CHM Viewer for VS Code

A VS Code extension that lets you open and browse Microsoft Compiled HTML Help (.chm) files directly in the editor.

Features

Open CHM files directly in VS Code with a familiar help viewer interface
Table of Contents (TOC) sidebar with collapsible tree navigation
Full-text search through topics in the sidebar
Back/Forward navigation history
Internal link support — clickable links between help topics
Embedded resources — images, CSS, and other assets are resolved from inside the CHM archive
LZX decompression — handles both compressed and uncompressed CHM sections

git clone <this-repo>
cd chm-viewer
npm install
npm run compile

Then package and install:

npx vsce package
code --install-extension chm-viewer-0.1.0.vsix

Or run directly in debug mode:

Open a .chm file (e.g., OakStreamCrb.chm) in VS Code
The CHM Viewer will open with:
- Left sidebar: Table of Contents and search
- Right pane: Rendered HTML help content
- Toolbar: Back/Forward navigation buttons
Click any topic in the TOC to navigate to it
Click internal links within help pages to jump between topics
Use the search box to filter topics by name

The extension parses the CHM (InfoTech Storage Format) file structure:

ITSF Header — locates the directory and data sections
PMGL Directory Chunks — lists all files in the archive (HTML, images, CSS, etc.)
LZXC Compression — decompresses LZX-compressed content blocks
HHC Sitemap Parsing — extracts the Table of Contents from the .hhc file
Webview Rendering — displays HTML content with intercepted resource loading

Extension	Description
`.chm`	Microsoft Compiled HTML Help files

JavaScript files inside CHM archives are not executed (for security)
Some very old or non-standard CHM files may not parse correctly
Binary TOC (stored in #TOPICS) is not yet supported — only .hhc file-based TOC

MIT