Add XWayland support (#16)

* save dev state

* fix xwayland-satellite supervisor lifecycle, readiness and cleanup

* remove wayland scanner protocol generated files

* default xwayland enabled with path

* remove jargons

* address x11 review: park unconfirmed cleanup, never signal a reaped group, fix storm test and notify dir mode

* fix resize tests: never build Size values from negative dimensions

* add min-width/min-height window rules that replace client minimum sizes

* rename effective_size_constraints to effective_minimum_size and minor cleanups

compositor/src/process.rs

@@ -52,9 +52,8 @@ pub(crate) fn spawn_client<S: AsRef<OsStr>>(
     let mut command = command(program);
     command.args(args);
     // Workers may already exist. Change only this child's environment.
-    command.env("WAYLAND_DISPLAY", &state.socket_name);
-    command.env_remove("WAYLAND_SOCKET");
-    command.env_remove("FERESE_SHELL_CONTROL_SOCKET");
+    // Apply before granting the child a private Wayland connection.
+    state.session_environment.apply_public(&mut command);
     command.env("FERESE_COMPOSITOR_WALLPAPER", "1");
     let private_connection = if capabilities.is_empty() {
         None
@@ -83,6 +82,11 @@ pub(crate) fn spawn_client<S: AsRef<OsStr>>(
 }
 
 pub(crate) fn pidfd(pid: u32) -> io::Result<OwnedFd> {
+    #[cfg(test)]
+    if crate::xwayland::test_hooks::PIDFD_UNAVAILABLE.load(std::sync::atomic::Ordering::SeqCst) {
+        return Err(io::Error::from_raw_os_error(libc::ENOSYS));
+    }
+
     // SAFETY: pidfd_open has no pointer arguments and returns a new owned fd.
     let fd = unsafe { libc::syscall(libc::SYS_pidfd_open, pid, 0) };
     if fd < 0 {