bevy/crates/bevy_render/src/extract_resource.rs

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use std::marker::PhantomData;
use bevy_app::{App, Plugin};
#[cfg(debug_assertions)]
use bevy_ecs::system::Local;
use bevy_ecs::system::{Commands, Res, ResMut, Resource};
pub use bevy_render_macros::ExtractResource;
Make `RenderStage::Extract` run on the render world (#4402) # Objective - Currently, the `Extract` `RenderStage` is executed on the main world, with the render world available as a resource. - However, when needing access to resources in the render world (e.g. to mutate them), the only way to do so was to get exclusive access to the whole `RenderWorld` resource. - This meant that effectively only one extract which wrote to resources could run at a time. - We didn't previously make `Extract`ing writing to the world a non-happy path, even though we want to discourage that. ## Solution - Move the extract stage to run on the render world. - Add the main world as a `MainWorld` resource. - Add an `Extract` `SystemParam` as a convenience to access a (read only) `SystemParam` in the main world during `Extract`. ## Future work It should be possible to avoid needing to use `get_or_spawn` for the render commands, since now the `Commands`' `Entities` matches up with the world being executed on. We need to determine how this interacts with https://github.com/bevyengine/bevy/pull/3519 It's theoretically possible to remove the need for the `value` method on `Extract`. However, that requires slightly changing the `SystemParam` interface, which would make it more complicated. That would probably mess up the `SystemState` api too. ## Todo I still need to add doc comments to `Extract`. --- ## Changelog ### Changed - The `Extract` `RenderStage` now runs on the render world (instead of the main world as before). You must use the `Extract` `SystemParam` to access the main world during the extract phase. Resources on the render world can now be accessed using `ResMut` during extract. ### Removed - `Commands::spawn_and_forget`. Use `Commands::get_or_spawn(e).insert_bundle(bundle)` instead ## Migration Guide The `Extract` `RenderStage` now runs on the render world (instead of the main world as before). You must use the `Extract` `SystemParam` to access the main world during the extract phase. `Extract` takes a single type parameter, which is any system parameter (such as `Res`, `Query` etc.). It will extract this from the main world, and returns the result of this extraction when `value` is called on it. For example, if previously your extract system looked like: ```rust fn extract_clouds(mut commands: Commands, clouds: Query<Entity, With<Cloud>>) { for cloud in clouds.iter() { commands.get_or_spawn(cloud).insert(Cloud); } } ``` the new version would be: ```rust fn extract_clouds(mut commands: Commands, mut clouds: Extract<Query<Entity, With<Cloud>>>) { for cloud in clouds.value().iter() { commands.get_or_spawn(cloud).insert(Cloud); } } ``` The diff is: ```diff --- a/src/clouds.rs +++ b/src/clouds.rs @@ -1,5 +1,5 @@ -fn extract_clouds(mut commands: Commands, clouds: Query<Entity, With<Cloud>>) { - for cloud in clouds.iter() { +fn extract_clouds(mut commands: Commands, mut clouds: Extract<Query<Entity, With<Cloud>>>) { + for cloud in clouds.value().iter() { commands.get_or_spawn(cloud).insert(Cloud); } } ``` You can now also access resources from the render world using the normal system parameters during `Extract`: ```rust fn extract_assets(mut render_assets: ResMut<MyAssets>, source_assets: Extract<Res<MyAssets>>) { *render_assets = source_assets.clone(); } ``` Please note that all existing extract systems need to be updated to match this new style; even if they currently compile they will not run as expected. A warning will be emitted on a best-effort basis if this is not met. Co-authored-by: Carter Anderson <mcanders1@gmail.com>
2022-07-08 23:56:33 +00:00
use crate::{Extract, 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
Make `RenderStage::Extract` run on the render world (#4402) # Objective - Currently, the `Extract` `RenderStage` is executed on the main world, with the render world available as a resource. - However, when needing access to resources in the render world (e.g. to mutate them), the only way to do so was to get exclusive access to the whole `RenderWorld` resource. - This meant that effectively only one extract which wrote to resources could run at a time. - We didn't previously make `Extract`ing writing to the world a non-happy path, even though we want to discourage that. ## Solution - Move the extract stage to run on the render world. - Add the main world as a `MainWorld` resource. - Add an `Extract` `SystemParam` as a convenience to access a (read only) `SystemParam` in the main world during `Extract`. ## Future work It should be possible to avoid needing to use `get_or_spawn` for the render commands, since now the `Commands`' `Entities` matches up with the world being executed on. We need to determine how this interacts with https://github.com/bevyengine/bevy/pull/3519 It's theoretically possible to remove the need for the `value` method on `Extract`. However, that requires slightly changing the `SystemParam` interface, which would make it more complicated. That would probably mess up the `SystemState` api too. ## Todo I still need to add doc comments to `Extract`. --- ## Changelog ### Changed - The `Extract` `RenderStage` now runs on the render world (instead of the main world as before). You must use the `Extract` `SystemParam` to access the main world during the extract phase. Resources on the render world can now be accessed using `ResMut` during extract. ### Removed - `Commands::spawn_and_forget`. Use `Commands::get_or_spawn(e).insert_bundle(bundle)` instead ## Migration Guide The `Extract` `RenderStage` now runs on the render world (instead of the main world as before). You must use the `Extract` `SystemParam` to