support empty head slots

src/heads/heads_ui.rs

@@ -21,7 +21,7 @@ struct HeadDamage(pub usize);
 #[reflect(Resource)]
 struct UiActiveHeads {
     heads: [Option<UiHeadState>; 5],
-    current_slot: usize,
+    selected_slot: usize,
 }
 
 pub fn plugin(app: &mut App) {
@@ -170,7 +170,7 @@ fn update(
             }
         }
         for (HeadSelector(head), mut vis) in head_selector.iter_mut() {
-            *vis = if *head == res.current_slot {
+            *vis = if *head == res.selected_slot {
                 Visibility::Visible
             } else {
                 Visibility::Hidden
@@ -224,7 +224,8 @@ fn sync(
     };
 
     if active_heads.is_changed() || active_heads.reloading() {
-        state.current_slot = active_heads.slot();
+        state.selected_slot = active_heads.selected_slot;
+
         for i in 0..HEAD_SLOTS {
             state.heads[i] = active_heads
                 .head(i)

src/heads/mod.rs

@@ -54,6 +54,7 @@ impl HeadState {
 pub struct ActiveHeads {
     heads: [Option<HeadState>; 5],
     current_slot: usize,
+    selected_slot: usize,
 }
 
 impl ActiveHeads {
@@ -61,6 +62,7 @@ impl ActiveHeads {
         Self {
             heads,
             current_slot: 0,
+            selected_slot: 0,
         }
     }
 
@@ -111,10 +113,6 @@ impl ActiveHeads {
         }
     }
 
-    pub fn slot(&self) -> usize {
-        self.current_slot
-    }
-
     pub fn head(&self, slot: usize) -> Option<HeadState> {
         self.heads[slot]
     }
@@ -221,19 +219,24 @@ fn on_select_active_head(
 
     match trigger.event() {
         SelectActiveHead::Right => {
-            active_heads.current_slot = (active_heads.current_slot + 1) % HEAD_SLOTS;
+            active_heads.selected_slot = (active_heads.selected_slot + 1) % HEAD_SLOTS;
         }
         SelectActiveHead::Left => {
-            active_heads.current_slot = (active_heads.current_slot + (HEAD_SLOTS - 1)) % HEAD_SLOTS;
+            active_heads.selected_slot =
+                (active_heads.selected_slot + (HEAD_SLOTS - 1)) % HEAD_SLOTS;
         }
     }
 
-    hp.set_health(active_heads.current().unwrap().health);
-
     commands.trigger(PlaySound::Selection);
-    commands.trigger(HeadChanged(
-        active_heads.heads[active_heads.current_slot].unwrap().head,
-    ));
+
+    if active_heads.head(active_heads.selected_slot).is_some() {
+        active_heads.current_slot = active_heads.selected_slot;
+        hp.set_health(active_heads.current().unwrap().health);
+
+        commands.trigger(HeadChanged(
+            active_heads.heads[active_heads.current_slot].unwrap().head,
+        ));
+    }
 }
 
 fn on_swap_backpack(
@@ -250,12 +253,12 @@ fn on_swap_backpack(
         return;
     };
 
-    let current_active_slot = active_heads.current_slot;
+    let selected_slot = active_heads.selected_slot;
 
-    let current_active_head = active_heads.heads[current_active_slot];
-    active_heads.heads[current_active_slot] = Some(*head);
+    let selected_head = active_heads.heads[selected_slot];
+    active_heads.heads[selected_slot] = Some(*head);
 
-    if let Some(old_active) = current_active_head {
+    if let Some(old_active) = selected_head {
         backpack.heads[backpack_slot] = old_active;
     } else {
         backpack.heads.remove(backpack_slot);
@@ -264,6 +267,6 @@ fn on_swap_backpack(
     hp.set_health(active_heads.current().unwrap().health);
 
     commands.trigger(HeadChanged(
-        active_heads.heads[active_heads.current_slot].unwrap().head,
+        active_heads.heads[active_heads.selected_slot].unwrap().head,
     ));
 }

src/player.rs

@@ -46,7 +46,7 @@ pub fn plugin(app: &mut App) {
             .run_if(in_state(GameState::Playing)),
     );
 
-    global_observer!(app, on_update_head);
+    global_observer!(app, on_update_head_mesh);
 }
 
 fn spawn(
@@ -78,7 +78,6 @@ fn spawn(
         CameraTarget,
         transform,
         Visibility::default(),
-        // LockedAxes::ROTATION_LOCKED, todo
         CollisionLayers::new(
             GameLayer::Player,
             LayerMask::ALL & !GameLayer::CollectiblePhysics.to_bits(),
@@ -200,7 +199,7 @@ fn toggle_animation(
     }
 }
 
-fn on_update_head(
+fn on_update_head_mesh(
     trigger: Trigger<HeadChanged>,
     mut commands: Commands,
     body_mesh: Single<Entity, With<PlayerBodyMesh>>,