The settings store, looked up each time it is used, since a host's store may be ready only later.
Where this host's layout goes.
The saved moves, oldest first; none when nothing is saved or the store is not ready.
The saved boxes, by surface key; none when nothing is saved or the store is not ready.
Whether the user hid their self-view: shown when nothing usable is saved, the store is not ready, or the host keeps no self-view setting (it named no key for it).
Saves the moves, the newest MEDIA_LAYOUT_SAVED_LIMIT of them.
Saves the boxes, the newest MEDIA_LAYOUT_SAVED_LIMIT of them (the last in the map's order).
Saves whether the user hid their self-view; nothing, for a host that keeps no self-view setting.
A host's saved layout: its moves, its picture-in-picture boxes and whether the user hid their self-view, in a per-user settings store under the host's own keys. Reading treats a store that is not ready (it throws) as nothing saved; writing skips one, or one that fails to save, so the layout then lasts for this session only. Writing keeps the newest MEDIA_LAYOUT_SAVED_LIMIT moves and boxes.