Add a class that represetns a generic auto-collapse behaviour

apps/web/src/viewmodels/structures/auto-collapse/behaviours/BaseCollapseBehaviour.ts

@@ -0,0 +1,42 @@
+/*
+ * Copyright 2026 Element Creations Ltd.
+ *
+ * SPDX-License-Identifier: AGPL-3.0-only OR GPL-3.0-only OR LicenseRef-Element-Commercial
+ * Please see LICENSE files in the repository root for full details.
+ */
+
+import type { CollapseHandler } from "../CollapseHandler";
+
+/**
+ * The left panel should be auto-collapsed under certain app states.
+ * This class provides a base for writing such logic.
+ */
+export class BaseCollapseBehaviour {
+    public constructor(protected readonly collapseHandler: CollapseHandler) {}
+
+    public dispose = (): void => {
+        return;
+    };
+
+    /**
+     * Whether currently arriving left panel resized events should be ignored according
+     * to this behaviour.
+     */
+    public get shouldIgnoreResize(): boolean {
+        return false;
+    }
+
+    /**
+     * Whether the panel should be collapsed at app start according to this behaviour.
+     */
+    public static shouldStartCollapsed(): boolean {
+        return false;
+    }
+
+    /**
+     * This method is called when the left panel is resized.
+     */
+    public onLeftPanelResized = (): void => {
+        return;
+    };
+}