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Asset management

Assets are objects that are created dynamically during the runtime of an application.

Most assets are loaded from files and require only a filepath. Whereas others may need extra options, or may be loaded from other sources. There is no general purpose asset loader that fits all. Therefore, given the chaotic nature of asset creation, the framework offers one powerful tool - Cached<LoadFunction>.

ddge::app::create()
    .plug_in(ddge::plugins::Assets{})
    .insert_loader(MyAssetLoader{});

You are free to define your own way of loading an asset. The only restriction is that it should be obvious what parameters your function takes and what asset it returns.

struct MyAssetLoader {
    auto operator()(std::string_view filename, int flags) -> Image;
};

The Cached wrapper will package your asset into an owning handle, and keep a weak reference to it, so the next time it won’t need to invoke your loader.

auto load_my_asset(Cached<MyAssetLoader> loader) -> void
{
    auto asset_handle = loader->load("frog.png", 0);

    // MyAssetLoader won't be called the second time
    asset_handle = loader->load("frog.png", 0);
}

Also, don’t forget to store your handle away somewhere, as your asset may get destroyed otherwise. One good practice is keeping your asset in a state.

Composite loaders

Let’s imagine you are writing a loader for a 3D model which also needs to load textures. In this case, your model loader will depend on the texture loader.

One solution is to take the other loader as a parameter, but this can get messy. The recommended approach is to inject a reference to the texture loader into your model loader instead.

class ModelLoader {
public:
    explicit ModelLoader(
        ddge::assets::Cached<TextureLoader>& texture_loader
    );

    // ...
};

ddge::app::create()
    .plug_in(ddge::plugins::Assets{})
    .insert_loader(TextureLoader{});
    .inject_loader(
        [](ddge::assets::Cached<TextureLoader>& texture_loader) {
            return ModelLoader{ texture_loader };
        }
    );