Host-side completion of Stage 5 (§6A many-clients-as-monitors), all unit-tested;
two-session on-glass validation still pending (no GPU on the dev VM):
- Per-group topology restore (§6.1): the KWin `exclusive` restore no longer rides
the per-session StopGuard (which re-enabled the physical the moment the FIRST of
several exclusive sessions dropped, under a live sibling). KWin hands its restore
to the registry as a closure (new trait `take_topology_restore`); the registry
keeps it in the display group (`Entry.topology_restore`) and, on teardown, floats
it to a surviving same-group sibling (`hand_off_restore`) or runs it when the group
empties — outside the lock, before the last output's keepalive drops, so the
compositor never sees zero outputs. All three teardown paths (lease drop / linger
expiry / mgmt release) honor it. Single-display path byte-for-byte unchanged.
Unit-tested: float / run-on-last / non-carrier-first / never-cross-backend.
- Mutter group-aware (new trait `set_first_in_group`): the registry tells each
backend whether it's the first display of its group; a non-first Mutter session
EXTENDS into the already-exclusive desktop instead of re-applying a sole-monitor
ApplyMonitorsConfig that would disable the first session's virtual. (Mutter
connectors are un-nameable, so it can't build a keep-all-virtuals config; skipping
is the safe equivalent.) Single-session unchanged. Residual APPLY_TEMPORARY revert
documented.
- gamescope groups (§6.1): `registry::group_key` makes each gamescope spawn its own
group (independent nested session, no shared desktop) — never auto-rowed against or
restore-/topology-grouped with another gamescope. Applied in both the /display/state
assembly and the acquire-time position computation. Unit-tested.
Remaining Stage 5: the web console arrangement table, on-glass validation, and the
documented residuals (wlroots exclusive, Mutter APPLY_TEMPORARY). design doc updated.
cargo build/test (214)/clippy --all-targets/fmt green.
Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>
enricobuehler
87435e6547