Refactor AsBindGroup to use a associated SystemParam. (#14909)

# Objective

Adding more features to `AsBindGroup` proc macro means making the trait
arguments uglier. Downstream implementors of the trait without the proc
macro might want to do different things than our default arguments.

## Solution

Make `AsBindGroup` take an associated `Param` type.

## Migration Guide

`AsBindGroup` now allows the user to specify a `SystemParam` to be used
for creating bind groups.

crates/bevy_pbr/src/extended_material.rs

@@ -1,14 +1,13 @@
 use bevy_asset::{Asset, Handle};
+use bevy_ecs::system::SystemParamItem;
 use bevy_reflect::{impl_type_path, Reflect};
 use bevy_render::{
     mesh::MeshVertexBufferLayoutRef,
-    render_asset::RenderAssets,
     render_resource::{
         AsBindGroup, AsBindGroupError, BindGroupLayout, RenderPipelineDescriptor, Shader,
         ShaderRef, SpecializedMeshPipelineError, UnpreparedBindGroup,
     },
     renderer::RenderDevice,
-    texture::{FallbackImage, GpuImage},
 };
 
 use crate::{Material, MaterialPipeline, MaterialPipelineKey, MeshPipeline, MeshPipelineKey};
@@ -147,26 +146,21 @@ impl_type_path!((in bevy_pbr::extended_material) ExtendedMaterial<B: Material, E
 
 impl<B: Material, E: MaterialExtension> AsBindGroup for ExtendedMaterial<B, E> {
     type Data = (<B as AsBindGroup>::Data, <E as AsBindGroup>::Data);
+    type Param = (<B as AsBindGroup>::Param, <E as AsBindGroup>::Param);
 
     fn unprepared_bind_group(
         &self,
         layout: &BindGroupLayout,
         render_device: &RenderDevice,
-        images: &RenderAssets<GpuImage>,
-        fallback_image: &FallbackImage,
+        (base_param, extended_param): &mut SystemParamItem<'_, '_, Self::Param>,
     ) -> Result<UnpreparedBindGroup<Self::Data>, AsBindGroupError> {
         // add together the bindings of the base material and the user material
         let UnpreparedBindGroup {
             mut bindings,
             data: base_data,
-        } = B::unprepared_bind_group(&self.base, layout, render_device, images, fallback_image)?;
-        let extended_bindgroup = E::unprepared_bind_group(
-            &self.extension,
-            layout,
-            render_device,
-            images,
-            fallback_image,
-        )?;
+        } = B::unprepared_bind_group(&self.base, layout, render_device, base_param)?;
+        let extended_bindgroup =
+            E::unprepared_bind_group(&self.extension, layout, render_device, extended_param)?;
 
         bindings.extend(extended_bindgroup.bindings);
 

crates/bevy_pbr/src/material.rs

@@ -30,7 +30,6 @@ use bevy_render::{
     render_phase::*,
     render_resource::*,
     renderer::RenderDevice,
-    texture::FallbackImage,
     view::{ExtractedView, Msaa, RenderVisibilityRanges, VisibleEntities, WithMesh},
 };
 use bevy_utils::tracing::error;
@@ -908,22 +907,16 @@ impl<M: Material> RenderAsset for PreparedMaterial<M> {
 
     type Param = (
         SRes<RenderDevice>,
-        SRes<RenderAssets<GpuImage>>,
-        SRes<FallbackImage>,
         SRes<MaterialPipeline<M>>,
         SRes<DefaultOpaqueRendererMethod>,
+        M::Param,
     );
 
     fn prepare_asset(
         material: Self::SourceAsset,
-        (render_device, images, fallback_image, pipeline, default_opaque_render_method): &mut SystemParamItem<Self::Param>,
+        (render_device, pipeline, default_opaque_render_method, ref mut material_param): &mut SystemParamItem<Self::Param>,
     ) -> Result<Self, PrepareAssetError<Self::SourceAsset>> {
-        match material.as_bind_group(
-            &pipeline.material_layout,
-            render_device,
-            images,
-            fallback_image,
-        ) {
+        match material.as_bind_group(&pipeline.material_layout, render_device, material_param) {
             Ok(prepared) => {
                 let method = match material.opaque_render_method() {
                     OpaqueRendererMethod::Forward => OpaqueRendererMethod::Forward,

crates/bevy_render/macros/src/as_bind_group.rs

@@ -42,6 +42,7 @@ pub fn derive_as_bind_group(ast: syn::DeriveInput) -> Result<TokenStream> {
     let manifest = BevyManifest::default();
     let render_path = manifest.get_path("bevy_render");
     let asset_path = manifest.get_path("bevy_asset");
+    let ecs_path = manifest.get_path("bevy_ecs");
 
