bevy-playground/src/camera.rs

use bevy::{
    prelude::*,
    sprite::{MaterialMesh2dBundle, Mesh2dHandle},
    window::PrimaryWindow,
};

use crate::player::Player;
use bevy::render::camera::Camera as BevyCamera;

pub struct CameraPlugin;

impl Plugin for CameraPlugin {
    fn build(&self, app: &mut App) {
        app.add_systems(Startup, spawn)
            .add_systems(PostUpdate, focus)
            .add_systems(Update, y_sort)
            .add_systems(Startup, spawn_crosshair)
            .add_systems(Update, rotate_crosshair);
    }
}

fn spawn(mut commands: Commands) {
    let mut bundle = Camera2dBundle::default();
    bundle.projection.scale = 1. / 2.;
    commands.spawn(bundle);
}

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

fn spawn_crosshair(
    mut commands: Commands,
    mut meshes: ResMut<Assets<Mesh>>,
    mut materials: ResMut<Assets<ColorMaterial>>,
) {
    let mesh = Mesh2dHandle(meshes.add(Capsule2d::new(3.0, 25.0)));
    let material = materials.add(Color::hsl(360. * 1 as f32 / 3 as f32, 0.95, 0.7));
    // let global_transform = GlobalTransform::from_xyz(
    //     0.0, 20.0,
    //     // TODO: need some way to ensure this draws above everything else?
    //     // a UI layer or something?
    //     1000.,
    // );

    let transform = Transform::from_xyz(
        0.0, 0.0,
        // TODO: need some way to ensure this draws above everything else?
        // a UI layer or something?
        1000.,
    );

    commands.spawn((
        Crosshair,
        MaterialMesh2dBundle {
            // global_transform,
            mesh,
            material,
            transform,
            ..default()
        },
    ));
}

fn focus(
    player: Query<&Transform, With<Player>>,
    mut camera: Query<&mut Transform, (With<BevyCamera>, Without<Player>)>,
) {
    let newpos = player.single().translation;
    // println!("Cam pos: {newpos}");
    camera.single_mut().translation = newpos
}

fn y_sort(mut q: Query<&mut Transform>) {
    q.iter_mut()
        .for_each(|mut tf| tf.translation.z = -tf.translation.y)
}

fn rotate_crosshair(
    mut q: Query<&mut Transform, With<Crosshair>>,
    win: Query<&Window, With<PrimaryWindow>>,
    q_cam: Query<(&Camera, &GlobalTransform), With<Camera>>,
) {
    let (camera, camera_transform) = q_cam.single();
    if let Some(world_position) = win
        .single()
        .cursor_position()
        .and_then(|cursor| camera.viewport_to_world(&GlobalTransform::from_xyz(0., 0., 0.), cursor))
        .map(|ray| ray.origin.truncate())
    {
        let mut t = q.single_mut();
        t.look_at(Vec3::ZERO, world_position.extend(0.));
        t.translation = camera_transform.translation();
    }
}