1bbd5c25c0
# Objective - Sometimes, people might load an asset as one type, then use it with an `Asset`s for a different type. - See e.g. #4784. - This is especially likely with the Gltf types, since users may not have a clear conceptual model of what types the assets will be. - We had an instance of this ourselves, in the `scene_viewer` example ## Solution - Make `Assets::get` require a type safe handle. --- ## Changelog ### Changed - `Assets::<T>::get` and `Assets::<T>::get_mut` now require that the passed handles are `Handle<T>`, improving the type safety of handles. ### Added - `HandleUntyped::typed_weak`, a helper function for creating a weak typed version of an exisitng `HandleUntyped`. ## Migration Guide `Assets::<T>::get` and `Assets::<T>::get_mut` now require that the passed handles are `Handle<T>`, improving the type safety of handles. If you were previously passing in: - a `HandleId`, use `&Handle::weak(id)` instead, to create a weak handle. You may have been able to store a type safe `Handle` instead. - a `HandleUntyped`, use `&handle_untyped.typed_weak()` to create a weak handle of the specified type. This is most likely to be the useful when using [load_folder](https://docs.rs/bevy_asset/latest/bevy_asset/struct.AssetServer.html#method.load_folder) - a `Handle<U>` of of a different type, consider whether this is the correct handle type to store. If it is (i.e. the same handle id is used for multiple different Asset types) use `Handle::weak(handle.id)` to cast to a different type.
84 lines
2.9 KiB
Rust
84 lines
2.9 KiB
Rust
//! In this example we generate a new texture atlas (sprite sheet) from a folder containing
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//! individual sprites.
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use bevy::{asset::LoadState, prelude::*};
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fn main() {
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App::new()
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.init_resource::<RpgSpriteHandles>()
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.add_plugins(DefaultPlugins)
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.add_state(AppState::Setup)
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.add_system_set(SystemSet::on_enter(AppState::Setup).with_system(load_textures))
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.add_system_set(SystemSet::on_update(AppState::Setup).with_system(check_textures))
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.add_system_set(SystemSet::on_enter(AppState::Finished).with_system(setup))
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.run();
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}
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#[derive(Debug, Clone, PartialEq, Eq, Hash)]
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enum AppState {
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Setup,
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Finished,
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}
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#[derive(Default)]
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struct RpgSpriteHandles {
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handles: Vec<HandleUntyped>,
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}
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fn load_textures(mut rpg_sprite_handles: ResMut<RpgSpriteHandles>, asset_server: Res<AssetServer>) {
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rpg_sprite_handles.handles = asset_server.load_folder("textures/rpg").unwrap();
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}
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fn check_textures(
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mut state: ResMut<State<AppState>>,
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rpg_sprite_handles: ResMut<RpgSpriteHandles>,
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asset_server: Res<AssetServer>,
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) {
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if let LoadState::Loaded =
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asset_server.get_group_load_state(rpg_sprite_handles.handles.iter().map(|handle| handle.id))
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{
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state.set(AppState::Finished).unwrap();
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}
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}
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fn setup(
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mut commands: Commands,
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rpg_sprite_handles: Res<RpgSpriteHandles>,
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asset_server: Res<AssetServer>,
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mut texture_atlases: ResMut<Assets<TextureAtlas>>,
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mut textures: ResMut<Assets<Image>>,
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) {
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let mut texture_atlas_builder = TextureAtlasBuilder::default();
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for handle in &rpg_sprite_handles.handles {
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let handle = handle.typed_weak();
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let texture = textures.get(&handle).expect("Textures folder contained a file which way matched by a loader which did not create an `Image` asset");
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texture_atlas_builder.add_texture(handle, texture);
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}
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let texture_atlas = texture_atlas_builder.finish(&mut textures).unwrap();
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let texture_atlas_texture = texture_atlas.texture.clone();
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let vendor_handle = asset_server.get_handle("textures/rpg/chars/vendor/generic-rpg-vendor.png");
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let vendor_index = texture_atlas.get_texture_index(&vendor_handle).unwrap();
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let atlas_handle = texture_atlases.add(texture_atlas);
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// set up a scene to display our texture atlas
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commands.spawn_bundle(OrthographicCameraBundle::new_2d());
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// draw a sprite from the atlas
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commands.spawn_bundle(SpriteSheetBundle {
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transform: Transform {
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translation: Vec3::new(150.0, 0.0, 0.0),
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scale: Vec3::splat(4.0),
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..default()
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},
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sprite: TextureAtlasSprite::new(vendor_index),
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texture_atlas: atlas_handle,
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..default()
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});
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// draw the atlas itself
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commands.spawn_bundle(SpriteBundle {
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texture: texture_atlas_texture,
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transform: Transform::from_xyz(-300.0, 0.0, 0.0),
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..default()
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});
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}
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