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Author SHA1 Message Date
Zachary Harrold
afa7b5cba5
Added Support for Extension-less Assets ()
# Objective

- Addresses **Support processing and loading files without extensions**
from 
- Addresses **More runtime loading configuration** from 
- Fixes 
- Fixes 

## Solution

`AssetServer::load::<A>` and `AssetServer::load_with_settings::<A>` can
now use the `Asset` type parameter `A` to select a registered
`AssetLoader` without inspecting the provided `AssetPath`. This change
cascades onto `LoadContext::load` and `LoadContext::load_with_settings`.
This allows the loading of assets which have incorrect or ambiguous file
extensions.

```rust
// Allow the type to be inferred by context
let handle = asset_server.load("data/asset_no_extension");

// Hint the type through the handle
let handle: Handle<CustomAsset> = asset_server.load("data/asset_no_extension");

// Explicit through turbofish
let handle = asset_server.load::<CustomAsset>("data/asset_no_extension");
```

Since a single `AssetPath` no longer maps 1:1 with an `Asset`, I've also
modified how assets are loaded to permit multiple asset types to be
loaded from a single path. This allows for two different `AssetLoaders`
(which return different types of assets) to both load a single path (if
requested).

```rust
// Uses GltfLoader
let model = asset_server.load::<Gltf>("cube.gltf");

// Hypothetical Blob loader for data transmission (for example)
let blob = asset_server.load::<Blob>("cube.gltf");
```

As these changes are reflected in the `LoadContext` as well as the
`AssetServer`, custom `AssetLoaders` can also take advantage of this
behaviour to create more complex assets.

---

## Change Log

- Updated `custom_asset` example to demonstrate extension-less assets.
- Added `AssetServer::get_handles_untyped` and Added
`AssetServer::get_path_ids`

## Notes

As a part of that refactor, I chose to store `AssetLoader`s (within
`AssetLoaders`) using a `HashMap<TypeId, ...>` instead of a `Vec<...>`.
My reasoning for this was I needed to add a relationship between `Asset`
`TypeId`s and the `AssetLoader`, so instead of having a `Vec` and a
`HashMap`, I combined the two, removing the `usize` index from the
adjacent maps.

---------

Co-authored-by: Alice Cecile <alice.i.cecile@gmail.com>
2024-01-31 14:58:08 +00:00
Zachary Harrold
46b8e904f4
Added Method to Allow Pipelined Asset Loading ()
# Objective

- Fixes 

## Solution

I've added a method to `LoadContext`, `load_direct_with_reader`, which
mirrors the behaviour of `load_direct` with a single key difference: it
is provided with the `Reader` by the caller, rather than getting it from
the contained `AssetServer`. This allows for an `AssetLoader` to process
its `Reader` stream, and then directly hand the results off to the
`LoadContext` to handle further loading. The outer `AssetLoader` can
control how the `Reader` is interpreted by providing a relevant
`AssetPath`.

