Marker

A reusable Markdown engine for native Swift apps — the school supply you write Markdown with.

Design principle: raw-string storage

The document text is the file's exact bytes. Every model type addresses the source by range and never mutates it; the editor styles attributes over the raw string instead of converting to a rich representation. A consumer's markdown therefore round-trips byte-exact by construction — there is no serializer to drift.

Products

Product	Contents
Marker	The pure engine: block parser, inline scanner, GFM pipe tables, code-block model + language detection, incremental block diffing, image path/remote resolution, document outline, and the editor state + command engine (EditorModel, EditorCommands, EditorTool, CommandPaletteModel). Foundation-level frameworks only — no AppKit, no UI.
MarkerEditor	The TextKit 2 gentle-syntax WYSIWYG layer, themed via MarkerTheme. Depends on the core only.
MarkerHighlighting	tree-sitter code-fence highlighting (grammars vendored), plugged into the editor via the core's CodeTokenProviding seam. Optional — light consumers skip the grammars entirely.

MarkerEditor ships four themed components:

• EditorView — the editor itself: live WYSIWYG or raw source mode, grid tables, boxed code wells with hover copy, inline images, task-checkbox clicks, Cmd+click link activation.
• CommandPaletteView — the caret-anchored ⌘K-style formatting palette (drive it with the core's CommandPaletteModel; the consumer owns the trigger key and presentation).
• FormatBar — a compact persistent formatting bar over the same EditorTool catalog as the palette.
• The wiki-link completion popup — appears automatically while typing inside [[… when the wikiCompletions seam is wired; keyboard-navigable, undo-registered insertion.

Consumer seams

App-specific behavior enters through closures and protocols — never by forking the package:

Seam	What it does
MarkerTheme	Every design token the editor renders with: 10 palette colors, prose/mono/ui font families (or system-font designs like .serif), accent defaults. Build one from your design system.
onLinkActivate	Cmd+click on [text](url), <url>, bare URLs, or [[wiki links]] — you resolve and open.
wikiCompletions	Candidates for the [[ completion popup; you rank and cap, the editor presents.
onDropFiles	Non-image file drops → the markdown to insert at the drop caret (or nil to decline).
onDropText	Plain-string drops (dragged list rows) → a markdown replacement (or nil for default insertion).
EditorModel.onDropImages	Image drops, each with a security-scoped bookmark minted while the drop grant is live.
CodeTokenProviding	Code-fence token provider — pass MarkerHighlighting's CodeHighlighter, your own, or nothing.

Requirements

Swift 6.2 (strict concurrency, MainActor default isolation), macOS 14+.

Usage

import Marker            // pure parsing, no UI
let document = MarkdownParser.parse("# Hello\n\nSome **bold** text.")
// Each block owns a UTF-16 range of the ORIGINAL source — slices tile it exactly.

import MarkerEditor      // the editor with a few seams wired

@State private var editor = EditorModel(text: markdown)

EditorView(model: editor, theme: myTheme,                    // MarkerTheme from your tokens
           highlighter: CodeHighlighter.shared,              // or nil — flat mono code
           onLinkActivate: { target in openLink(target) },   // .url(String) / .wiki(String)
           wikiCompletions: { query in myCandidates(query) },
           onDropFiles: { urls in wikiLinks(for: urls) })

See docs/Integration.md for the full consumer guide — choosing products, building a theme, wiring each seam, and the raw-string invariants to respect.

Tests: 188 (182 core + editor logic, 6 highlighting). Used by TrapperKeeper and ShabuBox.