Allow configuring fullscreen material system order (#23786)

# Objective

Fixes #23781

When Hdr is on, the order of `tonemapping` and
`fullscreen_material_system` is uncertain and the result of main pass
can be cleared. `run_in` `run_before` `run_after` can only specify
system set and can't specify a specific system and them hardcode
`Core3dSystems`.

## Solution

Replace `run_in` `run_before` `run_after` with `fn
schedule_configs(system: ScheduleConfigs<BoxedSystem>) ->
ScheduleConfigs<BoxedSystem>`

## Testing

Run fullscreen_material example with Hdr

Author: beicause

_release-content/migration-guides/fullscreen_material_schedule_configs.md

@@ -0,0 +1,37 @@
+---
+title: "`FullScreenMaterial` API changes"
+pull_requests: [23786]
+---
+
+`FullScreenMaterial::run_in`, `FullScreenMaterial::run_after` and `FullScreenMaterial::run_before` are replaced
+by `FullScreenMaterial::schedule_configs` to configure the system order.
+
+```rust
+// 0.18
+impl FullscreenMaterial for FullscreenEffect {
+    fn fragment_shader() -> ShaderRef {
+        "shaders/fullscreen_effect.wgsl".into()
+    }
+    fn run_in() -> impl SystemSet {
+        Core3dSystems::PostProcess
+    }
+    fn run_after() -> Option<Core3dSystems> {
+        None
+    }
+    fn run_before() -> Option<Core3dSystems> {
+        None
+    }
+}
+
+// 0.19
+impl FullscreenMaterial for FullscreenEffect {
+    fn fragment_shader() -> ShaderRef {
+        "shaders/fullscreen_effect.wgsl".into()
+    }
+    fn schedule_configs(system: ScheduleConfigs<BoxedSystem>) -> ScheduleConfigs<BoxedSystem> {
+        system
+            .in_set(Core3dSystems::PostProcess)
+            .before(tonemapping)
+    }
+}
+```

crates/bevy_core_pipeline/src/fullscreen_material.rs

@@ -7,7 +7,7 @@
 use core::any::type_name;
 use core::marker::PhantomData;
 
-use crate::{schedule::Core3d, Core3dSystems, FullscreenShader};
+use crate::{schedule::Core3d, tonemapping::tonemapping, Core3dSystems, FullscreenShader};
 use bevy_app::{App, Plugin};
 use bevy_asset::AssetServer;
 use bevy_ecs::{
@@ -16,8 +16,8 @@ use bevy_ecs::{
     error::BevyError,
     query::With,
     resource::Resource,
-    schedule::{IntoScheduleConfigs, ScheduleLabel, SystemSet},
-    system::{Commands, Query, Res, ResMut},
+    schedule::{IntoScheduleConfigs, ScheduleConfigs, ScheduleLabel},
+    system::{BoxedSystem, Commands, Query, Res, ResMut},
 };
 use bevy_render::{
     camera::ExtractedCamera,
@@ -68,13 +68,7 @@ impl<T: FullscreenMaterial> Plugin for FullscreenMaterialPlugin<T> {
                 ),
             );
 
-        let mut system = fullscreen_material_system::<T>.in_set(T::run_in());
-        if let Some(run_after) = T::run_after() {
-            system = system.after(run_after);
-        }
-        if let Some(run_before) = T::run_before() {
-            system = system.before(run_before);
-        }
+        let system = T::schedule_configs(fullscreen_material_system::<T>.into_configs());
         render_app.add_systems(T::schedule(), system);
     }
 }
@@ -93,30 +87,18 @@ pub trait FullscreenMaterial:
         Core3d
     }
 
-    /// The system set this effect belongs to.
-    ///
-    /// Defaults to [`Core3dSystems::PostProcess`].
-    fn run_in() -> impl SystemSet {
-        Core3dSystems::PostProcess
-    }
-
-    /// The system set this effect runs after.
-    ///
-    /// Defaults to `None`.
-    fn run_after() -> Option<Core3dSystems> {
-        None
-    }
-
-    /// The system set this effect runs before.
+    /// Configures this effect's system set and system order.
     ///
-    /// Defaults to `None`.
-    fn run_before() -> Option<Core3dSystems> {
-        None
+    /// By default it's in [`Core3dSystems::PostProcess`] and before [`tonemapping`].
+    fn schedule_configs(system: ScheduleConfigs<BoxedSystem>) -> ScheduleConfigs<BoxedSystem> {
+        system
+            .in_set(Core3dSystems::PostProcess)
+            .before(tonemapping)
     }
 }
 
 #[derive(Resource)]
-struct FullscreenMaterialPipeline<T: FullscreenMaterial> {
+pub struct FullscreenMaterialPipeline<T: FullscreenMaterial> {
     layout: BindGroupLayoutDescriptor,
     sampler: Sampler,
     variants: Variants<RenderPipeline, FullscreenMaterialPipelineSpecializer>,
@@ -203,7 +185,7 @@ fn init_pipeline<T: FullscreenMaterial>(
 }
 
 #[derive(Component)]
-struct FullscreenMaterialPipelineId(CachedRenderPipelineId);
+pub struct FullscreenMaterialPipelineId(pub CachedRenderPipelineId);
 
 fn prepare_fullscreen_material_pipelines<T: FullscreenMaterial>(
     mut commands: Commands,
@@ -232,7 +214,7 @@ fn prepare_fullscreen_material_pipelines<T: FullscreenMaterial>(
 /// We can't know ahead of time which one is the source or destination so we create a bind group
 /// for both
 #[derive(Component)]
-struct FullscreenMaterialBindGroup<T: FullscreenMaterial> {
+pub struct FullscreenMaterialBindGroup<T: FullscreenMaterial> {
     a: (TextureViewId, BindGroup),
     b: (TextureViewId, BindGroup),
     // This is in case someone wants multiple `FullscreenMaterial` per camera
@@ -295,7 +277,7 @@ fn prepare_bind_groups<T: FullscreenMaterial>(
     }
 }
 
-fn fullscreen_material_system<T: FullscreenMaterial>(
+pub fn fullscreen_material_system<T: FullscreenMaterial>(
     view: ViewQuery<(
         &ViewTarget,
         &DynamicUniformIndex<T>,

examples/shader_advanced/fullscreen_material.rs

@@ -91,7 +91,11 @@ impl FullscreenMaterial for FullscreenEffect {
     // fn schedule() -> impl bevy::ecs::schedule::ScheduleLabel + Clone {
     //     bevy::core_pipeline::Core2d
     // }
-    // fn run_in() -> impl SystemSet {
-    //     bevy::core_pipeline::Core2dSystems::PostProcess
+    // fn schedule_configs(
+    //     system: bevy::ecs::schedule::ScheduleConfigs<bevy::ecs::system::BoxedSystem>,
+    // ) -> bevy::ecs::schedule::ScheduleConfigs<bevy::ecs::system::BoxedSystem> {
+    //     system
+    //         .in_set(bevy::core_pipeline::Core2dSystems::PostProcess)
+    //         .before(bevy::core_pipeline::tonemapping::tonemapping)
     // }
 }