     let mut binding_states: Vec<BindingState> = Vec::new();
     let mut binding_impls = Vec::new();
@@ -62,7 +63,7 @@ pub fn derive_as_bind_group(ast: syn::DeriveInput) -> Result<TokenStream> {
                 binding_impls.push(quote! {{
                     use #render_path::render_resource::AsBindGroupShaderType;
                     let mut buffer = #render_path::render_resource::encase::UniformBuffer::new(Vec::new());
-                    let converted: #converted_shader_type = self.as_bind_group_shader_type(images);
+                    let converted: #converted_shader_type = self.as_bind_group_shader_type(&images);
                     buffer.write(&converted).unwrap();
                     (
                         #binding_index,
@@ -523,6 +524,11 @@ pub fn derive_as_bind_group(ast: syn::DeriveInput) -> Result<TokenStream> {
         impl #impl_generics #render_path::render_resource::AsBindGroup for #struct_name #ty_generics #where_clause {
             type Data = #prepared_data;
 
+            type Param = (
+                #ecs_path::system::lifetimeless::SRes<#render_path::render_asset::RenderAssets<#render_path::texture::GpuImage>>,
+                #ecs_path::system::lifetimeless::SRes<#render_path::texture::FallbackImage>,
+            );
+
             fn label() -> Option<&'static str> {
                 Some(#struct_name_literal)
             }
@@ -531,8 +537,7 @@ pub fn derive_as_bind_group(ast: syn::DeriveInput) -> Result<TokenStream> {
                 &self,
                 layout: &#render_path::render_resource::BindGroupLayout,
                 render_device: &#render_path::renderer::RenderDevice,
-                images: &#render_path::render_asset::RenderAssets<#render_path::texture::GpuImage>,
-                fallback_image: &#render_path::texture::FallbackImage,
+                (images, fallback_image): &mut #ecs_path::system::SystemParamItem<'_, '_, Self::Param>,
             ) -> Result<#render_path::render_resource::UnpreparedBindGroup<Self::Data>, #render_path::render_resource::AsBindGroupError> {
                 let bindings = vec![#(#binding_impls,)*];
 

