feat!: implement widget systems and system input parameters. (#193)

- This also removes the `SystemResult` and `EcsError` types from
`bones_ecs`. We don't really need systems to return results, and
`EcsError` was nearly unused.

demos/assets_minimal/src/main.rs

@@ -42,7 +42,7 @@ fn main() {
 
 /// System to render the home menu.
 fn menu_system(
-    egui_ctx: Res<EguiCtx>,
+    egui_ctx: Egui,
     // We can access our root asset by using the Root parameter.
     meta: Root<GameMeta>,
 ) {

demos/features/src/main.rs

@@ -136,17 +136,16 @@ fn menu_startup(
 /// Our main menu system.
 fn menu_system(
     meta: Root<GameMeta>,
-    egui_ctx: ResMut<EguiCtx>,
+    ctx: Egui,
     mut sessions: ResMut<Sessions>,
     mut session_options: ResMut<SessionOptions>,
-    egui_textures: Res<EguiTextures>,
     // Get the localization field from our `GameMeta`
     localization: Localization<GameMeta>,
 ) {
     // Render the menu.
     egui::CentralPanel::default()
         .frame(egui::Frame::none())
-        .show(&egui_ctx, |ui| {
+        .show(&ctx, |ui| {
             BorderedFrame::new(&meta.menu_border).show(ui, |ui| {
                 ui.vertical_centered(|ui| {
                     ui.add_space(20.0);
@@ -207,9 +206,11 @@ fn menu_system(
 
                     ui.add_space(30.0);
 
-                    // When using a bones image in egui, we have to get it's corresponding egui texture
-                    // from the egui textures resource.
-                    ui.image(egui_textures.get(meta.menu_image), [100., 100.]);
+                    // We can use the `widget()` method on the `Egui` to conveniently run bones
+                    // systems that can modify the `egui::Ui` and return an `egui::Response`.
+                    //
+                    // This makes it easier to compose widgets that have differing access to the bones world.
+                    ctx.widget(demo_widget, ui);
 
                     ui.add_space(30.0);
                 });
@@ -378,14 +379,14 @@ fn path2d_demo_startup(
 /// Simple UI system that shows a button at the bottom of the screen to delete the current session
 /// and  go back to the main menu.
 fn back_to_menu_ui(
-    egui_ctx: ResMut<EguiCtx>,
+    ctx: Egui,
     mut sessions: ResMut<Sessions>,
     mut session_options: ResMut<SessionOptions>,
     localization: Localization<GameMeta>,
 ) {
     egui::CentralPanel::default()
         .frame(egui::Frame::none())
-        .show(&egui_ctx, |ui| {
+        .show(&ctx, |ui| {
             ui.with_layout(egui::Layout::bottom_up(egui::Align::Center), |ui| {
                 ui.add_space(20.0);
                 if ui.button(localization.get("back-to-menu")).clicked() {
@@ -395,3 +396,18 @@ fn back_to_menu_ui(
             });
         });
 }
+
+/// This is an example widget system.
+fn demo_widget(
+    // Widget systems must have an `In<&mut egui::Ui>` parameter as their first argument.
+    mut ui: In<&mut egui::Ui>,
+    // They can have any normal bones system parameters
+    meta: Root<GameMeta>,
+    egui_textures: Res<EguiTextures>,
+    // And they may return an `egui::Response` or any other value.
+) -> egui::Response {
+    ui.label("Demo Widget");
+    // When using a bones image in egui, we have to get it's corresponding egui texture
+    // from the egui textures resource.
+    ui.image(egui_textures.get(meta.menu_image), [100., 100.])
+}

demos/hello_world/src/main.rs

@@ -18,8 +18,8 @@ fn main() {
 }
 
 /// System to render the home menu.
-fn menu_system(egui_ctx: Res<EguiCtx>) {
-    egui::CentralPanel::default().show(&egui_ctx, |ui| {
+fn menu_system(ctx: Egui) {
+    egui::CentralPanel::default().show(&ctx, |ui| {
         ui.label("Hello World");
     });
 }

framework_crates/bones_ecs/examples/pos_vel.rs

@@ -22,14 +22,12 @@ fn main() {
     // Initialize an empty world
     let mut world = World::new();
 
