12 — Network stack & the impossible catalog

Three link-time stubs (libcurl_stub.a, libgit2_stub.a, libnng_stub.a) gate a cluster of features. Two are revivable in the browser (HTTP libraries, local history); one is genuinely impossible (the IPC socket transport). This doc covers those plus the full catalog of what stays off and why — so the "everything web-feasible should work" policy has a clear boundary.

curl → emscripten Fetch (revives HTTP libraries)

wasm/stubs/curl_stub.c makes curl_easy_init() return NULL, so KICAD_CURL_EASY's ctor throws "Unable to initialize CURL session" (common/kicad_curl/kicad_curl_easy.cpp:127-130). That kills: the HTTP schematic library (SCH_IO_HTTP_LIB, which is otherwise compiled and registered — see 08), the update check, and PCM downloads.

The right move is not porting libcurl (browsers can't do raw TCP; the real libcurl-wasm ports tunnel TCP over WebSocket proxies — wrong tool). Instead, replace the stub with a functional implementation of the ~12 curl_easy_* entry points KICAD_CURL_EASY actually uses (setopt URL/headers/POST/writefunction, perform, getinfo response-code) over the emscripten Fetch API — Asyncify-friendly (the build already runs full Asyncify), same pattern as the clipboard. New file in wasm/stubs/, zero KiCad-file changes. Constraint: target servers must send CORS headers. ~2–4 days. Same shim revives every other curl consumer (version checks in pgm_base.cpp / build_version.cpp, currently failing silently).

libgit2 → real static build (fixes silently-broken local history)

wasm/stubs/libgit2_stub.c makes all git ops fail with -1. This kills two things:

Project git integration — UI lives in the kicad project-manager (not a wasm target), so mostly moot.
Local history — not moot. common/local_history.cpp (git-backed save snapshots) is wired into the shipped editors (pcb_edit_frame.cpp, files.cpp, sch_edit_frame.cpp, eda_base_frame.cpp) and currently fails silently on every save. This is a real product gap worth a deliberate decision.

Port (medium, ~1 week): build a real static libgit2.a for wasm (wasm-git / petersalomonsen proves libgit2 compiles to emscripten cleanly) and drop the stub for the editors. Local-only commits need no network. Remote push/pull would additionally need wasm-git's HTTP smart-transport — skip that. Alternatively, if local history isn't a priority, disable the feature via config so it stops failing silently — but pick one; the current state (compiled-in, failing every save) is the worst option.

nng / IPC API transport — keep stubbed (impossible)

KICAD_IPC_API=ON builds the API handlers + protobuf (that's what the ON flag is for), but api_server.cpp / api_plugin_manager.cpp are excluded and kinng isn't linked (common/CMakeLists.txt). nng is raw sockets and the IPC clients are external OS processes — neither exists in a browser sandbox. Keep libnng_stub.a.

The mainline-aligned future for plugins (post-SWIG KiCad 11) is this same IPC API, reachable from the browser only via a JS bridge (postMessage/WebSocket) implementing the request/reply surface — a different transport, not nng. That's a separate project; see ../../../features/python/research.md.

The impossible catalog (and why)

Feature	Why it can't work in a browser
3Dconnexion SpaceMouse / navlib	needs the native 3DxWare driver/daemon; WebHID can't replace the SDK protocol
Dynamic KIFACE / DSO loading	no `dlopen` of native DSOs in wasm; the static single-kiface architecture is correct (`kiway.cpp` / `kiway.h`)
ODBC database (`nanodbc`)	driver-manager + native driver model has no browser equivalent (08)
nng / IPC transport	raw sockets to external OS processes (above)
`wxUSE_FSWATCHER`	no inotify/kqueue; MEMFS has no change notification and nothing edits files externally
`wxUSE_WEBVIEW`	no browser backend for the wasm port; only the unshipped project-manager uses it
OS keychain (`wxUSE_SECRETSTORE`)	no OS credential service; only insecure approximations (localStorage) exist
Pointer warping (`WarpPointer`)	browsers can't move the OS pointer — handled by zoom-to-cursor (03)
System trash / host env / process info	sandbox (kiplatform `environment.cpp`, `sysinfo.cpp`)
`PYTHON_MANAGER` subprocess execution	no `fork`/subprocess in emscripten; an embedded interpreter is the only path (policy-off)

Policy-off (not impossible — chosen)

Python scripting — KICAD_SCRIPTING OFF + stubs. Stays off per the standing decision; the mainline path is the IPC API, not SWIG (see ../../../features/python/research.md).
PCM, update check — networking features the team skipped; the curl shim above would revive the update check if ever wanted.
kicad project manager, cvpcb, bitmap2component — never given wasm targets; the web app is the "manager" and the product ships per-tool editors (pcbnew, eeschema, symbol_editor, gerbview, pl_editor, calculator).

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