bevy/crates/bevy_scene/src/scene_spawner.rs

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use crate::Scene;
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use bevy_app::prelude::*;
use bevy_asset::{AssetEvent, Assets, Handle};
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use bevy_ecs::{Resources, World};
use bevy_type_registry::TypeRegistry;
use bevy_utils::HashMap;
use thiserror::Error;
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use uuid::Uuid;
struct InstanceInfo {
entity_map: HashMap<u32, bevy_ecs::Entity>,
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}
#[derive(Copy, Clone, Debug, Eq, PartialEq, Hash)]
struct InstanceId(Uuid);
impl InstanceId {
pub fn new() -> Self {
InstanceId(Uuid::new_v4())
}
}
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#[derive(Default)]
pub struct SceneSpawner {
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spawned_scenes: HashMap<Handle<Scene>, Vec<InstanceId>>,
spawned_instances: HashMap<InstanceId, InstanceInfo>,
scene_asset_event_reader: EventReader<AssetEvent<Scene>>,
scenes_to_instance: Vec<Handle<Scene>>,
scenes_to_despawn: Vec<Handle<Scene>>,
}
#[derive(Error, Debug)]
pub enum SceneSpawnError {
#[error("Scene contains an unregistered component.")]
UnregisteredComponent { type_name: String },
#[error("Scene does not exist. Perhaps it is still loading?")]
NonExistentScene { handle: Handle<Scene> },
}
impl SceneSpawner {
pub fn spawn(&mut self, scene_handle: Handle<Scene>) {
self.scenes_to_instance.push(scene_handle);
}
pub fn despawn(&mut self, scene_handle: Handle<Scene>) {
self.scenes_to_despawn.push(scene_handle);
}
pub fn despawn_sync(
&mut self,
world: &mut World,
scene_handle: Handle<Scene>,
) -> Result<(), SceneSpawnError> {
if let Some(instance_ids) = self.spawned_scenes.get(&scene_handle) {
for instance_id in instance_ids {
if let Some(instance) = self.spawned_instances.get(&instance_id) {
for entity in instance.entity_map.values() {
let _ = world.despawn(*entity); // Ignore the result, despawn only cares if it exists.
}
}
}
self.spawned_scenes.remove(&scene_handle);
}
Ok(())
}
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pub fn spawn_sync(
&mut self,
world: &mut World,
resources: &Resources,
scene_handle: Handle<Scene>,
) -> Result<(), SceneSpawnError> {
let instance_id = InstanceId::new();
let mut instance_info = InstanceInfo {
entity_map: HashMap::default(),
};
Self::spawn_internal(world, resources, scene_handle, &mut instance_info)?;
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self.spawned_instances.insert(instance_id, instance_info);
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let spawned = self
.spawned_scenes
.entry(scene_handle)
.or_insert_with(Vec::new);
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spawned.push(instance_id);
Ok(())
}
fn spawn_internal(
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world: &mut World,
resources: &Resources,
scene_handle: Handle<Scene>,
instance_info: &mut InstanceInfo,
) -> Result<(), SceneSpawnError> {
let type_registry = resources.get::<TypeRegistry>().unwrap();
let component_registry = type_registry.component.read();
let scenes = resources.get::<Assets<Scene>>().unwrap();
let scene = scenes
.get(&scene_handle)
.ok_or(SceneSpawnError::NonExistentScene {
handle: scene_handle,
})?;
for scene_entity in scene.entities.iter() {
let entity = *instance_info
.entity_map
.entry(scene_entity.entity)
.or_insert_with(|| world.reserve_entity());
for component in scene_entity.components.iter() {
let component_registration = component_registry
.get_with_name(&component.type_name)
.ok_or(SceneSpawnError::UnregisteredComponent {
type_name: component.type_name.to_string(),
})?;
if world.has_component_type(entity, component_registration.ty) {
if component.type_name != "Camera" {
component_registration.apply_component_to_entity(world, entity, component);
}
} else {
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component_registration
.add_component_to_entity(world, resources, entity, component);
}
}
}
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Ok(())
}
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pub fn update_spawned_scenes(
&mut self,
world: &mut World,
resources: &Resources,
scene_handles: &[Handle<Scene>],
) -> Result<(), SceneSpawnError> {
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for scene_handle in scene_handles {
if let Some(spawned_instances) = self.spawned_scenes.get(scene_handle) {
for instance_id in spawned_instances.iter() {
if let Some(instance_info) = self.spawned_instances.get_mut(instance_id) {
Self::spawn_internal(world, resources, *scene_handle, instance_info)?;
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}
}
}
}
Ok(())
}
pub fn despawn_queued_scenes(&mut self, world: &mut World) -> Result<(), SceneSpawnError> {
let scenes_to_despawn = std::mem::take(&mut self.scenes_to_despawn);
for scene_handle in scenes_to_despawn {
self.despawn_sync(world, scene_handle)?;
}
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Ok(())
}
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pub fn spawn_queued_scenes(
&mut self,
world: &mut World,
resources: &Resources,
) -> Result<(), SceneSpawnError> {
let scenes_to_spawn = std::mem::take(&mut self.scenes_to_instance);
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for scene_handle in scenes_to_spawn {
match self.spawn_sync(world, resources, scene_handle) {
Ok(_) => {}
Err(SceneSpawnError::NonExistentScene { .. }) => {
self.scenes_to_instance.push(scene_handle)
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}
Err(err) => return Err(err),
}
}
Ok(())
}
}
pub fn scene_spawner_system(world: &mut World, resources: &mut Resources) {
let mut scene_spawner = resources.get_mut::<SceneSpawner>().unwrap();
let scene_asset_events = resources.get::<Events<AssetEvent<Scene>>>().unwrap();
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let mut updated_spawned_scenes = Vec::new();
for event in scene_spawner
.scene_asset_event_reader
.iter(&scene_asset_events)
{
if let AssetEvent::Modified { handle } = event {
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if scene_spawner.spawned_scenes.contains_key(handle) {
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updated_spawned_scenes.push(*handle);
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}
}
}
scene_spawner.despawn_queued_scenes(world).unwrap();
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scene_spawner.spawn_queued_scenes(world, resources).unwrap();
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scene_spawner
.update_spawned_scenes(world, resources, &updated_spawned_scenes)
.unwrap();
}