Opens the display backend exactly as a session would, attaches a capturer
and reports the frames a named head actually produces, with no client
involved. `--monitor` names the head explicitly (it cannot go through
PUNKTFUNK_CAPTURE_MONITOR: pf_host_config parses the environment once and
startup already read it, so a tool setting it for itself would still see
the old snapshot — hence vdisplay::open_mirror); with no argument it
exercises the production routing through the pin.
A frame timeout is NOT treated as failure. Compositor capture is
damage-driven — the host's own capture diag logs new_fps=0 for virtual
outputs on an idle desktop for exactly this reason — so the first version
of this tool ended its measurement on the first idle gap and made a working
mirror look like a 2-frame stall.
Verified on KWin 6.7.3 (home-nobara-1), mirroring HDMI-A-1: 346 frames in
20s at 1920x1080, arriving while input was injected and pausing when the
desktop went quiet, on both the CPU (BGRx/MemFd) and zero-copy (NV12
dmabuf) paths, ownership=External.
Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>
enricobuehlerandClaude Opus 5
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