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Services and events

Every system service is a background thread with a cached snapshot and an event fd. Register the fd once and your surfaces rebuild only when something changed.

vw::App app;
app.surface(bar).surface(sidebar);
app.on_event(vw::network::event_fd(), vw::network::drain_events)
   .on_event(vw::bluetooth::event_fd(), vw::bluetooth::drain_events)
   .on_event(vw::upower::event_fd(), vw::upower::drain_events)
   .on_event(vw::pipewire::event_fd(), vw::pipewire::drain_events)
   .on_event(vw::mpris::event_fd(), vw::mpris::drain_events)
   .on_event(vw::notifications::event_fd(), vw::notifications::drain_events);

The pattern

Each service runs on its own thread: a GLib main loop for the D-Bus ones (NetworkManager, BlueZ, UPower, MPRIS, the tray, notifications), PipeWire’s own loop, inotify for backlights, sockets for compositors. When its state changes it refreshes a snapshot and makes its event fd readable.

  • Reads are cheap. vw::network::status(), vw::mpris::active(), vw::upower::display_device() return the cached snapshot; they never block on the bus. Call them from build functions freely.
  • Writes are calls. set_wifi_enabled, set_volume, play_pause, set_powered talk to the service and return whether it worked; the change comes back as an event.
  • Events are coalesced. drain_events() empties the fd and returns true if anything happened; the app then rebuilds every surface once.

Your own sources plug in the same way: any fd plus a function that drains it and says whether to rebuild — a signalfd, an inotify watch, a timerfd.

app.on_event(signal_fd, [] { /* read siginfo */ return true; });

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