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use crate::render_phase::{PhaseItem, TrackedRenderPass};
use bevy_app::{App, SubApp};
use bevy_ecs::{
entity::Entity,
query::{QueryState, ROQueryItem, ReadOnlyQueryData},
system::{ReadOnlySystemParam, Resource, SystemParam, SystemParamItem, SystemState},
world::World,
};
use bevy_utils::{all_tuples, TypeIdMap};
use std::{
any::TypeId,
fmt::Debug,
hash::Hash,
sync::{PoisonError, RwLock, RwLockReadGuard, RwLockWriteGuard},
};
/// A draw function used to draw [`PhaseItem`]s.
///
/// The draw function can retrieve and query the required ECS data from the render world.
///
/// This trait can either be implemented directly or implicitly composed out of multiple modular
/// [`RenderCommand`]s. For more details and an example see the [`RenderCommand`] documentation.
pub trait Draw<P: PhaseItem>: Send + Sync + 'static {
/// Prepares the draw function to be used. This is called once and only once before the phase
/// begins. There may be zero or more [`draw`](Draw::draw) calls following a call to this function.
/// Implementing this is optional.
#[allow(unused_variables)]
fn prepare(&mut self, world: &'_ World) {}
/// Draws a [`PhaseItem`] by issuing zero or more `draw` calls via the [`TrackedRenderPass`].
fn draw<'w>(
&mut self,
world: &'w World,
pass: &mut TrackedRenderPass<'w>,
view: Entity,
item: &P,
);
}
// TODO: make this generic?
/// An identifier for a [`Draw`] function stored in [`DrawFunctions`].
#[derive(Copy, Clone, Debug, Eq, PartialEq, PartialOrd, Ord, Hash)]
pub struct DrawFunctionId(u32);
/// Stores all [`Draw`] functions for the [`PhaseItem`] type.
///
/// For retrieval, the [`Draw`] functions are mapped to their respective [`TypeId`]s.
pub struct DrawFunctionsInternal<P: PhaseItem> {
pub draw_functions: Vec<Box<dyn Draw<P>>>,
pub indices: TypeIdMap<DrawFunctionId>,
}
impl<P: PhaseItem> DrawFunctionsInternal<P> {
/// Prepares all draw function. This is called once and only once before the phase begins.
pub fn prepare(&mut self, world: &World) {
for function in &mut self.draw_functions {
function.prepare(world);
}
}
/// Adds the [`Draw`] function and maps it to its own type.
pub fn add<T: Draw<P>>(&mut self, draw_function: T) -> DrawFunctionId {
self.add_with::<T, T>(draw_function)
}
/// Adds the [`Draw`] function and maps it to the type `T`
pub fn add_with<T: 'static, D: Draw<P>>(&mut self, draw_function: D) -> DrawFunctionId {
let id = DrawFunctionId(self.draw_functions.len().try_into().unwrap());
self.draw_functions.push(Box::new(draw_function));
self.indices.insert(TypeId::of::<T>(), id);
id
}
/// Retrieves the [`Draw`] function corresponding to the `id` mutably.
pub fn get_mut(&mut self, id: DrawFunctionId) -> Option<&mut dyn Draw<P>> {
self.draw_functions.get_mut(id.0 as usize).map(|f| &mut **f)
}
/// Retrieves the id of the [`Draw`] function corresponding to their associated type `T`.
pub fn get_id<T: 'static>(&self) -> Option<DrawFunctionId> {
self.indices.get(&TypeId::of::<T>()).copied()
}
/// Retrieves the id of the [`Draw`] function corresponding to their associated type `T`.
///
/// Fallible wrapper for [`Self::get_id()`]
///
/// ## Panics
/// If the id doesn't exist, this function will panic.
pub fn id<T: 'static>(&self) -> DrawFunctionId {
self.get_id::<T>().unwrap_or_else(|| {
panic!(
"Draw function {} not found for {}",
std::any::type_name::<T>(),
std::any::type_name::<P>()
)
})
}
}
/// Stores all draw functions for the [`PhaseItem`] type hidden behind a reader-writer lock.
///
/// To access them the [`DrawFunctions::read`] and [`DrawFunctions::write`] methods are used.
