KWin creates virtual outputs at a hardcoded 60 Hz and zkde stream_virtual_output has no
refresh argument, so the *source* composited at 60 Hz even when the client asked for 120/240
(confirmed live: stream paced a stable 240 fps but only ~60 unique frames/s). KWin 6.6+ allows
custom modes on virtual outputs, so after creating the output we install + select a mode at the
client's refresh, before capture connects PipeWire. First cut shells out to kscreen-doctor
(output is "Virtual-<name>"); the in-process kde_output_management_v2 client is a follow-up.
Best-effort — failure leaves the source at 60 Hz (stream still works). Verified the mode is
applied (Virtual-lumen -> 1280x720@120). Empirically de-risked that this headless QEMU VM's
software vsync accepts >60 Hz.
Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>
enricobuehler
22a982a1cb