virtual-image: Add a notify::removed handler

In general, we rely on the underlying transport layer to throw errors
which will abort the current operation. This does not work for the
virtual image device though, but we need it there for testing purposes.

Add a notify::removed handler that makes things work as expected. Let it
throw a protocol error which should not be visible to the outside.

libfprint/drivers/virtual-image.c

@@ -367,9 +367,36 @@ dev_deactivate (FpImageDevice *dev)
   fpi_device_add_timeout (FP_DEVICE (dev), 10, (FpTimeoutFunc) fpi_image_device_deactivate_complete, NULL, NULL);
 }
 
+static void
+dev_notify_removed_cb (FpDevice *dev)
+{
+  FpiImageDeviceState state;
+  gboolean removed;
+
+  g_object_get (dev,
+                "fpi-image-device-state", &state,
+                "removed", &removed,
+                NULL);
+
+  if (!removed || state == FPI_IMAGE_DEVICE_STATE_INACTIVE)
+    return;
+
+  /* This error will be converted to an FP_DEVICE_ERROR_REMOVED by the
+   * surrounding layers. */
+  fpi_image_device_session_error (FP_IMAGE_DEVICE (dev),
+                                  fpi_device_error_new (FP_DEVICE_ERROR_PROTO));
+}
+
 static void
 fpi_device_virtual_image_init (FpDeviceVirtualImage *self)
 {
+  /* NOTE: This is not nice, but we can generally rely on the underlying
+   *       system to throw errors on the transport layer.
+   */
+  g_signal_connect (self,
+                    "notify::removed",
+                    G_CALLBACK (dev_notify_removed_cb),
+                    NULL);
 }
 
 static const FpIdEntry driver_ids[] = {