--- /dev/null
+.. _fields_arch_gui_page:
+
+*****************
+FIELDS module GUI
+*****************
+
+FIELDS module uses the following components to manage and display presentations:
+
+* Standard SALOME *Object browser* represents structure of MED file within FIELDS module. When MED file is loaded, the following steps are performed:
+
+ #. Reading structure of MED file. For these purpose, ``MEDCALC::MedDataManager`` CORBA service (which uses *MEDCoupling* library) is used.
+ #. Creating structure of MED file (full path to MED file, name of a mesh, name and type (``ON_NODES`` or ``ON_CELLS``) of each field in MED file, and all timesteps for each field).
+ ``MED_ORB::MED`` CORBA component is used for that, and each item of the data tree structure is represented via standard SALOME data object ``SObject``.
+
+* *Presentation Parameters* panel allows managing parameters of presentations. This panel is implemented in the following way:
+
+ #. Interface of *Presentation Parameters* panel is described via `Qt Designer tool <https://doc.qt.io/qt-5/qtdesigner-manual.html>`__;
+ for details see ``WidgetPresentationParameters.ui`` (UI form) and ``WidgetPresentationParameters.cxx`` (C++ wrapping of UI) files.
+ The UI file contains all needed GUI controls which are used to manage parameters of all FIELDS presentations, i.e. single UI file is used for all types of presentations.
+ All these parameters are hidden by default; and parameters, required for specific presentation are shown at first usage, for example:
+
+ .. code-block:: cpp
+
+ void WidgetPresentationParameters::setSliceOrientation(MEDCALC::SliceOrientationType orient) {
+ ...
+ // Show the widgets:
+ _ui.labelSliceOrient->show();
+ _ui.comboBoxSliceOrient->show();
+ ...
+ ...
+ ...
+ }
+
+ Widget which contains all these parameters is displayed inside the dockable window which is created during the initialization of FIELDS module.
+
+ #. Interaction between GUI controls and ``medcalc`` Python package is implemented via several helper classes. The hierarchy of these classes is presented on the following diagram:
+
+ .. image:: images/image_helpers_hierarchy.png
+ :align: center
+
+ * ``MEDWidgetHelper`` - base abstract class to manage common parameters of all FIELDS presentations.
+ * ``MEDWidgetHelperComponent`` - base abstract class to manage parameters of all presentations having only one component to change.
+
+ These base classes contain one pure virtual method
+
+ .. code-block:: cpp
+
+ virtual std::string getPythonTag() const = 0;
+
+ This method must be implemented in all descendant classes; it should return the type of a presentation ("ScalarMap", "Slices" and etc.)
+
+ * All other classes (such as ``MEDWidgetHelperScalarMap``, ``MEDWidgetHelperSlices`` etc.) are descendants of classes ``MEDWidgetHelper`` or ``MEDWidgetHelperComponent``.
+
+ Helper classes send ``PresentationEvent`` event via emitting ``presentationUpdateSignal`` signal on any user action made in *Presentation Parameters* panel.
+
+ #. ``PresentationController`` class is aimed for
+
+ * Converting ``PresentationEvent`` events to calls of ``medcalc`` Python package API, and executing related commands in the embedded Python console, for example:
+
+ .. code-block:: cpp
+
+ QStringList commands;
+ ...
+ if ( event->eventtype == PresentationEvent::EVENT_CHANGE_COMPONENT ) {
+
+ // Get presentation type by calling getPythonTag() method
+ std::string typ = getPresTypeFromWidgetHelper(event->presentationId);
+
+ // Convert 'PresentationEvent' to set of python commands
+ commands += QString("params = medcalc.Get%1Parameters(%2)").arg(QString::fromStdString(typ)).arg(event->presentationId);
+ commands += QString("params.displayedComponent = '%1'").arg(QString::fromStdString(event->aString));
+ commands += QString("medcalc.Update%1(%2, params)").arg(QString::fromStdString(typ)).arg(event->presentationId);
+ }
+ ...
+ _consoleDriver->exec(commands);
+
+ * Updating content of *Presentation Parameters* panel according to the presentation, selected in the *Object browser*.
+
+* Standard SALOME *Displayer* mechanism is used to manage visiblity of FIELDS presentations in the ParaView viewer.
