refactor: get rid of fromJSON promise return

packages/topdown/tileset.js

@@ -1,10 +1,14 @@
-import {compose} from '@avocado/core';
+import {compose, EventEmitter, Property} from '@avocado/core';
 import {hasGraphics, Image} from '@avocado/graphics';
 import {Rectangle, Vector} from '@avocado/math';
 import {shapeFromJSON} from '@avocado/physics';
 import {Resource} from '@avocado/resource';
 
 const decorate = compose(
+  EventEmitter,
+  Property('image', {
+    track: true,
+  }),
   Vector.Mixin('tileSize', 'tileWidth', 'tileHeight', {
     default: [0, 0],
   }),
@@ -15,7 +19,6 @@ export class Tileset extends decorate(Resource) {
   constructor() {
     super();
     this._geometry = {};
-    this._image = undefined;
     this.subimages = [];
   }
 
@@ -38,13 +41,10 @@ export class Tileset extends decorate(Resource) {
       this.tileSize = json.tileSize;
     }
     if (hasGraphics && json.imageUri) {
-      promise = Image.load(json.imageUri).then((image) => {
+      Image.load(json.imageUri).then((image) => {
         this.image = image;
       });
     }
-    return Promise.resolve(promise).then(() => {
-      return this;
-    });
   }
 
   geometry(index) {
@@ -52,18 +52,20 @@ export class Tileset extends decorate(Resource) {
   }
 
   get image() {
-    return this._image;
+    return super.image;
   }
 
   set image(image) {
-    this._image = image
-    this.recalculateSubimages();
+    this.recalculateSubimages(image);
+    super.image = image;
   }
 
-  recalculateSubimages() {
-    const image = this._image;
+  recalculateSubimages(image) {
+    if (!image) {
+      return;
+    }
     const tileSize = this.tileSize;
-    if (!image || Vector.isZero(tileSize)) {
+    if (Vector.isZero(tileSize)) {
       return;
     }
     this.destroy();
@@ -90,7 +92,7 @@ export class Tileset extends decorate(Resource) {
 
   set tileSize(tileSize) {
     super.tileSize = tileSize;
-    this.recalculateSubimages();
+    this.recalculateSubimages(this.image);
   }
 
   toJSON() {