P3 of design/per-monitor-portal-capture.md. Mutter's mirror is the same
private ScreenCast session the virtual path already drives, one call
different — RecordMonitor instead of RecordVirtual — so it inherits what
makes that path work headlessly: a direct D-Bus API that needs no
interactive approval, unlike the xdg portal a background service could
never answer.
Deliberately not under TOPOLOGY_LOCK: that serializes operations which add
or remove a monitor or apply a monitor configuration, and mirroring does
neither. Nothing is created, no layout changes, and teardown is just Stop —
the SIGSEGV-adjacent ordering the virtual path must observe cannot arise
when no monitor is being removed.
The GNOME HDR probe now honors the pin. Asking "is ANY monitor in BT.2100
mode" was fair while capture took whatever head it was handed; once the
operator names one, an HDR TV on the next connector must not talk the host
into offering PQ formats for the SDR panel it is actually streaming. A pin
that names no live head reports SDR rather than falling back to "any" — the
session is about to fail on that same missing monitor, and an over-claimed
HDR offer would be a second, quieter wrong answer.
⚠️ RecordMonitor's exact signature is read from the interface, not yet
confirmed against a live gnome-shell; no GNOME box was reachable.
Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>
enricobuehlerandClaude Opus 5
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