Add more doxygen description about instance id

Change-Id: I8b0531afd9dfc0ead7c62d2fa430a350bfd63a53
Signed-off-by: Hyunho Kang <hhstark.kang@samsung.com>

diff --git a/include/widget_app.h b/include/widget_app.h
index 5e29aea..cf1b275 100755 (executable)
--- a/include/widget_app.h
+++ b/include/widget_app.h
@@ -326,13 +326,20 @@ int widget_app_remove_event_handler(app_event_handler_h event_handler);
  * @brief Gets a widget instance id.
  * @since_tizen 2.3.1
  * @remarks The specific error code can be obtained using the get_last_result() method. Error codes are described in Exception section.
- * @remark You must not free returned Widget ID
+ * @remark You must not free returned widget instance id
+ * @remark The returned widget instance id is volatile. If the device reboots or the widget's process restarts, it will be changed.\n
+ *      So, you should not assume this value is a persistent one.
+ * @remark widget_service_trigger_update(), widget_service_change_period(), widget_service_get_content_of_widget_instance()\n
+ *      can be called with returned instance id.
  * @param[in] context The context for widget instance
- * @return Widget ID on success,
- *         otherwise NULL
+ * @return widget instance id on success,
+ *      otherwise NULL
  * @exception #WIDGET_ERROR_NOT_SUPPORTED Not supported
  * @exception #WIDGET_ERROR_FAULT Unrecoverable error
  * @see get_last_result()
+ * @see widget_service_trigger_update()
+ * @see widget_service_change_period()
+ * @see widget_service_get_content_of_widget_instance()
  */
 const char *widget_app_get_id(widget_context_h context);