default()
        },
        TextLayout::new_with_justify(JustifyText::Center),
        TextBounds::new(600., 200.),
        Anchor::Center,
    ));
}

The text being above the center is intended. When TextBounds are present, the text block's offset is calculated using its TextBounds not the layout size returned by cosmic-text.

Probably we should add a vertical alignment setting for Text2d. Didn't do it here as this is intended for a 0.15.2 release.

[rparrett]

Looks good to me.