-    // Run our setup system once to spawn our entities
-    world.run_system(setup_system).ok();
-
     // Create a SystemStages to store the systems that we will run more than once.
     let mut stages = SystemStages::with_core_stages();
 
-    // Add our systems to the dispatcher
+    // Add our systems to the system stages
     stages
+        .add_startup_system(startup_system)
         .add_system_to_stage(CoreStage::Update, pos_vel_system)
         .add_system_to_stage(CoreStage::PostUpdate, print_system);
 
@@ -38,12 +36,12 @@ fn main() {
 
     // Run our game loop for 10 frames
     for _ in 0..10 {
-        stages.run(&mut world).unwrap();
+        stages.run(&mut world);
     }
 }
 
 /// Setup system that spawns two entities with a Pos and a Vel component.
-fn setup_system(
+fn startup_system(
     mut entities: ResMut<Entities>,
     mut positions: CompMut<Pos>,
     mut velocities: CompMut<Vel>,

framework_crates/bones_ecs/src/components.rs

@@ -23,6 +23,17 @@ pub struct ComponentStores {
     pub(crate) components: HashMap<SchemaId, Arc<AtomicCell<UntypedComponentStore>>>,
 }
 
+/// An error returned when trying to access an uninitialized component.
+#[derive(Debug)]
+pub struct NotInitialized;
+
+impl std::fmt::Display for NotInitialized {
+    fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
+        write!(f, "Component not initialized")
+    }
+}
+impl std::error::Error for NotInitialized {}
+
 // SOUND: all of the functions for ComponentStores requires that the types stored implement Sync +
 // Send.
 unsafe impl Sync for ComponentStores {}
@@ -52,7 +63,7 @@ impl ComponentStores {
     }
 
     /// Get the components of a certain type
-    pub fn get_cell<T: HasSchema>(&self) -> Result<AtomicComponentStore<T>, EcsError> {
+    pub fn get_cell<T: HasSchema>(&self) -> Result<AtomicComponentStore<T>, NotInitialized> {
         let untyped = self.get_cell_by_schema_id(T::schema().id())?;
 
         // Safe: We know the schema matches, and `ComponentStore<T>` is repr(transparent) over
@@ -68,13 +79,9 @@ impl ComponentStores {
     /// Borrow a component store.
     /// # Errors
     /// Errors if the component store has not been initialized yet.
-    pub fn get<T: HasSchema>(&self) -> Result<Ref<ComponentStore<T>>, EcsError> {
+    pub fn get<T: HasSchema>(&self) -> Result<Ref<ComponentStore<T>>, NotInitialized> {
         let id = T::schema().id();
-        let atomicref = self
-            .components
-            .get(&id)
-            .ok_or(EcsError::NotInitialized)?
-            .borrow();
+        let atomicref = self.components.get(&id).ok_or(NotInitialized)?.borrow();
 
         // SOUND: ComponentStore<T> is repr(transparent) over UntypedComponent store.
         let atomicref = Ref::map(atomicref, |x| unsafe {
@@ -87,13 +94,9 @@ impl ComponentStores {
     /// Borrow a component store.
     /// # Errors
     /// Errors if the component store has not been initialized yet.
-    pub fn get_mut<T: HasSchema>(&self) -> Result<RefMut<ComponentStore<T>>, EcsError> {
+    pub fn get_mut<T: HasSchema>(&self) -> Result<RefMut<ComponentStore<T>>, NotInitialized> {
         let id = T::schema().id();
-        let atomicref = self
-            .components
-            .get(&id)
-            .ok_or(EcsError::NotInitialized)?
-            .borrow_mut();
+        let atomicref = self.components.get(&id).ok_or(NotInitialized)?.borrow_mut();
 
