MARK IT DOWN
Mark It Down
页面 · Mark It Down

File-level Export Pipeline (TXT, DOCX, PDF)

Status: shipped in Phase 0.6 · Issue: #6

The previously-stub commands markItDown.exportPdf, exportDocx, exportTxt are now real. Right-click a .md file in the explorer, or invoke from the editor title bar / command palette, and Mark It Down generates the corresponding artifact server-side and offers a save dialog.

At a glance

FormatEngineOutput
TXTHand-rolled stripper using marked.lexerPlain text, no markdown markers; tables become aligned ASCII; lists use - / 1. prefixes; headings use # markers; code blocks fenced with ---
DOCXdocx npmReal Word document with headings, paragraphs, lists (with indent), bold/italic/strike runs, links (blue + underline), inline code (Courier), code blocks (light grey shading + Courier), real <table>s, blockquotes (italic + indent), HR centered
PDFpdfkitLETTER page, Helvetica/Courier mix, headings sized H1=22pt → H6=11pt, code blocks with grey background fill, tables with header row + column ruling, HRs as horizontal lines

All three exports share the same flow:

  1. User invokes the command (explorer context menu, editor title bar, command palette)
  2. Host reads the source .md file from disk
  3. Host parses to tokens via marked.lexer (in src/exporters/markdownTokens.ts)
  4. Host runs the format-specific renderer (TXT/DOCX/PDF)
  5. Host opens vscode.window.showSaveDialog with the .<ext> extension and the markdown filename's basename
  6. Host writes the buffer + offers Open / Reveal actions in an info toast

If anything throws, the host surfaces a clear error message — no silent failures.

Why these libraries

  • TXT doesn't need a library — marked.lexer gives us tokens, we walk and emit text. Hand-rolled is ~80 LOC and zero dep.
  • DOCX: the docx package is the de-facto standard for emitting .docx from Node. Outputs are openable in Word, Pages, LibreOffice. ~600KB.
  • PDF: the issue spec called for headless chromium (puppeteer-core). Bundling chromium in a .vsix is not viable — chromium itself is ~150MB and puppeteer-core requires the user to install Chrome separately. PDFKit is a pure-Node PDF generator that ships in ~250KB, runs in-process, and produces valid PDFs without any browser dependency. Tradeoff: PDFKit doesn't render arbitrary HTML, so we walk markdown tokens and emit PDF primitives directly. Mermaid diagrams, syntax-highlighted code, and complex tables look simpler in PDFKit output than they do in the webview rendering. For pixel-perfect "PDF that looks exactly like the View" output, a future iteration could shell out to a headless chromium if the user has one installed; for now, the in-process PDFKit path is the default and works offline.

Per-format detail

TXT export (markItDown.exportTxt)

Walks marked tokens and emits plain text with these conventions:

MarkdownTXT output
# Heading# Heading (markers preserved for readability)
_em_ / **strong**text content only (markers stripped)
[link](https://example.com)link (https://example.com)
`code`text content only
![alt](img.png)alt
Lists- item or 1. item with 2-space indent for nesting
Blockquotes> prefix, recursive
Code blocksfenced with --- lang --- … ---
Tablesaligned ASCII with `
HR---
HTML blockspreserved verbatim (the user added them on purpose)

Output is UTF-8, terminated by a single \n at EOF. Multiple consecutive blank lines collapse to at most two.

DOCX export (markItDown.exportDocx)

Uses docx builders to emit a Word document. Every block-level token maps to either a Paragraph or a Table:

  • Headings → Paragraph({ heading: HEADING_LEVEL_X }) so Word's outline pane and TOC pick them up
  • Paragraphs → Paragraph({ children: TextRun[] }) with inline styling (bold/italic/strike/underline/color)
  • Lists → indented paragraphs with • or 1. prefix; nested lists indent further by 360 twips per level
  • Code blocks → paragraph with grey shading + Courier New font at 10pt
  • Inline code → TextRun with Courier New
  • Links → blue (#0066CC) + single underline (note: docx v9 doesn't expose hyperlink targets through this builder — runs are visually styled but not clickable. A future fix is to use ExternalHyperlink)
  • Images → [image: alt] placeholder text in italic grey (binary embedding is a future addition; markdown image references remote URLs we shouldn't fetch synchronously during export)
  • Tables → Table({ rows: TableRow[] }) with shaded header row, full page width
  • Blockquotes → italic grey paragraphs indented 720 twips
  • HR → centered "— — —" glyph row

Output is a valid .docx zip. Word, Pages, Google Docs, LibreOffice all open it.

PDF export (markItDown.exportPdf)

Uses PDFKit to draw directly to PDF primitives. LETTER page, 56pt margins, Helvetica/Courier font mix.

Per-block:

  • Headings → Helvetica-Bold at sizes [22, 18, 15, 13, 12, 11] for H1–H6
  • Paragraphs → Helvetica 11pt, 4pt line gap
  • Lists → bullet/number prefix + indent; nested lists indent further
  • Code blocks → Courier 10pt over a light grey (#F5F5F5) background fill (drawn after text, then text re-rendered on top — PDFKit doesn't have a native "boxed" text primitive)
  • Tables → header row in bold, then a thin grey horizontal rule, then body rows; equal column widths fit to page
  • HR → thin horizontal line
  • Blockquotes → italic with #666 color

Output is a single PDF buffer with info metadata set: title = source basename, producer = "Mark It Down".

What's not in v0.6

The issue spec mentioned "preserve mermaid diagrams (rasterize them to images), code highlighting, and tables." Of those:

  • Tables: ✓ all three formats (DOCX as real table, PDF as ruled table, TXT as ASCII)
  • Code highlighting: ✗ in DOCX/PDF — token text only, no syntax color. The webview's html-to-image path (used by the per-block PNG export, F3) could be reused to embed colored code blocks; not in v0.6.
  • Mermaid rasterization: ✗ — exports treat mermaid as a regular code block (text). Rendering mermaid → PNG → embed requires running mermaid in a headless browser, which is what we explicitly avoided. Future-work seed: spawn a hidden webview, render mermaid blocks via the existing webview pipeline, capture as PNG via html-to-image, and embed in the DOCX/PDF.
  • File-level exports from the editor title bar: the title bar already has Mark It Down: Toggle View / Edit; file-level export commands are not added there in v0.6 — they live in the explorer context menu (already wired) and the command palette. Adding to the title bar is a 5-line change for a future cleanup.

Edge cases & limitations

  • Empty markdown: produces an empty TXT, a 1-paragraph DOCX, and a blank PDF page. No error.
  • Malformed markdown: marked.lexer is forgiving; whatever it outputs gets walked. Tags it doesn't recognize fall through to the default branch and either render their text or silently skip.
  • Very large files: TXT is fine to MBs. DOCX and PDF are O(N) over tokens; >10MB markdown files may take a few seconds to render. Streaming outputs are a future optimization.
  • Save cancelled: silent — no error toast.
  • Filename clashes: showSaveDialog handles overwrite confirmation.
  • Cross-platform paths: VSCode's Uri.joinPath handles separators; tested on macOS, structurally fine on Windows/Linux.

Files of interest