Next Generation Bevy Scenes

Cargo.toml

@@ -147,6 +147,7 @@ default = [
   "bevy_picking",
   "bevy_render",
   "bevy_scene",
+  "bevy_scene2",
   "bevy_image",
   "bevy_mesh",
   "bevy_camera",
@@ -178,6 +179,7 @@ default = [
   "wayland",
   "debug",
   "zstd_rust",
+  "experimental_bevy_feathers",
 ]
 
 # Recommended defaults for no_std applications
@@ -240,6 +242,9 @@ bevy_render = ["bevy_internal/bevy_render"]
 # Provides scene functionality
 bevy_scene = ["bevy_internal/bevy_scene"]
 
+# Provides scene functionality
+bevy_scene2 = ["bevy_internal/bevy_scene2", "bevy_asset"]
+
 # Provides raytraced lighting (experimental)
 bevy_solari = ["bevy_internal/bevy_solari"]
 
@@ -612,6 +617,7 @@ bevy_image = { path = "crates/bevy_image", version = "0.17.1", default-features
 bevy_reflect = { path = "crates/bevy_reflect", version = "0.17.1", default-features = false }
 bevy_render = { path = "crates/bevy_render", version = "0.17.1", default-features = false }
 bevy_state = { path = "crates/bevy_state", version = "0.17.1", default-features = false }
+bevy_scene2 = { path = "crates/bevy_scene2", version = "0.17.1", default-features = false }
 # Needed to poll Task examples
 futures-lite = "2.0.1"
 futures-timer = { version = "3", features = ["wasm-bindgen", "gloo-timers"] }
@@ -622,6 +628,7 @@ event-listener = "5.3.0"
 anyhow = "1"
 accesskit = "0.21"
 nonmax = "0.5"
+variadics_please = "1"
 
 [target.'cfg(not(target_family = "wasm"))'.dev-dependencies]
 ureq = { version = "3.0.8", features = ["json"] }
@@ -2824,6 +2831,14 @@ description = "Demonstrates loading from and saving scenes to files"
 category = "Scene"
 wasm = false
 
+[[example]]
+name = "bsn"
+path = "examples/scene/bsn.rs"
+
+[[example]]
+name = "ui_scene"
+path = "examples/scene/ui_scene.rs"
+
 # Shaders
 [[package.metadata.example_category]]
 name = "Shaders"

crates/bevy_a11y/src/lib.rs

@@ -222,7 +222,7 @@ impl ManageAccessibilityUpdates {
 ///
 /// This behavior may or may not be intended, so please utilize
 /// `AccessibilityNode`s with care.
-#[derive(Component, Clone, Deref, DerefMut)]
+#[derive(Component, Clone, Deref, DerefMut, Default)]
 #[cfg_attr(feature = "serialize", derive(Serialize, Deserialize))]
 pub struct AccessibilityNode(
     /// A representation of this component's entity to `AccessKit`.

crates/bevy_animation/src/graph.rs

@@ -131,10 +131,16 @@ pub struct AnimationGraph {
 }
 
 /// A [`Handle`] to the [`AnimationGraph`] to be used by the [`AnimationPlayer`](crate::AnimationPlayer) on the same entity.
-#[derive(Component, Clone, Debug, Default, Deref, DerefMut, Reflect, PartialEq, Eq, From)]
+#[derive(Component, Clone, Debug, Deref, DerefMut, Reflect, PartialEq, Eq, From)]
 #[reflect(Component, Default, Clone)]
 pub struct AnimationGraphHandle(pub Handle<AnimationGraph>);
 
