@nextgensoftwares/folio-plugin-file-preview

Previews inside file cards and an in-page file viewer. Guide: File previews.

Plugin

Export	Signature	Description
`filePreviewPlugin`	`(options: FilePreviewOptions) => FilePreviewPlugin`	size-aware `fileAttachment` renderer and painter, `Enter` binding, context-menu items, PDF/DOCX exporters
`type FilePreviewOptions`		`media`, `defaultSize?`, `limits?`, `cache?`, `worker?`, `pdfWorker?`, `viewer?`, `onOpen?`, `exportThumbnails?`
`type FilePreviewPlugin`		`FolioPlugin` plus `previews` (PreviewService), `viewer` (ViewerStore), `open(file, from?)`, `prepareExport(doc)`

Types

Export	Description
`PreviewKind`	`'pdf' \| 'sheet' \| 'csv' \| 'docx' \| 'odt' \| 'pptx' \| 'text' \| 'image' \| 'video' \| 'audio' \| 'none'`
`CardSize`, `CARD_SIZES`	`'compact' \| 'preview' \| 'large'`
`PreviewData`	card preview: `image` (url), `table` (rows, sheet?, more?), `lines` (PreviewLine[], mono?), `none` (reason)
`PreviewLine`	`{ text, level? }` (level 1–6 = heading)
`ViewerData`, `SheetBook`	viewer content: `sheet`, `html` (unsanitized; sanitized on insertion), `lines`, `slides`
`FileRef`	normalized file attrs: `src`, `name`, `mime`, `size`, `pages?`, `kind`, `attrs`
`PreviewLimits`, `DEFAULT_LIMITS`	`maxBytes` (50 MB), `viewerMaxBytes` (100 MB), `timeoutMs` (15 s), `rows` 6, `cols` 5, `lines` 8, `maxCells`, `maxTextChars`

Detection and layout

Export	Description
`previewKindOf(name, mime)`	kind from the extension, then the MIME type
`extensionOf(name)`	lowercase extension
`fileRefOf(attrs)`	`FileRef` from a node's attrs
`hasPreview(kind)`	false for `none`/`audio` (those cards stay compact)
`PARSED_KINDS`	kinds parsed from bytes (worker)
`PREVIEW_SIZE_ATTR`	`'previewSize'`, the global attr on `fileAttachment`
`previewSchema`	the schema contribution declaring it
`CARD_GEOMETRY`, `CARD_ROW`	card height/max width per size; info-row height
`cardSizeOf(attrs, fallback)`	the size a card is laid out at (synchronous)
`createPreviewRenderer(defaultSize)`	the `fileAttachment` block renderer

Previews and cache

Export	Description
`PreviewService`, `type PreviewServiceOptions`	memory LRU → store → generate; `key`, `peek`, `request(file, size, signal?)`, `generate`, `viewerData`, `bytes`
`THUMB_WIDTH`	thumbnail width rendered per card size
`indexedDbPreviewStore(opts?)`, `memoryPreviewStore()`, `type PreviewStore`	persistent cache backends (`get`, `set`, `clear?`)
`Lru`	small LRU map
`WorkQueue`	deduplicating, delayed, bounded-concurrency queue (newest first; dropped when every caller aborts)
`createExtractor(opts)`, `type ExtractorOptions`, `type RunExtract`	worker runner with time limits and in-thread fallback
`defaultWorker()`, `type WorkerLike`	the bundled parsing worker
`TimeoutError`, `InterruptedError`	a task overran / was stopped by another task's overrun
`type ExtractTask`, `type ExtractLimits`	a unit of parsing work (plain data)
`loadBytes(url, opts)`, `type LoadOptions`, `TooLargeError`	capped fetch
`resolveUrl(src, resolve)`, `isLoadableUrl(url)`	stored src → loadable URL; scheme allowlist

Parsing and safety

Export	Description
`sanitizeHtml(html, opts?)`	strict DOM-free allowlist; balanced output, ids prefixed (`idPrefix`, default `fp-`)
`parseCsv(text, opts?)`, `sniffDelimiter(text)`	RFC 4180, text-only cells, row/cell caps
`decodeText(bytes, maxChars?)`, `textLines(text, max, opts?)`	BOM-aware decoding; first lines (Markdown headings)
`loadPdfJs(createWorker?)`, `openPdf(bytes, createWorker?)`	pdf.js (legacy build) with eval/XFA/fetching off
`defaultPdfWorker()`, `type PdfWorkerFactory`	the bundled pdf.js worker
`safePdfLink(url)`	only `http(s)`/`mailto` links

Commands, export, React

Export	Description
`selectedFile(state)`	the selected file card (`{ pos, file }`) or null
`setCardSize(size)`	command: set the selected card's size
`openSelected(open)`	command (bound to Enter): open the selected card; declines otherwise
`createExporters(service, defaultSize, mode)`, `type ExportThumbnails`	PDF/DOCX mappings returning `PrintFallback` + `image`
`exportImage(service, attrs, size, mode)`	the thumbnail image for one card, or undefined
`previewToImage(data, width, height)`	table/lines preview → JPEG data URL (canvas)
`createCardPainter(deps)`, `type CardDeps`	the card painter
`PreviewBody`	draws a `PreviewData`
`usePreview(service, file, size, enabled)`, `useVisible(ref, margin?)`	hooks

Viewer

Export	Description
`ViewerStore`	`get`, `subscribe`, `open(state, restoreFocus)`, `close()` (focus goes back)
`type ViewerState`, `type FileViewerProps`, `type ViewerComponent`	what a (host) viewer component receives: `file`, `url`, `dark`, `service`, `onClose`
`loadFileViewer()`	the default viewer component, loaded on demand
`nextFocus(list, active, back)`	the focus trap's Tab order