MultiCameraProvider camera scanning (#139)

* make scan_for_cameras abstract and add it to multi_camera_provider

* code review

---------

Co-authored-by: Falko Schindler <falko@zauberzeug.com>

rosys/vision/camera_provider.py

@@ -72,3 +72,7 @@ def prune_images(self, max_age_seconds: Optional[float] = None):
             else:
                 while camera.images and camera.images[0].time < rosys.time() - max_age_seconds:
                     del camera.images[0]
+
+    @abc.abstractmethod
+    async def update_device_list(self) -> None:
+        pass

rosys/vision/multi_camera_provider.py

@@ -1,3 +1,5 @@
+import logging
+
 from .camera import Camera
 from .camera_provider import CameraProvider
 
@@ -11,11 +13,19 @@ class MultiCameraProvider(CameraProvider):
     def __init__(self, *camera_providers: CameraProvider) -> None:
         super().__init__()
         self.providers = camera_providers
+        self.log = logging.getLogger('rosys.multi_camera_provider')
         for camera_provider in self.providers:
             camera_provider.NEW_IMAGE.register(self.NEW_IMAGE.emit)
             camera_provider.CAMERA_ADDED.register(self.CAMERA_ADDED.emit)
             camera_provider.CAMERA_REMOVED.register(self.CAMERA_REMOVED.emit)
 
+    async def update_device_list(self) -> None:
+        for provider in self.providers:
+            try:
+                await provider.update_device_list()
+            except Exception as e:
+                self.log.error('Error while scanning for cameras in "%s": %s', provider.__class__.__name__, e)
+
     def request_backup(self) -> None:
         for provider in self.providers:
             provider.request_backup()