The Windows sibling of single_instance_qt.rs. Same three entry points and the
same present-or-defer behaviour, so main.rs reads identically on both.
A named mutex arbitrates and a named pipe carries the message, because those
are different problems. CreateMutexW answers "did it already exist" atomically,
with no window for a second launch to slip through. A pipe cannot be asked that
without FILE_FLAG_FIRST_PIPE_INSTANCE, and QLocalServer never passes it
(PIPE_UNLIMITED_INSTANCES), so two processes could both believe they were the
server.
The plan asked for QLocalServer here, which meant a new Q_OBJECT file in the
moc list and .qt_module("Network"). A raw named pipe is the same primitive
underneath with none of that build surface, for a protocol two verbs long.
The pipe name is QUALIFIED BY SESSION ID, and that is not cosmetic: the mutex
is `Local\`, which is per-session, while pipe names are machine-global. With
one fixed name and two users signed in, each takes its own mutex but only the
first creates the pipe -- the second primary then serves nothing and ITS later
launches would forward to the OTHER USER'S process. PIPE_REJECT_REMOTE_CLIENTS
because the namespace is reachable over SMB and nothing about a second launch
is remote.
What arrives on the pipe is VALIDATED before it is acted on. It is not argv:
any process running as this user can write a line, and the payload otherwise
went straight to link resolution. The read is bounded at 4 KB for the same
reason.
`qbz://` is rewritten to `qobuzapp://` rather than taught downstream. The
resolver knows qobuzapp and the Qobuz web shapes and nothing else -- a live
test of the forwarding path came back "unsupported or invalid music link" for
a qbz:// URL, and a test in this file already pinned that is_qobuz_link
excludes it. The two carry the same album/track/artist shape, so a prefix swap
is the whole translation, and the MSI's registration finally means something.
A parse alone is not a gate: Url::parse("qbz://") SUCCEEDS, a valid scheme with
an empty everything, so the check requires a non-empty authority -- which is
where every accepted shape carries its target.
The URL validation in select_link is Windows-gated. ShellExecute can split a
link across argv there; Linux and macOS have accepted whatever matched the
prefix since this shipped, and tightening that from a Windows port would change
behaviour on platforms that never asked.
present_or_defer re-reads UI_READY after publishing PENDING_PRESENT. bind_ui
can flip the flag and run its own swap in between, leaving the pending bit set
with nobody to consume it and a second launch looking ignored.
Verified on the box: a second launch carrying a deep link exits 0 in about four
milliseconds, the primary logs the handoff and resolves the rewritten URL.
571 tests pass.
cc
vicrodh
afa32d9bba