+impl Default for AnimationGraphHandle {
+    fn default() -> Self {
+        Self(Handle::default())
+    }
+}
+
 impl From<AnimationGraphHandle> for AssetId<AnimationGraph> {
     fn from(handle: AnimationGraphHandle) -> Self {
         handle.id()

crates/bevy_asset/src/handle.rs

@@ -1,9 +1,14 @@
 use crate::{
-    meta::MetaTransform, Asset, AssetId, AssetIndexAllocator, AssetPath, InternalAssetId,
-    UntypedAssetId,
+    meta::MetaTransform, Asset, AssetId, AssetIndexAllocator, AssetPath, AssetServer,
+    InternalAssetId, UntypedAssetId,
 };
 use alloc::sync::Arc;
-use bevy_reflect::{std_traits::ReflectDefault, Reflect, TypePath};
+use bevy_ecs::{
+    error::Result,
+    template::{GetTemplate, Template, TemplateContext},
+};
+use bevy_platform::collections::Equivalent;
+use bevy_reflect::{Reflect, TypePath};
 use core::{
     any::TypeId,
     hash::{Hash, Hasher},
@@ -130,7 +135,7 @@ impl core::fmt::Debug for StrongHandle {
 ///
 /// [`Handle::Strong`], via [`StrongHandle`] also provides access to useful [`Asset`] metadata, such as the [`AssetPath`] (if it exists).
 #[derive(Reflect)]
-#[reflect(Default, Debug, Hash, PartialEq, Clone)]
+#[reflect(Debug, Hash, PartialEq, Clone)]
 pub enum Handle<A: Asset> {
     /// A "strong" reference to a live (or loading) [`Asset`]. If a [`Handle`] is [`Handle::Strong`], the [`Asset`] will be kept
     /// alive until the [`Handle`] is dropped. Strong handles also provide access to additional asset metadata.
@@ -150,6 +155,9 @@ impl<T: Asset> Clone for Handle<T> {
 }
 
 impl<A: Asset> Handle<A> {
+    pub fn default() -> Self {
+        Handle::Uuid(AssetId::<A>::DEFAULT_UUID, PhantomData)
+    }
     /// Returns the [`AssetId`] of this [`Asset`].
     #[inline]
     pub fn id(&self) -> AssetId<A> {
@@ -189,9 +197,37 @@ impl<A: Asset> Handle<A> {
     }
 }
 
-impl<A: Asset> Default for Handle<A> {
+impl<T: Asset> GetTemplate for Handle<T> {
+    type Template = HandleTemplate<T>;
+}
+
+pub struct HandleTemplate<T> {
+    path: AssetPath<'static>,
+    marker: PhantomData<T>,
+}
+
+impl<T> Default for HandleTemplate<T> {
     fn default() -> Self {
-        Handle::Uuid(AssetId::<A>::DEFAULT_UUID, PhantomData)
+        Self {
+            path: Default::default(),
+            marker: Default::default(),
+        }
+    }
+}
+
+impl<I: Into<AssetPath<'static>>, T> From<I> for HandleTemplate<T> {
+    fn from(value: I) -> Self {
+        Self {
+            path: value.into(),
+            marker: PhantomData,
+        }
+    }
+}
+
+impl<T: Asset> Template for HandleTemplate<T> {
+    type Output = Handle<T>;
+    fn build(&mut self, context: &mut TemplateContext) -> Result<Handle<T>> {
+        Ok(context.resource::<AssetServer>().load(&self.path))
     }
 }
 
@@ -219,6 +255,13 @@ impl<A: Asset> Hash for Handle<A> {
     }
 }
 
+// Handle uses AssetId when hashing. This enables using AssetId instead of handle with hashsets and hashmaps.
+impl<T: Asset> Equivalent<Handle<T>> for AssetId<T> {
+    fn equivalent(&self, key: &Handle<T>) -> bool {
+        *self == key.id()
+    }
+}
+
 impl<A: Asset> PartialOrd for Handle<A> {
     fn partial_cmp(&self, other: &Self) -> Option<core::cmp::Ordering> {
         Some(self.cmp(other))

crates/bevy_asset/src/lib.rs

@@ -473,6 +473,12 @@ impl<A: Asset> VisitAssetDependencies for Option<Handle<A>> {
     }
 }
 
+impl VisitAssetDependencies for UntypedAssetId {
+    fn visit_dependencies(&self, visit: &mut impl FnMut(UntypedAssetId)) {
+        visit(*self);
+    }
+}
+
 impl VisitAssetDependencies for UntypedHandle {
     fn visit_dependencies(&self, visit: &mut impl FnMut(UntypedAssetId)) {
         visit(self.id());
@@ -503,34 +509,18 @@ impl<const N: usize> VisitAssetDependencies for [UntypedHandle; N] {
     }
 }
 
