mirror of
https://github.com/bevyengine/bevy
synced 2024-12-23 11:33:06 +00:00
a0a3d8798b
# Objective - Add an `ExtractResourcePlugin` for convenience and consistency ## Solution - Add an `ExtractResourcePlugin` similar to `ExtractComponentPlugin` but for ECS `Resource`s. The system that is executed simply clones the main world resource into a render world resource, if and only if the main world resource was either added or changed since the last execution of the system. - Add an `ExtractResource` trait with a `fn extract_resource(res: &Self) -> Self` function. This is used by the `ExtractResourcePlugin` to extract the resource - Add a derive macro for `ExtractResource` on a `Resource` with the `Clone` trait, that simply returns `res.clone()` - Use `ExtractResourcePlugin` wherever both possible and appropriate
46 lines
1.5 KiB
Rust
46 lines
1.5 KiB
Rust
use std::marker::PhantomData;
|
|
|
|
use bevy_app::{App, Plugin};
|
|
use bevy_ecs::system::{Commands, Res, Resource};
|
|
pub use bevy_render_macros::ExtractResource;
|
|
|
|
use crate::{RenderApp, RenderStage};
|
|
|
|
/// Describes how a resource gets extracted for rendering.
|
|
///
|
|
/// Therefore the resource is transferred from the "main world" into the "render world"
|
|
/// in the [`RenderStage::Extract`](crate::RenderStage::Extract) step.
|
|
pub trait ExtractResource: Resource {
|
|
type Source: Resource;
|
|
|
|
/// Defines how the resource is transferred into the "render world".
|
|
fn extract_resource(source: &Self::Source) -> Self;
|
|
}
|
|
|
|
/// This plugin extracts the resources into the "render world".
|
|
///
|
|
/// Therefore it sets up the [`RenderStage::Extract`](crate::RenderStage::Extract) step
|
|
/// for the specified [`Resource`].
|
|
pub struct ExtractResourcePlugin<R: ExtractResource>(PhantomData<R>);
|
|
|
|
impl<R: ExtractResource> Default for ExtractResourcePlugin<R> {
|
|
fn default() -> Self {
|
|
Self(PhantomData)
|
|
}
|
|
}
|
|
|
|
impl<R: ExtractResource> Plugin for ExtractResourcePlugin<R> {
|
|
fn build(&self, app: &mut App) {
|
|
if let Ok(render_app) = app.get_sub_app_mut(RenderApp) {
|
|
render_app.add_system_to_stage(RenderStage::Extract, extract_resource::<R>);
|
|
}
|
|
}
|
|
}
|
|
|
|
/// This system extracts the resource of the corresponding [`Resource`] type
|
|
/// by cloning it.
|
|
pub fn extract_resource<R: ExtractResource>(mut commands: Commands, resource: Res<R::Source>) {
|
|
if resource.is_changed() {
|
|
commands.insert_resource(R::extract_resource(resource.into_inner()));
|
|
}
|
|
}
|