Basic Letterboxing

letterboxing.rs

use bevy::{
    core_pipeline::clear_color::ClearColorConfig,
    prelude::*,
    render::{camera::RenderTarget, render_resource::*},
};

fn main() {
    App::new()
        .add_plugins(DefaultPlugins)
        .add_startup_system(setup)
        .run();
}

/// set up a simple 3D scene
fn setup(
    mut commands: Commands,
    asset_server: Res<AssetServer>,
    mut texture_atlases: ResMut<Assets<TextureAtlas>>,
    mut images: ResMut<Assets<Image>>,
) {
    // The size of the rendered area
    let size = Extent3d {
        width: 400,
        height: 300,
        ..default()
    };
    // This is the texture that will be rendered to
    let mut image = Image {
        texture_descriptor: TextureDescriptor {
            label: None,
            size,
            dimension: TextureDimension::D2,
            format: TextureFormat::Bgra8UnormSrgb,
            mip_level_count: 1,
            sample_count: 1,
            usage: TextureUsages::TEXTURE_BINDING
                | TextureUsages::COPY_DST
                | TextureUsages::RENDER_ATTACHMENT,
        },
        ..default()
    };

    // fill image.data with zeroes
    image.resize(size);

    let image_handle = images.add(image);

    // Main Camera
    commands
        .spawn_bundle(Camera2dBundle {
            camera: Camera {
                priority: -1,
                target: RenderTarget::Image(image_handle.clone()),
                ..default()
            },
            ..default()
        })
        // UI is assumed to be done on the "full sized primary window", so Bevy can't yet meaningfully render it to
        // a smaller image. This will be improved soon.
        .insert(CameraUi { is_enabled: false });

    // This is a lame hack to get "full screen full size" UI. We won't actually be drawing anything in 3d.
    // TODO: replace this with a Camera2dBundle with RenderLayers::none() once sprites have been ported to the render layers system
    commands.spawn_bundle(Camera3dBundle {
        camera_3d: Camera3d {
            clear_color: ClearColorConfig::Custom(Color::rgb(0.1, 0.1, 0.1)),
            ..default()
        },
        ..default()
    });

    commands.spawn_bundle(ImageBundle {
        style: Style {
            size: Size::new(Val::Auto, Val::Auto),
            margin: UiRect::all(Val::Auto),
            ..default()
        },
        image: image_handle.into(),
        ..default()
    });

    let texture_handle = asset_server.load("textures/rpg/chars/gabe/gabe-idle-run.png");
    let texture_atlas = TextureAtlas::from_grid(texture_handle, Vec2::new(24.0, 24.0), 7, 1);
    let texture_atlas_handle = texture_atlases.add(texture_atlas);

    // Spawn sprite
    commands.spawn_bundle(SpriteSheetBundle {
        texture_atlas: texture_atlas_handle,
        ..default()
    });
}