#[derive(Resource)]
pub struct DrawFunctions<P: PhaseItem> {
internal: RwLock<DrawFunctionsInternal<P>>,
}
impl<P: PhaseItem> Default for DrawFunctions<P> {
fn default() -> Self {
Self {
internal: RwLock::new(DrawFunctionsInternal {
draw_functions: Vec::new(),
indices: Default::default(),
}),
}
}
}
impl<P: PhaseItem> DrawFunctions<P> {
/// Accesses the draw functions in read mode.
pub fn read(&self) -> RwLockReadGuard<'_, DrawFunctionsInternal<P>> {
self.internal.read().unwrap_or_else(PoisonError::into_inner)
}
/// Accesses the draw functions in write mode.
pub fn write(&self) -> RwLockWriteGuard<'_, DrawFunctionsInternal<P>> {
self.internal
.write()
.unwrap_or_else(PoisonError::into_inner)
}
}
/// [`RenderCommand`]s are modular standardized pieces of render logic that can be composed into
/// [`Draw`] functions.
///
/// To turn a stateless render command into a usable draw function it has to be wrapped by a
/// [`RenderCommandState`].
/// This is done automatically when registering a render command as a [`Draw`] function via the
/// [`AddRenderCommand::add_render_command`] method.
///
/// Compared to the draw function the required ECS data is fetched automatically
/// (by the [`RenderCommandState`]) from the render world.
/// Therefore the three types [`Param`](RenderCommand::Param),
/// [`ViewQuery`](RenderCommand::ViewQuery) and
/// [`ItemQuery`](RenderCommand::ItemQuery) are used.
/// They specify which information is required to execute the render command.
///
/// Multiple render commands can be combined together by wrapping them in a tuple.
///
/// # Example
///
/// The `DrawMaterial` draw function is created from the following render command
/// tuple. Const generics are used to set specific bind group locations:
///
/// ```
/// # use bevy_render::render_phase::SetItemPipeline;
/// # struct SetMeshViewBindGroup<const N: usize>;
/// # struct SetMeshBindGroup<const N: usize>;
/// # struct SetMaterialBindGroup<M, const N: usize>(core::marker::PhantomData<M>);
/// # struct DrawMesh;
/// pub type DrawMaterial<M> = (
/// SetItemPipeline,
/// SetMeshViewBindGroup<0>,
/// SetMeshBindGroup<1>,
/// SetMaterialBindGroup<M, 2>,
/// DrawMesh,
/// );
/// ```
pub trait RenderCommand<P: PhaseItem> {
/// Specifies the general ECS data (e.g. resources) required by [`RenderCommand::render`].
///
/// When fetching resources, note that, due to lifetime limitations of the `Deref` trait,
/// [`SRes::into_inner`] must be called on each [`SRes`] reference in the
/// [`RenderCommand::render`] method, instead of being automatically dereferenced as is the
/// case in normal `systems`.
///
/// All parameters have to be read only.
///
/// [`SRes`]: bevy_ecs::system::lifetimeless::SRes
/// [`SRes::into_inner`]: bevy_ecs::system::lifetimeless::SRes::into_inner
type Param: SystemParam + 'static;
/// Specifies the ECS data of the view entity required by [`RenderCommand::render`].
///
/// The view entity refers to the camera, or shadow-casting light, etc. from which the phase
/// item will be rendered from.
/// All components have to be accessed read only.
type ViewQuery: ReadOnlyQueryData;
/// Specifies the ECS data of the item entity required by [`RenderCommand::render`].
///
/// The item is the entity that will be rendered for the corresponding view.
/// All components have to be accessed read only.
///
/// For efficiency reasons, Bevy doesn't always extract entities to the
/// render world; for instance, entities that simply consist of meshes are
/// often not extracted. If the entity doesn't exist in the render world,
/// the supplied query data will be `None`.
type ItemQuery: ReadOnlyQueryData;
/// Renders a [`PhaseItem`] by recording commands (e.g. setting pipelines, binding bind groups,
/// issuing draw calls, etc.) via the [`TrackedRenderPass`].
fn render<'w>(
item: &P,
view: ROQueryItem<'w, Self::ViewQuery>,
entity: Option<ROQueryItem<'w, Self::ItemQuery>>,
param: SystemParamItem<'w, '_, Self::Param>,
pass: &mut TrackedRenderPass<'w>,
) -> RenderCommandResult;
}
/// The result of a [`RenderCommand`].
