libei hands the injector one region per logical monitor with no output
name attached, so picking one meant matching the streamed mode's SIZE —
a coin flip the moment two heads share a mode, and it already resolved
wrong on-glass once (GNOME, a dummy HDMI beside the virtual primary: the
seat cursor never entered the streamed monitor, so neither cursor path
could see it).
The ladder is now mapping_id -> origin -> size -> first. Two outputs can
share a size but never a top-left, and a mirrored head's region is not the
client's size at all, so the size rung cannot find it — this is what makes
per-monitor capture land its input on the monitor it is showing.
An anchor that matches nothing falls back down the ladder rather than
stranding input: the region set is the truth and the anchor is our belief
about it. It warns once per distinct anchor, because the failure this
exists to prevent is a pointer that silently lands elsewhere.
P1 of design/per-monitor-portal-capture.md — mechanism and tests only.
Nothing sets an anchor yet; the pin wires it in P2, and the doc comment
records why it is host-level and not per-session.
Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>
enricobuehlerandClaude Opus 5
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