set the correct active camera number when it starts

src/components/PhotoDialog.vue

@@ -211,6 +211,12 @@ export default class PhotoDialog extends Vue {
     if (cameraComponent) {
       this.numDevices = (await cameraComponent.devices(["videoinput"])).length;
       this.mirror = cameraComponent.facingMode === "user";
+      // figure out which device is active
+      const currentDeviceId = cameraComponent.currentDeviceID();
+      const devices = await cameraComponent.devices(["videoinput"]);
+      this.activeDeviceNumber = devices.findIndex(
+        (device) => device.deviceId === currentDeviceId,
+      );
     }
   }
 
@@ -218,7 +224,9 @@ export default class PhotoDialog extends Vue {
     const cameraComponent = this.$refs.camera as InstanceType<typeof Camera>;
     this.activeDeviceNumber = (this.activeDeviceNumber + 1) % this.numDevices;
     const devices = await cameraComponent?.devices(["videoinput"]);
-    cameraComponent?.changeCamera(devices[this.activeDeviceNumber].deviceId);
+    await cameraComponent?.changeCamera(
+      devices[this.activeDeviceNumber].deviceId,
+    );
   }
 
   async takeImage(/* payload: MouseEvent */) {