[engine] 为动态图集管理器增加一些实用接口（getUnusedAtlas, deleteAtlas, destroyUnusedAtlases）

engine/cocos2d/core/renderer/utils/dynamic-atlas/manager.js

@@ -366,6 +366,36 @@ let dynamicAtlasManager = {
             _atlases[i].update();
         }
     },
+
+    getUnusedAtlas() {
+        if (!this.enabled) return null;
+
+        for (let i = 0; i <= _atlasIndex; i++) {
+            if (_atlases[i].isEmpty()) {
+                return _atlases[i];
+            }
+        }
+
+        return null;
+    },
+
+    deleteAtlas(index) {
+        if (!this.enabled) return;
+
+        _atlases[index].destroy();
+        _atlases.splice(index, 1);
+        _atlasIndex--;
+    },
+
+    destroyUnusedAtlases() {
+        if (!this.enabled) return;
+
+        for (let i = 0; i <= _atlasIndex; i++) {
+            if (_atlases[i].isEmpty()) {
+                _atlases[i].destroy();
+            }
+        }
+    },
 };
 
 /**

engine/cocos2d/core/renderer/utils/dynamic-atlas/reusable-atlas.ts

@@ -623,6 +623,8 @@ export class Atlas {
 
     /**
      * 销毁
+     *
+     * 请勿直接调用
      */
     destroy() {
         this.reset();

engine/cocos2d/core/sp/multi-batcher.ts

@@ -61,10 +61,11 @@ export class MultiBatcher {
 
 
     /**
-     * 重置多纹理材质数组，再次使用请先初始化
+     * 重置
      */
     reset() {
         this.handlers.length = 0;
+        this.nextHandler = null!;
     }
 
 }