Implement dual output for camera using QVideoWidget and QVideoSink, add camera permission handling, and enhance overlay error messaging

duck_preview/camera/service.py

@@ -9,6 +9,7 @@ from PySide6.QtMultimedia import (
     QMediaDevices,
     QVideoSink,
 )
+from PySide6.QtMultimediaWidgets import QVideoWidget
 
 
 class CameraService(QObject):
@@ -17,18 +18,18 @@ class CameraService(QObject):
     def __init__(self, parent: QObject | None = None) -> None:
         super().__init__(parent)
         self._session = QMediaCaptureSession()
-        self._sink = QVideoSink()
-        self._session.setVideoOutput(self._sink)
         self._camera: QCamera | None = None
 
-    @property
-    def sink(self) -> QVideoSink:
-        return self._sink
-
     @property
     def session(self) -> QMediaCaptureSession:
         return self._session
 
+    def set_video_widget(self, widget: QVideoWidget) -> None:
+        self._session.setVideoOutput(widget)
+
+    def set_video_sink(self, sink: QVideoSink) -> None:
+        self._session.setVideoSink(sink)
+
     @staticmethod
     def available_cameras() -> list[QCameraDevice]:
         return QMediaDevices.videoInputs()