transform: TransformPlugin

crates/bevy_app/src/app_builder.rs

@@ -74,6 +74,10 @@ impl AppBuilder {
         self.add_system_to_stage(stage::UPDATE, system)
     }
 
+    pub fn add_systems(&mut self, systems: Vec<Box<dyn System>>) -> &mut Self {
+        self.add_systems_to_stage(stage::UPDATE, systems)
+    }
+
     pub fn init_system(
         &mut self,
         build: impl FnMut(&mut Resources) -> Box<dyn System>,
@@ -101,13 +105,30 @@ impl AppBuilder {
         self
     }
 
+    pub fn add_startup_systems_to_stage(
+        &mut self,
+        stage_name: &'static str,
+        systems: Vec<Box<dyn System>>,
+    ) -> &mut Self {
+        for system in systems {
+            self.app
+                .startup_schedule
+                .add_system_to_stage(stage_name, system);
+        }
+        self
+    }
+
     pub fn add_startup_system(&mut self, system: Box<dyn System>) -> &mut Self {
         self.app
             .startup_schedule
             .add_system_to_stage(startup_stage::STARTUP, system);
         self
     }
 
+    pub fn add_startup_systems(&mut self, systems: Vec<Box<dyn System>>) -> &mut Self {
+        self.add_startup_systems_to_stage(startup_stage::STARTUP, systems)
+    }
+
     pub fn init_startup_system(
         &mut self,
         build: impl FnMut(&mut Resources) -> Box<dyn System>,
@@ -144,6 +165,17 @@ impl AppBuilder {
         self
     }
 
+    pub fn add_systems_to_stage(
+        &mut self,
+        stage_name: &'static str,
+        systems: Vec<Box<dyn System>>,
+    ) -> &mut Self {
+        for system in systems {
+            self.app.schedule.add_system_to_stage(stage_name, system);
+        }
+        self
+    }
+
     pub fn add_event<T>(&mut self) -> &mut Self
     where
         T: Send + Sync + 'static,

crates/bevy_core/Cargo.toml

@@ -10,5 +10,4 @@ bevy_derive = { path = "../bevy_derive" }
 bevy_ecs = { path = "../bevy_ecs" }
 bevy_property = { path = "../bevy_property" }
 bevy_type_registry = { path = "../bevy_type_registry" }
-bevy_transform = { path = "../bevy_transform" }
 glam = "0.8.7"

crates/bevy_core/src/lib.rs

@@ -1,16 +1,10 @@
 pub mod bytes;
 pub mod float_ord;
 pub mod time;
-pub mod transform;
+pub mod math;
 
-use bevy_app::{stage, startup_stage, AppBuilder, AppPlugin};
+use bevy_app::{stage, AppBuilder, AppPlugin};
 use bevy_ecs::IntoQuerySystem;
-use bevy_transform::{
-    build_systems,
-    components::{
-        Children, LocalTransform, NonUniformScale, Rotation, Scale, Transform, Translation,
-    },
-};
 use bevy_type_registry::RegisterType;
 use glam::{Mat3, Mat4, Quat, Vec2, Vec3};
 use time::{time_system, timer_system, Time, Timer};
@@ -20,22 +14,7 @@ pub struct CorePlugin;
 
 impl AppPlugin for CorePlugin {
     fn build(&self, app: &mut AppBuilder) {
-        // we also add a copy of transform systems to startup to ensure we begin with correct transform/parent state
-        for transform_system in build_systems() {
-            app.add_startup_system_to_stage(startup_stage::POST_STARTUP, transform_system);
-        }
-        for transform_system in build_systems() {
-            app.add_system_to_stage(stage::POST_UPDATE, transform_system);
-        }
-
         app.init_resource::<Time>()
-            .register_component::<Children>()
-            .register_component::<LocalTransform>()
-            .register_component::<Transform>()
-            .register_component::<Translation>()
-            .register_component::<Rotation>()
-            .register_component::<Scale>()
-            .register_component::<NonUniformScale>()
             .register_component::<Timer>()
             .register_property_type::<Vec2>()
             .register_property_type::<Vec3>()

crates/bevy_core/src/transform/mod.rs → crates/bevy_core/src/math/mod.rs

@@ -1,5 +1,3 @@
 mod face_toward;
-mod hierarchy;
 
 pub use face_toward::*;
-pub use hierarchy::*;

crates/bevy_transform/Cargo.toml

@@ -7,8 +7,10 @@ edition = "2018"
 license = "MIT"
 
 [dependencies]
+bevy_app = { path = "../bevy_app"}
 bevy_ecs = { path = "../bevy_ecs"}
 bevy_property = { path =  "../bevy_property" }
+bevy_type_registry = { path =  "../bevy_type_registry" }
 glam = "0.8.7"
 log = "0.4"
 smallvec = { version = "1.4", features = ["serde"] }

crates/bevy_core/src/transform/hierarchy.rs → crates/bevy_transform/src/hierarchy/hierarchy.rs

@@ -1,5 +1,5 @@
+use crate::components::Children;
 use bevy_ecs::{Entity, Query};
-use bevy_transform::prelude::Children;
 
 pub fn run_on_hierarchy<T, S>(
     children_query: &Query<&Children>,

crates/bevy_transform/src/hierarchy_maintenance_system.rs → crates/bevy_transform/src/hierarchy/hierarchy_maintenance_system.rs