access the main world during the extract phase. `Extract` takes a single type parameter, which is any system parameter (such as `Res`, `Query` etc.). It will extract this from the main world, and returns the result of this extraction when `value` is called on it. For example, if previously your extract system looked like: ```rust fn extract_clouds(mut commands: Commands, clouds: Query<Entity, With<Cloud>>) { for cloud in clouds.iter() { commands.get_or_spawn(cloud).insert(Cloud); } } ``` the new version would be: ```rust fn extract_clouds(mut commands: Commands, mut clouds: Extract<Query<Entity, With<Cloud>>>) { for cloud in clouds.value().iter() { commands.get_or_spawn(cloud).insert(Cloud); } } ``` The diff is: ```diff --- a/src/clouds.rs +++ b/src/clouds.rs @@ -1,5 +1,5 @@ -fn extract_clouds(mut commands: Commands, clouds: Query<Entity, With<Cloud>>) { - for cloud in clouds.iter() { +fn extract_clouds(mut commands: Commands, mut clouds: Extract<Query<Entity, With<Cloud>>>) { + for cloud in clouds.value().iter() { commands.get_or_spawn(cloud).insert(Cloud); } } ``` You can now also access resources from the render world using the normal system parameters during `Extract`: ```rust fn extract_assets(mut render_assets: ResMut<MyAssets>, source_assets: Extract<Res<MyAssets>>) { *render_assets = source_assets.clone(); } ``` Please note that all existing extract systems need to be updated to match this new style; even if they currently compile they will not run as expected. A warning will be emitted on a best-effort basis if this is not met. Co-authored-by: Carter Anderson <mcanders1@gmail.com>
2022-07-08 23:56:33 +00:00
pub fn extract_resource<R: ExtractResource>(
mut commands: Commands,
main_resource: Extract<Res<R::Source>>,
target_resource: Option<ResMut<R>>,
#[cfg(debug_assertions)] mut has_warned_on_remove: Local<bool>,
Make `RenderStage::Extract` run on the render world (#4402) # Objective - Currently, the `Extract` `RenderStage` is executed on the main world, with the render world available as a resource. - However, when needing access to resources in the render world (e.g. to mutate them), the only way to do so was to get exclusive access to the whole `RenderWorld` resource. - This meant that effectively only one extract which wrote to resources could run at a time. - We didn't previously make `Extract`ing writing to the world a non-happy path, even though we want to discourage that. ## Solution - Move the extract stage to run on the render world. - Add the main world as a `MainWorld` resource. - Add an `Extract` `SystemParam` as a convenience to access a (read only) `SystemParam` in the main world during `Extract`. ## Future work It should be possible to avoid needing to use `get_or_spawn` for the render commands, since now the `Commands`' `Entities` matches up with the world being executed on. We need to determine how this interacts with https://github.com/bevyengine/bevy/pull/3519 It's theoretically possible to remove the need for the `value` method on `Extract`. However, that requires slightly changing the `SystemParam` interface, which would make it more complicated. That would probably mess up the `SystemState` api too. ## Todo I still need to add doc comments to `Extract`. --- ## Changelog ### Changed - The `Extract` `RenderStage` now runs on the render world (instead of the main world as before). You must use the `Extract` `SystemParam` to access the main world during the extract phase. Resources on the render world can now be accessed using `ResMut` during extract. ### Removed - `Commands::spawn_and_forget`. Use `Commands::get_or_spawn(e).insert_bundle(bundle)` instead ## Migration Guide The `Extract` `RenderStage` now runs on the render world (instead of the main world as before). You must use the `Extract` `SystemParam` to access the main world during the extract phase. `Extract` takes a single type parameter, which is any system parameter (such as `Res`, `Query` etc.). It will extract this from the main world, and returns the result of this extraction when `value` is called on it. For example, if previously your extract system looked like: ```rust fn extract_clouds(mut commands: Commands, clouds: Query<Entity, With<Cloud>>) { for cloud in clouds.iter() { commands.get_or_spawn(cloud).insert(Cloud); } } ``` the new version would be: ```rust fn extract_clouds(mut commands: Commands, mut clouds: Extract<Query<Entity, With<Cloud>>>) { for cloud in clouds.value().iter() { commands.get_or_spawn(cloud).insert(Cloud); } } ``` The diff is: ```diff --- a/src/clouds.rs +++ b/src/clouds.rs @@ -1,5 +1,5 @@ -fn extract_clouds(mut commands: Commands, clouds: Query<Entity, With<Cloud>>) { - for cloud in clouds.iter() { +fn extract_clouds(mut commands: Commands, mut clouds: Extract<Query<Entity, With<Cloud>>>) { + for cloud in clouds.value().iter() { commands.get_or_spawn(cloud).insert(Cloud); } } ``` You can now also access resources from the render world using the normal system parameters during `Extract`: ```rust fn extract_assets(mut render_assets: ResMut<MyAssets>, source_assets: Extract<Res<MyAssets>>) { *render_assets = source_assets.clone(); } ``` Please note that all existing extract systems need to be updated to match this new style; even if they currently compile they will not run as expected. A warning will be emitted on a best-effort basis if this is not met. Co-authored-by: Carter Anderson <mcanders1@gmail.com>
2022-07-08 23:56:33 +00:00
) {
if let Some(mut target_resource) = target_resource {
if main_resource.is_changed() {
*target_resource = R::extract_resource(&main_resource);
}
} else {
#[cfg(debug_assertions)]
if !main_resource.is_added() && !*has_warned_on_remove {
*has_warned_on_remove = true;
bevy_log::warn!(
"Removing resource {} from render world not expected, adding using `Commands`.
This may decrease performance",
std::any::type_name::<R>()
);
}
commands.insert_resource(R::extract_resource(&main_resource));
}
}