`gst-launch-1.0` and `pipewiresrc` ship in separate packages on most
distros (Arch: `gst-plugin-pipewire`, Debian: `gstreamer1.0-pipewire`,
Fedora/openSUSE: `pipewire-gstreamer`). Having the gst binary present
was no guarantee the Wayland capture pipeline would actually work —
without the plugin gst would bail at runtime with `no element
"pipewiresrc"`, which then cascaded into ffmpeg seeing EOF on its
stdin and exiting before its HTTP listener bound, then the host
hitting "Connection refused" against its own port. Confusing.
Now `deps::check_host_binaries` probes `gst-inspect-1.0 --exists
pipewiresrc` on Wayland and fails early with a per-distro install
hint pointing at the right package.
Implements the Wayland host pipeline from plan §4.5:
ashpd ScreenCast portal
-> CreateSession + SelectSources + Start + OpenPipeWireRemote
-> (pipewire fd, node_id, width, height)
gst-launch-1.0 pipewiresrc fd=N path=NODE_ID ! videoconvert
! video/x-raw,format=NV12 ! fdsink fd=1
ffmpeg
-f rawvideo -pix_fmt nv12 -video_size WxH -i pipe:0
-f pulse -i default
-c:v libx264 -preset ultrafast -tune zerolatency
-c:a aac -f mpegts -listen 1 http://127.0.0.1:<rand>
Phase 1 ships software x264 per plan §7; VAAPI is Phase 2.
src/host/wayland.rs is the new module. capture.rs becomes a thin
dispatcher with a CaptureHandle enum (Wayland today, X11 next).
host/mod.rs swaps the 150ms sleep for a poll-until-listener-ready
helper, and calls handle.shutdown().await for an orderly SIGTERM /
1s grace / SIGKILL teardown. The Drop impl is the panic backstop.
The pipewire fd handoff clears CLOEXEC before gst-launch spawn and
closes the parent's copy of the raw fd after the child has it.
Also deletes the empty src/host/tunnel.rs and src/viewer/tunnel.rs
placeholder files — the generic bridge in common/tunnel.rs is doing
the work, and there's no host- or viewer-specific tunnel concern
worth a module yet.
mollusk