added TabCachingWidget

src/public/javascripts/widgets/tab_caching_widget.js

@@ -0,0 +1,32 @@
+import TabAwareWidget from "./tab_aware_widget.js";
+
+export default class TabCachingWidget extends TabAwareWidget {
+    constructor(appContext, widgetFactory) {
+        super(appContext);
+
+        this.widgetFactory = widgetFactory;
+        /** @type {JQuery} */
+        this.$parent = null;
+        this.widgets = {};
+    }
+
+    renderTo($parent) {
+        this.$parent = $parent;
+    }
+
+    activeTabChanged() {
+        for (const widget of Object.values(this.widgets)) {
+            widget.toggle(false);
+        }
+
+        let widget = this.widgets[this.tabContext.tabId];
+
+        if (!widget) {
+            widget = this.widgets[this.tabContext.tabId] = this.widgetFactory();
+            widget.renderTo(this.$parent);
+            widget.activeTabChangedListener();
+        }
+
+        widget.toggle(true);
+    }
+}