8de03b0839
# Objective - Extracting resources currently always uses commands, which requires *at least* one additional move of the extracted value, as well as dynamic dispatch. - Addresses https://github.com/bevyengine/bevy/pull/4402#discussion_r911634931 ## Solution - Write the resource into a `ResMut<R>` directly. - Fall-back to commands if the resource hasn't been added yet.
64 lines
2.2 KiB
Rust
64 lines
2.2 KiB
Rust
use std::marker::PhantomData;
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use bevy_app::{App, Plugin};
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use bevy_ecs::system::{Commands, Local, Res, ResMut, Resource};
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pub use bevy_render_macros::ExtractResource;
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use crate::{Extract, RenderApp, RenderStage};
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/// Describes how a resource gets extracted for rendering.
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///
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/// Therefore the resource is transferred from the "main world" into the "render world"
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/// in the [`RenderStage::Extract`](crate::RenderStage::Extract) step.
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pub trait ExtractResource: Resource {
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type Source: Resource;
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/// Defines how the resource is transferred into the "render world".
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fn extract_resource(source: &Self::Source) -> Self;
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}
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/// This plugin extracts the resources into the "render world".
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///
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/// Therefore it sets up the [`RenderStage::Extract`](crate::RenderStage::Extract) step
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/// for the specified [`Resource`].
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pub struct ExtractResourcePlugin<R: ExtractResource>(PhantomData<R>);
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impl<R: ExtractResource> Default for ExtractResourcePlugin<R> {
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fn default() -> Self {
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Self(PhantomData)
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}
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}
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impl<R: ExtractResource> Plugin for ExtractResourcePlugin<R> {
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fn build(&self, app: &mut App) {
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if let Ok(render_app) = app.get_sub_app_mut(RenderApp) {
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render_app.add_system_to_stage(RenderStage::Extract, extract_resource::<R>);
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}
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}
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}
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/// This system extracts the resource of the corresponding [`Resource`] type
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pub fn extract_resource<R: ExtractResource>(
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mut commands: Commands,
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main_resource: Extract<Res<R::Source>>,
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target_resource: Option<ResMut<R>>,
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#[cfg(debug_assertions)] mut has_warned_on_remove: Local<bool>,
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) {
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if let Some(mut target_resource) = target_resource {
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if main_resource.is_changed() {
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*target_resource = R::extract_resource(&*main_resource);
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}
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} else {
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#[cfg(debug_assertions)]
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if !main_resource.is_added() && !*has_warned_on_remove {
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*has_warned_on_remove = true;
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bevy_log::warn!(
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"Removing resource {} from render world not expected, adding using `Commands`.
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This may decrease performance",
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std::any::type_name::<R>()
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);
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}
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commands.insert_resource(R::extract_resource(&*main_resource));
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}
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}
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