client: Save content of mind map

src/public/app/widgets/type_widgets/mind_map.js

@@ -29,14 +29,33 @@ export default class MindMapWidget extends TypeWidget {
         libraryLoader
             .requireLibrary(libraryLoader.MIND_ELIXIR)
             .then(() => {
+                this.#onLibraryLoaded();
+            });
+
+        super.doRender();
+    }
+
+    #onLibraryLoaded() {
         const mind = new MindElixir({
             el: this.$content[0],
             direction: MindElixir.LEFT
         });
+        this.mind = mind;
         mind.init(MindElixir.new());
+        mind.bus.addListener("operation", (operation) => {
+            this.spacedUpdate.scheduleUpdate();
         });
+    }
 
-        super.doRender();
+    async getData() {
+        const mind = this.mind;
+        if (!mind) {
+            return;
+        }
+
+        return {
+            content: mind.getDataString()
+        };
     }
 
     async entitiesReloadedEvent({loadResults}) {