feat: round bar on smart corners

also take in the i3 ipc code to support custom messages

sims/services/smart_corners.py

@@ -0,0 +1,48 @@
+"""Smart-corners IPC subscriber.
+
+Listens to fenster's `:smart_corners` event and emits a per-output signal
+when the WM's smart-corners state flips. Caches the latest state per output
+so widgets created after the event can ask for the current value.
+"""
+from fabric.core.service import Service, Signal
+from loguru import logger
+
+from sims.services.fenster import get_i3_connection
+
+
+_service: "SmartCornersService | None" = None
+
+
+class SmartCornersService(Service):
+    @Signal
+    def state_changed(self, output: str, active: bool) -> None:
+        """Emitted when a fenster output flips smart-corners state."""
+
+    def __init__(self, **kwargs):
+        super().__init__(**kwargs)
+        self._state: dict[str, bool] = {}
+        i3 = get_i3_connection()
+        i3.connect("event::smart_corners", self._on_event)
+
+    def get(self, output: str) -> bool:
+        """Latest known state for an output, or False if unseen."""
+        return self._state.get(output, False)
+
+    def _on_event(self, _i3, event):
+        change = event.data.get("change")
+        output = event.data.get("output")
+        if not isinstance(output, str) or change not in ("active", "inactive"):
+            logger.warning(f"[SmartCorners] unexpected event payload: {event.data!r}")
+            return
+        active = change == "active"
+        if self._state.get(output) == active:
+            return
+        self._state[output] = active
+        self.state_changed(output, active)
+
+
+def get_smart_corners_service() -> SmartCornersService:
+    global _service
+    if _service is None:
+        _service = SmartCornersService()
+    return _service