version: "1.0.1" name: "layouts-internals" description: "Deep layout system implementation knowledge: ILayoutStorage contracts, IndexedDB schema, sync operation computation, mutex-locked LayoutManager, conflict resolution, WriteThroughLayoutCache, NamespacedLayoutStorage, and CurrentLayoutProvider reducers."

Layouts Internals Skill

ILayoutStorage Interface

Defined in packages/suite-base/src/services/ILayoutStorage.ts. Every CRUD method takes a namespace argument — there are no sync-time methods like getLastSyncTime.

export interface ILayoutStorage {
  list(namespace: string): Promise<readonly Layout[]>;
  get(namespace: string, id: LayoutID): Promise<Layout | undefined>;
  put(namespace: string, layout: Layout): Promise<Layout>;
  delete(namespace: string, id: LayoutID): Promise<void>;
  // Optional one-time migration of pre-namespace local layouts
  migrateUnnamespacedLayouts?(namespace: string): Promise<void>;
  // Convert local layouts to personal layouts on login
  importLayouts(params: { fromNamespace: string; toNamespace: string }): Promise<void>;
}

The Layout type tracks baseline (last explicit save), working (unsaved edits, or undefined), and syncInfo (remote status). LayoutSyncStatus is "new" | "updated" | "tracked" | "locally-deleted" | "remotely-deleted".

IdbLayoutStorage (IndexedDB Detail)

packages/suite-base/src/IdbLayoutStorage.ts:

// DB name: `${KEY_WORKSPACE_PREFIX}lichtblick-layouts` (version 1)
// Object store: "layouts"
//   keyPath: ["namespace", "layout.id"]   (composite primary key)
//   index "namespace": keyPath "namespace" (non-unique)
interface LayoutsDB extends DBSchema {
  layouts: {
    key: [namespace: string, id: LayoutID];
    value: { namespace: string; layout: Layout };
    indexes: { namespace: string };
  };
}

• list() uses getAllFromIndex("layouts", "namespace", namespace)
• Every read passes the record through migrateLayout() before returning
• The stored value wraps the layout: { namespace, layout } — the primary key reaches into

layout.id via the "layout.id" keyPath segment

NamespacedLayoutStorage

packages/suite-base/src/services/LayoutManager/NamespacedLayoutStorage.ts — wraps an ILayoutStorage and binds a namespace so callers omit it. It is not itself an ILayoutStorage (its methods drop the namespace argument). The constructor kicks off an async migration/import:

export class NamespacedLayoutStorage {
  #migration: Promise<void>;
  constructor(
    private storage: ILayoutStorage,
    private namespace: string,
    opts: { migrateUnnamespacedLayouts: boolean; importFromNamespace: string | undefined },
  ) {
    // runs migrateUnnamespacedLayouts?() and/or importLayouts() once
  }
  async list(): Promise<readonly Layout[]>   { await this.#migration; return this.storage.list(this.namespace); }
  async get(id: LayoutID)                     { await this.#migration; return this.storage.get(this.namespace, id); }
  async put(layout: Layout)                   { await this.#migration; return this.storage.put(this.namespace, layout); }
  async delete(id: LayoutID)                  { await this.#migration; return this.storage.delete(this.namespace, id); }
}

WriteThroughLayoutCache

packages/suite-base/src/services/LayoutManager/WriteThroughLayoutCache.ts — an ILayoutStorage that calls the underlying list() once per namespace (via LazilyInitialized) and serves subsequent reads from an in-memory Map, writing through to the inner storage on put/delete. Assumes nothing else mutates the underlying storage.

export default class WriteThroughLayoutCache implements ILayoutStorage {
  #cacheByNamespace = new Map<string, LazilyInitialized<Map<string, Layout>>>();
  constructor(private storage: ILayoutStorage) {}
  async put(namespace: string, layout: Layout): Promise<Layout> {
    const result = await this.storage.put(namespace, layout);
    (await this.#getOrCreateCache(namespace).get()).set(result.id, result);
    return result;
  }
  // get/list/delete read/write the per-namespace cache map
}

LayoutManager (Sync Orchestrator)

packages/suite-base/src/services/LayoutManager/LayoutManager.ts.

