4b446c020e
# Objective - Provide feedback when an extraction plugin fails to add its system. I had some troubleshooting pain when this happened to me, as the panic only tells you a resource is missing. This PR adds an error when the ExtractResource plugin is added before the render world exists, instead of silently failing. 
69 lines
2.3 KiB
Rust
69 lines
2.3 KiB
Rust
use std::marker::PhantomData;
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use bevy_app::{App, Plugin};
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use bevy_ecs::prelude::*;
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pub use bevy_render_macros::ExtractResource;
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use crate::{Extract, ExtractSchedule, RenderApp};
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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 [`ExtractSchedule`] 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[`ExtractSchedule`] 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 Some(render_app) = app.get_sub_app_mut(RenderApp) {
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render_app.add_systems(ExtractSchedule, extract_resource::<R>);
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} else {
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bevy_utils::error_once!(
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"Render app did not exist when trying to add `extract_resource` for <{}>.",
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std::any::type_name::<R>()
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);
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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<Option<Res<R::Source>>>,
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target_resource: Option<ResMut<R>>,
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) {
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if let Some(main_resource) = main_resource.as_ref() {
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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() {
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bevy_utils::warn_once!(
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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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}
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