For example, a Gzip decompression loader could process the asset
`images/my_image.png.gz` by decompressing the bytes, then handing the
decompressed result to the `LoadContext` with the new path
`images/my_image.png.gz/my_image.png`. This intuitively reflects the
nature of contained assets, whilst avoiding unintended behaviour, since
the generated path cannot be a real file path (a file and folder of the
same name cannot coexist in most file-systems).

```rust
#[derive(Asset, TypePath)]
pub struct GzAsset {
    pub uncompressed: ErasedLoadedAsset,
}

#[derive(Default)]
pub struct GzAssetLoader;

impl AssetLoader for GzAssetLoader {
    type Asset = GzAsset;
    type Settings = ();
    type Error = GzAssetLoaderError;
    fn load<'a>(
        &'a self,
        reader: &'a mut Reader,
        _settings: &'a (),
        load_context: &'a mut LoadContext,
    ) -> BoxedFuture<'a, Result<Self::Asset, Self::Error>> {
        Box::pin(async move {
            let compressed_path = load_context.path();
            let file_name = compressed_path
                .file_name()
                .ok_or(GzAssetLoaderError::IndeterminateFilePath)?
                .to_string_lossy();
            let uncompressed_file_name = file_name
                .strip_suffix(".gz")
                .ok_or(GzAssetLoaderError::IndeterminateFilePath)?;
            let contained_path = compressed_path.join(uncompressed_file_name);

            let mut bytes_compressed = Vec::new();

            reader.read_to_end(&mut bytes_compressed).await?;

            let mut decoder = GzDecoder::new(bytes_compressed.as_slice());

            let mut bytes_uncompressed = Vec::new();

            decoder.read_to_end(&mut bytes_uncompressed)?;

            // Now that we have decompressed the asset, let's pass it back to the
            // context to continue loading

            let mut reader = VecReader::new(bytes_uncompressed);

            let uncompressed = load_context
                .load_direct_with_reader(&mut reader, contained_path)
                .await?;

            Ok(GzAsset { uncompressed })
        })
    }

    fn extensions(&self) -> &[&str] {
        &["gz"]
    }
}
```

Because this example is so prudent, I've included an
`asset_decompression` example which implements this exact behaviour:

```rust
fn main() {
    App::new()
        .add_plugins(DefaultPlugins)
        .init_asset::<GzAsset>()
        .init_asset_loader::<GzAssetLoader>()
        .add_systems(Startup, setup)
        .add_systems(Update, decompress::<Image>)
        .run();
}

fn setup(mut commands: Commands, asset_server: Res<AssetServer>) {
    commands.spawn(Camera2dBundle::default());

    commands.spawn((
        Compressed::<Image> {
            compressed: asset_server.load("data/compressed_image.png.gz"),
            ..default()
        },
        Sprite::default(),
        TransformBundle::default(),
        VisibilityBundle::default(),
    ));
}

fn decompress<A: Asset>(
    mut commands: Commands,
    asset_server: Res<AssetServer>,
    mut compressed_assets: ResMut<Assets<GzAsset>>,
    query: Query<(Entity, &Compressed<A>)>,
) {
    for (entity, Compressed { compressed, .. }) in query.iter() {
        let Some(GzAsset { uncompressed }) = compressed_assets.remove(compressed) else {
            continue;
        };

        let uncompressed = uncompressed.take::<A>().unwrap();

        commands
            .entity(entity)
            .remove::<Compressed<A>>()
            .insert(asset_server.add(uncompressed));
    }
}
```

A key limitation to this design is how to type the internally loaded
asset, since the example `GzAssetLoader` is unaware of the internal
asset type `A`. As such, in this example I store the contained asset as
an `ErasedLoadedAsset`, and leave it up to the consumer of the `GzAsset`
to handle typing the final result, which is the purpose of the
`decompress` system. This limitation can be worked around by providing
type information to the `GzAssetLoader`, such as `GzAssetLoader<Image,
ImageAssetLoader>`, but this would require registering the asset loader
for every possible decompression target.

Aside from this limitation, nested asset containerisation works as an
end user would expect; if the user registers a `TarAssetLoader`, and a
`GzAssetLoader`, then they can load assets with compound
containerisation, such as `images.tar.gz`.

---

## Changelog

- Added `LoadContext::load_direct_with_reader`
- Added `asset_decompression` example

## Notes

- While I believe my implementation of a Gzip asset loader is
reasonable, I haven't included it as a public feature of `bevy_asset` to
keep the scope of this PR as focussed as possible.
- I have included `flate2` as a `dev-dependency` for the example; it is
not included in the main dependency graph.
2023-11-16 17:47:31 +00:00
Carter Anderson
c32e637384
Asset system rework and GLTF scene loading () 2020-10-18 13:48:15 -07:00
Will Hart
1beee4fd28
Add AppBuilder::asset_loader_from_instance ()
* Implement add_asset_loader_from_instance

* Add example of different data loaders
2020-10-01 11:31:06 -07:00