Walkable mask painting

ts/tile_factory.ts

@@ -1,9 +1,11 @@
+import { Mask } from './mask.js';
 import { Tile } from './tile.js';
 
 export abstract class TileFactory {
   layer_name: string;
   width: number;
   height: number;
+  masks: Map<string, Mask> = new Map<string, Mask>();
 
   constructor(layer_name: string, width: number, height: number) {
     this.layer_name = layer_name;
@@ -11,6 +13,18 @@ export abstract class TileFactory {
     this.height = height;
   }
 
+  add_mask(name: string, mask: Mask) {
+    this.masks.set(name, mask);
+  }
+
+  tile_args(): [number, number, Map<string, Mask>] {
+    return [
+      this.width,
+      this.height,
+      this.masks,
+    ];
+  }
+
   abstract build(tileset: string): Tile;
 
   abstract copy(): TileFactory;