pixelpass/src/host/wayland.rs

//! Wayland capture: ashpd ScreenCast portal → PipeWire fd → `pipewiresrc`.
//! This module owns only the portal handshake and the source-element args;
//! the shared encode/mux tail, gst spawn, and serving live in
//! [`super::pipeline`].

use anyhow::{Context, Result};
use ashpd::{
    WindowIdentifier,
    desktop::{
        PersistMode,
        screencast::{CursorMode, Screencast, SourceType},
    },
};
use nix::fcntl::{FcntlArg, FdFlag, fcntl};
use nix::unistd::close;
use std::os::fd::{AsFd, IntoRawFd, OwnedFd, RawFd};

use super::pipeline::{self, CaptureHandle};
use super::quality::EffectiveQuality;
use crate::cli::HostOpts;

pub async fn start(opts: &HostOpts, quality: &EffectiveQuality) -> Result<CaptureHandle> {
    // 1. Negotiate the screencast session with the portal.
    let proxy = Screencast::new()
        .await
        .context("could not reach the xdg-desktop-portal ScreenCast interface")?;
    let session = proxy.create_session().await?;

    let source = if opts.window { SourceType::Window } else { SourceType::Monitor };
    proxy
        .select_sources(
            &session,
            CursorMode::Embedded,
            source.into(),
            false,
            None,
            PersistMode::DoNot,
        )
        .await
        .context("select_sources failed")?;

    let response = proxy
        .start(&session, &WindowIdentifier::default())
        .await
        .context("portal Start failed (did the user cancel the picker?)")?
        .response()?;

    let stream = response
        .streams()
        .first()
        .context("portal returned no screencast streams")?;
    let node_id = stream.pipe_wire_node_id();
    let (w, h) = stream
        .size()
        .context("portal returned a stream with no size — pipewiresrc can't infer dimensions")?;

    let pw_fd: OwnedFd = proxy.open_pipe_wire_remote(&session).await?;
    tracing::info!(node_id, width = w, height = h, "portal handshake complete");
    // The fd is CLOEXEC by default; the gst child needs to inherit it across
    // exec. We then leak it via into_raw_fd so its lifetime spans the spawn,
    // and close the parent's copy once gst is running (the pipeline's
    // after_spawn hook below).
    clear_cloexec(&pw_fd)?;
    let raw_fd: RawFd = pw_fd.into_raw_fd();

    let source_args = vec![
        "pipewiresrc".to_string(),
        format!("fd={raw_fd}"),
        format!("path={node_id}"),
        "do-timestamp=true".to_string(),
    ];

    pipeline::spawn(opts, quality, Some((w as u32, h as u32)), source_args, move || {
        // Parent no longer needs the pipewire fd — gst inherited its own copy.
        let _ = close(raw_fd);
    })
    .await
}

fn clear_cloexec(fd: &impl AsFd) -> Result<()> {
    let flags_int = fcntl(fd.as_fd(), FcntlArg::F_GETFD).context("F_GETFD on pipewire fd")?;
    let mut flags = FdFlag::from_bits_truncate(flags_int);
    flags.remove(FdFlag::FD_CLOEXEC);
    fcntl(fd.as_fd(), FcntlArg::F_SETFD(flags)).context("F_SETFD on pipewire fd")?;
    Ok(())
}