Vastly improve belt performance

src/js/game/components/belt.js

@@ -7,6 +7,40 @@ import { enumLayer } from "../root";
 
 export const curvedBeltLength = /* Math.PI / 4 */ 0.78;
 
+/** @type {import("./item_acceptor").ItemAcceptorSlot} */
+export const FAKE_BELT_ACCEPTOR_SLOT = {
+    pos: new Vector(0, 0),
+    directions: [enumDirection.bottom],
+    layer: enumLayer.regular,
+};
+
+/** @type {Object<enumDirection, import("./item_ejector").ItemEjectorSlot>} */
+export const FAKE_BELT_EJECTOR_SLOT_BY_DIRECTION = {
+    [enumDirection.top]: {
+        pos: new Vector(0, 0),
+        direction: enumDirection.top,
+        item: null,
+        layer: enumLayer.regular,
+        progress: 0,
+    },
+
+    [enumDirection.right]: {
+        pos: new Vector(0, 0),
+        direction: enumDirection.right,
+        item: null,
+        layer: enumLayer.regular,
+        progress: 0,
+    },
+
+    [enumDirection.left]: {
+        pos: new Vector(0, 0),
+        direction: enumDirection.left,
+        item: null,
+        layer: enumLayer.regular,
+        progress: 0,
+    },
+};
+
 export class BeltComponent extends Component {
     static getId() {
         return "Belt";
@@ -56,6 +90,27 @@ export class BeltComponent extends Component {
         return this.direction === enumDirection.top ? 1.0 : curvedBeltLength;
     }
 
+    /**
+     * Returns fake acceptor slot used for matching
+     * @returns {import("./item_acceptor").ItemAcceptorSlot}
+     */
+    getFakeAcceptorSlot() {
+        return FAKE_BELT_ACCEPTOR_SLOT;
+    }
+
+    /**
+     * Returns fake acceptor slot used for matching
+     * @returns {import("./item_ejector").ItemEjectorSlot}
+     */
+    getFakeEjectorSlots() {
+        assert(
+            FAKE_BELT_EJECTOR_SLOT_BY_DIRECTION[this.direction],
+            "Invalid belt direction: ",
+            this.direction
+        );
+        return FAKE_BELT_EJECTOR_SLOT_BY_DIRECTION[this.direction];
+    }
+
     /**
      * Converts from belt space (0 = start of belt ... 1 = end of belt) to the local
      * belt coordinates (-0.5|-0.5 to 0.5|0.5)

src/js/game/components/item_ejector.js

@@ -5,6 +5,7 @@ import { types } from "../../savegame/serialization";
 import { gItemRegistry } from "../../core/global_registries";
 import { Entity } from "../entity";
 import { enumLayer } from "../root";
+import { BeltPath } from "../belt_path";
 
 /**
  * @typedef {{
@@ -14,6 +15,7 @@ import { enumLayer } from "../root";
  *    layer: enumLayer,
  *    progress: number?,
  *    cachedDestSlot?: import("./item_acceptor").ItemAcceptorLocatedSlot,
+ *    cachedBeltPath?: BeltPath,
  *    cachedTargetEntity?: Entity
  * }} ItemEjectorSlot
  */
@@ -24,7 +26,7 @@ export class ItemEjectorComponent extends Component {
     }
 
     static getSchema() {
-        // The cachedDestSlot, cachedTargetEntity, and cachedConnectedSlots fields
+        // The cachedDestSlot, cachedTargetEntity fields
         // are not serialized.
         return {
             instantEject: types.bool,
@@ -73,9 +75,6 @@ export class ItemEjectorComponent extends Component {
 
         this.setSlots(slots);
 
-        /** @type {ItemEjectorSlot[]} */
-        this.cachedConnectedSlots = null;
-
         /**
          * Whether this ejector slot is enabled
          */