# WinHelp decompiler for johnmcm.com

The WebAssembly module behind johnmcm.com's HLP viewer (/hlp-viewer).

It is [helpdeco](https://github.com/pmachapman/helpdeco), the WinHelp
decompiler by Manfred Winterhoff, Ben Collver and Paul Wise, compiled with
Emscripten as a program: each help file is decompiled by a fresh instance with
its own in-memory file system, and the page reads back the files it writes
(the RTF topics, the help project, pictures, phrases, icon). helpdeco's files
say GPL version 2 or later and its LICENSE file is GPL version 3; this site
publishes exactly what it builds:

- `source/`: helpdeco's source at commit
  `785273788af17fde4fba7df7162d547f8645d7d8`, unmodified, with its README and
  LICENSE.
- `src/run.mjs`: one decompile (writes the .hlp into the file system, runs
  helpdeco, collects its output). helpdeco asks "Press CR to continue" when a
  file is partly damaged; stdin always answers with a carriage return.
- `src/worker.mjs`: the worker the page talks to.
- `Dockerfile` and `build.ps1`: the build, with the Emscripten image pinned
  by digest. Run `build.ps1` with Docker Desktop running; the module goes to
  `frontend/vendor/local/helpdeco@1/`.

The module is loaded as a separate file by the page, so it can be replaced
with one built from modified source. (The package's splitmrb tool is not
built: it assumes 16-bit integers and writes SHG and MRB pictures out garbled;
the page decodes those pictures itself, in TypeScript.)