scale_factor_override.rs

//! This example illustrates how to override the window scale factor imposed by the
//! operating system.

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

#[derive(Component)]
struct CustomText;

fn main() {
    App::new()
        .add_plugins(DefaultPlugins.set(WindowPlugin {
            primary_window: Some(Window {
                resolution: WindowResolution::new(500, 300).with_scale_factor_override(1.0),
                ..default()
            }),
            ..default()
        }))
        .add_systems(Startup, setup)
        .add_systems(
            Update,
            (display_override, toggle_override, change_scale_factor),
        )
        .run();
}

fn setup(mut commands: Commands) {
    // camera
    commands.spawn(Camera2d);
    // root node
    commands.spawn((
        Node {
            width: percent(100),
            height: percent(100),
            justify_content: JustifyContent::SpaceBetween,
            ..default()
        },
        children![(
            Node {
                width: px(300),
                height: percent(100),
                border: UiRect::all(px(2)),
                ..default()
            },
            BackgroundColor(Color::srgb(0.65, 0.65, 0.65)),
            children![(
                CustomText,
                Text::new("Example text"),
                TextFont {
                    font_size: 25.0,
                    ..default()
                },
                Node {
                    align_self: AlignSelf::FlexEnd,
                    ..default()
                },
            )]
        )],
    ));
}

/// Set the title of the window to the current override
fn display_override(
    mut window: Single<&mut Window>,
    mut custom_text: Single<&mut Text, With<CustomText>>,
) {
    let text = format!(
        "Scale factor: {:.1} {}",
        window.scale_factor(),
        if window.resolution.scale_factor_override().is_some() {
            "(overridden)"
        } else {
            "(default)"
        }
    );

    window.title.clone_from(&text);
    custom_text.0 = text;
}

/// This system toggles scale factor overrides when enter is pressed
fn toggle_override(input: Res<ButtonInput<KeyCode>>, mut window: Single<&mut Window>) {
    if input.just_pressed(KeyCode::Enter) {
        let scale_factor_override = window.resolution.scale_factor_override();
        window
            .resolution
            .set_scale_factor_override(scale_factor_override.xor(Some(1.0)));
    }
}

/// This system changes the scale factor override when up or down is pressed
fn change_scale_factor(input: Res<ButtonInput<KeyCode>>, mut window: Single<&mut Window>) {
    let scale_factor_override = window.resolution.scale_factor_override();
    if input.just_pressed(KeyCode::ArrowUp) {
        window
            .resolution
            .set_scale_factor_override(scale_factor_override.map(|n| n + 1.0));
    } else if input.just_pressed(KeyCode::ArrowDown) {
        window
            .resolution
            .set_scale_factor_override(scale_factor_override.map(|n| (n - 1.0).max(1.0)));
    }
}