Mutex Pattern

All local storage access is wrapped in a MutexLocked (from @lichtblick/den/async) so multi-step operations are atomic. A single in-flight sync is tracked by currentSync?: Promise<void>.

class LayoutManager {
  private local: MutexLocked<NamespacedLayoutStorage>;
  private currentSync?: Promise<void>;
  async getLayouts(): Promise<readonly Layout[]> {
    return await this.local.runExclusive(async (local) => await local.list());
  }
}

⚠️ LayoutManager does not implement exponential backoff / jitter / #baseInterval /

#maxInterval. Sync scheduling (and any retry/online-trigger behavior) lives in the provider

layer, not in LayoutManager. Do not assume a built-in backoff timer here.

computeLayoutSyncOperations() (Detail)

packages/suite-base/src/services/LayoutManager/utils/computeLayoutSyncOperations.ts. The real SyncOperation is a tagged union carrying a local boolean and the operation type:

export type SyncOperation =
  | { local: true;  type: "add-to-cache";   remoteLayout: RemoteLayout }
  | { local: true;  type: "delete-local";   localLayout: Layout }
  | { local: true;  type: "mark-deleted";   localLayout: Layout }
  | { local: false; type: "delete-remote";  localLayout: Layout }
  | { local: false; type: "upload-new";     localLayout: Layout }
  | { local: false; type: "upload-updated"; localLayout: Layout }
  | {
      local: true;
      type: "update-baseline";
      localLayout: Layout & { syncInfo: NonNullable<Layout["syncInfo"]> };
      remoteLayout: RemoteLayout;
    };

⚠️ There is no "upload" | "download" | "conflict" union, no layoutId field, and no

syncStatus/baseline.savedAt comparison as shown previously. Operations are keyed by

localLayout / remoteLayout, and the local flag indicates whether the op mutates local

(cache) or remote storage.

The function iterates local layouts (matching against a remoteLayoutsById map) and then any remaining remote-only layouts, pushing the appropriate operation for each.

CurrentLayoutProvider Reducers

packages/suite-base/src/providers/CurrentLayoutProvider/reducers.ts. The actual action type values handled are:

CHANGE_PANEL_LAYOUT, SAVE_PANEL_CONFIGS, SAVE_FULL_PANEL_CONFIG, CREATE_TAB_PANEL, OVERWRITE_GLOBAL_DATA, SET_GLOBAL_DATA, SET_USER_NODES, SET_PLAYBACK_CONFIG, CLOSE_PANEL, SPLIT_PANEL, SWAP_PANEL, MOVE_TAB, ADD_PANEL, DROP_PANEL, START_DRAG, END_DRAG.

⚠️ There are no REMOVE_PANEL, MOVE_PANEL, or UPDATE_PANEL_CONFIG actions. Panel removal is

CLOSE_PANEL; config writes go through SAVE_PANEL_CONFIGS / SAVE_FULL_PANEL_CONFIG.

Panel Tree Operations (examples)

ADD_PANEL — find insertion point → add new leaf to the mosaic tree.

CLOSE_PANEL — remove leaf → if parent collapses to a single child, hoist it.

SPLIT_PANEL:

Replace leaf with { direction, first: existingLeaf, second: newLeaf, splitPercentage: 50 }

Config Update Pattern (SAVE_PANEL_CONFIGS)

case "SAVE_PANEL_CONFIGS":
  // merges each { id, config } entry into state's configById,
  // optionally via a per-panel override function

DesktopLayoutLoader

packages/suite-desktop/src/renderer/services/DesktopLayoutLoader.ts — namespace = "local". Reads layouts from the desktop file system through the preload storageBridge (list / get / put / delete), not a desktopBridge.fetchLayouts() call.

Common Issues

1. Sync conflicts: User edits while offline → both sides changed → manual resolution needed
2. Mutex deadlock: If sync operation throws without releasing → next sync hangs (mitigated by timeout)
3. IndexedDB quota: Large layouts with many panels → check quota before save
4. Baseline drift: If baseline gets corrupted → all syncs show as conflicts (reset baseline)