-impl<A: Asset> VisitAssetDependencies for Vec<Handle<A>> {
-    fn visit_dependencies(&self, visit: &mut impl FnMut(UntypedAssetId)) {
-        for dependency in self {
-            visit(dependency.id().untyped());
-        }
-    }
-}
-
-impl VisitAssetDependencies for Vec<UntypedHandle> {
-    fn visit_dependencies(&self, visit: &mut impl FnMut(UntypedAssetId)) {
-        for dependency in self {
-            visit(dependency.id());
-        }
-    }
-}
-
-impl<A: Asset> VisitAssetDependencies for HashSet<Handle<A>> {
+impl<V: VisitAssetDependencies> VisitAssetDependencies for Vec<V> {
     fn visit_dependencies(&self, visit: &mut impl FnMut(UntypedAssetId)) {
         for dependency in self {
-            visit(dependency.id().untyped());
+            dependency.visit_dependencies(visit);
         }
     }
 }
 
-impl VisitAssetDependencies for HashSet<UntypedHandle> {
+impl<V: VisitAssetDependencies> VisitAssetDependencies for HashSet<V> {
     fn visit_dependencies(&self, visit: &mut impl FnMut(UntypedAssetId)) {
         for dependency in self {
-            visit(dependency.id());
+            dependency.visit_dependencies(visit);
         }
     }
 }

crates/bevy_asset/src/server/mod.rs

@@ -873,6 +873,20 @@ impl AssetServer {
         self.load_asset(LoadedAsset::new_with_dependencies(asset))
     }
 
+    // TODO: this is a hack: this allows the asset to pretend to be from the path, but this will cause issues in practice
+    #[must_use = "not using the returned strong handle may result in the unexpected release of the asset"]
+    pub fn load_with_path<'a, A: Asset>(
+        &self,
+        path: impl Into<AssetPath<'a>>,
+        asset: A,
+    ) -> Handle<A> {
+        let loaded_asset: LoadedAsset<A> = asset.into();
+        let erased_loaded_asset: ErasedLoadedAsset = loaded_asset.into();
+        let path: AssetPath = path.into();
+        self.load_asset_untyped(Some(path.into_owned()), erased_loaded_asset)
+            .typed_debug_checked()
+    }
+
     pub(crate) fn load_asset<A: Asset>(&self, asset: impl Into<LoadedAsset<A>>) -> Handle<A> {
         let loaded_asset: LoadedAsset<A> = asset.into();
         let erased_loaded_asset: ErasedLoadedAsset = loaded_asset.into();

crates/bevy_ecs/Cargo.toml

@@ -122,6 +122,7 @@ log = { version = "0.4", default-features = false }
 bumpalo = "3"
 subsecond = { version = "0.7.0-rc.0", optional = true }
 slotmap = { version = "1.0.7", default-features = false }
+downcast-rs = { version = "2", default-features = false, features = ["std"] }
 
 concurrent-queue = { version = "2.5.0", default-features = false }
 [target.'cfg(not(all(target_has_atomic = "8", target_has_atomic = "16", target_has_atomic = "32", target_has_atomic = "64", target_has_atomic = "ptr")))'.dependencies]

crates/bevy_ecs/macros/src/lib.rs

@@ -9,6 +9,8 @@ mod event;
 mod message;
 mod query_data;
 mod query_filter;
+mod template;
+mod variant_defaults;
 mod world_query;
 
 use crate::{
@@ -754,3 +756,15 @@ pub fn derive_from_world(input: TokenStream) -> TokenStream {
             }
     })
 }
+
+/// Derives GetTemplate.
+#[proc_macro_derive(GetTemplate, attributes(template, default))]
+pub fn derive_get_template(input: TokenStream) -> TokenStream {
+    template::derive_get_template(input)
+}
+
+/// Derives VariantDefaults.
+#[proc_macro_derive(VariantDefaults)]
+pub fn derive_variant_defaults(input: TokenStream) -> TokenStream {
+    variant_defaults::derive_variant_defaults(input)
+}