Split the current document into two panes with Split Editor in Group (one tab, primary/secondary), with continuous newspaper-style columns and synchronized scrolling (document-line based visibleRanges + revealRange).

Features

Multicol Reading: Toggle Two-Column Reading (multicol.toggleTwoColumn): switch between single pane and two panes (editor title bar button, status bar, Ctrl+Alt+N / Cmd+Alt+N).
Turn On Two-Column Reading / Restore Single Column: explicit commands in the Command Palette.
multicol.overlapLines: optional vertical overlap between columns (0–10 document lines).
Page Down / Page Up when multicol is active: step by one column height.
Per-file editor state (persisted in the workspace): each document URI can independently be “two-column on” or off; missing entry means single column. Reload restores split per URI that was left on, including scroll anchor (best-effort).

About the author

雷鹏（Lei Peng） — The founder of Terark Inc, the creator of TerarkDB, and the new ToplingDB.

Debug

Run npm install in the repo root.
Open this folder in VS Code.
Press F5 (Run Extension) to launch an Extension Development Host.
Open a text file and run Multicol Reading: Toggle Two-Column Reading.

Package: npm install -g @vscode/vsce then vsce package, install the VSIX from VS Code.

Layout

Path	Role
`package.json`	Manifest: commands, keybindings, configuration
`src/extension.ts`	Activation: commands, status bar, per-document persistence (`multicol.documents.v1` map)
`src/session.ts`	`MulticolSession`: scroll sync via `revealRange(AtTop)`
`src/layout.ts`	`workbench.action.splitEditorInGroup` / `joinEditorInGroup`
`src/editorMetrics.ts`	Lines-per-column heuristic from `visibleRanges`

Limits (VS Code API)

No public pixel scroll API on TextEditor; scrolling uses revealRange — not pixel-identical to native wheel/trackpad in all themes.
Layout uses Split Editor in Group only (two panes per tab); there is no supported third column in the same group.
Restore single column runs joinEditorInGroup (not joinTwoGroups).
If split fails mid-flight, the extension best-effort rolls back with joinEditorInGroup until visible editor count for that document is back to what it was before the attempt.
Some editor types cannot split in group (non-text editors); split may fail with a clear error.

Publish (maintainer)

GitHub Release + VSIX
Push a version tag v* (e.g. v0.1.1). The Release workflow compiles, runs vsce package, and attaches the .vsix to a GitHub Release.
Visual Studio Marketplace
- Create a publisher (ID must match package.json → publisher, here rockeet).
- Create a Personal Access Token: Azure DevOps → User settings → Personal access tokens → Custom defined → scope Marketplace (Manage).
- CI (recommended): In the GitHub repo → Settings → Secrets and variables → Actions, add secret VSCE_PAT. Pushing a tag v* runs release.yml: it uploads the VSIX to the GitHub Release and publishes that same VSIX to the Marketplace when VSCE_PAT is set.
- Local: In PowerShell: $env:VSCE_PAT = 'your_token_here' → npm run package → npx vsce publish (or npx vsce publish -p $env:VSCE_PAT).