@floatboat/nexus-core

Framework-agnostic Markdown editor engine powering Nexus-Editor — CodeMirror 6 + Lezer with Obsidian-style live preview. See the repository README for the full feature tour; this file documents core-specific public APIs.

Install

pnpm add @floatboat/nexus-core

import { createEditor } from "@floatboat/nexus-core";

const editor = createEditor({
  container: document.querySelector("#editor")!,
  initialValue: "# Hello",
  livePreview: true,
});

Multi-cursor / multi-selection

Opt-in via multiCursor: true (off by default — it swaps the native caret/selection rendering for CodeMirror-drawn layers):

const editor = createEditor({
  container,
  initialValue: "# Hello",
  multiCursor: true,
});

When enabled:

| Interaction | Effect | |---|---| | Alt+Click | Add a cursor at the clicked position | | Mod-d | Select word under cursor, then next occurrence of the selection (VS Code style, wraps around) | | Mod-Alt-ArrowUp / Mod-Alt-ArrowDown | Add a cursor on the previous / next line, column preserved | | Escape | Collapse to the main selection (falls through to other Escape handlers when already single) |

Mod is Cmd on macOS and Ctrl elsewhere. Markdown niceties are multi-range aware: Enter continues lists/blockquotes at every cursor, and the ` / ** / ~~ auto-pairing wraps every selection. Live preview reveals raw syntax at every cursor position.

The commands are exported standalone for hosts that want custom bindings, plus the bundled keymap and extension:

import {
  selectNextOccurrence,
  addCursorAbove,
  addCursorBelow,
  collapseToMainSelection,
  multiCursorKeymap,
  multiCursorExtension,
} from "@floatboat/nexus-core";

Selections API

editor.getSelection();   // main range: { anchor, head }
editor.getSelections();  // all ranges: { ranges: [{ anchor, head }, ...], mainIndex }

editor.setSelection(5);                                  // single cursor
editor.setSelections([{ anchor: 2 }, { anchor: 9, head: 14 }]);  // multiple ranges
editor.setSelections([{ anchor: 2 }, { anchor: 9 }], 0);         // explicit main range

editor.on("selectionChange", ({ anchor, head, ranges, mainIndex }) => {
  // anchor/head describe the main range; ranges carries all of them
});

Multiple ranges in setSelections require multiCursor: true — without the flag CodeMirror collapses the selection to its main range.

Other config highlights

See the EditorConfig type for the full surface: livePreview, plugins, theme / setTheme, locale, readOnly, tabSize, direction, indentGuides, parseDelayMs, slashMenuLimit, onChange / onFocus / onBlur / onAssetUpload.