#20: Configurations
===================

Project Configurations
**********************

Karabo stores device configurations in the so-called Karabo *projects*.

.. figure:: images/project_device_configurations.png
   :align: center
   :alt: Project device with a default configuration
   :figclass: align-center

   Project device with a default configuration

The software configurations can be altered **offline** via the **Configurator** before device
instantiation. The project will become modified and thus the changes can be saved
in the project data base.
In reality, it may happen that some devices are rejecting a software configuration
if the hardware resident configuration is not editable on instantiation, e.g. PLC devices.

Technical: Why persist OFFLINE configurations?
----------------------------------------------

Many devices in the control system have a dynamic structure (schema).
This device structure depends on data unavailable to the offline device when instantiated.

For example:

- A device that builds its own structure from the hardware configuration, or firmware version (e.g. MPOD).

- A device retrieves a system definition from the hardware at connection (e.g. PLC devices).

- A device with a table element for an extensible definition (e.g. Beam Imager).
  After instantiation the device building itself up from the table element.

- A middlelayer device connects to driver devices to fetch their structure and configurations and then builds itself up.

**Online device configurations are likely to conflict with the offline device structure (schema).**

Configuration From Past
-----------------------

In Karabo, all devices are archived while they are online. Every property change is send
to the datalogger devices and stored (disk and/or database). If the changes are not
older than ~a month, they can be retrieved and viewed. Either via the trendline widgets for
single properties or via the **Configuration From Past** feature.
This can be done via the following steps:

   1. Right-click the **Device** object. A context menu will show up.
   2. Select **Get Configuration** option. A *Configuration Timepoint* dialog
      will appear.
   3. Supply the **Timepoint** (date-time) of the configuration to be retrieved.
      For convenience, the user can utilize the calendar on the dropdown menu
      and/or use the preset time buttons.

.. figure:: images/configuration_from_past.png
   :align: center
   :alt: Configuration from past dialog
   :figclass: align-center

   The configuration from past dialog

After the configuration request a notification window will pop up once the data logger replied.
The operator gets a notification about the failure or success. The reply might take a while as the configuration has to be
searched.
If the configuration request is successful, it will appear in the configurator.
For an online device, the respective changes are highlighted with a blue box and
need to be applied.
In case of an offline device, the retrieved configuration is merged into
the offline configuration.