mirror of
https://github.com/bevyengine/bevy
synced 2024-12-22 11:03:06 +00:00
67aa2953d0
# Objective
In simple cases we might want to derive the `ExtractComponent` trait.
This adds symmetry to the existing `ExtractResource` derive.
## Solution
Add an implementation of `#[derive(ExtractComponent)]`.
The implementation is adapted from the existing `ExtractResource` derive macro.
Additionally, there is an attribute called `extract_component_filter`. This allows specifying a query filter type used when extracting.
If not specified, no filter (equal to `()`) is used.
So:
```rust
#[derive(Component, Clone, ExtractComponent)]
#[extract_component_filter(With<Fuel>)]
pub struct Car {
pub wheels: usize,
}
```
would expand to (a bit cleaned up here):
```rust
impl ExtractComponent for Car
{
type Query = &'static Self;
type Filter = With<Fuel>;
type Out = Self;
fn extract_component(item: QueryItem<'_, Self::Query>) -> Option<Self::Out> {
Some(item.clone())
}
}
```
---
## Changelog
- Added the ability to `#[derive(ExtractComponent)]` with an optional filter.
60 lines
2 KiB
Rust
60 lines
2 KiB
Rust
mod as_bind_group;
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mod extract_component;
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mod extract_resource;
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use bevy_macro_utils::BevyManifest;
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use proc_macro::TokenStream;
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use syn::{parse_macro_input, DeriveInput};
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pub(crate) fn bevy_render_path() -> syn::Path {
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BevyManifest::default()
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.maybe_get_path("bevy_render")
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// NOTE: If the derivation is within bevy_render, then we need to return 'crate'
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.unwrap_or_else(|| BevyManifest::parse_str("crate"))
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}
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#[proc_macro_derive(ExtractResource)]
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pub fn derive_extract_resource(input: TokenStream) -> TokenStream {
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extract_resource::derive_extract_resource(input)
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}
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/// Implements `ExtractComponent` trait for a component.
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/// The component must implement [`Clone`].
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/// The component will be extracted into the render world via cloning.
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/// Note that this only enables extraction of the component, it does not execute the extraction.
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/// See `ExtractComponentPlugin` to actually perform the extraction.
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///
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/// If you only want to extract a component conditionally, you may use the `extract_component_filter` attribute.
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///
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/// # Example
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///
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/// ```no_compile
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/// use bevy_ecs::component::Component;
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/// use bevy_render_macros::ExtractComponent;
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///
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/// #[derive(Component, Clone, ExtractComponent)]
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/// #[extract_component_filter(With<Camera>)]
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/// pub struct Foo {
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/// pub should_foo: bool,
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/// }
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///
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/// // Without a filter (unconditional).
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/// #[derive(Component, Clone, ExtractComponent)]
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/// pub struct Bar {
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/// pub should_bar: bool,
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/// }
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/// ```
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#[proc_macro_derive(ExtractComponent, attributes(extract_component_filter))]
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pub fn derive_extract_component(input: TokenStream) -> TokenStream {
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extract_component::derive_extract_component(input)
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}
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#[proc_macro_derive(
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AsBindGroup,
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attributes(uniform, texture, sampler, bind_group_data, storage)
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)]
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pub fn derive_as_bind_group(input: TokenStream) -> TokenStream {
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let input = parse_macro_input!(input as DeriveInput);
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as_bind_group::derive_as_bind_group(input).unwrap_or_else(|err| err.to_compile_error().into())
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}
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