crates/bevy_render/src/render_resource/bind_group.rs

@@ -3,8 +3,9 @@ use crate::{
     render_asset::RenderAssets,
     render_resource::{resource_macros::*, BindGroupLayout, Buffer, Sampler, TextureView},
     renderer::RenderDevice,
-    texture::{FallbackImage, GpuImage},
+    texture::GpuImage,
 };
+use bevy_ecs::system::{SystemParam, SystemParamItem};
 pub use bevy_render_macros::AsBindGroup;
 use encase::ShaderType;
 use std::ops::Deref;
@@ -57,7 +58,7 @@ impl Deref for BindGroup {
 ///
 /// This is an opinionated trait that is intended to make it easy to generically
 /// convert a type into a [`BindGroup`]. It provides access to specific render resources,
-/// such as [`RenderAssets<GpuImage>`] and [`FallbackImage`]. If a type has a [`Handle<Image>`](bevy_asset::Handle),
+/// such as [`RenderAssets<GpuImage>`] and [`crate::texture::FallbackImage`]. If a type has a [`Handle<Image>`](bevy_asset::Handle),
 /// these can be used to retrieve the corresponding [`Texture`](crate::render_resource::Texture) resource.
 ///
 /// [`AsBindGroup::as_bind_group`] is intended to be called once, then the result cached somewhere. It is generally
@@ -115,7 +116,7 @@ impl Deref for BindGroup {
 ///     * This field's [`Handle<Image>`](bevy_asset::Handle) will be used to look up the matching [`Texture`](crate::render_resource::Texture)
 ///         GPU resource, which will be bound as a texture in shaders. The field will be assumed to implement [`Into<Option<Handle<Image>>>`]. In practice,
 ///         most fields should be a [`Handle<Image>`](bevy_asset::Handle) or [`Option<Handle<Image>>`]. If the value of an [`Option<Handle<Image>>`] is
-///         [`None`], the [`FallbackImage`] resource will be used instead. This attribute can be used in conjunction with a `sampler` binding attribute
+///         [`None`], the [`crate::texture::FallbackImage`] resource will be used instead. This attribute can be used in conjunction with a `sampler` binding attribute
 ///         (with a different binding index) if a binding of the sampler for the [`Image`](crate::texture::Image) is also required.
 ///
 /// | Arguments             | Values                                                                  | Default              |
@@ -130,7 +131,7 @@ impl Deref for BindGroup {
 ///     * This field's [`Handle<Image>`](bevy_asset::Handle) will be used to look up the matching [`Texture`](crate::render_resource::Texture)
 ///         GPU resource, which will be bound as a storage texture in shaders. The field will be assumed to implement [`Into<Option<Handle<Image>>>`]. In practice,
 ///         most fields should be a [`Handle<Image>`](bevy_asset::Handle) or [`Option<Handle<Image>>`]. If the value of an [`Option<Handle<Image>>`] is
-///         [`None`], the [`FallbackImage`] resource will be used instead.
+///         [`None`], the [`crate::texture::FallbackImage`] resource will be used instead.
 ///
 /// | Arguments              | Values                                                                                     | Default       |
 /// |------------------------|--------------------------------------------------------------------------------------------|---------------|
@@ -143,7 +144,7 @@ impl Deref for BindGroup {
 ///     * This field's [`Handle<Image>`](bevy_asset::Handle) will be used to look up the matching [`Sampler`] GPU
 ///         resource, which will be bound as a sampler in shaders. The field will be assumed to implement [`Into<Option<Handle<Image>>>`]. In practice,
 ///         most fields should be a [`Handle<Image>`](bevy_asset::Handle) or [`Option<Handle<Image>>`]. If the value of an [`Option<Handle<Image>>`] is
-///         [`None`], the [`FallbackImage`] resource will be used instead. This attribute can be used in conjunction with a `texture` binding attribute
+///         [`None`], the [`crate::texture::FallbackImage`] resource will be used instead. This attribute can be used in conjunction with a `texture` binding attribute
 ///         (with a different binding index) if a binding of the texture for the [`Image`](crate::texture::Image) is also required.
 ///
 /// | Arguments              | Values                                                                  | Default                |
@@ -187,7 +188,7 @@ impl Deref for BindGroup {
 ///     color_texture: Option<Handle<Image>>,
 /// }
 /// ```
-/// This is useful if you want a texture to be optional. When the value is [`None`], the [`FallbackImage`] will be used for the binding instead, which defaults
+/// This is useful if you want a texture to be optional. When the value is [`None`], the [`crate::texture::FallbackImage`] will be used for the binding instead, which defaults
 /// to "pure white".
 ///
 /// Field uniforms with the same index will be combined into a single binding:
@@ -284,6 +285,8 @@ pub trait AsBindGroup {
     /// Data that will be stored alongside the "prepared" bind group.
     type Data: Send + Sync;
 
+    type Param: SystemParam + 'static;
+
     /// label
     fn label() -> Option<&'static str> {
         None
@@ -294,11 +297,10 @@ pub trait AsBindGroup {
         &self,
         layout: &BindGroupLayout,
         render_device: &RenderDevice,
-        images: &RenderAssets<GpuImage>,
-        fallback_image: &FallbackImage,
+        param: &mut SystemParamItem<'_, '_, Self::Param>,
     ) -> Result<PreparedBindGroup<Self::Data>, AsBindGroupError> {
         let UnpreparedBindGroup { bindings, data } =
-            Self::unprepared_bind_group(self, layout, render_device, images, fallback_image)?;
+            Self::unprepared_bind_group(self, layout, render_device, param)?;
 
         let entries = bindings
             .iter()
@@ -325,8 +327,7 @@ pub trait AsBindGroup {
         &self,
         layout: &BindGroupLayout,
         render_device: &RenderDevice,
-        images: &RenderAssets<GpuImage>,
-        fallback_image: &FallbackImage,
+        param: &mut SystemParamItem<'_, '_, Self::Param>,
     ) -> Result<UnpreparedBindGroup<Self::Data>, AsBindGroupError>;
 
     /// Creates the bind group layout matching all bind groups returned by [`AsBindGroup::as_bind_group`]

crates/bevy_sprite/src/mesh2d/material.rs

@@ -28,7 +28,6 @@ use bevy_render::{
         SpecializedMeshPipeline, SpecializedMeshPipelineError, SpecializedMeshPipelines,
     },
     renderer::RenderDevice,
-    texture::{FallbackImage, GpuImage},
     view::{ExtractedView, InheritedVisibility, Msaa, ViewVisibility, Visibility, VisibleEntities},
     Extract, ExtractSchedule, Render, RenderApp, RenderSet,
 };
@@ -581,23 +580,13 @@ impl<T: Material2d> PreparedMaterial2d<T> {
 impl<M: Material2d> RenderAsset for PreparedMaterial2d<M> {
     type SourceAsset = M;
 
