The three topology levels become distinct behaviors (Stage 0 only did
extend-vs-exclusive, faking primary):
- vdisplay::effective_topology() -> the concrete level (console policy > legacy
*_VIRTUAL_PRIMARY env > Auto default). Backends read it directly at create
time; apply_session_env no longer writes the boolean env (one fewer connect-
path env mutation).
- Mutter: extend (no config), primary (virtual primary + physicals kept as
secondaries — build_primary_keeping_physicals), exclusive (sole, physicals
disabled). KWin: extend (no-op), primary (kscreen primary only), exclusive
(primary + disable others).
- Windows should_isolate treats primary as isolate (the primary-only CCD variant
is a follow-up); wlroots exclusive + the physical-keep effect need a
display-attached box (headless lab boxes can't observe primary vs exclusive).
Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>
enricobuehler
cb7ddc0411