         // SOUND: ComponentStore<T> is repr(transparent) over UntypedComponent store.
         let atomicref = RefMut::map(atomicref, |x| unsafe {
@@ -107,11 +110,8 @@ impl ComponentStores {
     pub fn get_cell_by_schema_id(
         &self,
         id: SchemaId,
-    ) -> Result<Arc<AtomicCell<UntypedComponentStore>>, EcsError> {
-        self.components
-            .get(&id)
-            .cloned()
-            .ok_or(EcsError::NotInitialized)
+    ) -> Result<Arc<AtomicCell<UntypedComponentStore>>, NotInitialized> {
+        self.components.get(&id).cloned().ok_or(NotInitialized)
     }
 }
 
@@ -125,44 +125,42 @@ mod test {
 
     #[test]
     fn borrow_many_mut() {
-        World::new()
-            .run_system(
-                |mut entities: ResMut<Entities>, mut my_datas: CompMut<MyData>| {
-                    let ent1 = entities.create();
-                    let ent2 = entities.create();
-
-                    my_datas.insert(ent1, MyData(7));
-                    my_datas.insert(ent2, MyData(8));
-
-                    {
-                        let [data2, data1] = my_datas.get_many_mut([ent2, ent1]).unwrap_many();
-
-                        data1.0 = 0;
-                        data2.0 = 1;
-                    }
-
-                    assert_eq!(my_datas.get(ent1).unwrap().0, 0);
-                    assert_eq!(my_datas.get(ent2).unwrap().0, 1);
-                },
-            )
-            .unwrap();
+        World::new().run_system(
+            |mut entities: ResMut<Entities>, mut my_datas: CompMut<MyData>| {
+                let ent1 = entities.create();
+                let ent2 = entities.create();
+
+                my_datas.insert(ent1, MyData(7));
+                my_datas.insert(ent2, MyData(8));
+
+                {
+                    let [data2, data1] = my_datas.get_many_mut([ent2, ent1]).unwrap_many();
+
+                    data1.0 = 0;
+                    data2.0 = 1;
+                }
+
+                assert_eq!(my_datas.get(ent1).unwrap().0, 0);
+                assert_eq!(my_datas.get(ent2).unwrap().0, 1);
+            },
+            (),
+        );
     }
 
     #[test]
     #[should_panic = "must be unique"]
     fn borrow_many_overlapping_mut() {
-        World::new()
-            .run_system(
-                |mut entities: ResMut<Entities>, mut my_datas: CompMut<MyData>| {
-                    let ent1 = entities.create();
-                    let ent2 = entities.create();
-
-                    my_datas.insert(ent1, MyData(1));
-                    my_datas.insert(ent2, MyData(2));
-
-                    my_datas.get_many_mut([ent1, ent2, ent1]).unwrap_many();
-                },
-            )
-            .unwrap();
+        World::new().run_system(
+            |mut entities: ResMut<Entities>, mut my_datas: CompMut<MyData>| {
+                let ent1 = entities.create();
+                let ent2 = entities.create();
+
+                my_datas.insert(ent1, MyData(1));
+                my_datas.insert(ent2, MyData(2));
+
+                my_datas.get_many_mut([ent1, ent2, ent1]).unwrap_many();
+            },
+            (),
+        )
     }
 }

framework_crates/bones_ecs/src/lib.rs

@@ -21,9 +21,6 @@ pub mod system;
 pub use bones_schema as schema;
 pub use bones_utils as utils;
 
-mod error;
-pub use error::EcsError;
-
 mod world;
 pub use world::{FromWorld, World};
 
@@ -37,7 +34,6 @@ pub mod prelude {
         bitset::*,
         components::*,
         entities::*,
-        error::*,
         resources::*,
         stage::{CoreStage::*, *},
         system::*,
@@ -96,7 +92,7 @@ mod test {
                 let e = entities.create();
                 comps.insert(e, default());
             },
+            (),
         )
-        .unwrap();
     }
 }