This is the white screen. Not graphics, not the bundle, not pairing.
The app constructs @pokusew/pcsclite at startup. That calls
SCardEstablishContext(), which calls SCardCheckDaemonAvailability(), which
— finding no pcscd — BUSY-LOOPS in fstatat64 at ~92% CPU rather than
returning an error. It runs on Electron's main thread before the
BrowserWindow is created, so no window is ever made and the panel stays
white.
It is a hang, not a crash, which is why it presented so badly. Nothing
throws. Nothing is logged after "[StateStore] Initialized database". The
process looks healthy: systemd reports the service active, Electron is
running, and there is even a gpu-process. But a setInterval registered
before startup never fires once in 32 seconds, the main thread sits in
state R, and the remote debugger reports zero page targets.
V8's own tooling cannot see it either, because the thread never yields to
the inspector: Debugger.pause returns nothing and Profiler.stop times out.
A native backtrace was the only thing that worked:
#0 fstatat64 libc
#1 SCardCheckDaemonAvailability libpcsclite
#2 SCardEstablishContext libpcsclite
#3 PCSCLite::PCSCLite() pcsclite.node
#4 PCSCLite::New(...)
Ruled out along the way, each by direct test on the machine: graphics (it
fails identically with the GPU fully disabled), Electron on aarch64 (a
minimal app renders fine), the Vue bundle (loading the real index.html
from a minimal main process mounts the app and reaches "[ATM] State
machine initialized"), the preload script, the CSP, kiosk and fullscreen
window options, better-sqlite3, /dev/shm, memory, page size, X
authorisation, and isDev.
upboard.nix and batm3.nix both enable pcscd for their real readers, which
is why no x86 machine has ever hit this. This module did not, and that was
the entire difference. pcscd with no reader attached simply idles, so
enabling it costs nothing.
Worth noting for the wider fleet: any future board that omits pcscd
inherits this, and it presents as a blank screen with a healthy-looking
service. The robust fix is for the app to not block its main thread on a
card-reader handshake at all — the NFC path is already documented as
best-effort — but that is an app change and this unblocks the hardware.
Padreug
2572a14c61