OptionalreadAcquires bytes for a workbook and decodes them (via ReadRequest.decode).
The decoded workbook, or null if the store could not produce one (e.g. the user
cancelled an open picker, or the store does not recognize the source).
Optional. IWorkbookIO.read uses the active store's read when present, and otherwise
falls back to the built-in platform store — so a store that only overrides write still gets
the default read behavior.
OptionalwritePersists the workbook described by the request.
The IWorkbookIO.Origin actually written — request.origin when the store
persisted to it, a new origin when it resolved a destination — or null if cancelled.
Optional. A read-only store omits it; IWorkbookIO.canWrite then reports false and
IWorkbookIO.write throws. A store must implement at least one of read / write.
A destination (and, optionally, source) for persisting workbooks — for example the local file system, a browser download, a VSCode host, or a cloud service.
Remarks
The active store is used by IWorkbookIO.write and can be replaced via IWorkbookIO.setBackingStore. A store is conceptually stateless from the caller's point of view; any session state it keeps (such as a browser
FileSystemFileHandlefor silent re-save) is a private implementation detail and never appears in these types.