Text wraps incorrectly for a frame after a change to its font size

[ickshonpe]

Bevy version

main 038d113

What you did

use bevy::prelude::*;

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

fn setup(
    mut commands: Commands,
) {
    commands.spawn(Camera2dBundle::default());
    commands.spawn(TextBundle::from("Hello, world!"));
}

fn update(
    mut text_query: Query<&mut Text>,
) {
    for mut text in text_query.iter_mut() {
        text.sections[0].style.font_size *= 1.001;
    }
}

What went wrong

As the text increases in size it flickers between being displayed on one line and wrapped across two lines
It should always be on one line.

Additional Information

Could just be a system ordering issue

[rparrett]

I think that this is scale-factor dependent. I am able reproduce on every run with e.g.

app.add_plugins(DefaultPlugins.set(WindowPlugin {
    primary_window: Some(Window {
        resolution: WindowResolution::default().with_scale_factor_override(7. / 3.),
        ..default()
    }),
    ..default()
}))

But not 2.0 or 1.0.

[ickshonpe]

I think that this is scale-factor dependent. I am able reproduce on every run with e.g.

app.add_plugins(DefaultPlugins.set(WindowPlugin {
    primary_window: Some(Window {
        resolution: WindowResolution::default().with_scale_factor_override(7. / 3.),
        ..default()
    }),
    ..default()
}))

But not 2.0 or 1.0.

Probably not a system ordering issue then, most likely the bounds calculated by the measure func and the text system are different at certain scale factors. The text systems badly need more tests I think.

[rparrett]

Simplified the repro slightly, although maybe there's more going on than just this.

use bevy::{prelude::*, window::WindowResolution};

fn main() {
    App::new()
        .add_plugins(DefaultPlugins.set(WindowPlugin {
            primary_window: Some(Window {
                resolution: WindowResolution::default().with_scale_factor_override(7. / 3.),
                ..default()
            }),
            ..default()
        }))
        .add_systems(Startup, setup)
        .run();
}

fn setup(mut commands: Commands) {
    commands.spawn(Camera2dBundle::default());
    commands.spawn(TextBundle::from_section(
        "Hello, world!",
        TextStyle {
            font_size: 12.02,
            ..default()
        },
    ));
}

[rparrett]

Bisected the modified repro just above:

After #9784, text appears on two lines instead of one, but both lines are rendered.
After #9637, second line disappears