Expand the dummy_machines spawner

Spawn a machine entity for each kind of machine. This is where the trait
impl becomes important -- now the compiler will make copies of that
function for each concrete machine struct so I don't have to.

src/main.rs

@@ -1,9 +1,10 @@
-use bevy::{color::palettes::css::GREEN, prelude::*, window::WindowResolution};
+use bevy::{color::palettes::css::*, prelude::*, window::WindowResolution};
 use bevy_inspector_egui::{bevy_egui::EguiPlugin, quick::WorldInspectorPlugin};
 
 use crate::{
   game::machines::{CuttingMachine, RotatingMachine},
   resources::UiTheme,
+  widgets::SpawnUi,
 };
 
 mod assets;
@@ -24,7 +25,7 @@ fn main() {
     .add_plugins(EguiPlugin::default())
     .add_plugins(WorldInspectorPlugin::new())
     .add_plugins(widgets::GameUiPlugin)
-    .add_systems(Startup, (setup, assets::load_assets, dummy_machine))
+    .add_systems(Startup, (setup, assets::load_assets, dummy_machines))
     .run();
 }
 
@@ -39,26 +40,35 @@ fn despawn<T: Component>(mut commands: Commands, to_despawn: Query<Entity, With<
   }
 }
 
-fn dummy_machine(
-  mut commands: Commands,
-  // mut meshes: ResMut<Assets<Mesh>>,
-  // mut materials: ResMut<Assets<ColorMaterial>>,
-) {
+/// Dev tool for spawning dummy entities. I'm developing their UIs by hooking
+/// up to these while the TileMap gets ready.
+fn dummy_machines(mut commands: Commands) {
+  // Spawn a dummy Cutting Machine
   commands
     .spawn((
-      Sprite::from_color(GREEN, Vec2::splat(40.0)),
-      // WARN: Mesh picking is not part of the `DefaultPlugins` plugin collection!
-      // (but sprite picking is!)
-
-      // Mesh2d(meshes.add(Rectangle::new(25., 25.))),
-      // MeshMaterial2d(materials.add(ColorMaterial::from_color(GREEN))),
+      Sprite::from_color(RED, Vec2::splat(40.0)),
       Transform::default(),
       Pickable::default(),
     ))
-    .observe(
-      |event: Trigger<Pointer<Click>>, commands: Commands, theme: Res<UiTheme>| {
-        let entity = event.target;
-        CuttingMachine::spawn_ui(commands, theme);
-      },
-    );
+    .observe(spawn_machine_ui::<CuttingMachine>);
+
+  commands
+    .spawn((
+      Sprite::from_color(GREEN, Vec2::splat(40.0)),
+      Transform::from_translation(Vec3::new(80.0, 0.0, 0.0)),
+      Pickable::default(),
+    ))
+    .observe(spawn_machine_ui::<RotatingMachine>);
+
+  // TODO: The other machines, once they have a spawner struct & impl.
+}
+
+fn spawn_machine_ui<M: SpawnUi>(
+  event: Trigger<Pointer<Click>>,
+  commands: Commands,
+  theme: Res<UiTheme>,
+) {
+  let _entity = event.target;
+  // TODO: Hook up the Fuel component (and spawn one so that I can)
+  M::spawn_ui(commands, theme);
 }

src/widgets/machines.rs

@@ -3,11 +3,11 @@ use bevy::{color::palettes::css::*, prelude::*, ui::Val::*};
 use crate::{
   game::machines::*,
   resources::UiTheme,
-  widgets::{BigRedButton, machine_ui_base},
+  widgets::{BigRedButton, SpawnUi, machine_ui_base},
 };
 
-impl CuttingMachine {
-  pub fn spawn_ui(mut commands: Commands, theme: Res<UiTheme>) {
+impl SpawnUi for CuttingMachine {
+  fn spawn_ui(mut commands: Commands, theme: Res<UiTheme>) {
     let base_entity = machine_ui_base(&mut commands, "Cutting Machine", &theme);
     commands.entity(base_entity).with_children(|commands| {
       // Left panel. For fuel or machine stats or whatever.
@@ -51,8 +51,8 @@ impl CuttingMachine {
   }
 }
 
-impl RotatingMachine {
-  pub fn spawn_ui(mut commands: Commands, theme: Res<UiTheme>) {
+impl SpawnUi for RotatingMachine {
+  fn spawn_ui(mut commands: Commands, theme: Res<UiTheme>) {
     let base_entity = machine_ui_base(&mut commands, "Rotating Machine", &theme);
     commands.entity(base_entity).with_children(|commands| {
       commands.spawn((

src/widgets/mod.rs

@@ -28,6 +28,14 @@ impl Plugin for GameUiPlugin {
   }
 }
 
+/// Anything that can spawn a themed UI should impl this trait.
+///
+/// This exists mainly so that I can write generic functions and have the *compiler*
+/// expand the code for me, instead of doing it by hand.
+pub trait SpawnUi {
+  fn spawn_ui(commands: Commands, theme: Res<UiTheme>);
+}
+
 /// The base panel for the machines that manipulate the room cards.
 ///
 /// This function is not a valid Bevy System because of how the Commands struct