Rendered previews
A preview is usually a browser in a panel: a web view, a stylesheet, and a rendering engine that has nothing to do with the editor around it. Here the plugin returns a description of the document and Linelark draws every pixel of it in the same SwiftUI the rest of the app is built from.
The mechanism
Handing a plugin a web view would make previews easy and make three other things impossible: theme fidelity, a reading position that survives the switch, and the guarantee that a document cannot reach the network while being read.
The Preview toggle (⇧⌘V, or View ▸ Preview) is live for a document some installed plugin has claimed by extension or language, and disabled otherwise. It never offers a rendering nobody can produce.
Which is what keeps your place across the switch, in both directions: rendered from the paragraph you were editing, back to the line the block you were reading began at.
So the same file can be source in one split and rendered in the other, which is the arrangement most people actually want while writing.
Because the blocks are drawn by the same views the built-in panels use. There is no second stylesheet to keep in step with Light, Dark, and the five themes.
There is no document, no script engine and no stylesheet loader in the rendering path. A Markdown file that references a remote image cannot cause a request.
The parser runs interpreted in JavaScriptCore, so the example Markdown renderer caps itself at 256 KB rather than stall the editor on every keystroke of a very large document.
Specifics
A plugin picks from this vocabulary. A node type the app does not recognise is skipped rather than drawn wrong, which is why a plugin declares the API generation it was written against.
| Node | Drawn as |
|---|---|
| Heading | A themed heading at one of the document’s levels. |
| Prose | A paragraph with inline emphasis, strong, code and links. |
| Code block | Monospaced, in the editor’s own font, with its language label. |
| Quote | An indented block with a rule down its edge. |
| List | Ordered or unordered, nested. |
| Table | A native table with aligned columns. |
| Rule | A horizontal divider. |
Read from the Linelark Studio 1.6.1 source, not from its documentation. Where the two disagree, this is the one that ships.
Before you rely on it
It is a reading view drawn by the editor. Several things a browser-based preview would give you for free are genuinely absent.
Free, and staying free
Apple-notarized, macOS 14 and newer, Intel and Apple silicon.
Download Studio 1.6.1 6.8 MB · every version, with checksums