@@ -109,7 +109,7 @@ pub fn hierarchy_maintenance_systems() -> Vec<Box<dyn System>> {
 #[cfg(test)]
 mod test {
     use super::*;
-    use crate::build_systems;
+    use crate::transform_systems;
     use bevy_ecs::{Resources, Schedule, World};
 
     #[test]
@@ -119,7 +119,7 @@ mod test {
 
         let mut schedule = Schedule::default();
         schedule.add_stage("update");
-        for system in build_systems() {
+        for system in transform_systems() {
             schedule.add_system_to_stage("update", system);
         }
 

crates/bevy_transform/src/hierarchy/mod.rs

@@ -0,0 +1,9 @@
+mod child_builder;
+mod hierarchy;
+mod hierarchy_maintenance_system;
+mod world_child_builder;
+
+pub use child_builder::*;
+pub use hierarchy::*;
+pub use hierarchy_maintenance_system::*;
+pub use world_child_builder::*;

crates/bevy_transform/src/lib.rs

@@ -1,27 +1,45 @@
 pub use glam as math;
 
-pub mod child_builder;
+pub mod hierarchy;
 pub mod components;
-pub mod hierarchy_maintenance_system;
 pub mod local_transform_systems;
 pub mod transform_propagate_system;
 pub mod transform_systems;
-pub mod world_child_builder;
 
 pub mod prelude {
-    pub use crate::{build_systems, child_builder::*, components::*, world_child_builder::*};
+    pub use crate::{components::*, hierarchy::*, TransformPlugin};
 }
 
+use bevy_app::{AppBuilder, AppPlugin};
 use bevy_ecs::{IntoQuerySystem, System};
+use bevy_type_registry::RegisterType;
+use prelude::{Children, LocalTransform, NonUniformScale, Rotation, Scale, Transform, Translation};
 
-// TODO: make this a plugin
-pub fn build_systems() -> Vec<Box<dyn System>> {
-    let mut all_systems = Vec::with_capacity(5);
+pub(crate) fn transform_systems() -> Vec<Box<dyn System>> {
+    let mut systems = Vec::with_capacity(5);
 
-    all_systems.append(&mut hierarchy_maintenance_system::hierarchy_maintenance_systems());
-    all_systems.append(&mut local_transform_systems::local_transform_systems());
-    all_systems.append(&mut transform_systems::transform_systems());
-    all_systems.push(transform_propagate_system::transform_propagate_system.system());
+    systems.append(&mut hierarchy::hierarchy_maintenance_systems());
+    systems.append(&mut local_transform_systems::local_transform_systems());
+    systems.append(&mut transform_systems::transform_systems());
+    systems.push(transform_propagate_system::transform_propagate_system.system());
 
-    all_systems
+    systems
+}
+
+#[derive(Default)]
+pub struct TransformPlugin;
+
+impl AppPlugin for TransformPlugin {
+    fn build(&self, app: &mut AppBuilder) {
+        app.register_component::<Children>()
+            .register_component::<LocalTransform>()
+            .register_component::<Transform>()
+            .register_component::<Translation>()
+            .register_component::<Rotation>()
+            .register_component::<Scale>()
+            .register_component::<NonUniformScale>()
+            // add transform systems to startup so the first update is "correct"
+            .add_startup_systems(transform_systems())
+            .add_systems(transform_systems());
+    }
 }

crates/bevy_transform/src/transform_propagate_system.rs

@@ -70,7 +70,7 @@ fn propagate_recursive(
 #[cfg(test)]
 mod test {
     use super::*;
-    use crate::build_systems;
+    use crate::transform_systems;
     use bevy_ecs::{Resources, Schedule, World};
     use glam::{Mat4, Vec3};
 
@@ -81,7 +81,7 @@ mod test {
 
         let mut schedule = Schedule::default();
         schedule.add_stage("update");
-        for system in build_systems() {
+        for system in transform_systems() {
             schedule.add_system_to_stage("update", system);
         }
 

crates/bevy_ui/Cargo.toml

@@ -8,7 +8,6 @@ edition = "2018"
 bevy_app = { path = "../bevy_app" }
 bevy_asset = { path = "../bevy_asset" }
 bevy_type_registry = { path = "../bevy_type_registry" }
-bevy_core = { path = "../bevy_core" }
 bevy_derive = { path = "../bevy_derive" }
 bevy_ecs = { path = "../bevy_ecs" }
 bevy_sprite = { path = "../bevy_sprite" }

crates/bevy_ui/src/ui_update_system.rs

@@ -1,7 +1,9 @@
 use super::Node;
-use bevy_core::transform::run_on_hierarchy;
 use bevy_ecs::{Entity, Query, Res, Without};
-use bevy_transform::prelude::{Children, Parent, Translation};
+use bevy_transform::{
+    hierarchy,
+    prelude::{Children, Parent, Translation},
+};
 use bevy_window::Windows;
 use glam::Vec2;
 
@@ -39,7 +41,7 @@ pub fn ui_update_system(
         size: window_size,
     });
     for entity in orphan_nodes {
-        previous_sibling_result = run_on_hierarchy(
+        previous_sibling_result = hierarchy::run_on_hierarchy(
             &children_query,
             &mut node_query,
             entity,

src/prelude.rs

@@ -7,7 +7,7 @@ pub use crate::{
     audio::{AudioOutput, AudioSource},
     core::{
         time::{Time, Timer},
-        transform::FaceToward,
+        math::FaceToward,
     },
     diagnostic::DiagnosticsPlugin,
     ecs::{