-    type Param = (
-        SRes<RenderDevice>,
-        SRes<RenderAssets<GpuImage>>,
-        SRes<FallbackImage>,
-        SRes<Material2dPipeline<M>>,
-    );
+    type Param = (SRes<RenderDevice>, SRes<Material2dPipeline<M>>, M::Param);
 
     fn prepare_asset(
         material: Self::SourceAsset,
-        (render_device, images, fallback_image, pipeline): &mut SystemParamItem<Self::Param>,
+        (render_device, pipeline, material_param): &mut SystemParamItem<Self::Param>,
     ) -> Result<Self, PrepareAssetError<Self::SourceAsset>> {
-        match material.as_bind_group(
-            &pipeline.material2d_layout,
-            render_device,
-            images,
-            fallback_image,
-        ) {
+        match material.as_bind_group(&pipeline.material2d_layout, render_device, material_param) {
             Ok(prepared) => {
                 let mut mesh_pipeline_key_bits = Mesh2dPipelineKey::empty();
                 mesh_pipeline_key_bits.insert(alpha_mode_pipeline_key(material.alpha_mode()));

crates/bevy_ui/src/render/ui_material_pipeline.rs

@@ -16,7 +16,7 @@ use bevy_render::{
     render_phase::*,
     render_resource::{binding_types::uniform_buffer, *},
     renderer::{RenderDevice, RenderQueue},
-    texture::{BevyDefault, FallbackImage, GpuImage},
+    texture::BevyDefault,
     view::*,
     Extract, ExtractSchedule, Render, RenderSet,
 };
@@ -604,18 +604,13 @@ pub struct PreparedUiMaterial<T: UiMaterial> {
 impl<M: UiMaterial> RenderAsset for PreparedUiMaterial<M> {
     type SourceAsset = M;
 
-    type Param = (
-        SRes<RenderDevice>,
-        SRes<RenderAssets<GpuImage>>,
-        SRes<FallbackImage>,
-        SRes<UiMaterialPipeline<M>>,
-    );
+    type Param = (SRes<RenderDevice>, SRes<UiMaterialPipeline<M>>, M::Param);
 
     fn prepare_asset(
         material: Self::SourceAsset,
-        (render_device, images, fallback_image, pipeline): &mut SystemParamItem<Self::Param>,
+        (render_device, pipeline, ref mut material_param): &mut SystemParamItem<Self::Param>,
     ) -> Result<Self, PrepareAssetError<Self::SourceAsset>> {
-        match material.as_bind_group(&pipeline.ui_layout, render_device, images, fallback_image) {
+        match material.as_bind_group(&pipeline.ui_layout, render_device, material_param) {
             Ok(prepared) => Ok(PreparedUiMaterial {
                 bindings: prepared.bindings,
                 bind_group: prepared.bind_group,

examples/shader/texture_binding_array.rs

@@ -1,6 +1,8 @@
 //! A shader that binds several textures onto one
 //! `binding_array<texture<f32>>` shader binding slot and sample non-uniformly.
 
+use bevy::ecs::system::lifetimeless::SRes;
+use bevy::ecs::system::SystemParamItem;
 use bevy::{
     prelude::*,
     reflect::TypePath,
@@ -97,12 +99,13 @@ struct BindlessMaterial {
 impl AsBindGroup for BindlessMaterial {
     type Data = ();
 
+    type Param = (SRes<RenderAssets<GpuImage>>, SRes<FallbackImage>);
+
     fn as_bind_group(
         &self,
         layout: &BindGroupLayout,
         render_device: &RenderDevice,
-        image_assets: &RenderAssets<GpuImage>,
-        fallback_image: &FallbackImage,
+        (image_assets, fallback_image): &mut SystemParamItem<'_, '_, Self::Param>,
     ) -> Result<PreparedBindGroup<Self::Data>, AsBindGroupError> {
         // retrieve the render resources from handles
         let mut images = vec![];
@@ -140,10 +143,9 @@ impl AsBindGroup for BindlessMaterial {
 
     fn unprepared_bind_group(
         &self,
-        _: &BindGroupLayout,
-        _: &RenderDevice,
-        _: &RenderAssets<GpuImage>,
-        _: &FallbackImage,
+        _layout: &BindGroupLayout,
+        _render_device: &RenderDevice,
+        _param: &mut SystemParamItem<'_, '_, Self::Param>,
     ) -> Result<UnpreparedBindGroup<Self::Data>, AsBindGroupError> {
         // we implement as_bind_group directly because
         panic!("bindless texture arrays can't be owned")