<br />

Enabling the device's flash unit during an AR session can help improve
visibility.

## Check that the current camera configuration supports flash

Not all camera configurations support enabling a flash unit.
Before enabling the flash or offering users the option to enable the flash,
ensure that the flash unit is available for the active camera
configuration:

```c
// Get the camera ID from the current session.
ArCameraConfig* ar_camera_config = NULL;
ArCameraConfig_create(ar_session, &ar_camera_config);
ArSession_getCameraConfig(ar_session, ar_camera_config);
char* camera_id = NULL;
ArCameraConfig_getCameraId(ar_session, ar_camera_config, &camera_id);
ArCameraConfig_destroy(ar_camera_config);

// Get the camera characteristics.
ACameraManager* camera_manager = ACameraManager_create();
CHECK(camera_manager != NULL);
ACameraMetadata* characteristics = NULL;
camera_status_t status = ACameraManager_getCameraCharacteristics(camera_manager, camera_id, &characteristics);
ArString_release(camera_id);
CHECK(status == ACAMERA_OK);
CHECK(characteristics != NULL);

// Check if flash is supported.
ACameraMetadata_const_entry entry;
status = ACameraMetadata_getConstEntry(characteristics, ACAMERA_FLASH_INFO_AVAILABLE, &entry);
CHECK(status == ACAMERA_OK);
uint32_t is_flash_supported = false;
if (entry.count == 1 && entry.data.u8[0] == ACAMERA_FLASH_INFO_AVAILABLE_TRUE) {
  is_flash_supported = true;
}

ACameraManager_delete(camera_manager);
```

## Enable the flash unit

Enable the flash unit by configuring the AR session with
[`AR_FLASH_MODE_TORCH`](https://developers.google.com/ar/reference/c/group/ar-config#arflashmode):

```c
ArConfig* ar_config = NULL;
ArConfig_create(ar_session, &ar_config);
ArSession_getConfig(ar_session, ar_config);
if (is_flash_supported) {
  ArConfig_setFlashMode(ar_session, ar_config, AR_FLASH_MODE_TORCH);
}
CHECK(ArSession_configure(ar_session, ar_config) == AR_SUCCESS);
ArConfig_destroy(ar_config);
```

> [!NOTE]
> **Note:** Configuring [`AR_FLASH_MODE_TORCH`](https://developers.google.com/ar/reference/c/group/ar-config#arflashmode) with a camera configuration that does not support a flash unit will have no effect.

## Disable the flash unit

Disable the flash unit by configuring the AR session with
[`AR_FLASH_MODE_OFF`](https://developers.google.com/ar/reference/c/group/ar-config#arflashmode):

```c
ArConfig* ar_config = NULL;
ArConfig_create(ar_session, &ar_config);
ArSession_getConfig(ar_session, ar_config);
if (is_flash_supported) {
  ArConfig_setFlashMode(ar_session, ar_config, AR_FLASH_MODE_OFF);
}
CHECK(ArSession_configure(ar_session, ar_config) == AR_SUCCESS);
ArConfig_destroy(ar_config);
```