#[derive(Debug)]
pub enum RenderCommandResult {
Success,
Failure,
}
macro_rules! render_command_tuple_impl {
($(($name: ident, $view: ident, $entity: ident)),*) => {
impl<P: PhaseItem, $($name: RenderCommand<P>),*> RenderCommand<P> for ($($name,)*) {
type Param = ($($name::Param,)*);
type ViewQuery = ($($name::ViewQuery,)*);
type ItemQuery = ($($name::ItemQuery,)*);
#[allow(non_snake_case)]
fn render<'w>(
_item: &P,
($($view,)*): ROQueryItem<'w, Self::ViewQuery>,
maybe_entities: Option<ROQueryItem<'w, Self::ItemQuery>>,
($($name,)*): SystemParamItem<'w, '_, Self::Param>,
_pass: &mut TrackedRenderPass<'w>,
) -> RenderCommandResult {
match maybe_entities {
None => {
$(if let RenderCommandResult::Failure = $name::render(_item, $view, None, $name, _pass) {
return RenderCommandResult::Failure;
})*
}
Some(($($entity,)*)) => {
$(if let RenderCommandResult::Failure = $name::render(_item, $view, Some($entity), $name, _pass) {
return RenderCommandResult::Failure;
})*
}
}
RenderCommandResult::Success
}
}
};
}
all_tuples!(render_command_tuple_impl, 0, 15, C, V, E);
/// Wraps a [`RenderCommand`] into a state so that it can be used as a [`Draw`] function.
///
/// The [`RenderCommand::Param`], [`RenderCommand::ViewQuery`] and
/// [`RenderCommand::ItemQuery`] are fetched from the ECS and passed to the command.
pub struct RenderCommandState<P: PhaseItem + 'static, C: RenderCommand<P>> {
state: SystemState<C::Param>,
view: QueryState<C::ViewQuery>,
entity: QueryState<C::ItemQuery>,
}
impl<P: PhaseItem, C: RenderCommand<P>> RenderCommandState<P, C> {
/// Creates a new [`RenderCommandState`] for the [`RenderCommand`].
pub fn new(world: &mut World) -> Self {
Self {
state: SystemState::new(world),
view: world.query(),
entity: world.query(),
}
}
}
impl<P: PhaseItem, C: RenderCommand<P> + Send + Sync + 'static> Draw<P> for RenderCommandState<P, C>
where
C::Param: ReadOnlySystemParam,
{
/// Prepares the render command to be used. This is called once and only once before the phase
/// begins. There may be zero or more [`draw`](RenderCommandState::draw) calls following a call to this function.
fn prepare(&mut self, world: &'_ World) {
self.state.update_archetypes(world);
self.view.update_archetypes(world);
self.entity.update_archetypes(world);
}
/// Fetches the ECS parameters for the wrapped [`RenderCommand`] and then renders it.
fn draw<'w>(
&mut self,
world: &'w World,
pass: &mut TrackedRenderPass<'w>,
view: Entity,
item: &P,
) {
let param = self.state.get_manual(world);
let view = self.view.get_manual(world, view).unwrap();
let entity = self.entity.get_manual(world, item.entity()).ok();
// TODO: handle/log `RenderCommand` failure
C::render(item, view, entity, param, pass);
}
}
/// Registers a [`RenderCommand`] as a [`Draw`] function.
/// They are stored inside the [`DrawFunctions`] resource of the app.
pub trait AddRenderCommand {
/// Adds the [`RenderCommand`] for the specified render phase to the app.
fn add_render_command<P: PhaseItem, C: RenderCommand<P> + Send + Sync + 'static>(
&mut self,
) -> &mut Self
where
C::Param: ReadOnlySystemParam;
}
impl AddRenderCommand for SubApp {
fn add_render_command<P: PhaseItem, C: RenderCommand<P> + Send + Sync + 'static>(
&mut self,
) -> &mut Self
where
C::Param: ReadOnlySystemParam,
{
let draw_function = RenderCommandState::<P, C>::new(self.world_mut());
let draw_functions = self
.world()
.get_resource::<DrawFunctions<P>>()
.unwrap_or_else(|| {
panic!(
"DrawFunctions<{}> must be added to the world as a resource \
before adding render commands to it",
std::any::type_name::<P>(),
);
});
draw_functions.write().add_with::<C, _>(draw_function);
self
}
}
impl AddRenderCommand for App {
fn add_render_command<P: PhaseItem, C: RenderCommand<P> + Send + Sync + 'static>(
&mut self,
) -> &mut Self
where
C::Param: ReadOnlySystemParam,
{
SubApp::add_render_command::<P, C>(self.main_mut());
self
}
}