bevy-playground/src/camera.rs

use crate::prelude::*;
use bevy::render::camera::{Camera, ScalingMode};

// #[derive(Component)]
// struct GameCamera;

pub fn startup(mut commands: Commands, mut ui_scale: ResMut<UiScale>) {
    let mut bundle = Camera2dBundle::default();
    bundle.projection = OrthographicProjection {
        near: f32::MIN,
        far: f32::MAX,
        scaling_mode: ScalingMode::FixedVertical(360.0 / 1.),
        ..default()
    };
    commands.spawn((bundle, IsDefaultUiCamera));

    ui_scale.0 = 1.;
}

#[derive(Component, Debug)]
pub struct Watched;

pub fn update(
    watched: Query<&Transform, With<Watched>>,
    mut camera: Query<&mut Transform, (With<Camera>, Without<Watched>)>,
) {
    if let Ok(mut camera) = camera.get_single_mut() {
        if let Ok(watched) = watched.get_single() {
            camera.translation.x = watched.translation.x;
            camera.translation.y = watched.translation.y;
        } else {
            camera.translation = Vec3::ZERO;
        }
    }
}