A tiny Windows 9x–style desktop that runs real Win32 C applications compiled to WebAssembly — by its own small lcc-wasm toolchain, with no Emscripten. The window manager is DOM-based, GDI is a <canvas> facade, and you can edit, compile and run C apps from inside the browser.

🖥️ Live demo · 📝 Write-up

Opening Minesweeper, then opening a program's source, compiling a hello-world and running it — all in the browser.

Every program is real Win32 C (written with WinMain / RegisterClass / a message loop / GDI), compiled to standalone wasm:

• Minesweeper — the classic, on WM_PAINT / BitBlt / DrawEdge
• Notepad — edits files on the virtual C:
• Command Prompt (cmd) — cd / dir / type, runs programs by name
• cc / msbuild — the C compiler & project builder… in the browser
• IconsDemo, greet (a console app), Hello

System libraries are real files too: C:\Windows\System32\{user32,gdi32,kernel32}.wasm. Apps import Win32 functions from them; those wasm "DLLs" forward to the JS facade. The call chain is honest: app.wasm → user32.wasm → JS.

Requires Node 18+ and Yarn.

yarn install
yarn dev          # dev server at http://localhost:5050 (uses the committed pre-built wasm)
yarn build        # production build -> dist/

Recompile the bundled C apps to wasm (needs clang, used only as the C preprocessor):

yarn build:wasm   # compiles src/cdrive/Projects/*.vcxproj via lcc-wasm -> public/cdrive/...

Deploy under a sub-path (e.g. a blog at /demo/winweb/):

WINWEB_BASE=/demo/winweb/ yarn build

Create a project under src/cdrive/Projects/<App>/:

• <App>.c — standard Win32 C (WinMain for a GUI app, main for a console one)
• <App>.vcxproj — a minimal MSBuild-style descriptor (name, console/GUI subsystem, optional icon)

then yarn build:wasm — or build it from inside the running desktop with msbuild <App> in cmd.

• Compiler. lcc-wasm — the LCC C compiler retargeted to WebAssembly and then compiled to wasm itself (rcc.wasm, ~280 KB). It compiles C89 straight to wasm, both under Node (the build) and in the browser (cc / msbuild). No Emscripten, no LLVM. See the companion write-up.
• Standalone modules. Each app exports its own memory + function table, so two instances run fully independently.
• Windowing. A DOM window manager (each window is a <div> with a title bar, menu and taskbar button). CreateWindowEx / RegisterClass / GetMessage / DispatchMessage drive real messages (WM_PAINT, WM_COMMAND, WM_TIMER, WM_SIZE).
• GDI. Rectangle, TextOut, CreateFontW, BitBlt, … rendered onto <canvas>.
• Filesystem. A virtual C: on IndexedDB, seeded from a generated manifest; case-insensitive; persists your edits and in-browser builds.

TypeScript · Vite · WebAssembly · LCC (via lcc-wasm)

MIT