refactoring of pane => split, "pane" keeps its old meaning (left-pane, center-pane, right-pane)

src/public/app/widgets/buttons/left_pane_toggle.js

@@ -0,0 +1,39 @@
+import ButtonWidget from "./button_widget.js";
+import options from "../../services/options.js";
+import splitService from "../../services/split.js";
+
+export default class LeftPaneToggleWidget extends ButtonWidget {
+    refreshIcon() {
+        const isLeftPaneVisible = options.is('leftPaneVisible');
+
+        this.settings.icon = isLeftPaneVisible
+            ? "bx-chevrons-left"
+            : "bx-chevrons-right";
+
+        this.settings.title = isLeftPaneVisible
+            ? "Hide sidebar."
+            : "Open sidebar.";
+
+        this.settings.command = isLeftPaneVisible
+            ? "hideSidebar"
+            : "showSidebar";
+
+        super.refreshIcon();
+
+        splitService.setupSplit(isLeftPaneVisible);
+    }
+
+    hideSidebarCommand() {
+        options.save(`leftPaneVisible`, "false");
+    }
+
+    showSidebarCommand() {
+        options.save(`leftPaneVisible`, "true");
+    }
+
+    entitiesReloadedEvent({loadResults}) {
+        if (loadResults.isOptionReloaded("leftPaneVisible")) {
+            this.refreshIcon();
+        }
+    }
+}